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From z..@apache.org
Subject [26/50] [abbrv] hadoop git commit: HADOOP-11938. Enhance ByteBuffer version encode/decode API of raw erasure coder. Contributed by Kai Zheng.
Date Tue, 26 May 2015 19:34:56 GMT
HADOOP-11938. Enhance ByteBuffer version encode/decode API of raw erasure coder. Contributed by Kai Zheng.


Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/343c0e76
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/343c0e76
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/343c0e76

Branch: refs/heads/HDFS-7285
Commit: 343c0e76fcd95ac739ca7cd6742c9d617e19fc37
Parents: b64f674
Author: Zhe Zhang <zhz@apache.org>
Authored: Mon May 18 10:14:54 2015 -0700
Committer: Zhe Zhang <zhezhang@cloudera.com>
Committed: Tue May 26 12:02:31 2015 -0700

----------------------------------------------------------------------
 .../hadoop-common/CHANGES-HDFS-EC-7285.txt      |   3 +
 .../apache/hadoop/io/erasurecode/ECChunk.java   |  35 ++---
 .../rawcoder/AbstractRawErasureCoder.java       |  77 +++++------
 .../rawcoder/AbstractRawErasureDecoder.java     |  69 ++++++++--
 .../rawcoder/AbstractRawErasureEncoder.java     |  66 ++++++++--
 .../io/erasurecode/rawcoder/RSRawDecoder.java   |  22 ++--
 .../io/erasurecode/rawcoder/RSRawEncoder.java   |  41 +++---
 .../io/erasurecode/rawcoder/XORRawDecoder.java  |  30 +++--
 .../io/erasurecode/rawcoder/XORRawEncoder.java  |  40 +++---
 .../erasurecode/rawcoder/util/GaloisField.java  | 112 ++++++++++++----
 .../hadoop/io/erasurecode/TestCoderBase.java    | 131 +++++++++++++++----
 .../erasurecode/coder/TestErasureCoderBase.java |  21 ++-
 .../io/erasurecode/rawcoder/TestRSRawCoder.java |  12 +-
 .../rawcoder/TestRSRawCoderBase.java            |  12 +-
 .../erasurecode/rawcoder/TestRawCoderBase.java  |  57 +++++++-
 .../erasurecode/rawcoder/TestXORRawCoder.java   |  19 +++
 16 files changed, 535 insertions(+), 212 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/CHANGES-HDFS-EC-7285.txt
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/CHANGES-HDFS-EC-7285.txt b/hadoop-common-project/hadoop-common/CHANGES-HDFS-EC-7285.txt
index 34dfc9e..c799b4f 100644
--- a/hadoop-common-project/hadoop-common/CHANGES-HDFS-EC-7285.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES-HDFS-EC-7285.txt
@@ -51,3 +51,6 @@
 
     HADOOP-11566. Add tests and fix for erasure coders to recover erased parity 
     units. (Kai Zheng via Zhe Zhang)
+
+    HADOOP-11938. Enhance ByteBuffer version encode/decode API of raw erasure 
+    coder. (Kai Zheng via Zhe Zhang)

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/ECChunk.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/ECChunk.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/ECChunk.java
index 69a8343..310c738 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/ECChunk.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/ECChunk.java
@@ -72,34 +72,15 @@ public class ECChunk {
   }
 
   /**
-   * Convert an array of this chunks to an array of byte array.
-   * Note the chunk buffers are not affected.
-   * @param chunks
-   * @return an array of byte array
+   * Convert to a bytes array, just for test usage.
+   * @return bytes array
    */
-  public static byte[][] toArrays(ECChunk[] chunks) {
-    byte[][] bytesArr = new byte[chunks.length][];
-
-    ByteBuffer buffer;
-    ECChunk chunk;
-    for (int i = 0; i < chunks.length; i++) {
-      chunk = chunks[i];
-      if (chunk == null) {
-        bytesArr[i] = null;
-        continue;
-      }
-
-      buffer = chunk.getBuffer();
-      if (buffer.hasArray()) {
-        bytesArr[i] = buffer.array();
-      } else {
-        bytesArr[i] = new byte[buffer.remaining()];
-        // Avoid affecting the original one
-        buffer.mark();
-        buffer.get(bytesArr[i]);
-        buffer.reset();
-      }
-    }
+  public byte[] toBytesArray() {
+    byte[] bytesArr = new byte[chunkBuffer.remaining()];
+    // Avoid affecting the original one
+    chunkBuffer.mark();
+    chunkBuffer.get(bytesArr);
+    chunkBuffer.reset();
 
     return bytesArr;
   }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java
index 2400313..5268962 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureCoder.java
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.io.erasurecode.rawcoder;
 
+import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.conf.Configured;
 
 import java.nio.ByteBuffer;
@@ -30,9 +31,6 @@ import java.util.Arrays;
 public abstract class AbstractRawErasureCoder
     extends Configured implements RawErasureCoder {
 
-  // Hope to reset coding buffers a little faster using it
-  private byte[] zeroChunkBytes;
-
   private int numDataUnits;
   private int numParityUnits;
   private int chunkSize;
@@ -43,8 +41,6 @@ public abstract class AbstractRawErasureCoder
     this.numDataUnits = numDataUnits;
     this.numParityUnits = numParityUnits;
     this.chunkSize = chunkSize;
-
-    zeroChunkBytes = new byte[chunkSize]; // With ZERO by default
   }
 
   @Override
@@ -73,55 +69,60 @@ public abstract class AbstractRawErasureCoder
   }
 
   /**
-   * Convert an array of heap ByteBuffers to an array of byte array.
-   * @param buffers
-   * @return an array of byte array
+   * Ensure output buffer filled with ZERO bytes fully in chunkSize.
+   * @param buffer a buffer ready to write chunk size bytes
+   * @return the buffer itself, with ZERO bytes written, the position and limit
+   *         are not changed after the call
    */
-  protected static byte[][] toArrays(ByteBuffer[] buffers) {
-    byte[][] bytesArr = new byte[buffers.length][];
-
-    ByteBuffer buffer;
-    for (int i = 0; i < buffers.length; i++) {
-      buffer = buffers[i];
-      if (buffer == null) {
-        bytesArr[i] = null;
-        continue;
-      }
-
-      if (buffer.hasArray()) {
-        bytesArr[i] = buffer.array();
-      } else {
-        throw new IllegalArgumentException("Invalid ByteBuffer passed, " +
-            "expecting heap buffer");
-      }
+  protected ByteBuffer resetOutputBuffer(ByteBuffer buffer) {
+    int pos = buffer.position();
+    for (int i = pos; i < buffer.limit(); ++i) {
+      buffer.put((byte) 0);
     }
+    buffer.position(pos);
 
-    return bytesArr;
+    return buffer;
   }
 
   /**
    * Ensure the buffer (either input or output) ready to read or write with ZERO
    * bytes fully in chunkSize.
-   * @param buffer
+   * @param buffer bytes array buffer
    * @return the buffer itself
    */
-  protected ByteBuffer resetBuffer(ByteBuffer buffer) {
-    buffer.clear();
-    buffer.put(zeroChunkBytes);
-    buffer.position(0);
+  protected byte[] resetBuffer(byte[] buffer, int offset, int len) {
+    for (int i = offset; i < len; ++i) {
+      buffer[i] = (byte) 0;
+    }
 
     return buffer;
   }
 
   /**
-   * Ensure the buffer (either input or output) ready to read or write with ZERO
-   * bytes fully in chunkSize.
-   * @param buffer bytes array buffer
-   * @return the buffer itself
+   * Check and ensure the buffers are of the length specified by dataLen.
+   * @param buffers
+   * @param dataLen
    */
-  protected byte[] resetBuffer(byte[] buffer) {
-    System.arraycopy(zeroChunkBytes, 0, buffer, 0, buffer.length);
+  protected void ensureLength(ByteBuffer[] buffers, int dataLen) {
+    for (int i = 0; i < buffers.length; ++i) {
+      if (buffers[i].remaining() != dataLen) {
+        throw new HadoopIllegalArgumentException(
+            "Invalid buffer, not of length " + dataLen);
+      }
+    }
+  }
 
-    return buffer;
+  /**
+   * Check and ensure the buffers are of the length specified by dataLen.
+   * @param buffers
+   * @param dataLen
+   */
+  protected void ensureLength(byte[][] buffers, int dataLen) {
+    for (int i = 0; i < buffers.length; ++i) {
+      if (buffers[i].length != dataLen) {
+        throw new HadoopIllegalArgumentException(
+            "Invalid buffer not of length " + dataLen);
+      }
+    }
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java
index b247543..31f4fb8 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureDecoder.java
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.io.erasurecode.rawcoder;
 
+import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.io.erasurecode.ECChunk;
 
 import java.nio.ByteBuffer;
@@ -33,14 +34,43 @@ public abstract class AbstractRawErasureDecoder extends AbstractRawErasureCoder
   public void decode(ByteBuffer[] inputs, int[] erasedIndexes,
                      ByteBuffer[] outputs) {
     checkParameters(inputs, erasedIndexes, outputs);
+    int dataLen = inputs[0].remaining();
+    if (dataLen == 0) {
+      return;
+    }
+    ensureLength(inputs, dataLen);
+    ensureLength(outputs, dataLen);
 
-    boolean hasArray = inputs[0].hasArray();
-    if (hasArray) {
-      byte[][] newInputs = toArrays(inputs);
-      byte[][] newOutputs = toArrays(outputs);
-      doDecode(newInputs, erasedIndexes, newOutputs);
-    } else {
+    boolean usingDirectBuffer = inputs[0].isDirect();
+    if (usingDirectBuffer) {
       doDecode(inputs, erasedIndexes, outputs);
+      return;
+    }
+
+    int[] inputOffsets = new int[inputs.length];
+    int[] outputOffsets = new int[outputs.length];
+    byte[][] newInputs = new byte[inputs.length][];
+    byte[][] newOutputs = new byte[outputs.length][];
+
+    ByteBuffer buffer;
+    for (int i = 0; i < inputs.length; ++i) {
+      buffer = inputs[i];
+      inputOffsets[i] = buffer.position();
+      newInputs[i] = buffer.array();
+    }
+
+    for (int i = 0; i < outputs.length; ++i) {
+      buffer = outputs[i];
+      outputOffsets[i] = buffer.position();
+      newOutputs[i] = buffer.array();
+    }
+
+    doDecode(newInputs, inputOffsets, dataLen,
+        erasedIndexes, newOutputs, outputOffsets);
+
+    for (int i = 0; i < inputs.length; ++i) {
+      buffer = inputs[i];
+      buffer.position(inputOffsets[i] + dataLen); // dataLen bytes consumed
     }
   }
 
@@ -56,18 +86,33 @@ public abstract class AbstractRawErasureDecoder extends AbstractRawErasureCoder
   @Override
   public void decode(byte[][] inputs, int[] erasedIndexes, byte[][] outputs) {
     checkParameters(inputs, erasedIndexes, outputs);
+    int dataLen = inputs[0].length;
+    if (dataLen == 0) {
+      return;
+    }
+    ensureLength(inputs, dataLen);
+    ensureLength(outputs, dataLen);
+
+    int[] inputOffsets = new int[inputs.length]; // ALL ZERO
+    int[] outputOffsets = new int[outputs.length]; // ALL ZERO
 
-    doDecode(inputs, erasedIndexes, outputs);
+    doDecode(inputs, inputOffsets, dataLen, erasedIndexes, outputs,
+        outputOffsets);
   }
 
   /**
-   * Perform the real decoding using bytes array
+   * Perform the real decoding using bytes array, supporting offsets and
+   * lengths.
    * @param inputs
+   * @param inputOffsets
+   * @param dataLen
    * @param erasedIndexes
    * @param outputs
+   * @param outputOffsets
    */
-  protected abstract void doDecode(byte[][] inputs, int[] erasedIndexes,
-                                   byte[][] outputs);
+  protected abstract void doDecode(byte[][] inputs, int[] inputOffsets,
+                                   int dataLen, int[] erasedIndexes,
+                                   byte[][] outputs, int[] outputOffsets);
 
   @Override
   public void decode(ECChunk[] inputs, int[] erasedIndexes,
@@ -91,12 +136,12 @@ public abstract class AbstractRawErasureDecoder extends AbstractRawErasureCoder
     }
 
     if (erasedIndexes.length != outputs.length) {
-      throw new IllegalArgumentException(
+      throw new HadoopIllegalArgumentException(
           "erasedIndexes and outputs mismatch in length");
     }
 
     if (erasedIndexes.length > getNumParityUnits()) {
-      throw new IllegalArgumentException(
+      throw new HadoopIllegalArgumentException(
           "Too many erased, not recoverable");
     }
   }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java
index 06e88bf..0ae54c5 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/AbstractRawErasureEncoder.java
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.io.erasurecode.rawcoder;
 
+import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.io.erasurecode.ECChunk;
 
 import java.nio.ByteBuffer;
@@ -32,14 +33,42 @@ public abstract class AbstractRawErasureEncoder extends AbstractRawErasureCoder
   @Override
   public void encode(ByteBuffer[] inputs, ByteBuffer[] outputs) {
     checkParameters(inputs, outputs);
+    int dataLen = inputs[0].remaining();
+    if (dataLen == 0) {
+      return;
+    }
+    ensureLength(inputs, dataLen);
+    ensureLength(outputs, dataLen);
 
-    boolean hasArray = inputs[0].hasArray();
-    if (hasArray) {
-      byte[][] newInputs = toArrays(inputs);
-      byte[][] newOutputs = toArrays(outputs);
-      doEncode(newInputs, newOutputs);
-    } else {
+    boolean usingDirectBuffer = inputs[0].isDirect();
+    if (usingDirectBuffer) {
       doEncode(inputs, outputs);
+      return;
+    }
+
+    int[] inputOffsets = new int[inputs.length];
+    int[] outputOffsets = new int[outputs.length];
+    byte[][] newInputs = new byte[inputs.length][];
+    byte[][] newOutputs = new byte[outputs.length][];
+
+    ByteBuffer buffer;
+    for (int i = 0; i < inputs.length; ++i) {
+      buffer = inputs[i];
+      inputOffsets[i] = buffer.position();
+      newInputs[i] = buffer.array();
+    }
+
+    for (int i = 0; i < outputs.length; ++i) {
+      buffer = outputs[i];
+      outputOffsets[i] = buffer.position();
+      newOutputs[i] = buffer.array();
+    }
+
+    doEncode(newInputs, inputOffsets, dataLen, newOutputs, outputOffsets);
+
+    for (int i = 0; i < inputs.length; ++i) {
+      buffer = inputs[i];
+      buffer.position(buffer.position() + dataLen); // dataLen bytes consumed
     }
   }
 
@@ -53,16 +82,31 @@ public abstract class AbstractRawErasureEncoder extends AbstractRawErasureCoder
   @Override
   public void encode(byte[][] inputs, byte[][] outputs) {
     checkParameters(inputs, outputs);
+    int dataLen = inputs[0].length;
+    if (dataLen == 0) {
+      return;
+    }
+    ensureLength(inputs, dataLen);
+    ensureLength(outputs, dataLen);
+
+    int[] inputOffsets = new int[inputs.length]; // ALL ZERO
+    int[] outputOffsets = new int[outputs.length]; // ALL ZERO
 
-    doEncode(inputs, outputs);
+    doEncode(inputs, inputOffsets, dataLen, outputs, outputOffsets);
   }
 
   /**
-   * Perform the real encoding work using bytes array
+   * Perform the real encoding work using bytes array, supporting offsets
+   * and lengths.
    * @param inputs
+   * @param inputOffsets
+   * @param dataLen
    * @param outputs
+   * @param outputOffsets
    */
-  protected abstract void doEncode(byte[][] inputs, byte[][] outputs);
+  protected abstract void doEncode(byte[][] inputs, int[] inputOffsets,
+                                   int dataLen, byte[][] outputs,
+                                   int[] outputOffsets);
 
   @Override
   public void encode(ECChunk[] inputs, ECChunk[] outputs) {
@@ -78,10 +122,10 @@ public abstract class AbstractRawErasureEncoder extends AbstractRawErasureCoder
    */
   protected void checkParameters(Object[] inputs, Object[] outputs) {
     if (inputs.length != getNumDataUnits()) {
-      throw new IllegalArgumentException("Invalid inputs length");
+      throw new HadoopIllegalArgumentException("Invalid inputs length");
     }
     if (outputs.length != getNumParityUnits()) {
-      throw new IllegalArgumentException("Invalid outputs length");
+      throw new HadoopIllegalArgumentException("Invalid outputs length");
     }
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java
index 24fa637..ff1162f 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawDecoder.java
@@ -36,9 +36,9 @@ public class RSRawDecoder extends AbstractRawErasureDecoder {
     super.initialize(numDataUnits, numParityUnits, chunkSize);
     assert (getNumDataUnits() + getNumParityUnits() < RSUtil.GF.getFieldSize());
 
-    this.errSignature = new int[getNumParityUnits()];
-    this.primitivePower = RSUtil.getPrimitivePower(getNumDataUnits(),
-        getNumParityUnits());
+    this.errSignature = new int[numParityUnits];
+    this.primitivePower = RSUtil.getPrimitivePower(numDataUnits,
+        numParityUnits);
   }
 
   @Override
@@ -49,21 +49,21 @@ public class RSRawDecoder extends AbstractRawErasureDecoder {
       RSUtil.GF.substitute(inputs, outputs[i], primitivePower[i]);
     }
 
-    int dataLen = inputs[0].remaining();
-    RSUtil.GF.solveVandermondeSystem(errSignature, outputs,
-        erasedIndexes.length, dataLen);
+    RSUtil.GF.solveVandermondeSystem(errSignature,
+        outputs, erasedIndexes.length);
   }
 
   @Override
-  protected void doDecode(byte[][] inputs, int[] erasedIndexes,
-                          byte[][] outputs) {
+  protected void doDecode(byte[][] inputs, int[] inputOffsets,
+                          int dataLen, int[] erasedIndexes,
+                          byte[][] outputs, int[] outputOffsets) {
     for (int i = 0; i < erasedIndexes.length; i++) {
       errSignature[i] = primitivePower[erasedIndexes[i]];
-      RSUtil.GF.substitute(inputs, outputs[i], primitivePower[i]);
+      RSUtil.GF.substitute(inputs, inputOffsets, dataLen, outputs[i],
+          outputOffsets[i], primitivePower[i]);
     }
 
-    int dataLen = inputs[0].length;
-    RSUtil.GF.solveVandermondeSystem(errSignature, outputs,
+    RSUtil.GF.solveVandermondeSystem(errSignature, outputs, outputOffsets,
         erasedIndexes.length, dataLen);
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawEncoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawEncoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawEncoder.java
index 7b501ce..9136331 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawEncoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/RSRawEncoder.java
@@ -34,12 +34,12 @@ public class RSRawEncoder extends AbstractRawErasureEncoder {
     super.initialize(numDataUnits, numParityUnits, chunkSize);
     assert (getNumDataUnits() + getNumParityUnits() < RSUtil.GF.getFieldSize());
 
-    int[] primitivePower = RSUtil.getPrimitivePower(getNumDataUnits(),
-        getNumParityUnits());
+    int[] primitivePower = RSUtil.getPrimitivePower(numDataUnits,
+        numParityUnits);
     // compute generating polynomial
     int[] gen = {1};
     int[] poly = new int[2];
-    for (int i = 0; i < getNumParityUnits(); i++) {
+    for (int i = 0; i < numParityUnits; i++) {
       poly[0] = primitivePower[i];
       poly[1] = 1;
       gen = RSUtil.GF.multiply(gen, poly);
@@ -50,29 +50,30 @@ public class RSRawEncoder extends AbstractRawErasureEncoder {
 
   @Override
   protected void doEncode(ByteBuffer[] inputs, ByteBuffer[] outputs) {
-    ByteBuffer[] data = new ByteBuffer[getNumDataUnits() + getNumParityUnits()];
-    for (int i = 0; i < getNumParityUnits(); i++) {
-      data[i] = outputs[i];
-    }
-    for (int i = 0; i < getNumDataUnits(); i++) {
-      data[i + getNumParityUnits()] = inputs[i];
-    }
+    // parity units + data units
+    ByteBuffer[] all = new ByteBuffer[outputs.length + inputs.length];
+    System.arraycopy(outputs, 0, all, 0, outputs.length);
+    System.arraycopy(inputs, 0, all, outputs.length, inputs.length);
 
     // Compute the remainder
-    RSUtil.GF.remainder(data, generatingPolynomial);
+    RSUtil.GF.remainder(all, generatingPolynomial);
   }
 
   @Override
-  protected void doEncode(byte[][] inputs, byte[][] outputs) {
-    byte[][] data = new byte[getNumDataUnits() + getNumParityUnits()][];
-    for (int i = 0; i < getNumParityUnits(); i++) {
-      data[i] = outputs[i];
-    }
-    for (int i = 0; i < getNumDataUnits(); i++) {
-      data[i + getNumParityUnits()] = inputs[i];
-    }
+  protected void doEncode(byte[][] inputs, int[] inputOffsets,
+                          int dataLen, byte[][] outputs,
+                          int[] outputOffsets) {
+    // parity units + data units
+    byte[][] all = new byte[outputs.length + inputs.length][];
+    System.arraycopy(outputs, 0, all, 0, outputs.length);
+    System.arraycopy(inputs, 0, all, outputs.length, inputs.length);
+
+    int[] offsets = new int[inputOffsets.length + outputOffsets.length];
+    System.arraycopy(outputOffsets, 0, offsets, 0, outputOffsets.length);
+    System.arraycopy(inputOffsets, 0, offsets,
+        outputOffsets.length, inputOffsets.length);
 
     // Compute the remainder
-    RSUtil.GF.remainder(data, generatingPolynomial);
+    RSUtil.GF.remainder(all, offsets, dataLen, generatingPolynomial);
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java
index 2ea1b3d..bf6e894 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawDecoder.java
@@ -21,47 +21,57 @@ import java.nio.ByteBuffer;
 
 /**
  * A raw decoder in XOR code scheme in pure Java, adapted from HDFS-RAID.
+ *
+ * XOR code is an important primitive code scheme in erasure coding and often
+ * used in advanced codes, like HitchHiker and LRC, though itself is rarely
+ * deployed independently.
  */
 public class XORRawDecoder extends AbstractRawErasureDecoder {
 
   @Override
   protected void doDecode(ByteBuffer[] inputs, int[] erasedIndexes,
                           ByteBuffer[] outputs) {
-    resetBuffer(outputs[0]);
+    ByteBuffer output = outputs[0];
+    resetOutputBuffer(output);
 
-    int bufSize = getChunkSize();
     int erasedIdx = erasedIndexes[0];
 
     // Process the inputs.
+    int iIdx, oIdx;
     for (int i = 0; i < inputs.length; i++) {
       // Skip the erased location.
       if (i == erasedIdx) {
         continue;
       }
 
-      for (int j = 0; j < bufSize; j++) {
-        outputs[0].put(j, (byte) (outputs[0].get(j) ^ inputs[i].get(j)));
+      for (iIdx = inputs[i].position(), oIdx = output.position();
+           iIdx < inputs[i].limit();
+           iIdx++, oIdx++) {
+        output.put(oIdx, (byte) (output.get(oIdx) ^ inputs[i].get(iIdx)));
       }
     }
   }
 
   @Override
-  protected void doDecode(byte[][] inputs,
-                          int[] erasedIndexes, byte[][] outputs) {
-    resetBuffer(outputs[0]);
+  protected void doDecode(byte[][] inputs, int[] inputOffsets, int dataLen,
+                          int[] erasedIndexes, byte[][] outputs,
+                          int[] outputOffsets) {
+    byte[] output = outputs[0];
+    resetBuffer(output, outputOffsets[0], dataLen);
 
-    int bufSize = getChunkSize();
     int erasedIdx = erasedIndexes[0];
 
     // Process the inputs.
+    int iIdx, oIdx;
     for (int i = 0; i < inputs.length; i++) {
       // Skip the erased location.
       if (i == erasedIdx) {
         continue;
       }
 
-      for (int j = 0; j < bufSize; j++) {
-        outputs[0][j] ^= inputs[i][j];
+      for (iIdx = inputOffsets[i], oIdx = outputOffsets[0];
+           iIdx < inputOffsets[i] + dataLen; iIdx++, oIdx++) {
+        output[oIdx] ^= inputs[i][iIdx];
       }
     }
   }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java
index 116cb91..feffbbf 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/XORRawEncoder.java
@@ -21,43 +21,53 @@ import java.nio.ByteBuffer;
 
 /**
  * A raw encoder in XOR code scheme in pure Java, adapted from HDFS-RAID.
+ *
+ * XOR code is an important primitive code scheme in erasure coding and often
+ * used in advanced codes, like HitchHiker and LRC, though itself is rarely
+ * deployed independently.
  */
 public class XORRawEncoder extends AbstractRawErasureEncoder {
 
-  @Override
   protected void doEncode(ByteBuffer[] inputs, ByteBuffer[] outputs) {
-    resetBuffer(outputs[0]);
+    ByteBuffer output = outputs[0];
+    resetOutputBuffer(output);
 
-    int bufSize = getChunkSize();
     // Get the first buffer's data.
-    for (int j = 0; j < bufSize; j++) {
-      outputs[0].put(j, inputs[0].get(j));
+    int iIdx, oIdx;
+    for (iIdx = inputs[0].position(), oIdx = output.position();
+         iIdx < inputs[0].limit(); iIdx++, oIdx++) {
+      output.put(oIdx, inputs[0].get(iIdx));
     }
 
     // XOR with everything else.
     for (int i = 1; i < inputs.length; i++) {
-      for (int j = 0; j < bufSize; j++) {
-        outputs[0].put(j, (byte) (outputs[0].get(j) ^ inputs[i].get(j)));
+      for (iIdx = inputs[i].position(), oIdx = output.position();
+           iIdx < inputs[i].limit();
+           iIdx++, oIdx++) {
+        output.put(oIdx, (byte) (output.get(oIdx) ^ inputs[i].get(iIdx)));
       }
     }
   }
 
   @Override
-  protected void doEncode(byte[][] inputs, byte[][] outputs) {
-    resetBuffer(outputs[0]);
+  protected void doEncode(byte[][] inputs, int[] inputOffsets, int dataLen,
+                          byte[][] outputs, int[] outputOffsets) {
+    byte[] output = outputs[0];
+    resetBuffer(output, outputOffsets[0], dataLen);
 
-    int bufSize = getChunkSize();
     // Get the first buffer's data.
-    for (int j = 0; j < bufSize; j++) {
-      outputs[0][j] = inputs[0][j];
+    int iIdx, oIdx;
+    for (iIdx = inputOffsets[0], oIdx = outputOffsets[0];
+         iIdx < inputOffsets[0] + dataLen; iIdx++, oIdx++) {
+      output[oIdx] = inputs[0][iIdx];
     }
 
     // XOR with everything else.
     for (int i = 1; i < inputs.length; i++) {
-      for (int j = 0; j < bufSize; j++) {
-        outputs[0][j] ^= inputs[i][j];
+      for (iIdx = inputOffsets[i], oIdx = outputOffsets[0];
+           iIdx < inputOffsets[i] + dataLen; iIdx++, oIdx++) {
+        output[oIdx] ^= inputs[i][iIdx];
       }
     }
   }
-
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/util/GaloisField.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/util/GaloisField.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/util/GaloisField.java
index 77544c6..62b22c9 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/util/GaloisField.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/erasurecode/rawcoder/util/GaloisField.java
@@ -235,26 +235,30 @@ public class GaloisField {
   /**
    * A "bulk" version to the solving of Vandermonde System
    */
-  public void solveVandermondeSystem(int[] x, byte[][] y,
+  public void solveVandermondeSystem(int[] x, byte[][] y, int[] outputOffsets,
                                      int len, int dataLen) {
+    int idx1, idx2;
     for (int i = 0; i < len - 1; i++) {
       for (int j = len - 1; j > i; j--) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j][k] = (byte) (y[j][k] ^ mulTable[x[i]][y[j - 1][k] &
+        for (idx2 = outputOffsets[j-1], idx1 = outputOffsets[j];
+             idx1 < outputOffsets[j] + dataLen; idx1++, idx2++) {
+          y[j][idx1] = (byte) (y[j][idx1] ^ mulTable[x[i]][y[j - 1][idx2] &
               0x000000FF]);
         }
       }
     }
     for (int i = len - 1; i >= 0; i--) {
       for (int j = i + 1; j < len; j++) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j][k] = (byte) (divTable[y[j][k] & 0x000000FF][x[j] ^
+        for (idx1 = outputOffsets[j];
+             idx1 < outputOffsets[j] + dataLen; idx1++) {
+          y[j][idx1] = (byte) (divTable[y[j][idx1] & 0x000000FF][x[j] ^
               x[j - i - 1]]);
         }
       }
       for (int j = i; j < len - 1; j++) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j][k] = (byte) (y[j][k] ^ y[j + 1][k]);
+        for (idx2 = outputOffsets[j+1], idx1 = outputOffsets[j];
+             idx1 < outputOffsets[j] + dataLen; idx1++, idx2++) {
+          y[j][idx1] = (byte) (y[j][idx1] ^ y[j + 1][idx2]);
         }
       }
     }
@@ -263,26 +267,34 @@ public class GaloisField {
   /**
    * A "bulk" version of the solveVandermondeSystem, using ByteBuffer.
    */
-  public void solveVandermondeSystem(int[] x, ByteBuffer[] y,
-                                     int len, int dataLen) {
+  public void solveVandermondeSystem(int[] x, ByteBuffer[] y, int len) {
+    ByteBuffer p;
+    int idx1, idx2;
     for (int i = 0; i < len - 1; i++) {
       for (int j = len - 1; j > i; j--) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j].put(k, (byte) (y[j].get(k) ^ mulTable[x[i]][y[j - 1].get(k) &
+        p = y[j];
+        for (idx1 = p.position(), idx2 = y[j-1].position();
+             idx1 < p.limit(); idx1++, idx2++) {
+          p.put(idx1, (byte) (p.get(idx1) ^ mulTable[x[i]][y[j-1].get(idx2) &
               0x000000FF]));
         }
       }
     }
+
     for (int i = len - 1; i >= 0; i--) {
       for (int j = i + 1; j < len; j++) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j].put(k, (byte) (divTable[y[j].get(k) & 0x000000FF][x[j] ^
-              x[j - i - 1]]));
+        p = y[j];
+        for (idx1 = p.position(); idx1 < p.limit(); idx1++) {
+          p.put(idx1, (byte) (divTable[p.get(idx1) &
+              0x000000FF][x[j] ^ x[j - i - 1]]));
         }
       }
+
       for (int j = i; j < len - 1; j++) {
-        for (int k = 0; k < dataLen; k++) {
-          y[j].put(k, (byte) (y[j].get(k) ^ y[j + 1].get(k)));
+        p = y[j];
+        for (idx1 = p.position(), idx2 = y[j+1].position();
+             idx1 < p.limit(); idx1++, idx2++) {
+          p.put(idx1, (byte) (p.get(idx1) ^ y[j+1].get(idx2)));
         }
       }
     }
@@ -394,6 +406,31 @@ public class GaloisField {
   }
 
   /**
+   * A "bulk" version of the substitute.
+   * Tends to be 2X faster than the "int" substitute in a loop.
+   *
+   * @param p input polynomial
+   * @param offsets
+   * @param len
+   * @param q store the return result
+   * @param offset
+   * @param x input field
+   */
+  public void substitute(byte[][] p, int[] offsets,
+                         int len, byte[] q, int offset, int x) {
+    int y = 1, iIdx, oIdx;
+    for (int i = 0; i < p.length; i++) {
+      byte[] pi = p[i];
+      for (iIdx = offsets[i], oIdx = offset;
+           iIdx < offsets[i] + len; iIdx++, oIdx++) {
+        int pij = pi[iIdx] & 0x000000FF;
+        q[oIdx] = (byte) (q[oIdx] ^ mulTable[pij][y]);
+      }
+      y = mulTable[x][y];
+    }
+  }
+
+  /**
    * A "bulk" version of the substitute, using ByteBuffer.
    * Tends to be 2X faster than the "int" substitute in a loop.
    *
@@ -402,13 +439,13 @@ public class GaloisField {
    * @param x input field
    */
   public void substitute(ByteBuffer[] p, ByteBuffer q, int x) {
-    int y = 1;
+    int y = 1, iIdx, oIdx;
     for (int i = 0; i < p.length; i++) {
       ByteBuffer pi = p[i];
-      int len = pi.remaining();
-      for (int j = 0; j < len; j++) {
-        int pij = pi.get(j) & 0x000000FF;
-        q.put(j, (byte) (q.get(j) ^ mulTable[pij][y]));
+      for (iIdx = pi.position(), oIdx = q.position();
+           iIdx < pi.limit(); iIdx++, oIdx++) {
+        int pij = pi.get(iIdx) & 0x000000FF;
+        q.put(oIdx, (byte) (q.get(oIdx) ^ mulTable[pij][y]));
       }
       y = mulTable[x][y];
     }
@@ -432,17 +469,42 @@ public class GaloisField {
   }
 
   /**
+   * The "bulk" version of the remainder.
+   * Warning: This function will modify the "dividend" inputs.
+   */
+  public void remainder(byte[][] dividend, int[] offsets,
+                        int len, int[] divisor) {
+    int idx1, idx2;
+    for (int i = dividend.length - divisor.length; i >= 0; i--) {
+      for (int j = 0; j < divisor.length; j++) {
+        for (idx2 = offsets[j + i], idx1 = offsets[i + divisor.length - 1];
+             idx1 < offsets[i + divisor.length - 1] + len;
+             idx1++, idx2++) {
+          int ratio = divTable[dividend[i + divisor.length - 1][idx1] &
+              0x00FF][divisor[divisor.length - 1]];
+          dividend[j + i][idx2] = (byte) ((dividend[j + i][idx2] & 0x00FF) ^
+              mulTable[ratio][divisor[j]]);
+        }
+      }
+    }
+  }
+
+  /**
    * The "bulk" version of the remainder, using ByteBuffer.
    * Warning: This function will modify the "dividend" inputs.
    */
   public void remainder(ByteBuffer[] dividend, int[] divisor) {
+    int idx1, idx2;
+    ByteBuffer b1, b2;
     for (int i = dividend.length - divisor.length; i >= 0; i--) {
-      int width = dividend[i].remaining();
       for (int j = 0; j < divisor.length; j++) {
-        for (int k = 0; k < width; k++) {
-          int ratio = divTable[dividend[i + divisor.length - 1].get(k) &
+        b1 = dividend[i + divisor.length - 1];
+        b2 = dividend[j + i];
+        for (idx1 = b1.position(), idx2 = b2.position();
+             idx1 < b1.limit(); idx1++, idx2++) {
+          int ratio = divTable[b1.get(idx1) &
               0x00FF][divisor[divisor.length - 1]];
-          dividend[j + i].put(k, (byte) ((dividend[j + i].get(k) & 0x00FF) ^
+          b2.put(idx2, (byte) ((b2.get(idx2) & 0x00FF) ^
               mulTable[ratio][divisor[j]]));
         }
       }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/TestCoderBase.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/TestCoderBase.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/TestCoderBase.java
index 769427d..cc3617c 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/TestCoderBase.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/TestCoderBase.java
@@ -35,7 +35,12 @@ public abstract class TestCoderBase {
   private Configuration conf;
   protected int numDataUnits;
   protected int numParityUnits;
-  protected int chunkSize = 16 * 1024;
+  protected int baseChunkSize = 16 * 1024;
+  private int chunkSize = baseChunkSize;
+
+  private byte[] zeroChunkBytes;
+
+  private boolean startBufferWithZero = true;
 
   // Indexes of erased data units.
   protected int[] erasedDataIndexes = new int[] {0};
@@ -47,6 +52,15 @@ public abstract class TestCoderBase {
   // may go to different coding implementations.
   protected boolean usingDirectBuffer = true;
 
+  protected int getChunkSize() {
+    return chunkSize;
+  }
+
+  protected void setChunkSize(int chunkSize) {
+    this.chunkSize = chunkSize;
+    this.zeroChunkBytes = new byte[chunkSize]; // With ZERO by default
+  }
+
   /**
    * Prepare before running the case.
    * @param numDataUnits
@@ -80,8 +94,8 @@ public abstract class TestCoderBase {
    */
   protected void compareAndVerify(ECChunk[] erasedChunks,
                                   ECChunk[] recoveredChunks) {
-    byte[][] erased = ECChunk.toArrays(erasedChunks);
-    byte[][] recovered = ECChunk.toArrays(recoveredChunks);
+    byte[][] erased = toArrays(erasedChunks);
+    byte[][] recovered = toArrays(recoveredChunks);
     boolean result = Arrays.deepEquals(erased, recovered);
     assertTrue("Decoding and comparing failed.", result);
   }
@@ -171,16 +185,19 @@ public abstract class TestCoderBase {
 
   /**
    * Erase data from the specified chunk, putting ZERO bytes to the buffer.
-   * @param chunk
+   * @param chunk with a buffer ready to read at the current position
    */
   protected void eraseDataFromChunk(ECChunk chunk) {
     ByteBuffer chunkBuffer = chunk.getBuffer();
-    // erase the data
-    chunkBuffer.position(0);
-    for (int i = 0; i < chunkSize; i++) {
-      chunkBuffer.put((byte) 0);
-    }
+    // Erase the data at the position, and restore the buffer ready for reading
+    // same many bytes but all ZERO.
+    int pos = chunkBuffer.position();
+    int len = chunkBuffer.remaining();
+    chunkBuffer.put(zeroChunkBytes, 0, len);
+    // Back to readable again after data erased
     chunkBuffer.flip();
+    chunkBuffer.position(pos);
+    chunkBuffer.limit(pos + len);
   }
 
   /**
@@ -190,7 +207,7 @@ public abstract class TestCoderBase {
    * @param chunks
    * @return
    */
-  protected static ECChunk[] cloneChunksWithData(ECChunk[] chunks) {
+  protected ECChunk[] cloneChunksWithData(ECChunk[] chunks) {
     ECChunk[] results = new ECChunk[chunks.length];
     for (int i = 0; i < chunks.length; i++) {
       results[i] = cloneChunkWithData(chunks[i]);
@@ -206,22 +223,19 @@ public abstract class TestCoderBase {
    * @param chunk
    * @return a new chunk
    */
-  protected static ECChunk cloneChunkWithData(ECChunk chunk) {
+  protected ECChunk cloneChunkWithData(ECChunk chunk) {
     ByteBuffer srcBuffer = chunk.getBuffer();
-    ByteBuffer destBuffer;
 
     byte[] bytesArr = new byte[srcBuffer.remaining()];
     srcBuffer.mark();
-    srcBuffer.get(bytesArr);
+    srcBuffer.get(bytesArr, 0, bytesArr.length);
     srcBuffer.reset();
 
-    if (srcBuffer.hasArray()) {
-      destBuffer = ByteBuffer.wrap(bytesArr);
-    } else {
-      destBuffer = ByteBuffer.allocateDirect(srcBuffer.remaining());
-      destBuffer.put(bytesArr);
-      destBuffer.flip();
-    }
+    ByteBuffer destBuffer = allocateOutputBuffer(bytesArr.length);
+    int pos = destBuffer.position();
+    destBuffer.put(bytesArr);
+    destBuffer.flip();
+    destBuffer.position(pos);
 
     return new ECChunk(destBuffer);
   }
@@ -231,18 +245,30 @@ public abstract class TestCoderBase {
    * @return
    */
   protected ECChunk allocateOutputChunk() {
-    ByteBuffer buffer = allocateOutputBuffer();
+    ByteBuffer buffer = allocateOutputBuffer(chunkSize);
 
     return new ECChunk(buffer);
   }
 
   /**
-   * Allocate a buffer for output or writing.
-   * @return
+   * Allocate a buffer for output or writing. It can prepare for two kinds of
+   * data buffers: one with position as 0, the other with position > 0
+   * @return a buffer ready to write chunkSize bytes from current position
    */
-  protected ByteBuffer allocateOutputBuffer() {
+  protected ByteBuffer allocateOutputBuffer(int bufferLen) {
+    /**
+     * When startBufferWithZero, will prepare a buffer as:---------------
+     * otherwise, the buffer will be like:             ___TO--BE--WRITTEN___,
+     * and in the beginning, dummy data are prefixed, to simulate a buffer of
+     * position > 0.
+     */
+    int startOffset = startBufferWithZero ? 0 : 11; // 11 is arbitrary
+    int allocLen = startOffset + bufferLen + startOffset;
     ByteBuffer buffer = usingDirectBuffer ?
-        ByteBuffer.allocateDirect(chunkSize) : ByteBuffer.allocate(chunkSize);
+        ByteBuffer.allocateDirect(allocLen) : ByteBuffer.allocate(allocLen);
+    buffer.limit(startOffset + bufferLen);
+    fillDummyData(buffer, startOffset);
+    startBufferWithZero = ! startBufferWithZero;
 
     return buffer;
   }
@@ -265,16 +291,35 @@ public abstract class TestCoderBase {
    * @return
    */
   protected ECChunk generateDataChunk() {
-    ByteBuffer buffer = allocateOutputBuffer();
-    for (int i = 0; i < chunkSize; i++) {
-      buffer.put((byte) RAND.nextInt(256));
-    }
+    ByteBuffer buffer = allocateOutputBuffer(chunkSize);
+    int pos = buffer.position();
+    buffer.put(generateData(chunkSize));
     buffer.flip();
+    buffer.position(pos);
 
     return new ECChunk(buffer);
   }
 
   /**
+   * Fill len of dummy data in the buffer at the current position.
+   * @param buffer
+   * @param len
+   */
+  protected void fillDummyData(ByteBuffer buffer, int len) {
+    byte[] dummy = new byte[len];
+    RAND.nextBytes(dummy);
+    buffer.put(dummy);
+  }
+
+  protected byte[] generateData(int len) {
+    byte[] buffer = new byte[len];
+    for (int i = 0; i < buffer.length; i++) {
+      buffer[i] = (byte) RAND.nextInt(256);
+    }
+    return buffer;
+  }
+
+  /**
    * Prepare parity chunks for encoding, each chunk for each parity unit.
    * @return
    */
@@ -303,4 +348,32 @@ public abstract class TestCoderBase {
     return chunks;
   }
 
+  /**
+   * Convert an array of this chunks to an array of byte array.
+   * Note the chunk buffers are not affected.
+   * @param chunks
+   * @return an array of byte array
+   */
+  protected byte[][] toArrays(ECChunk[] chunks) {
+    byte[][] bytesArr = new byte[chunks.length][];
+
+    for (int i = 0; i < chunks.length; i++) {
+      bytesArr[i] = chunks[i].toBytesArray();
+    }
+
+    return bytesArr;
+  }
+
+
+  /**
+   * Make some chunk messy or not correct any more
+   * @param chunks
+   */
+  protected void corruptSomeChunk(ECChunk[] chunks) {
+    int idx = new Random().nextInt(chunks.length);
+    ByteBuffer buffer = chunks[idx].getBuffer();
+    if (buffer.hasRemaining()) {
+      buffer.position(buffer.position() + 1);
+    }
+  }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/coder/TestErasureCoderBase.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/coder/TestErasureCoderBase.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/coder/TestErasureCoderBase.java
index f30323b..154ec18 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/coder/TestErasureCoderBase.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/coder/TestErasureCoderBase.java
@@ -59,6 +59,19 @@ public abstract class TestErasureCoderBase extends TestCoderBase {
     this.usingDirectBuffer = usingDirectBuffer;
     prepareCoders();
 
+    /**
+     * The following runs will use 3 different chunkSize for inputs and outputs,
+     * to verify the same encoder/decoder can process variable width of data.
+     */
+    performTestCoding(baseChunkSize);
+    performTestCoding(baseChunkSize - 17);
+    performTestCoding(baseChunkSize + 16);
+  }
+
+  private void performTestCoding(int chunkSize) {
+    setChunkSize(chunkSize);
+
+
     // Generate data and encode
     ECBlockGroup blockGroup = prepareBlockGroupForEncoding();
     // Backup all the source chunks for later recovering because some coders
@@ -138,7 +151,7 @@ public abstract class TestErasureCoderBase extends TestCoderBase {
       throw new RuntimeException("Failed to create encoder", e);
     }
 
-    encoder.initialize(numDataUnits, numParityUnits, chunkSize);
+    encoder.initialize(numDataUnits, numParityUnits, getChunkSize());
     encoder.setConf(getConf());
     return encoder;
   }
@@ -165,7 +178,7 @@ public abstract class TestErasureCoderBase extends TestCoderBase {
       throw new RuntimeException("Failed to create decoder", e);
     }
 
-    decoder.initialize(numDataUnits, numParityUnits, chunkSize);
+    decoder.initialize(numDataUnits, numParityUnits, getChunkSize());
     decoder.setConf(getConf());
     return decoder;
   }
@@ -249,7 +262,7 @@ public abstract class TestErasureCoderBase extends TestCoderBase {
    * @param blocks
    * @return
    */
-  protected static TestBlock[] cloneBlocksWithData(TestBlock[] blocks) {
+  protected TestBlock[] cloneBlocksWithData(TestBlock[] blocks) {
     TestBlock[] results = new TestBlock[blocks.length];
     for (int i = 0; i < blocks.length; ++i) {
       results[i] = cloneBlockWithData(blocks[i]);
@@ -263,7 +276,7 @@ public abstract class TestErasureCoderBase extends TestCoderBase {
    * @param block
    * @return a new block
    */
-  protected static TestBlock cloneBlockWithData(TestBlock block) {
+  protected TestBlock cloneBlockWithData(TestBlock block) {
     ECChunk[] newChunks = cloneChunksWithData(block.chunks);
 
     return new TestBlock(newChunks);

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoder.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoder.java
index 84bad92..02b9eea 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoder.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoder.java
@@ -44,7 +44,7 @@ public class TestRSRawCoder extends TestRSRawCoderBase {
 
   @Test
   public void testCodingDirectBuffer_10x4_erasing_p1() {
-    prepare(null, 10, 4, new int[] {}, new int[] {1});
+    prepare(null, 10, 4, new int[0], new int[] {1});
     testCoding(true);
     testCoding(true);
   }
@@ -101,4 +101,14 @@ public class TestRSRawCoder extends TestRSRawCoderBase {
     prepare(null, 3, 3, new int[] {0}, new int[] {0});
     testCoding(true);
   }
+
+  @Test
+  public void testCodingNegative_10x4_erasing_d2_d4() {
+    prepare(null, 10, 4, new int[]{2, 4}, new int[0]);
+
+    testCodingWithBadInput(true);
+    testCodingWithBadOutput(false);
+    testCodingWithBadInput(true);
+    testCodingWithBadOutput(false);
+  }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoderBase.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoderBase.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoderBase.java
index f9e8a6b..c06aded 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoderBase.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRSRawCoderBase.java
@@ -39,13 +39,11 @@ public abstract class TestRSRawCoderBase extends TestRawCoderBase {
   }
 
   @Override
-  protected ECChunk generateDataChunk() {
-    ByteBuffer buffer = allocateOutputBuffer();
-    for (int i = 0; i < chunkSize; i++) {
-      buffer.put((byte) RAND.nextInt(symbolMax));
+  protected byte[] generateData(int len) {
+    byte[] buffer = new byte[len];
+    for (int i = 0; i < len; i++) {
+      buffer[i] = (byte) RAND.nextInt(symbolMax);
     }
-    buffer.flip();
-
-    return new ECChunk(buffer);
+    return buffer;
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRawCoderBase.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRawCoderBase.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRawCoderBase.java
index 8543c4d..4582317 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRawCoderBase.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestRawCoderBase.java
@@ -19,6 +19,7 @@ package org.apache.hadoop.io.erasurecode.rawcoder;
 
 import org.apache.hadoop.io.erasurecode.ECChunk;
 import org.apache.hadoop.io.erasurecode.TestCoderBase;
+import org.junit.Assert;
 
 /**
  * Raw coder test base with utilities.
@@ -41,8 +42,57 @@ public abstract class TestRawCoderBase extends TestCoderBase {
     this.usingDirectBuffer = usingDirectBuffer;
     prepareCoders();
 
+    /**
+     * The following runs will use 3 different chunkSize for inputs and outputs,
+     * to verify the same encoder/decoder can process variable width of data.
+     */
+    performTestCoding(baseChunkSize, false, false);
+    performTestCoding(baseChunkSize - 17, false, false);
+    performTestCoding(baseChunkSize + 16, false, false);
+  }
+
+  /**
+   * Similar to above, but perform negative cases using bad input for encoding.
+   * @param usingDirectBuffer
+   */
+  protected void testCodingWithBadInput(boolean usingDirectBuffer) {
+    this.usingDirectBuffer = usingDirectBuffer;
+    prepareCoders();
+
+    try {
+      performTestCoding(baseChunkSize, true, false);
+      Assert.fail("Encoding test with bad input should fail");
+    } catch (Exception e) {
+      // Expected
+    }
+  }
+
+  /**
+   * Similar to above, but perform negative cases using bad output for decoding.
+   * @param usingDirectBuffer
+   */
+  protected void testCodingWithBadOutput(boolean usingDirectBuffer) {
+    this.usingDirectBuffer = usingDirectBuffer;
+    prepareCoders();
+
+    try {
+      performTestCoding(baseChunkSize, false, true);
+      Assert.fail("Decoding test with bad output should fail");
+    } catch (Exception e) {
+      // Expected
+    }
+  }
+
+  private void performTestCoding(int chunkSize,
+                                 boolean useBadInput, boolean useBadOutput) {
+    setChunkSize(chunkSize);
+
     // Generate data and encode
     ECChunk[] dataChunks = prepareDataChunksForEncoding();
+    if (useBadInput) {
+      corruptSomeChunk(dataChunks);
+    }
+
     ECChunk[] parityChunks = prepareParityChunksForEncoding();
 
     // Backup all the source chunks for later recovering because some coders
@@ -59,6 +109,9 @@ public abstract class TestRawCoderBase extends TestCoderBase {
         clonedDataChunks, parityChunks);
 
     ECChunk[] recoveredChunks = prepareOutputChunksForDecoding();
+    if (useBadOutput) {
+      corruptSomeChunk(recoveredChunks);
+    }
 
     decoder.decode(inputChunks, getErasedIndexesForDecoding(), recoveredChunks);
 
@@ -88,7 +141,7 @@ public abstract class TestRawCoderBase extends TestCoderBase {
       throw new RuntimeException("Failed to create encoder", e);
     }
 
-    encoder.initialize(numDataUnits, numParityUnits, chunkSize);
+    encoder.initialize(numDataUnits, numParityUnits, getChunkSize());
     encoder.setConf(getConf());
     return encoder;
   }
@@ -105,7 +158,7 @@ public abstract class TestRawCoderBase extends TestCoderBase {
       throw new RuntimeException("Failed to create decoder", e);
     }
 
-    decoder.initialize(numDataUnits, numParityUnits, chunkSize);
+    decoder.initialize(numDataUnits, numParityUnits, getChunkSize());
     decoder.setConf(getConf());
     return decoder;
   }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/343c0e76/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestXORRawCoder.java
----------------------------------------------------------------------
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestXORRawCoder.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestXORRawCoder.java
index b8912a9..327174e 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestXORRawCoder.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/erasurecode/rawcoder/TestXORRawCoder.java
@@ -49,6 +49,15 @@ public class TestXORRawCoder extends TestRawCoderBase {
   @Test
   public void testCodingDirectBuffer_erasing_p0() {
     prepare(null, 10, 1, new int[0], new int[] {0});
+
+    testCoding(true);
+    testCoding(true);
+  }
+
+  @Test
+  public void testCodingDirectBuffer_erasing_d0() {
+    prepare(null, 10, 1, new int[] {0}, new int[0]);
+
     testCoding(true);
     testCoding(true);
   }
@@ -67,4 +76,14 @@ public class TestXORRawCoder extends TestRawCoderBase {
     testCoding(true);
     testCoding(false);
   }
+
+  @Test
+  public void testCodingNegative_erasing_d5() {
+    prepare(null, 10, 1, new int[]{5}, new int[0]);
+
+    testCodingWithBadInput(true);
+    testCodingWithBadOutput(false);
+    testCodingWithBadInput(true);
+    testCodingWithBadOutput(false);
+  }
 }


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