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From: joshelser <git@git.apache.org>
To: dev@accumulo.apache.org
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Subject: [GitHub] accumulo pull request: ACCUMULO-4164 Avoid copying rfile
 index whe...
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Message-Id: <20160319191459.A074BDFB7D@git1-us-west.apache.org>
Date: Sat, 19 Mar 2016 19:14:59 +0000 (UTC)

Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/80#discussion_r56753672
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/file/blockfile/impl/SeekableByteArrayInputStream.java ---
    @@ -0,0 +1,132 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one or more
    + * contributor license agreements.  See the NOTICE file distributed with
    + * this work for additional information regarding copyright ownership.
    + * The ASF licenses this file to You under the Apache License, Version 2.0
    + * (the "License"); you may not use this file except in compliance with
    + * the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.accumulo.core.file.blockfile.impl;
    +
    +import java.io.IOException;
    +import java.io.InputStream;
    +
    +/**
    + * This class is like byte array input stream with two differences. It supports seeking and avoids synchronization.
    + */
    +public class SeekableByteArrayInputStream extends InputStream {
    +
    +  // make this volatile to ensure data set by one thread can be seen by another
    +  private volatile byte buffer[];
    +  private int cur;
    +  private int max;
    +
    +  @Override
    +  public int read() {
    +    if (cur < max) {
    +      return buffer[cur++] & 0xff;
    +    } else {
    +      return -1;
    +    }
    +  }
    +
    +  @Override
    +  public int read(byte b[], int offset, int length) {
    +    if (b == null) {
    +      throw new NullPointerException();
    +    }
    +
    +    if (length < 0 || offset < 0 || length > b.length - offset) {
    +      throw new IndexOutOfBoundsException();
    +    }
    +
    +    if (length == 0) {
    +      return 0;
    +    }
    +
    +    int avail = max - cur;
    +
    +    if (avail <= 0) {
    +      return -1;
    +    }
    +
    +    if (length > avail) {
    +      length = avail;
    +    }
    +
    +    System.arraycopy(buffer, cur, b, offset, length);
    +    cur += length;
    +    return length;
    +  }
    +
    +  @Override
    +  public long skip(long requestedSkip) {
    +    long actualSkip = max - cur;
    +    if (requestedSkip < actualSkip)
    +      if (requestedSkip < 0)
    +        actualSkip = 0;
    +      else
    +        actualSkip = requestedSkip;
    +
    +    cur += actualSkip;
    +    return actualSkip;
    +  }
    +
    +  @Override
    +  public int available() {
    +    return max - cur;
    +  }
    +
    +  @Override
    +  public boolean markSupported() {
    +    return false;
    +  }
    +
    +  @Override
    +  public void mark(int readAheadLimit) {
    +    throw new UnsupportedOperationException();
    +  }
    +
    +  @Override
    +  public void reset() {
    +    throw new UnsupportedOperationException();
    +  }
    +
    +  @Override
    +  public void close() throws IOException {}
    +
    +  public SeekableByteArrayInputStream(byte[] buf) {
    +    this.buffer = buf;
    +    this.cur = 0;
    +    this.max = buf.length;
    +  }
    +
    +  public SeekableByteArrayInputStream(byte[] buf, int maxOffset) {
    +    this.buffer = buf;
    +    this.cur = 0;
    +    this.max = maxOffset;
    +  }
    +
    +  public void seek(int position) {
    +    if (position < 0 || position >= max)
    +      throw new IllegalArgumentException("position = " + position + " maxOffset = " + max);
    +    this.cur = position;
    +  }
    +
    +  public int getPosition() {
    +    return this.cur;
    +  }
    +
    +  public byte[] getBuffer() {
    --- End diff --
    
    Javadoc to be explicit that this is the actual array (changes to it will be represented in the InputStream? Do we want this do be `public`?


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