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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.io;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
/**
* Forwards input from a source InputStream while making a copy of it into an outputstream.
* Note that it also does read-ahead and copies up to 64K of data more than was used.
*
* @author arnej
*/
class TeeInputStream extends InputStream {
final InputStream src;
final OutputStream dst;
static final int CAPACITY = 65536;
byte[] buf = new byte[CAPACITY];
int readPos = 0;
int writePos = 0;
private int inBuf() { return writePos - readPos; }
private void fillBuf() throws IOException {
if (readPos == writePos) {
readPos = 0;
writePos = 0;
}
if (readPos * 3 > CAPACITY) {
int had = inBuf();
System.arraycopy(buf, readPos, buf, 0, had);
readPos = 0;
writePos = had;
}
int wantToRead = CAPACITY - writePos;
if (inBuf() > 0) {
// if we have data already, do not block, read only what is available
wantToRead = Math.min(wantToRead, src.available());
}
if (wantToRead > 0) {
int got = src.read(buf, writePos, wantToRead);
if (got > 0) {
dst.write(buf, writePos, got);
writePos += got;
}
}
}
/** Construct a Tee */
public TeeInputStream(InputStream from, OutputStream to) {
super();
this.src = from;
this.dst = to;
}
@Override
public int available() throws IOException {
return inBuf() + src.available();
}
@Override
public void close() throws IOException {
src.close();
dst.close();
}
@Override
public int read() throws IOException {
fillBuf();
if (inBuf() > 0) {
int r = buf[readPos++];
return r & 0xff;
}
return -1;
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (len <= 0) {
return 0;
}
fillBuf();
int had = inBuf();
if (had > 0) {
len = Math.min(len, had);
System.arraycopy(buf, readPos, b, off, len);
readPos += len;
return len;
}
return -1;
}
}
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