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// Copyright 2008 Google Inc. All Rights Reserved.
package com.google.common.io.protocol;
import java.io.*;
/**
* An input stream backed by another input stream, where reading from the
* underlying input stream is limited to a fixed number of bytes. Also does
* some buffering.
*
*/
public class BoundInputStream extends InputStream {
/** Buffer size */
static final int BUF_SIZE = 4096;
/** Number of bytes that may still be read from the underlying stream */
private int remaining;
/** Small buffer to avoid making OS calls for each byte read. */
private byte[] buf;
/** Current position in the buffer */
private int bufPos;
/** Filled size of the buffer */
private int bufSize;
/** Underlying stream to read from */
private InputStream base;
public BoundInputStream(InputStream base, int len) {
this.base = base;
this.remaining = len;
buf = new byte[Math.min(len, BUF_SIZE)];
}
/**
* Make sure there is at least one byte in the buffer. If not possible,
* return false.
*/
private boolean checkBuf() throws IOException {
if (remaining <= 0) {
return false;
}
if (bufPos >= bufSize) {
bufSize = base.read(buf, 0, Math.min(remaining, buf.length));
if (bufSize <= 0) {
remaining = 0;
return false;
}
bufPos = 0;
}
return true;
}
public int available() {
return bufSize - bufPos;
}
public int read() throws IOException {
if (!checkBuf()) {
return -1;
}
remaining--;
return buf[bufPos++] & 255;
}
public int read(byte[] data, int start, int count) throws IOException {
if (!checkBuf()) {
return -1;
}
count = Math.min(count, bufSize - bufPos);
System.arraycopy(buf, bufPos, data, start, count);
bufPos += count;
remaining -= count;
return count;
}
/**
* How many bytes are remaining, based on the length provided to the
* constructor. The underlying stream may terminate earlier. Provided mainly
* for testing purposes.
*/
public int getRemaining() {
return remaining;
}
}
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