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From whe...@apache.org
Subject [43/50] [abbrv] hadoop git commit: [partial-ns] Import snappy in hdfsdb.
Date Tue, 05 Jan 2016 19:52:43 GMT
http://git-wip-us.apache.org/repos/asf/hadoop/blob/cb5ba73b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.cc
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.cc b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.cc
new file mode 100644
index 0000000..4619410
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.cc
@@ -0,0 +1,606 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Various stubs for the unit tests for the open-source version of Snappy.
+
+#include "snappy-test.h"
+
+#ifdef HAVE_WINDOWS_H
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#endif
+
+#include <algorithm>
+
+DEFINE_bool(run_microbenchmarks, true,
+            "Run microbenchmarks before doing anything else.");
+
+namespace snappy {
+
+string ReadTestDataFile(const string& base, size_t size_limit) {
+  string contents;
+  const char* srcdir = getenv("srcdir");  // This is set by Automake.
+  string prefix;
+  if (srcdir) {
+    prefix = string(srcdir) + "/";
+  }
+  file::GetContents(prefix + "testdata/" + base, &contents, file::Defaults()
+      ).CheckSuccess();
+  if (size_limit > 0) {
+    contents = contents.substr(0, size_limit);
+  }
+  return contents;
+}
+
+string ReadTestDataFile(const string& base) {
+  return ReadTestDataFile(base, 0);
+}
+
+string StringPrintf(const char* format, ...) {
+  char buf[4096];
+  va_list ap;
+  va_start(ap, format);
+  vsnprintf(buf, sizeof(buf), format, ap);
+  va_end(ap);
+  return buf;
+}
+
+bool benchmark_running = false;
+int64 benchmark_real_time_us = 0;
+int64 benchmark_cpu_time_us = 0;
+string *benchmark_label = NULL;
+int64 benchmark_bytes_processed = 0;
+
+void ResetBenchmarkTiming() {
+  benchmark_real_time_us = 0;
+  benchmark_cpu_time_us = 0;
+}
+
+#ifdef WIN32
+LARGE_INTEGER benchmark_start_real;
+FILETIME benchmark_start_cpu;
+#else  // WIN32
+struct timeval benchmark_start_real;
+struct rusage benchmark_start_cpu;
+#endif  // WIN32
+
+void StartBenchmarkTiming() {
+#ifdef WIN32
+  QueryPerformanceCounter(&benchmark_start_real);
+  FILETIME dummy;
+  CHECK(GetProcessTimes(
+      GetCurrentProcess(), &dummy, &dummy, &dummy, &benchmark_start_cpu));
+#else
+  gettimeofday(&benchmark_start_real, NULL);
+  if (getrusage(RUSAGE_SELF, &benchmark_start_cpu) == -1) {
+    perror("getrusage(RUSAGE_SELF)");
+    exit(1);
+  }
+#endif
+  benchmark_running = true;
+}
+
+void StopBenchmarkTiming() {
+  if (!benchmark_running) {
+    return;
+  }
+
+#ifdef WIN32
+  LARGE_INTEGER benchmark_stop_real;
+  LARGE_INTEGER benchmark_frequency;
+  QueryPerformanceCounter(&benchmark_stop_real);
+  QueryPerformanceFrequency(&benchmark_frequency);
+
+  double elapsed_real = static_cast<double>(
+      benchmark_stop_real.QuadPart - benchmark_start_real.QuadPart) /
+      benchmark_frequency.QuadPart;
+  benchmark_real_time_us += elapsed_real * 1e6 + 0.5;
+
+  FILETIME benchmark_stop_cpu, dummy;
+  CHECK(GetProcessTimes(
+      GetCurrentProcess(), &dummy, &dummy, &dummy, &benchmark_stop_cpu));
+
+  ULARGE_INTEGER start_ulargeint;
+  start_ulargeint.LowPart = benchmark_start_cpu.dwLowDateTime;
+  start_ulargeint.HighPart = benchmark_start_cpu.dwHighDateTime;
+
+  ULARGE_INTEGER stop_ulargeint;
+  stop_ulargeint.LowPart = benchmark_stop_cpu.dwLowDateTime;
+  stop_ulargeint.HighPart = benchmark_stop_cpu.dwHighDateTime;
+
+  benchmark_cpu_time_us +=
+      (stop_ulargeint.QuadPart - start_ulargeint.QuadPart + 5) / 10;
+#else  // WIN32
+  struct timeval benchmark_stop_real;
+  gettimeofday(&benchmark_stop_real, NULL);
+  benchmark_real_time_us +=
+      1000000 * (benchmark_stop_real.tv_sec - benchmark_start_real.tv_sec);
+  benchmark_real_time_us +=
+      (benchmark_stop_real.tv_usec - benchmark_start_real.tv_usec);
+
+  struct rusage benchmark_stop_cpu;
+  if (getrusage(RUSAGE_SELF, &benchmark_stop_cpu) == -1) {
+    perror("getrusage(RUSAGE_SELF)");
+    exit(1);
+  }
+  benchmark_cpu_time_us += 1000000 * (benchmark_stop_cpu.ru_utime.tv_sec -
+                                      benchmark_start_cpu.ru_utime.tv_sec);
+  benchmark_cpu_time_us += (benchmark_stop_cpu.ru_utime.tv_usec -
+                            benchmark_start_cpu.ru_utime.tv_usec);
+#endif  // WIN32
+
+  benchmark_running = false;
+}
+
+void SetBenchmarkLabel(const string& str) {
+  if (benchmark_label) {
+    delete benchmark_label;
+  }
+  benchmark_label = new string(str);
+}
+
+void SetBenchmarkBytesProcessed(int64 bytes) {
+  benchmark_bytes_processed = bytes;
+}
+
+struct BenchmarkRun {
+  int64 real_time_us;
+  int64 cpu_time_us;
+};
+
+struct BenchmarkCompareCPUTime {
+  bool operator() (const BenchmarkRun& a, const BenchmarkRun& b) const {
+    return a.cpu_time_us < b.cpu_time_us;
+  }
+};
+
+void Benchmark::Run() {
+  for (int test_case_num = start_; test_case_num <= stop_; ++test_case_num) {
+    // Run a few iterations first to find out approximately how fast
+    // the benchmark is.
+    const int kCalibrateIterations = 100;
+    ResetBenchmarkTiming();
+    StartBenchmarkTiming();
+    (*function_)(kCalibrateIterations, test_case_num);
+    StopBenchmarkTiming();
+
+    // Let each test case run for about 200ms, but at least as many
+    // as we used to calibrate.
+    // Run five times and pick the median.
+    const int kNumRuns = 5;
+    const int kMedianPos = kNumRuns / 2;
+    int num_iterations = 0;
+    if (benchmark_real_time_us > 0) {
+      num_iterations = 200000 * kCalibrateIterations / benchmark_real_time_us;
+    }
+    num_iterations = max(num_iterations, kCalibrateIterations);
+    BenchmarkRun benchmark_runs[kNumRuns];
+
+    for (int run = 0; run < kNumRuns; ++run) {
+      ResetBenchmarkTiming();
+      StartBenchmarkTiming();
+      (*function_)(num_iterations, test_case_num);
+      StopBenchmarkTiming();
+
+      benchmark_runs[run].real_time_us = benchmark_real_time_us;
+      benchmark_runs[run].cpu_time_us = benchmark_cpu_time_us;
+    }
+
+    string heading = StringPrintf("%s/%d", name_.c_str(), test_case_num);
+    string human_readable_speed;
+
+    nth_element(benchmark_runs,
+                benchmark_runs + kMedianPos,
+                benchmark_runs + kNumRuns,
+                BenchmarkCompareCPUTime());
+    int64 real_time_us = benchmark_runs[kMedianPos].real_time_us;
+    int64 cpu_time_us = benchmark_runs[kMedianPos].cpu_time_us;
+    if (cpu_time_us <= 0) {
+      human_readable_speed = "?";
+    } else {
+      int64 bytes_per_second =
+          benchmark_bytes_processed * 1000000 / cpu_time_us;
+      if (bytes_per_second < 1024) {
+        human_readable_speed = StringPrintf("%dB/s", bytes_per_second);
+      } else if (bytes_per_second < 1024 * 1024) {
+        human_readable_speed = StringPrintf(
+            "%.1fkB/s", bytes_per_second / 1024.0f);
+      } else if (bytes_per_second < 1024 * 1024 * 1024) {
+        human_readable_speed = StringPrintf(
+            "%.1fMB/s", bytes_per_second / (1024.0f * 1024.0f));
+      } else {
+        human_readable_speed = StringPrintf(
+            "%.1fGB/s", bytes_per_second / (1024.0f * 1024.0f * 1024.0f));
+      }
+    }
+
+    fprintf(stderr,
+#ifdef WIN32
+            "%-18s %10I64d %10I64d %10d %s  %s\n",
+#else
+            "%-18s %10lld %10lld %10d %s  %s\n",
+#endif
+            heading.c_str(),
+            static_cast<long long>(real_time_us * 1000 / num_iterations),
+            static_cast<long long>(cpu_time_us * 1000 / num_iterations),
+            num_iterations,
+            human_readable_speed.c_str(),
+            benchmark_label->c_str());
+  }
+}
+
+#ifdef HAVE_LIBZ
+
+ZLib::ZLib()
+    : comp_init_(false),
+      uncomp_init_(false) {
+  Reinit();
+}
+
+ZLib::~ZLib() {
+  if (comp_init_)   { deflateEnd(&comp_stream_); }
+  if (uncomp_init_) { inflateEnd(&uncomp_stream_); }
+}
+
+void ZLib::Reinit() {
+  compression_level_ = Z_DEFAULT_COMPRESSION;
+  window_bits_ = MAX_WBITS;
+  mem_level_ =  8;  // DEF_MEM_LEVEL
+  if (comp_init_) {
+    deflateEnd(&comp_stream_);
+    comp_init_ = false;
+  }
+  if (uncomp_init_) {
+    inflateEnd(&uncomp_stream_);
+    uncomp_init_ = false;
+  }
+  first_chunk_ = true;
+}
+
+void ZLib::Reset() {
+  first_chunk_ = true;
+}
+
+// --------- COMPRESS MODE
+
+// Initialization method to be called if we hit an error while
+// compressing. On hitting an error, call this method before returning
+// the error.
+void ZLib::CompressErrorInit() {
+  deflateEnd(&comp_stream_);
+  comp_init_ = false;
+  Reset();
+}
+
+int ZLib::DeflateInit() {
+  return deflateInit2(&comp_stream_,
+                      compression_level_,
+                      Z_DEFLATED,
+                      window_bits_,
+                      mem_level_,
+                      Z_DEFAULT_STRATEGY);
+}
+
+int ZLib::CompressInit(Bytef *dest, uLongf *destLen,
+                       const Bytef *source, uLong *sourceLen) {
+  int err;
+
+  comp_stream_.next_in = (Bytef*)source;
+  comp_stream_.avail_in = (uInt)*sourceLen;
+  if ((uLong)comp_stream_.avail_in != *sourceLen) return Z_BUF_ERROR;
+  comp_stream_.next_out = dest;
+  comp_stream_.avail_out = (uInt)*destLen;
+  if ((uLong)comp_stream_.avail_out != *destLen) return Z_BUF_ERROR;
+
+  if ( !first_chunk_ )   // only need to set up stream the first time through
+    return Z_OK;
+
+  if (comp_init_) {      // we've already initted it
+    err = deflateReset(&comp_stream_);
+    if (err != Z_OK) {
+      LOG(WARNING) << "ERROR: Can't reset compress object; creating a new one";
+      deflateEnd(&comp_stream_);
+      comp_init_ = false;
+    }
+  }
+  if (!comp_init_) {     // first use
+    comp_stream_.zalloc = (alloc_func)0;
+    comp_stream_.zfree = (free_func)0;
+    comp_stream_.opaque = (voidpf)0;
+    err = DeflateInit();
+    if (err != Z_OK) return err;
+    comp_init_ = true;
+  }
+  return Z_OK;
+}
+
+// In a perfect world we'd always have the full buffer to compress
+// when the time came, and we could just call Compress().  Alas, we
+// want to do chunked compression on our webserver.  In this
+// application, we compress the header, send it off, then compress the
+// results, send them off, then compress the footer.  Thus we need to
+// use the chunked compression features of zlib.
+int ZLib::CompressAtMostOrAll(Bytef *dest, uLongf *destLen,
+                              const Bytef *source, uLong *sourceLen,
+                              int flush_mode) {   // Z_FULL_FLUSH or Z_FINISH
+  int err;
+
+  if ( (err=CompressInit(dest, destLen, source, sourceLen)) != Z_OK )
+    return err;
+
+  // This is used to figure out how many bytes we wrote *this chunk*
+  int compressed_size = comp_stream_.total_out;
+
+  // Some setup happens only for the first chunk we compress in a run
+  if ( first_chunk_ ) {
+    first_chunk_ = false;
+  }
+
+  // flush_mode is Z_FINISH for all mode, Z_SYNC_FLUSH for incremental
+  // compression.
+  err = deflate(&comp_stream_, flush_mode);
+
+  *sourceLen = comp_stream_.avail_in;
+
+  if ((err == Z_STREAM_END || err == Z_OK)
+      && comp_stream_.avail_in == 0
+      && comp_stream_.avail_out != 0 ) {
+    // we processed everything ok and the output buffer was large enough.
+    ;
+  } else if (err == Z_STREAM_END && comp_stream_.avail_in > 0) {
+    return Z_BUF_ERROR;                            // should never happen
+  } else if (err != Z_OK && err != Z_STREAM_END && err != Z_BUF_ERROR) {
+    // an error happened
+    CompressErrorInit();
+    return err;
+  } else if (comp_stream_.avail_out == 0) {     // not enough space
+    err = Z_BUF_ERROR;
+  }
+
+  assert(err == Z_OK || err == Z_STREAM_END || err == Z_BUF_ERROR);
+  if (err == Z_STREAM_END)
+    err = Z_OK;
+
+  // update the crc and other metadata
+  compressed_size = comp_stream_.total_out - compressed_size;  // delta
+  *destLen = compressed_size;
+
+  return err;
+}
+
+int ZLib::CompressChunkOrAll(Bytef *dest, uLongf *destLen,
+                             const Bytef *source, uLong sourceLen,
+                             int flush_mode) {   // Z_FULL_FLUSH or Z_FINISH
+  const int ret =
+    CompressAtMostOrAll(dest, destLen, source, &sourceLen, flush_mode);
+  if (ret == Z_BUF_ERROR)
+    CompressErrorInit();
+  return ret;
+}
+
+// This routine only initializes the compression stream once.  Thereafter, it
+// just does a deflateReset on the stream, which should be faster.
+int ZLib::Compress(Bytef *dest, uLongf *destLen,
+                   const Bytef *source, uLong sourceLen) {
+  int err;
+  if ( (err=CompressChunkOrAll(dest, destLen, source, sourceLen,
+                               Z_FINISH)) != Z_OK )
+    return err;
+  Reset();         // reset for next call to Compress
+
+  return Z_OK;
+}
+
+
+// --------- UNCOMPRESS MODE
+
+int ZLib::InflateInit() {
+  return inflateInit2(&uncomp_stream_, MAX_WBITS);
+}
+
+// Initialization method to be called if we hit an error while
+// uncompressing. On hitting an error, call this method before
+// returning the error.
+void ZLib::UncompressErrorInit() {
+  inflateEnd(&uncomp_stream_);
+  uncomp_init_ = false;
+  Reset();
+}
+
+int ZLib::UncompressInit(Bytef *dest, uLongf *destLen,
+                         const Bytef *source, uLong *sourceLen) {
+  int err;
+
+  uncomp_stream_.next_in = (Bytef*)source;
+  uncomp_stream_.avail_in = (uInt)*sourceLen;
+  // Check for source > 64K on 16-bit machine:
+  if ((uLong)uncomp_stream_.avail_in != *sourceLen) return Z_BUF_ERROR;
+
+  uncomp_stream_.next_out = dest;
+  uncomp_stream_.avail_out = (uInt)*destLen;
+  if ((uLong)uncomp_stream_.avail_out != *destLen) return Z_BUF_ERROR;
+
+  if ( !first_chunk_ )   // only need to set up stream the first time through
+    return Z_OK;
+
+  if (uncomp_init_) {    // we've already initted it
+    err = inflateReset(&uncomp_stream_);
+    if (err != Z_OK) {
+      LOG(WARNING)
+        << "ERROR: Can't reset uncompress object; creating a new one";
+      UncompressErrorInit();
+    }
+  }
+  if (!uncomp_init_) {
+    uncomp_stream_.zalloc = (alloc_func)0;
+    uncomp_stream_.zfree = (free_func)0;
+    uncomp_stream_.opaque = (voidpf)0;
+    err = InflateInit();
+    if (err != Z_OK) return err;
+    uncomp_init_ = true;
+  }
+  return Z_OK;
+}
+
+// If you compressed your data a chunk at a time, with CompressChunk,
+// you can uncompress it a chunk at a time with UncompressChunk.
+// Only difference bewteen chunked and unchunked uncompression
+// is the flush mode we use: Z_SYNC_FLUSH (chunked) or Z_FINISH (unchunked).
+int ZLib::UncompressAtMostOrAll(Bytef *dest, uLongf *destLen,
+                                const Bytef *source, uLong *sourceLen,
+                                int flush_mode) {  // Z_SYNC_FLUSH or Z_FINISH
+  int err = Z_OK;
+
+  if ( (err=UncompressInit(dest, destLen, source, sourceLen)) != Z_OK ) {
+    LOG(WARNING) << "UncompressInit: Error: " << err << " SourceLen: "
+                 << *sourceLen;
+    return err;
+  }
+
+  // This is used to figure out how many output bytes we wrote *this chunk*:
+  const uLong old_total_out = uncomp_stream_.total_out;
+
+  // This is used to figure out how many input bytes we read *this chunk*:
+  const uLong old_total_in = uncomp_stream_.total_in;
+
+  // Some setup happens only for the first chunk we compress in a run
+  if ( first_chunk_ ) {
+    first_chunk_ = false;                          // so we don't do this again
+
+    // For the first chunk *only* (to avoid infinite troubles), we let
+    // there be no actual data to uncompress.  This sometimes triggers
+    // when the input is only the gzip header, say.
+    if ( *sourceLen == 0 ) {
+      *destLen = 0;
+      return Z_OK;
+    }
+  }
+
+  // We'll uncompress as much as we can.  If we end OK great, otherwise
+  // if we get an error that seems to be the gzip footer, we store the
+  // gzip footer and return OK, otherwise we return the error.
+
+  // flush_mode is Z_SYNC_FLUSH for chunked mode, Z_FINISH for all mode.
+  err = inflate(&uncomp_stream_, flush_mode);
+
+  // Figure out how many bytes of the input zlib slurped up:
+  const uLong bytes_read = uncomp_stream_.total_in - old_total_in;
+  CHECK_LE(source + bytes_read, source + *sourceLen);
+  *sourceLen = uncomp_stream_.avail_in;
+
+  if ((err == Z_STREAM_END || err == Z_OK)  // everything went ok
+             && uncomp_stream_.avail_in == 0) {    // and we read it all
+    ;
+  } else if (err == Z_STREAM_END && uncomp_stream_.avail_in > 0) {
+    LOG(WARNING)
+      << "UncompressChunkOrAll: Received some extra data, bytes total: "
+      << uncomp_stream_.avail_in << " bytes: "
+      << string(reinterpret_cast<const char *>(uncomp_stream_.next_in),
+                min(int(uncomp_stream_.avail_in), 20));
+    UncompressErrorInit();
+    return Z_DATA_ERROR;       // what's the extra data for?
+  } else if (err != Z_OK && err != Z_STREAM_END && err != Z_BUF_ERROR) {
+    // an error happened
+    LOG(WARNING) << "UncompressChunkOrAll: Error: " << err
+                 << " avail_out: " << uncomp_stream_.avail_out;
+    UncompressErrorInit();
+    return err;
+  } else if (uncomp_stream_.avail_out == 0) {
+    err = Z_BUF_ERROR;
+  }
+
+  assert(err == Z_OK || err == Z_BUF_ERROR || err == Z_STREAM_END);
+  if (err == Z_STREAM_END)
+    err = Z_OK;
+
+  *destLen = uncomp_stream_.total_out - old_total_out;  // size for this call
+
+  return err;
+}
+
+int ZLib::UncompressChunkOrAll(Bytef *dest, uLongf *destLen,
+                               const Bytef *source, uLong sourceLen,
+                               int flush_mode) {  // Z_SYNC_FLUSH or Z_FINISH
+  const int ret =
+    UncompressAtMostOrAll(dest, destLen, source, &sourceLen, flush_mode);
+  if (ret == Z_BUF_ERROR)
+    UncompressErrorInit();
+  return ret;
+}
+
+int ZLib::UncompressAtMost(Bytef *dest, uLongf *destLen,
+                          const Bytef *source, uLong *sourceLen) {
+  return UncompressAtMostOrAll(dest, destLen, source, sourceLen, Z_SYNC_FLUSH);
+}
+
+// We make sure we've uncompressed everything, that is, the current
+// uncompress stream is at a compressed-buffer-EOF boundary.  In gzip
+// mode, we also check the gzip footer to make sure we pass the gzip
+// consistency checks.  We RETURN true iff both types of checks pass.
+bool ZLib::UncompressChunkDone() {
+  assert(!first_chunk_ && uncomp_init_);
+  // Make sure we're at the end-of-compressed-data point.  This means
+  // if we call inflate with Z_FINISH we won't consume any input or
+  // write any output
+  Bytef dummyin, dummyout;
+  uLongf dummylen = 0;
+  if ( UncompressChunkOrAll(&dummyout, &dummylen, &dummyin, 0, Z_FINISH)
+       != Z_OK ) {
+    return false;
+  }
+
+  // Make sure that when we exit, we can start a new round of chunks later
+  Reset();
+
+  return true;
+}
+
+// Uncompresses the source buffer into the destination buffer.
+// The destination buffer must be long enough to hold the entire
+// decompressed contents.
+//
+// We only initialize the uncomp_stream once.  Thereafter, we use
+// inflateReset, which should be faster.
+//
+// Returns Z_OK on success, otherwise, it returns a zlib error code.
+int ZLib::Uncompress(Bytef *dest, uLongf *destLen,
+                     const Bytef *source, uLong sourceLen) {
+  int err;
+  if ( (err=UncompressChunkOrAll(dest, destLen, source, sourceLen,
+                                 Z_FINISH)) != Z_OK ) {
+    Reset();                           // let us try to compress again
+    return err;
+  }
+  if ( !UncompressChunkDone() )        // calls Reset()
+    return Z_DATA_ERROR;
+  return Z_OK;  // stream_end is ok
+}
+
+#endif  // HAVE_LIBZ
+
+}  // namespace snappy

http://git-wip-us.apache.org/repos/asf/hadoop/blob/cb5ba73b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.h
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.h b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.h
new file mode 100644
index 0000000..0f18bf1
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy-test.h
@@ -0,0 +1,582 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Various stubs for the unit tests for the open-source version of Snappy.
+
+#ifndef UTIL_SNAPPY_OPENSOURCE_SNAPPY_TEST_H_
+#define UTIL_SNAPPY_OPENSOURCE_SNAPPY_TEST_H_
+
+#include <iostream>
+#include <string>
+
+#include "snappy-stubs-internal.h"
+
+#include <stdio.h>
+#include <stdarg.h>
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+
+#ifdef HAVE_SYS_RESOURCE_H
+#include <sys/resource.h>
+#endif
+
+#ifdef HAVE_SYS_TIME_H
+#include <sys/time.h>
+#endif
+
+#ifdef HAVE_WINDOWS_H
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#endif
+
+#include <string>
+
+#ifdef HAVE_GTEST
+
+#include <gtest/gtest.h>
+#undef TYPED_TEST
+#define TYPED_TEST TEST
+#define INIT_GTEST(argc, argv) ::testing::InitGoogleTest(argc, *argv)
+
+#else
+
+// Stubs for if the user doesn't have Google Test installed.
+
+#define TEST(test_case, test_subcase) \
+  void Test_ ## test_case ## _ ## test_subcase()
+#define INIT_GTEST(argc, argv)
+
+#define TYPED_TEST TEST
+#define EXPECT_EQ CHECK_EQ
+#define EXPECT_NE CHECK_NE
+#define EXPECT_FALSE(cond) CHECK(!(cond))
+
+#endif
+
+#ifdef HAVE_GFLAGS
+
+#include <gflags/gflags.h>
+
+// This is tricky; both gflags and Google Test want to look at the command line
+// arguments. Google Test seems to be the most happy with unknown arguments,
+// though, so we call it first and hope for the best.
+#define InitGoogle(argv0, argc, argv, remove_flags) \
+  INIT_GTEST(argc, argv); \
+  google::ParseCommandLineFlags(argc, argv, remove_flags);
+
+#else
+
+// If we don't have the gflags package installed, these can only be
+// changed at compile time.
+#define DEFINE_int32(flag_name, default_value, description) \
+  static int FLAGS_ ## flag_name = default_value;
+
+#define InitGoogle(argv0, argc, argv, remove_flags) \
+  INIT_GTEST(argc, argv)
+
+#endif
+
+#ifdef HAVE_LIBZ
+#include "zlib.h"
+#endif
+
+#ifdef HAVE_LIBLZO2
+#include "lzo/lzo1x.h"
+#endif
+
+#ifdef HAVE_LIBLZF
+extern "C" {
+#include "lzf.h"
+}
+#endif
+
+#ifdef HAVE_LIBFASTLZ
+#include "fastlz.h"
+#endif
+
+#ifdef HAVE_LIBQUICKLZ
+#include "quicklz.h"
+#endif
+
+namespace {
+
+namespace File {
+  void Init() { }
+}  // namespace File
+
+namespace file {
+  int Defaults() { }
+
+  class DummyStatus {
+   public:
+    void CheckSuccess() { }
+  };
+
+  DummyStatus GetContents(const string& filename, string* data, int unused) {
+    FILE* fp = fopen(filename.c_str(), "rb");
+    if (fp == NULL) {
+      perror(filename.c_str());
+      exit(1);
+    }
+
+    data->clear();
+    while (!feof(fp)) {
+      char buf[4096];
+      size_t ret = fread(buf, 1, 4096, fp);
+      if (ret == 0 && ferror(fp)) {
+        perror("fread");
+        exit(1);
+      }
+      data->append(string(buf, ret));
+    }
+
+    fclose(fp);
+  }
+
+  DummyStatus SetContents(const string& filename,
+                          const string& str,
+                          int unused) {
+    FILE* fp = fopen(filename.c_str(), "wb");
+    if (fp == NULL) {
+      perror(filename.c_str());
+      exit(1);
+    }
+
+    int ret = fwrite(str.data(), str.size(), 1, fp);
+    if (ret != 1) {
+      perror("fwrite");
+      exit(1);
+    }
+
+    fclose(fp);
+  }
+}  // namespace file
+
+}  // namespace
+
+namespace snappy {
+
+#define FLAGS_test_random_seed 301
+typedef string TypeParam;
+
+void Test_CorruptedTest_VerifyCorrupted();
+void Test_Snappy_SimpleTests();
+void Test_Snappy_MaxBlowup();
+void Test_Snappy_RandomData();
+void Test_Snappy_FourByteOffset();
+void Test_SnappyCorruption_TruncatedVarint();
+void Test_SnappyCorruption_UnterminatedVarint();
+void Test_Snappy_ReadPastEndOfBuffer();
+void Test_Snappy_FindMatchLength();
+void Test_Snappy_FindMatchLengthRandom();
+
+string ReadTestDataFile(const string& base, size_t size_limit);
+
+string ReadTestDataFile(const string& base);
+
+// A sprintf() variant that returns a std::string.
+// Not safe for general use due to truncation issues.
+string StringPrintf(const char* format, ...);
+
+// A simple, non-cryptographically-secure random generator.
+class ACMRandom {
+ public:
+  explicit ACMRandom(uint32 seed) : seed_(seed) {}
+
+  int32 Next();
+
+  int32 Uniform(int32 n) {
+    return Next() % n;
+  }
+  uint8 Rand8() {
+    return static_cast<uint8>((Next() >> 1) & 0x000000ff);
+  }
+  bool OneIn(int X) { return Uniform(X) == 0; }
+
+  // Skewed: pick "base" uniformly from range [0,max_log] and then
+  // return "base" random bits.  The effect is to pick a number in the
+  // range [0,2^max_log-1] with bias towards smaller numbers.
+  int32 Skewed(int max_log);
+
+ private:
+  static const uint32 M = 2147483647L;   // 2^31-1
+  uint32 seed_;
+};
+
+inline int32 ACMRandom::Next() {
+  static const uint64 A = 16807;  // bits 14, 8, 7, 5, 2, 1, 0
+  // We are computing
+  //       seed_ = (seed_ * A) % M,    where M = 2^31-1
+  //
+  // seed_ must not be zero or M, or else all subsequent computed values
+  // will be zero or M respectively.  For all other values, seed_ will end
+  // up cycling through every number in [1,M-1]
+  uint64 product = seed_ * A;
+
+  // Compute (product % M) using the fact that ((x << 31) % M) == x.
+  seed_ = (product >> 31) + (product & M);
+  // The first reduction may overflow by 1 bit, so we may need to repeat.
+  // mod == M is not possible; using > allows the faster sign-bit-based test.
+  if (seed_ > M) {
+    seed_ -= M;
+  }
+  return seed_;
+}
+
+inline int32 ACMRandom::Skewed(int max_log) {
+  const int32 base = (Next() - 1) % (max_log+1);
+  return (Next() - 1) & ((1u << base)-1);
+}
+
+// A wall-time clock. This stub is not super-accurate, nor resistant to the
+// system time changing.
+class CycleTimer {
+ public:
+  CycleTimer() : real_time_us_(0) {}
+
+  void Start() {
+#ifdef WIN32
+    QueryPerformanceCounter(&start_);
+#else
+    gettimeofday(&start_, NULL);
+#endif
+  }
+
+  void Stop() {
+#ifdef WIN32
+    LARGE_INTEGER stop;
+    LARGE_INTEGER frequency;
+    QueryPerformanceCounter(&stop);
+    QueryPerformanceFrequency(&frequency);
+
+    double elapsed = static_cast<double>(stop.QuadPart - start_.QuadPart) /
+        frequency.QuadPart;
+    real_time_us_ += elapsed * 1e6 + 0.5;
+#else
+    struct timeval stop;
+    gettimeofday(&stop, NULL);
+
+    real_time_us_ += 1000000 * (stop.tv_sec - start_.tv_sec);
+    real_time_us_ += (stop.tv_usec - start_.tv_usec);
+#endif
+  }
+
+  double Get() {
+    return real_time_us_ * 1e-6;
+  }
+
+ private:
+  int64 real_time_us_;
+#ifdef WIN32
+  LARGE_INTEGER start_;
+#else
+  struct timeval start_;
+#endif
+};
+
+// Minimalistic microbenchmark framework.
+
+typedef void (*BenchmarkFunction)(int, int);
+
+class Benchmark {
+ public:
+  Benchmark(const string& name, BenchmarkFunction function) :
+      name_(name), function_(function) {}
+
+  Benchmark* DenseRange(int start, int stop) {
+    start_ = start;
+    stop_ = stop;
+    return this;
+  }
+
+  void Run();
+
+ private:
+  const string name_;
+  const BenchmarkFunction function_;
+  int start_, stop_;
+};
+#define BENCHMARK(benchmark_name) \
+  Benchmark* Benchmark_ ## benchmark_name = \
+          (new Benchmark(#benchmark_name, benchmark_name))
+
+extern Benchmark* Benchmark_BM_UFlat;
+extern Benchmark* Benchmark_BM_UIOVec;
+extern Benchmark* Benchmark_BM_UValidate;
+extern Benchmark* Benchmark_BM_ZFlat;
+
+void ResetBenchmarkTiming();
+void StartBenchmarkTiming();
+void StopBenchmarkTiming();
+void SetBenchmarkLabel(const string& str);
+void SetBenchmarkBytesProcessed(int64 bytes);
+
+#ifdef HAVE_LIBZ
+
+// Object-oriented wrapper around zlib.
+class ZLib {
+ public:
+  ZLib();
+  ~ZLib();
+
+  // Wipe a ZLib object to a virgin state.  This differs from Reset()
+  // in that it also breaks any state.
+  void Reinit();
+
+  // Call this to make a zlib buffer as good as new.  Here's the only
+  // case where they differ:
+  //    CompressChunk(a); CompressChunk(b); CompressChunkDone();   vs
+  //    CompressChunk(a); Reset(); CompressChunk(b); CompressChunkDone();
+  // You'll want to use Reset(), then, when you interrupt a compress
+  // (or uncompress) in the middle of a chunk and want to start over.
+  void Reset();
+
+  // According to the zlib manual, when you Compress, the destination
+  // buffer must have size at least src + .1%*src + 12.  This function
+  // helps you calculate that.  Augment this to account for a potential
+  // gzip header and footer, plus a few bytes of slack.
+  static int MinCompressbufSize(int uncompress_size) {
+    return uncompress_size + uncompress_size/1000 + 40;
+  }
+
+  // Compresses the source buffer into the destination buffer.
+  // sourceLen is the byte length of the source buffer.
+  // Upon entry, destLen is the total size of the destination buffer,
+  // which must be of size at least MinCompressbufSize(sourceLen).
+  // Upon exit, destLen is the actual size of the compressed buffer.
+  //
+  // This function can be used to compress a whole file at once if the
+  // input file is mmap'ed.
+  //
+  // Returns Z_OK if success, Z_MEM_ERROR if there was not
+  // enough memory, Z_BUF_ERROR if there was not enough room in the
+  // output buffer. Note that if the output buffer is exactly the same
+  // size as the compressed result, we still return Z_BUF_ERROR.
+  // (check CL#1936076)
+  int Compress(Bytef *dest, uLongf *destLen,
+               const Bytef *source, uLong sourceLen);
+
+  // Uncompresses the source buffer into the destination buffer.
+  // The destination buffer must be long enough to hold the entire
+  // decompressed contents.
+  //
+  // Returns Z_OK on success, otherwise, it returns a zlib error code.
+  int Uncompress(Bytef *dest, uLongf *destLen,
+                 const Bytef *source, uLong sourceLen);
+
+  // Uncompress data one chunk at a time -- ie you can call this
+  // more than once.  To get this to work you need to call per-chunk
+  // and "done" routines.
+  //
+  // Returns Z_OK if success, Z_MEM_ERROR if there was not
+  // enough memory, Z_BUF_ERROR if there was not enough room in the
+  // output buffer.
+
+  int UncompressAtMost(Bytef *dest, uLongf *destLen,
+                       const Bytef *source, uLong *sourceLen);
+
+  // Checks gzip footer information, as needed.  Mostly this just
+  // makes sure the checksums match.  Whenever you call this, it
+  // will assume the last 8 bytes from the previous UncompressChunk
+  // call are the footer.  Returns true iff everything looks ok.
+  bool UncompressChunkDone();
+
+ private:
+  int InflateInit();       // sets up the zlib inflate structure
+  int DeflateInit();       // sets up the zlib deflate structure
+
+  // These init the zlib data structures for compressing/uncompressing
+  int CompressInit(Bytef *dest, uLongf *destLen,
+                   const Bytef *source, uLong *sourceLen);
+  int UncompressInit(Bytef *dest, uLongf *destLen,
+                     const Bytef *source, uLong *sourceLen);
+  // Initialization method to be called if we hit an error while
+  // uncompressing. On hitting an error, call this method before
+  // returning the error.
+  void UncompressErrorInit();
+
+  // Helper function for Compress
+  int CompressChunkOrAll(Bytef *dest, uLongf *destLen,
+                         const Bytef *source, uLong sourceLen,
+                         int flush_mode);
+  int CompressAtMostOrAll(Bytef *dest, uLongf *destLen,
+                          const Bytef *source, uLong *sourceLen,
+                          int flush_mode);
+
+  // Likewise for UncompressAndUncompressChunk
+  int UncompressChunkOrAll(Bytef *dest, uLongf *destLen,
+                           const Bytef *source, uLong sourceLen,
+                           int flush_mode);
+
+  int UncompressAtMostOrAll(Bytef *dest, uLongf *destLen,
+                            const Bytef *source, uLong *sourceLen,
+                            int flush_mode);
+
+  // Initialization method to be called if we hit an error while
+  // compressing. On hitting an error, call this method before
+  // returning the error.
+  void CompressErrorInit();
+
+  int compression_level_;   // compression level
+  int window_bits_;         // log base 2 of the window size used in compression
+  int mem_level_;           // specifies the amount of memory to be used by
+                            // compressor (1-9)
+  z_stream comp_stream_;    // Zlib stream data structure
+  bool comp_init_;          // True if we have initialized comp_stream_
+  z_stream uncomp_stream_;  // Zlib stream data structure
+  bool uncomp_init_;        // True if we have initialized uncomp_stream_
+
+  // These are used only with chunked compression.
+  bool first_chunk_;       // true if we need to emit headers with this chunk
+};
+
+#endif  // HAVE_LIBZ
+
+}  // namespace snappy
+
+DECLARE_bool(run_microbenchmarks);
+
+static void RunSpecifiedBenchmarks() {
+  if (!FLAGS_run_microbenchmarks) {
+    return;
+  }
+
+  fprintf(stderr, "Running microbenchmarks.\n");
+#ifndef NDEBUG
+  fprintf(stderr, "WARNING: Compiled with assertions enabled, will be slow.\n");
+#endif
+#ifndef __OPTIMIZE__
+  fprintf(stderr, "WARNING: Compiled without optimization, will be slow.\n");
+#endif
+  fprintf(stderr, "Benchmark            Time(ns)    CPU(ns) Iterations\n");
+  fprintf(stderr, "---------------------------------------------------\n");
+
+  snappy::Benchmark_BM_UFlat->Run();
+  snappy::Benchmark_BM_UIOVec->Run();
+  snappy::Benchmark_BM_UValidate->Run();
+  snappy::Benchmark_BM_ZFlat->Run();
+
+  fprintf(stderr, "\n");
+}
+
+#ifndef HAVE_GTEST
+
+static inline int RUN_ALL_TESTS() {
+  fprintf(stderr, "Running correctness tests.\n");
+  snappy::Test_CorruptedTest_VerifyCorrupted();
+  snappy::Test_Snappy_SimpleTests();
+  snappy::Test_Snappy_MaxBlowup();
+  snappy::Test_Snappy_RandomData();
+  snappy::Test_Snappy_FourByteOffset();
+  snappy::Test_SnappyCorruption_TruncatedVarint();
+  snappy::Test_SnappyCorruption_UnterminatedVarint();
+  snappy::Test_Snappy_ReadPastEndOfBuffer();
+  snappy::Test_Snappy_FindMatchLength();
+  snappy::Test_Snappy_FindMatchLengthRandom();
+  fprintf(stderr, "All tests passed.\n");
+
+  return 0;
+}
+
+#endif  // HAVE_GTEST
+
+// For main().
+namespace snappy {
+
+static void CompressFile(const char* fname);
+static void UncompressFile(const char* fname);
+static void MeasureFile(const char* fname);
+
+// Logging.
+
+#define LOG(level) LogMessage()
+#define VLOG(level) true ? (void)0 : \
+    snappy::LogMessageVoidify() & snappy::LogMessage()
+
+class LogMessage {
+ public:
+  LogMessage() { }
+  ~LogMessage() {
+    cerr << endl;
+  }
+
+  LogMessage& operator<<(const std::string& msg) {
+    cerr << msg;
+    return *this;
+  }
+  LogMessage& operator<<(int x) {
+    cerr << x;
+    return *this;
+  }
+};
+
+// Asserts, both versions activated in debug mode only,
+// and ones that are always active.
+
+#define CRASH_UNLESS(condition) \
+    PREDICT_TRUE(condition) ? (void)0 : \
+    snappy::LogMessageVoidify() & snappy::LogMessageCrash()
+
+class LogMessageCrash : public LogMessage {
+ public:
+  LogMessageCrash() { }
+  ~LogMessageCrash() {
+    cerr << endl;
+    abort();
+  }
+};
+
+// This class is used to explicitly ignore values in the conditional
+// logging macros.  This avoids compiler warnings like "value computed
+// is not used" and "statement has no effect".
+
+class LogMessageVoidify {
+ public:
+  LogMessageVoidify() { }
+  // This has to be an operator with a precedence lower than << but
+  // higher than ?:
+  void operator&(const LogMessage&) { }
+};
+
+#define CHECK(cond) CRASH_UNLESS(cond)
+#define CHECK_LE(a, b) CRASH_UNLESS((a) <= (b))
+#define CHECK_GE(a, b) CRASH_UNLESS((a) >= (b))
+#define CHECK_EQ(a, b) CRASH_UNLESS((a) == (b))
+#define CHECK_NE(a, b) CRASH_UNLESS((a) != (b))
+#define CHECK_LT(a, b) CRASH_UNLESS((a) < (b))
+#define CHECK_GT(a, b) CRASH_UNLESS((a) > (b))
+
+}  // namespace
+
+using snappy::CompressFile;
+using snappy::UncompressFile;
+using snappy::MeasureFile;
+
+#endif  // UTIL_SNAPPY_OPENSOURCE_SNAPPY_TEST_H_

http://git-wip-us.apache.org/repos/asf/hadoop/blob/cb5ba73b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy.cc
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy.cc b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy.cc
new file mode 100644
index 0000000..f8d0d23
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfsdb/src/main/native/snappy/snappy.cc
@@ -0,0 +1,1306 @@
+// Copyright 2005 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "snappy.h"
+#include "snappy-internal.h"
+#include "snappy-sinksource.h"
+
+#include <stdio.h>
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+
+namespace snappy {
+
+// Any hash function will produce a valid compressed bitstream, but a good
+// hash function reduces the number of collisions and thus yields better
+// compression for compressible input, and more speed for incompressible
+// input. Of course, it doesn't hurt if the hash function is reasonably fast
+// either, as it gets called a lot.
+static inline uint32 HashBytes(uint32 bytes, int shift) {
+  uint32 kMul = 0x1e35a7bd;
+  return (bytes * kMul) >> shift;
+}
+static inline uint32 Hash(const char* p, int shift) {
+  return HashBytes(UNALIGNED_LOAD32(p), shift);
+}
+
+size_t MaxCompressedLength(size_t source_len) {
+  // Compressed data can be defined as:
+  //    compressed := item* literal*
+  //    item       := literal* copy
+  //
+  // The trailing literal sequence has a space blowup of at most 62/60
+  // since a literal of length 60 needs one tag byte + one extra byte
+  // for length information.
+  //
+  // Item blowup is trickier to measure.  Suppose the "copy" op copies
+  // 4 bytes of data.  Because of a special check in the encoding code,
+  // we produce a 4-byte copy only if the offset is < 65536.  Therefore
+  // the copy op takes 3 bytes to encode, and this type of item leads
+  // to at most the 62/60 blowup for representing literals.
+  //
+  // Suppose the "copy" op copies 5 bytes of data.  If the offset is big
+  // enough, it will take 5 bytes to encode the copy op.  Therefore the
+  // worst case here is a one-byte literal followed by a five-byte copy.
+  // I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
+  //
+  // This last factor dominates the blowup, so the final estimate is:
+  return 32 + source_len + source_len/6;
+}
+
+enum {
+  LITERAL = 0,
+  COPY_1_BYTE_OFFSET = 1,  // 3 bit length + 3 bits of offset in opcode
+  COPY_2_BYTE_OFFSET = 2,
+  COPY_4_BYTE_OFFSET = 3
+};
+static const int kMaximumTagLength = 5;  // COPY_4_BYTE_OFFSET plus the actual offset.
+
+// Copy "len" bytes from "src" to "op", one byte at a time.  Used for
+// handling COPY operations where the input and output regions may
+// overlap.  For example, suppose:
+//    src    == "ab"
+//    op     == src + 2
+//    len    == 20
+// After IncrementalCopy(src, op, len), the result will have
+// eleven copies of "ab"
+//    ababababababababababab
+// Note that this does not match the semantics of either memcpy()
+// or memmove().
+static inline void IncrementalCopy(const char* src, char* op, ssize_t len) {
+  assert(len > 0);
+  do {
+    *op++ = *src++;
+  } while (--len > 0);
+}
+
+// Equivalent to IncrementalCopy except that it can write up to ten extra
+// bytes after the end of the copy, and that it is faster.
+//
+// The main part of this loop is a simple copy of eight bytes at a time until
+// we've copied (at least) the requested amount of bytes.  However, if op and
+// src are less than eight bytes apart (indicating a repeating pattern of
+// length < 8), we first need to expand the pattern in order to get the correct
+// results. For instance, if the buffer looks like this, with the eight-byte
+// <src> and <op> patterns marked as intervals:
+//
+//    abxxxxxxxxxxxx
+//    [------]           src
+//      [------]         op
+//
+// a single eight-byte copy from <src> to <op> will repeat the pattern once,
+// after which we can move <op> two bytes without moving <src>:
+//
+//    ababxxxxxxxxxx
+//    [------]           src
+//        [------]       op
+//
+// and repeat the exercise until the two no longer overlap.
+//
+// This allows us to do very well in the special case of one single byte
+// repeated many times, without taking a big hit for more general cases.
+//
+// The worst case of extra writing past the end of the match occurs when
+// op - src == 1 and len == 1; the last copy will read from byte positions
+// [0..7] and write to [4..11], whereas it was only supposed to write to
+// position 1. Thus, ten excess bytes.
+
+namespace {
+
+const int kMaxIncrementCopyOverflow = 10;
+
+inline void IncrementalCopyFastPath(const char* src, char* op, ssize_t len) {
+  while (op - src < 8) {
+    UnalignedCopy64(src, op);
+    len -= op - src;
+    op += op - src;
+  }
+  while (len > 0) {
+    UnalignedCopy64(src, op);
+    src += 8;
+    op += 8;
+    len -= 8;
+  }
+}
+
+}  // namespace
+
+static inline char* EmitLiteral(char* op,
+                                const char* literal,
+                                int len,
+                                bool allow_fast_path) {
+  int n = len - 1;      // Zero-length literals are disallowed
+  if (n < 60) {
+    // Fits in tag byte
+    *op++ = LITERAL | (n << 2);
+
+    // The vast majority of copies are below 16 bytes, for which a
+    // call to memcpy is overkill. This fast path can sometimes
+    // copy up to 15 bytes too much, but that is okay in the
+    // main loop, since we have a bit to go on for both sides:
+    //
+    //   - The input will always have kInputMarginBytes = 15 extra
+    //     available bytes, as long as we're in the main loop, and
+    //     if not, allow_fast_path = false.
+    //   - The output will always have 32 spare bytes (see
+    //     MaxCompressedLength).
+    if (allow_fast_path && len <= 16) {
+      UnalignedCopy64(literal, op);
+      UnalignedCopy64(literal + 8, op + 8);
+      return op + len;
+    }
+  } else {
+    // Encode in upcoming bytes
+    char* base = op;
+    int count = 0;
+    op++;
+    while (n > 0) {
+      *op++ = n & 0xff;
+      n >>= 8;
+      count++;
+    }
+    assert(count >= 1);
+    assert(count <= 4);
+    *base = LITERAL | ((59+count) << 2);
+  }
+  memcpy(op, literal, len);
+  return op + len;
+}
+
+static inline char* EmitCopyLessThan64(char* op, size_t offset, int len) {
+  assert(len <= 64);
+  assert(len >= 4);
+  assert(offset < 65536);
+
+  if ((len < 12) && (offset < 2048)) {
+    size_t len_minus_4 = len - 4;
+    assert(len_minus_4 < 8);            // Must fit in 3 bits
+    *op++ = COPY_1_BYTE_OFFSET + ((len_minus_4) << 2) + ((offset >> 8) << 5);
+    *op++ = offset & 0xff;
+  } else {
+    *op++ = COPY_2_BYTE_OFFSET + ((len-1) << 2);
+    LittleEndian::Store16(op, offset);
+    op += 2;
+  }
+  return op;
+}
+
+static inline char* EmitCopy(char* op, size_t offset, int len) {
+  // Emit 64 byte copies but make sure to keep at least four bytes reserved
+  while (len >= 68) {
+    op = EmitCopyLessThan64(op, offset, 64);
+    len -= 64;
+  }
+
+  // Emit an extra 60 byte copy if have too much data to fit in one copy
+  if (len > 64) {
+    op = EmitCopyLessThan64(op, offset, 60);
+    len -= 60;
+  }
+
+  // Emit remainder
+  op = EmitCopyLessThan64(op, offset, len);
+  return op;
+}
+
+
+bool GetUncompressedLength(const char* start, size_t n, size_t* result) {
+  uint32 v = 0;
+  const char* limit = start + n;
+  if (Varint::Parse32WithLimit(start, limit, &v) != NULL) {
+    *result = v;
+    return true;
+  } else {
+    return false;
+  }
+}
+
+namespace internal {
+uint16* WorkingMemory::GetHashTable(size_t input_size, int* table_size) {
+  // Use smaller hash table when input.size() is smaller, since we
+  // fill the table, incurring O(hash table size) overhead for
+  // compression, and if the input is short, we won't need that
+  // many hash table entries anyway.
+  assert(kMaxHashTableSize >= 256);
+  size_t htsize = 256;
+  while (htsize < kMaxHashTableSize && htsize < input_size) {
+    htsize <<= 1;
+  }
+
+  uint16* table;
+  if (htsize <= ARRAYSIZE(small_table_)) {
+    table = small_table_;
+  } else {
+    if (large_table_ == NULL) {
+      large_table_ = new uint16[kMaxHashTableSize];
+    }
+    table = large_table_;
+  }
+
+  *table_size = htsize;
+  memset(table, 0, htsize * sizeof(*table));
+  return table;
+}
+}  // end namespace internal
+
+// For 0 <= offset <= 4, GetUint32AtOffset(GetEightBytesAt(p), offset) will
+// equal UNALIGNED_LOAD32(p + offset).  Motivation: On x86-64 hardware we have
+// empirically found that overlapping loads such as
+//  UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)
+// are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to uint32.
+//
+// We have different versions for 64- and 32-bit; ideally we would avoid the
+// two functions and just inline the UNALIGNED_LOAD64 call into
+// GetUint32AtOffset, but GCC (at least not as of 4.6) is seemingly not clever
+// enough to avoid loading the value multiple times then. For 64-bit, the load
+// is done when GetEightBytesAt() is called, whereas for 32-bit, the load is
+// done at GetUint32AtOffset() time.
+
+#ifdef ARCH_K8
+
+typedef uint64 EightBytesReference;
+
+static inline EightBytesReference GetEightBytesAt(const char* ptr) {
+  return UNALIGNED_LOAD64(ptr);
+}
+
+static inline uint32 GetUint32AtOffset(uint64 v, int offset) {
+  assert(offset >= 0);
+  assert(offset <= 4);
+  return v >> (LittleEndian::IsLittleEndian() ? 8 * offset : 32 - 8 * offset);
+}
+
+#else
+
+typedef const char* EightBytesReference;
+
+static inline EightBytesReference GetEightBytesAt(const char* ptr) {
+  return ptr;
+}
+
+static inline uint32 GetUint32AtOffset(const char* v, int offset) {
+  assert(offset >= 0);
+  assert(offset <= 4);
+  return UNALIGNED_LOAD32(v + offset);
+}
+
+#endif
+
+// Flat array compression that does not emit the "uncompressed length"
+// prefix. Compresses "input" string to the "*op" buffer.
+//
+// REQUIRES: "input" is at most "kBlockSize" bytes long.
+// REQUIRES: "op" points to an array of memory that is at least
+// "MaxCompressedLength(input.size())" in size.
+// REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+// REQUIRES: "table_size" is a power of two
+//
+// Returns an "end" pointer into "op" buffer.
+// "end - op" is the compressed size of "input".
+namespace internal {
+char* CompressFragment(const char* input,
+                       size_t input_size,
+                       char* op,
+                       uint16* table,
+                       const int table_size) {
+  // "ip" is the input pointer, and "op" is the output pointer.
+  const char* ip = input;
+  assert(input_size <= kBlockSize);
+  assert((table_size & (table_size - 1)) == 0); // table must be power of two
+  const int shift = 32 - Bits::Log2Floor(table_size);
+  assert(static_cast<int>(kuint32max >> shift) == table_size - 1);
+  const char* ip_end = input + input_size;
+  const char* base_ip = ip;
+  // Bytes in [next_emit, ip) will be emitted as literal bytes.  Or
+  // [next_emit, ip_end) after the main loop.
+  const char* next_emit = ip;
+
+  const size_t kInputMarginBytes = 15;
+  if (PREDICT_TRUE(input_size >= kInputMarginBytes)) {
+    const char* ip_limit = input + input_size - kInputMarginBytes;
+
+    for (uint32 next_hash = Hash(++ip, shift); ; ) {
+      assert(next_emit < ip);
+      // The body of this loop calls EmitLiteral once and then EmitCopy one or
+      // more times.  (The exception is that when we're close to exhausting
+      // the input we goto emit_remainder.)
+      //
+      // In the first iteration of this loop we're just starting, so
+      // there's nothing to copy, so calling EmitLiteral once is
+      // necessary.  And we only start a new iteration when the
+      // current iteration has determined that a call to EmitLiteral will
+      // precede the next call to EmitCopy (if any).
+      //
+      // Step 1: Scan forward in the input looking for a 4-byte-long match.
+      // If we get close to exhausting the input then goto emit_remainder.
+      //
+      // Heuristic match skipping: If 32 bytes are scanned with no matches
+      // found, start looking only at every other byte. If 32 more bytes are
+      // scanned, look at every third byte, etc.. When a match is found,
+      // immediately go back to looking at every byte. This is a small loss
+      // (~5% performance, ~0.1% density) for compressible data due to more
+      // bookkeeping, but for non-compressible data (such as JPEG) it's a huge
+      // win since the compressor quickly "realizes" the data is incompressible
+      // and doesn't bother looking for matches everywhere.
+      //
+      // The "skip" variable keeps track of how many bytes there are since the
+      // last match; dividing it by 32 (ie. right-shifting by five) gives the
+      // number of bytes to move ahead for each iteration.
+      uint32 skip = 32;
+
+      const char* next_ip = ip;
+      const char* candidate;
+      do {
+        ip = next_ip;
+        uint32 hash = next_hash;
+        assert(hash == Hash(ip, shift));
+        uint32 bytes_between_hash_lookups = skip++ >> 5;
+        next_ip = ip + bytes_between_hash_lookups;
+        if (PREDICT_FALSE(next_ip > ip_limit)) {
+          goto emit_remainder;
+        }
+        next_hash = Hash(next_ip, shift);
+        candidate = base_ip + table[hash];
+        assert(candidate >= base_ip);
+        assert(candidate < ip);
+
+        table[hash] = ip - base_ip;
+      } while (PREDICT_TRUE(UNALIGNED_LOAD32(ip) !=
+                            UNALIGNED_LOAD32(candidate)));
+
+      // Step 2: A 4-byte match has been found.  We'll later see if more
+      // than 4 bytes match.  But, prior to the match, input
+      // bytes [next_emit, ip) are unmatched.  Emit them as "literal bytes."
+      assert(next_emit + 16 <= ip_end);
+      op = EmitLiteral(op, next_emit, ip - next_emit, true);
+
+      // Step 3: Call EmitCopy, and then see if another EmitCopy could
+      // be our next move.  Repeat until we find no match for the
+      // input immediately after what was consumed by the last EmitCopy call.
+      //
+      // If we exit this loop normally then we need to call EmitLiteral next,
+      // though we don't yet know how big the literal will be.  We handle that
+      // by proceeding to the next iteration of the main loop.  We also can exit
+      // this loop via goto if we get close to exhausting the input.
+      EightBytesReference input_bytes;
+      uint32 candidate_bytes = 0;
+
+      do {
+        // We have a 4-byte match at ip, and no need to emit any
+        // "literal bytes" prior to ip.
+        const char* base = ip;
+        int matched = 4 + FindMatchLength(candidate + 4, ip + 4, ip_end);
+        ip += matched;
+        size_t offset = base - candidate;
+        assert(0 == memcmp(base, candidate, matched));
+        op = EmitCopy(op, offset, matched);
+        // We could immediately start working at ip now, but to improve
+        // compression we first update table[Hash(ip - 1, ...)].
+        const char* insert_tail = ip - 1;
+        next_emit = ip;
+        if (PREDICT_FALSE(ip >= ip_limit)) {
+          goto emit_remainder;
+        }
+        input_bytes = GetEightBytesAt(insert_tail);
+        uint32 prev_hash = HashBytes(GetUint32AtOffset(input_bytes, 0), shift);
+        table[prev_hash] = ip - base_ip - 1;
+        uint32 cur_hash = HashBytes(GetUint32AtOffset(input_bytes, 1), shift);
+        candidate = base_ip + table[cur_hash];
+        candidate_bytes = UNALIGNED_LOAD32(candidate);
+        table[cur_hash] = ip - base_ip;
+      } while (GetUint32AtOffset(input_bytes, 1) == candidate_bytes);
+
+      next_hash = HashBytes(GetUint32AtOffset(input_bytes, 2), shift);
+      ++ip;
+    }
+  }
+
+ emit_remainder:
+  // Emit the remaining bytes as a literal
+  if (next_emit < ip_end) {
+    op = EmitLiteral(op, next_emit, ip_end - next_emit, false);
+  }
+
+  return op;
+}
+}  // end namespace internal
+
+// Signature of output types needed by decompression code.
+// The decompression code is templatized on a type that obeys this
+// signature so that we do not pay virtual function call overhead in
+// the middle of a tight decompression loop.
+//
+// class DecompressionWriter {
+//  public:
+//   // Called before decompression
+//   void SetExpectedLength(size_t length);
+//
+//   // Called after decompression
+//   bool CheckLength() const;
+//
+//   // Called repeatedly during decompression
+//   bool Append(const char* ip, size_t length);
+//   bool AppendFromSelf(uint32 offset, size_t length);
+//
+//   // The rules for how TryFastAppend differs from Append are somewhat
+//   // convoluted:
+//   //
+//   //  - TryFastAppend is allowed to decline (return false) at any
+//   //    time, for any reason -- just "return false" would be
+//   //    a perfectly legal implementation of TryFastAppend.
+//   //    The intention is for TryFastAppend to allow a fast path
+//   //    in the common case of a small append.
+//   //  - TryFastAppend is allowed to read up to <available> bytes
+//   //    from the input buffer, whereas Append is allowed to read
+//   //    <length>. However, if it returns true, it must leave
+//   //    at least five (kMaximumTagLength) bytes in the input buffer
+//   //    afterwards, so that there is always enough space to read the
+//   //    next tag without checking for a refill.
+//   //  - TryFastAppend must always return decline (return false)
+//   //    if <length> is 61 or more, as in this case the literal length is not
+//   //    decoded fully. In practice, this should not be a big problem,
+//   //    as it is unlikely that one would implement a fast path accepting
+//   //    this much data.
+//   //
+//   bool TryFastAppend(const char* ip, size_t available, size_t length);
+// };
+
+// -----------------------------------------------------------------------
+// Lookup table for decompression code.  Generated by ComputeTable() below.
+// -----------------------------------------------------------------------
+
+// Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits
+static const uint32 wordmask[] = {
+  0u, 0xffu, 0xffffu, 0xffffffu, 0xffffffffu
+};
+
+// Data stored per entry in lookup table:
+//      Range   Bits-used       Description
+//      ------------------------------------
+//      1..64   0..7            Literal/copy length encoded in opcode byte
+//      0..7    8..10           Copy offset encoded in opcode byte / 256
+//      0..4    11..13          Extra bytes after opcode
+//
+// We use eight bits for the length even though 7 would have sufficed
+// because of efficiency reasons:
+//      (1) Extracting a byte is faster than a bit-field
+//      (2) It properly aligns copy offset so we do not need a <<8
+static const uint16 char_table[256] = {
+  0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
+  0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
+  0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
+  0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
+  0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
+  0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
+  0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
+  0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
+  0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
+  0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
+  0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
+  0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
+  0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
+  0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
+  0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
+  0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
+  0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
+  0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
+  0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
+  0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
+  0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
+  0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
+  0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
+  0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
+  0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
+  0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
+  0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
+  0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
+  0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
+  0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
+  0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
+  0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
+};
+
+// In debug mode, allow optional computation of the table at startup.
+// Also, check that the decompression table is correct.
+#ifndef NDEBUG
+DEFINE_bool(snappy_dump_decompression_table, false,
+            "If true, we print the decompression table at startup.");
+
+static uint16 MakeEntry(unsigned int extra,
+                        unsigned int len,
+                        unsigned int copy_offset) {
+  // Check that all of the fields fit within the allocated space
+  assert(extra       == (extra & 0x7));          // At most 3 bits
+  assert(copy_offset == (copy_offset & 0x7));    // At most 3 bits
+  assert(len         == (len & 0x7f));           // At most 7 bits
+  return len | (copy_offset << 8) | (extra << 11);
+}
+
+static void ComputeTable() {
+  uint16 dst[256];
+
+  // Place invalid entries in all places to detect missing initialization
+  int assigned = 0;
+  for (int i = 0; i < 256; i++) {
+    dst[i] = 0xffff;
+  }
+
+  // Small LITERAL entries.  We store (len-1) in the top 6 bits.
+  for (unsigned int len = 1; len <= 60; len++) {
+    dst[LITERAL | ((len-1) << 2)] = MakeEntry(0, len, 0);
+    assigned++;
+  }
+
+  // Large LITERAL entries.  We use 60..63 in the high 6 bits to
+  // encode the number of bytes of length info that follow the opcode.
+  for (unsigned int extra_bytes = 1; extra_bytes <= 4; extra_bytes++) {
+    // We set the length field in the lookup table to 1 because extra
+    // bytes encode len-1.
+    dst[LITERAL | ((extra_bytes+59) << 2)] = MakeEntry(extra_bytes, 1, 0);
+    assigned++;
+  }
+
+  // COPY_1_BYTE_OFFSET.
+  //
+  // The tag byte in the compressed data stores len-4 in 3 bits, and
+  // offset/256 in 5 bits.  offset%256 is stored in the next byte.
+  //
+  // This format is used for length in range [4..11] and offset in
+  // range [0..2047]
+  for (unsigned int len = 4; len < 12; len++) {
+    for (unsigned int offset = 0; offset < 2048; offset += 256) {
+      dst[COPY_1_BYTE_OFFSET | ((len-4)<<2) | ((offset>>8)<<5)] =
+        MakeEntry(1, len, offset>>8);
+      assigned++;
+    }
+  }
+
+  // COPY_2_BYTE_OFFSET.
+  // Tag contains len-1 in top 6 bits, and offset in next two bytes.
+  for (unsigned int len = 1; len <= 64; len++) {
+    dst[COPY_2_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(2, len, 0);
+    assigned++;
+  }
+
+  // COPY_4_BYTE_OFFSET.
+  // Tag contents len-1 in top 6 bits, and offset in next four bytes.
+  for (unsigned int len = 1; len <= 64; len++) {
+    dst[COPY_4_BYTE_OFFSET | ((len-1)<<2)] = MakeEntry(4, len, 0);
+    assigned++;
+  }
+
+  // Check that each entry was initialized exactly once.
+  if (assigned != 256) {
+    fprintf(stderr, "ComputeTable: assigned only %d of 256\n", assigned);
+    abort();
+  }
+  for (int i = 0; i < 256; i++) {
+    if (dst[i] == 0xffff) {
+      fprintf(stderr, "ComputeTable: did not assign byte %d\n", i);
+      abort();
+    }
+  }
+
+  if (FLAGS_snappy_dump_decompression_table) {
+    printf("static const uint16 char_table[256] = {\n  ");
+    for (int i = 0; i < 256; i++) {
+      printf("0x%04x%s",
+             dst[i],
+             ((i == 255) ? "\n" : (((i%8) == 7) ? ",\n  " : ", ")));
+    }
+    printf("};\n");
+  }
+
+  // Check that computed table matched recorded table
+  for (int i = 0; i < 256; i++) {
+    if (dst[i] != char_table[i]) {
+      fprintf(stderr, "ComputeTable: byte %d: computed (%x), expect (%x)\n",
+              i, static_cast<int>(dst[i]), static_cast<int>(char_table[i]));
+      abort();
+    }
+  }
+}
+#endif /* !NDEBUG */
+
+// Helper class for decompression
+class SnappyDecompressor {
+ private:
+  Source*       reader_;         // Underlying source of bytes to decompress
+  const char*   ip_;             // Points to next buffered byte
+  const char*   ip_limit_;       // Points just past buffered bytes
+  uint32        peeked_;         // Bytes peeked from reader (need to skip)
+  bool          eof_;            // Hit end of input without an error?
+  char          scratch_[kMaximumTagLength];  // See RefillTag().
+
+  // Ensure that all of the tag metadata for the next tag is available
+  // in [ip_..ip_limit_-1].  Also ensures that [ip,ip+4] is readable even
+  // if (ip_limit_ - ip_ < 5).
+  //
+  // Returns true on success, false on error or end of input.
+  bool RefillTag();
+
+ public:
+  explicit SnappyDecompressor(Source* reader)
+      : reader_(reader),
+        ip_(NULL),
+        ip_limit_(NULL),
+        peeked_(0),
+        eof_(false) {
+  }
+
+  ~SnappyDecompressor() {
+    // Advance past any bytes we peeked at from the reader
+    reader_->Skip(peeked_);
+  }
+
+  // Returns true iff we have hit the end of the input without an error.
+  bool eof() const {
+    return eof_;
+  }
+
+  // Read the uncompressed length stored at the start of the compressed data.
+  // On succcess, stores the length in *result and returns true.
+  // On failure, returns false.
+  bool ReadUncompressedLength(uint32* result) {
+    assert(ip_ == NULL);       // Must not have read anything yet
+    // Length is encoded in 1..5 bytes
+    *result = 0;
+    uint32 shift = 0;
+    while (true) {
+      if (shift >= 32) return false;
+      size_t n;
+      const char* ip = reader_->Peek(&n);
+      if (n == 0) return false;
+      const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));
+      reader_->Skip(1);
+      *result |= static_cast<uint32>(c & 0x7f) << shift;
+      if (c < 128) {
+        break;
+      }
+      shift += 7;
+    }
+    return true;
+  }
+
+  // Process the next item found in the input.
+  // Returns true if successful, false on error or end of input.
+  template <class Writer>
+  void DecompressAllTags(Writer* writer) {
+    const char* ip = ip_;
+
+    // We could have put this refill fragment only at the beginning of the loop.
+    // However, duplicating it at the end of each branch gives the compiler more
+    // scope to optimize the <ip_limit_ - ip> expression based on the local
+    // context, which overall increases speed.
+    #define MAYBE_REFILL() \
+        if (ip_limit_ - ip < kMaximumTagLength) { \
+          ip_ = ip; \
+          if (!RefillTag()) return; \
+          ip = ip_; \
+        }
+
+    MAYBE_REFILL();
+    for ( ;; ) {
+      const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip++));
+
+      if ((c & 0x3) == LITERAL) {
+        size_t literal_length = (c >> 2) + 1u;
+        if (writer->TryFastAppend(ip, ip_limit_ - ip, literal_length)) {
+          assert(literal_length < 61);
+          ip += literal_length;
+          // NOTE(user): There is no MAYBE_REFILL() here, as TryFastAppend()
+          // will not return true unless there's already at least five spare
+          // bytes in addition to the literal.
+          continue;
+        }
+        if (PREDICT_FALSE(literal_length >= 61)) {
+          // Long literal.
+          const size_t literal_length_length = literal_length - 60;
+          literal_length =
+              (LittleEndian::Load32(ip) & wordmask[literal_length_length]) + 1;
+          ip += literal_length_length;
+        }
+
+        size_t avail = ip_limit_ - ip;
+        while (avail < literal_length) {
+          if (!writer->Append(ip, avail)) return;
+          literal_length -= avail;
+          reader_->Skip(peeked_);
+          size_t n;
+          ip = reader_->Peek(&n);
+          avail = n;
+          peeked_ = avail;
+          if (avail == 0) return;  // Premature end of input
+          ip_limit_ = ip + avail;
+        }
+        if (!writer->Append(ip, literal_length)) {
+          return;
+        }
+        ip += literal_length;
+        MAYBE_REFILL();
+      } else {
+        const uint32 entry = char_table[c];
+        const uint32 trailer = LittleEndian::Load32(ip) & wordmask[entry >> 11];
+        const uint32 length = entry & 0xff;
+        ip += entry >> 11;
+
+        // copy_offset/256 is encoded in bits 8..10.  By just fetching
+        // those bits, we get copy_offset (since the bit-field starts at
+        // bit 8).
+        const uint32 copy_offset = entry & 0x700;
+        if (!writer->AppendFromSelf(copy_offset + trailer, length)) {
+          return;
+        }
+        MAYBE_REFILL();
+      }
+    }
+
+#undef MAYBE_REFILL
+  }
+};
+
+bool SnappyDecompressor::RefillTag() {
+  const char* ip = ip_;
+  if (ip == ip_limit_) {
+    // Fetch a new fragment from the reader
+    reader_->Skip(peeked_);   // All peeked bytes are used up
+    size_t n;
+    ip = reader_->Peek(&n);
+    peeked_ = n;
+    if (n == 0) {
+      eof_ = true;
+      return false;
+    }
+    ip_limit_ = ip + n;
+  }
+
+  // Read the tag character
+  assert(ip < ip_limit_);
+  const unsigned char c = *(reinterpret_cast<const unsigned char*>(ip));
+  const uint32 entry = char_table[c];
+  const uint32 needed = (entry >> 11) + 1;  // +1 byte for 'c'
+  assert(needed <= sizeof(scratch_));
+
+  // Read more bytes from reader if needed
+  uint32 nbuf = ip_limit_ - ip;
+  if (nbuf < needed) {
+    // Stitch together bytes from ip and reader to form the word
+    // contents.  We store the needed bytes in "scratch_".  They
+    // will be consumed immediately by the caller since we do not
+    // read more than we need.
+    memmove(scratch_, ip, nbuf);
+    reader_->Skip(peeked_);  // All peeked bytes are used up
+    peeked_ = 0;
+    while (nbuf < needed) {
+      size_t length;
+      const char* src = reader_->Peek(&length);
+      if (length == 0) return false;
+      uint32 to_add = min<uint32>(needed - nbuf, length);
+      memcpy(scratch_ + nbuf, src, to_add);
+      nbuf += to_add;
+      reader_->Skip(to_add);
+    }
+    assert(nbuf == needed);
+    ip_ = scratch_;
+    ip_limit_ = scratch_ + needed;
+  } else if (nbuf < kMaximumTagLength) {
+    // Have enough bytes, but move into scratch_ so that we do not
+    // read past end of input
+    memmove(scratch_, ip, nbuf);
+    reader_->Skip(peeked_);  // All peeked bytes are used up
+    peeked_ = 0;
+    ip_ = scratch_;
+    ip_limit_ = scratch_ + nbuf;
+  } else {
+    // Pass pointer to buffer returned by reader_.
+    ip_ = ip;
+  }
+  return true;
+}
+
+template <typename Writer>
+static bool InternalUncompress(Source* r, Writer* writer) {
+  // Read the uncompressed length from the front of the compressed input
+  SnappyDecompressor decompressor(r);
+  uint32 uncompressed_len = 0;
+  if (!decompressor.ReadUncompressedLength(&uncompressed_len)) return false;
+  return InternalUncompressAllTags(&decompressor, writer, uncompressed_len);
+}
+
+template <typename Writer>
+static bool InternalUncompressAllTags(SnappyDecompressor* decompressor,
+                                      Writer* writer,
+                                      uint32 uncompressed_len) {
+  writer->SetExpectedLength(uncompressed_len);
+
+  // Process the entire input
+  decompressor->DecompressAllTags(writer);
+  return (decompressor->eof() && writer->CheckLength());
+}
+
+bool GetUncompressedLength(Source* source, uint32* result) {
+  SnappyDecompressor decompressor(source);
+  return decompressor.ReadUncompressedLength(result);
+}
+
+size_t Compress(Source* reader, Sink* writer) {
+  size_t written = 0;
+  size_t N = reader->Available();
+  char ulength[Varint::kMax32];
+  char* p = Varint::Encode32(ulength, N);
+  writer->Append(ulength, p-ulength);
+  written += (p - ulength);
+
+  internal::WorkingMemory wmem;
+  char* scratch = NULL;
+  char* scratch_output = NULL;
+
+  while (N > 0) {
+    // Get next block to compress (without copying if possible)
+    size_t fragment_size;
+    const char* fragment = reader->Peek(&fragment_size);
+    assert(fragment_size != 0);  // premature end of input
+    const size_t num_to_read = min(N, kBlockSize);
+    size_t bytes_read = fragment_size;
+
+    size_t pending_advance = 0;
+    if (bytes_read >= num_to_read) {
+      // Buffer returned by reader is large enough
+      pending_advance = num_to_read;
+      fragment_size = num_to_read;
+    } else {
+      // Read into scratch buffer
+      if (scratch == NULL) {
+        // If this is the last iteration, we want to allocate N bytes
+        // of space, otherwise the max possible kBlockSize space.
+        // num_to_read contains exactly the correct value
+        scratch = new char[num_to_read];
+      }
+      memcpy(scratch, fragment, bytes_read);
+      reader->Skip(bytes_read);
+
+      while (bytes_read < num_to_read) {
+        fragment = reader->Peek(&fragment_size);
+        size_t n = min<size_t>(fragment_size, num_to_read - bytes_read);
+        memcpy(scratch + bytes_read, fragment, n);
+        bytes_read += n;
+        reader->Skip(n);
+      }
+      assert(bytes_read == num_to_read);
+      fragment = scratch;
+      fragment_size = num_to_read;
+    }
+    assert(fragment_size == num_to_read);
+
+    // Get encoding table for compression
+    int table_size;
+    uint16* table = wmem.GetHashTable(num_to_read, &table_size);
+
+    // Compress input_fragment and append to dest
+    const int max_output = MaxCompressedLength(num_to_read);
+
+    // Need a scratch buffer for the output, in case the byte sink doesn't
+    // have room for us directly.
+    if (scratch_output == NULL) {
+      scratch_output = new char[max_output];
+    } else {
+      // Since we encode kBlockSize regions followed by a region
+      // which is <= kBlockSize in length, a previously allocated
+      // scratch_output[] region is big enough for this iteration.
+    }
+    char* dest = writer->GetAppendBuffer(max_output, scratch_output);
+    char* end = internal::CompressFragment(fragment, fragment_size,
+                                           dest, table, table_size);
+    writer->Append(dest, end - dest);
+    written += (end - dest);
+
+    N -= num_to_read;
+    reader->Skip(pending_advance);
+  }
+
+  delete[] scratch;
+  delete[] scratch_output;
+
+  return written;
+}
+
+// -----------------------------------------------------------------------
+// IOVec interfaces
+// -----------------------------------------------------------------------
+
+// A type that writes to an iovec.
+// Note that this is not a "ByteSink", but a type that matches the
+// Writer template argument to SnappyDecompressor::DecompressAllTags().
+class SnappyIOVecWriter {
+ private:
+  const struct iovec* output_iov_;
+  const size_t output_iov_count_;
+
+  // We are currently writing into output_iov_[curr_iov_index_].
+  int curr_iov_index_;
+
+  // Bytes written to output_iov_[curr_iov_index_] so far.
+  size_t curr_iov_written_;
+
+  // Total bytes decompressed into output_iov_ so far.
+  size_t total_written_;
+
+  // Maximum number of bytes that will be decompressed into output_iov_.
+  size_t output_limit_;
+
+  inline char* GetIOVecPointer(int index, size_t offset) {
+    return reinterpret_cast<char*>(output_iov_[index].iov_base) +
+        offset;
+  }
+
+ public:
+  // Does not take ownership of iov. iov must be valid during the
+  // entire lifetime of the SnappyIOVecWriter.
+  inline SnappyIOVecWriter(const struct iovec* iov, size_t iov_count)
+      : output_iov_(iov),
+        output_iov_count_(iov_count),
+        curr_iov_index_(0),
+        curr_iov_written_(0),
+        total_written_(0),
+        output_limit_(-1) {
+  }
+
+  inline void SetExpectedLength(size_t len) {
+    output_limit_ = len;
+  }
+
+  inline bool CheckLength() const {
+    return total_written_ == output_limit_;
+  }
+
+  inline bool Append(const char* ip, size_t len) {
+    if (total_written_ + len > output_limit_) {
+      return false;
+    }
+
+    while (len > 0) {
+      assert(curr_iov_written_ <= output_iov_[curr_iov_index_].iov_len);
+      if (curr_iov_written_ >= output_iov_[curr_iov_index_].iov_len) {
+        // This iovec is full. Go to the next one.
+        if (curr_iov_index_ + 1 >= output_iov_count_) {
+          return false;
+        }
+        curr_iov_written_ = 0;
+        ++curr_iov_index_;
+      }
+
+      const size_t to_write = std::min(
+          len, output_iov_[curr_iov_index_].iov_len - curr_iov_written_);
+      memcpy(GetIOVecPointer(curr_iov_index_, curr_iov_written_),
+             ip,
+             to_write);
+      curr_iov_written_ += to_write;
+      total_written_ += to_write;
+      ip += to_write;
+      len -= to_write;
+    }
+
+    return true;
+  }
+
+  inline bool TryFastAppend(const char* ip, size_t available, size_t len) {
+    const size_t space_left = output_limit_ - total_written_;
+    if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16 &&
+        output_iov_[curr_iov_index_].iov_len - curr_iov_written_ >= 16) {
+      // Fast path, used for the majority (about 95%) of invocations.
+      char* ptr = GetIOVecPointer(curr_iov_index_, curr_iov_written_);
+      UnalignedCopy64(ip, ptr);
+      UnalignedCopy64(ip + 8, ptr + 8);
+      curr_iov_written_ += len;
+      total_written_ += len;
+      return true;
+    }
+
+    return false;
+  }
+
+  inline bool AppendFromSelf(size_t offset, size_t len) {
+    if (offset > total_written_ || offset == 0) {
+      return false;
+    }
+    const size_t space_left = output_limit_ - total_written_;
+    if (len > space_left) {
+      return false;
+    }
+
+    // Locate the iovec from which we need to start the copy.
+    int from_iov_index = curr_iov_index_;
+    size_t from_iov_offset = curr_iov_written_;
+    while (offset > 0) {
+      if (from_iov_offset >= offset) {
+        from_iov_offset -= offset;
+        break;
+      }
+
+      offset -= from_iov_offset;
+      --from_iov_index;
+      assert(from_iov_index >= 0);
+      from_iov_offset = output_iov_[from_iov_index].iov_len;
+    }
+
+    // Copy <len> bytes starting from the iovec pointed to by from_iov_index to
+    // the current iovec.
+    while (len > 0) {
+      assert(from_iov_index <= curr_iov_index_);
+      if (from_iov_index != curr_iov_index_) {
+        const size_t to_copy = std::min(
+            output_iov_[from_iov_index].iov_len - from_iov_offset,
+            len);
+        Append(GetIOVecPointer(from_iov_index, from_iov_offset), to_copy);
+        len -= to_copy;
+        if (len > 0) {
+          ++from_iov_index;
+          from_iov_offset = 0;
+        }
+      } else {
+        assert(curr_iov_written_ <= output_iov_[curr_iov_index_].iov_len);
+        size_t to_copy = std::min(output_iov_[curr_iov_index_].iov_len -
+                                      curr_iov_written_,
+                                  len);
+        if (to_copy == 0) {
+          // This iovec is full. Go to the next one.
+          if (curr_iov_index_ + 1 >= output_iov_count_) {
+            return false;
+          }
+          ++curr_iov_index_;
+          curr_iov_written_ = 0;
+          continue;
+        }
+        if (to_copy > len) {
+          to_copy = len;
+        }
+        IncrementalCopy(GetIOVecPointer(from_iov_index, from_iov_offset),
+                        GetIOVecPointer(curr_iov_index_, curr_iov_written_),
+                        to_copy);
+        curr_iov_written_ += to_copy;
+        from_iov_offset += to_copy;
+        total_written_ += to_copy;
+        len -= to_copy;
+      }
+    }
+
+    return true;
+  }
+
+};
+
+bool RawUncompressToIOVec(const char* compressed, size_t compressed_length,
+                          const struct iovec* iov, size_t iov_cnt) {
+  ByteArraySource reader(compressed, compressed_length);
+  return RawUncompressToIOVec(&reader, iov, iov_cnt);
+}
+
+bool RawUncompressToIOVec(Source* compressed, const struct iovec* iov,
+                          size_t iov_cnt) {
+  SnappyIOVecWriter output(iov, iov_cnt);
+  return InternalUncompress(compressed, &output);
+}
+
+// -----------------------------------------------------------------------
+// Flat array interfaces
+// -----------------------------------------------------------------------
+
+// A type that writes to a flat array.
+// Note that this is not a "ByteSink", but a type that matches the
+// Writer template argument to SnappyDecompressor::DecompressAllTags().
+class SnappyArrayWriter {
+ private:
+  char* base_;
+  char* op_;
+  char* op_limit_;
+
+ public:
+  inline explicit SnappyArrayWriter(char* dst)
+      : base_(dst),
+        op_(dst) {
+  }
+
+  inline void SetExpectedLength(size_t len) {
+    op_limit_ = op_ + len;
+  }
+
+  inline bool CheckLength() const {
+    return op_ == op_limit_;
+  }
+
+  inline bool Append(const char* ip, size_t len) {
+    char* op = op_;
+    const size_t space_left = op_limit_ - op;
+    if (space_left < len) {
+      return false;
+    }
+    memcpy(op, ip, len);
+    op_ = op + len;
+    return true;
+  }
+
+  inline bool TryFastAppend(const char* ip, size_t available, size_t len) {
+    char* op = op_;
+    const size_t space_left = op_limit_ - op;
+    if (len <= 16 && available >= 16 + kMaximumTagLength && space_left >= 16) {
+      // Fast path, used for the majority (about 95%) of invocations.
+      UnalignedCopy64(ip, op);
+      UnalignedCopy64(ip + 8, op + 8);
+      op_ = op + len;
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+  inline bool AppendFromSelf(size_t offset, size_t len) {
+    char* op = op_;
+    const size_t space_left = op_limit_ - op;
+
+    // Check if we try to append from before the start of the buffer.
+    // Normally this would just be a check for "produced < offset",
+    // but "produced <= offset - 1u" is equivalent for every case
+    // except the one where offset==0, where the right side will wrap around
+    // to a very big number. This is convenient, as offset==0 is another
+    // invalid case that we also want to catch, so that we do not go
+    // into an infinite loop.
+    assert(op >= base_);
+    size_t produced = op - base_;
+    if (produced <= offset - 1u) {
+      return false;
+    }
+    if (len <= 16 && offset >= 8 && space_left >= 16) {
+      // Fast path, used for the majority (70-80%) of dynamic invocations.
+      UnalignedCopy64(op - offset, op);
+      UnalignedCopy64(op - offset + 8, op + 8);
+    } else {
+      if (space_left >= len + kMaxIncrementCopyOverflow) {
+        IncrementalCopyFastPath(op - offset, op, len);
+      } else {
+        if (space_left < len) {
+          return false;
+        }
+        IncrementalCopy(op - offset, op, len);
+      }
+    }
+
+    op_ = op + len;
+    return true;
+  }
+};
+
+bool RawUncompress(const char* compressed, size_t n, char* uncompressed) {
+  ByteArraySource reader(compressed, n);
+  return RawUncompress(&reader, uncompressed);
+}
+
+bool RawUncompress(Source* compressed, char* uncompressed) {
+  SnappyArrayWriter output(uncompressed);
+  return InternalUncompress(compressed, &output);
+}
+
+bool Uncompress(const char* compressed, size_t n, string* uncompressed) {
+  size_t ulength;
+  if (!GetUncompressedLength(compressed, n, &ulength)) {
+    return false;
+  }
+  // On 32-bit builds: max_size() < kuint32max.  Check for that instead
+  // of crashing (e.g., consider externally specified compressed data).
+  if (ulength > uncompressed->max_size()) {
+    return false;
+  }
+  STLStringResizeUninitialized(uncompressed, ulength);
+  return RawUncompress(compressed, n, string_as_array(uncompressed));
+}
+
+
+// A Writer that drops everything on the floor and just does validation
+class SnappyDecompressionValidator {
+ private:
+  size_t expected_;
+  size_t produced_;
+
+ public:
+  inline SnappyDecompressionValidator() : produced_(0) { }
+  inline void SetExpectedLength(size_t len) {
+    expected_ = len;
+  }
+  inline bool CheckLength() const {
+    return expected_ == produced_;
+  }
+  inline bool Append(const char* ip, size_t len) {
+    produced_ += len;
+    return produced_ <= expected_;
+  }
+  inline bool TryFastAppend(const char* ip, size_t available, size_t length) {
+    return false;
+  }
+  inline bool AppendFromSelf(size_t offset, size_t len) {
+    // See SnappyArrayWriter::AppendFromSelf for an explanation of
+    // the "offset - 1u" trick.
+    if (produced_ <= offset - 1u) return false;
+    produced_ += len;
+    return produced_ <= expected_;
+  }
+};
+
+bool IsValidCompressedBuffer(const char* compressed, size_t n) {
+  ByteArraySource reader(compressed, n);
+  SnappyDecompressionValidator writer;
+  return InternalUncompress(&reader, &writer);
+}
+
+void RawCompress(const char* input,
+                 size_t input_length,
+                 char* compressed,
+                 size_t* compressed_length) {
+  ByteArraySource reader(input, input_length);
+  UncheckedByteArraySink writer(compressed);
+  Compress(&reader, &writer);
+
+  // Compute how many bytes were added
+  *compressed_length = (writer.CurrentDestination() - compressed);
+}
+
+size_t Compress(const char* input, size_t input_length, string* compressed) {
+  // Pre-grow the buffer to the max length of the compressed output
+  compressed->resize(MaxCompressedLength(input_length));
+
+  size_t compressed_length;
+  RawCompress(input, input_length, string_as_array(compressed),
+              &compressed_length);
+  compressed->resize(compressed_length);
+  return compressed_length;
+}
+
+
+} // end namespace snappy
+


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