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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.jrt;
import java.nio.ByteBuffer;
class Buffer {
static final int MAX_IO = 65000;
private ByteBuffer buf;
private int readPos;
private int writePos;
private boolean readMode;
private void setReadMode() {
if (readMode) {
buf.limit(writePos);
return;
}
writePos = buf.position();
buf.position(readPos);
buf.limit(writePos);
readMode = true;
}
private void setWriteMode() {
if (!readMode) {
buf.limit(buf.capacity());
return;
}
readPos = buf.position();
buf.limit(buf.capacity());
if (readPos == writePos) {
readPos = 0;
writePos = 0;
}
buf.position(writePos);
readMode = false;
}
private void ensureFree(int minFree) {
// assumes setWriteMode called just before
if (buf.remaining() >= minFree) {
return;
}
writePos = buf.position();
int used = writePos - readPos;
int free = buf.remaining() + readPos;
if (free >= minFree && free >= used) {
buf.position(readPos);
buf.limit(writePos);
buf.compact();
readPos = 0;
} else {
int size = buf.capacity() * 2;
if (buf.capacity() + free < minFree) {
size = buf.capacity() + minFree;
}
ByteBuffer tmp = ByteBuffer.allocate(size);
tmp.order(buf.order());
buf.position(readPos);
buf.limit(writePos);
tmp.put(buf);
buf = tmp;
readPos = 0;
}
}
public Buffer(int size) {
buf = ByteBuffer.allocate(size);
readPos = 0;
writePos = 0;
readMode = false;
}
public boolean shrink(int size) {
int rpos = readMode? buf.position() : readPos;
int wpos = readMode? writePos : buf.position();
int used = wpos - rpos;
if (used > size || buf.capacity() <= size) {
return false;
}
ByteBuffer tmp = ByteBuffer.allocate(size);
tmp.order(buf.order());
buf.position(rpos);
buf.limit(wpos);
tmp.put(buf);
buf = tmp;
readPos = 0;
writePos = used;
buf.position(readMode? readPos : writePos);
buf.limit(readMode? writePos : buf.capacity());
return true;
}
public int bytes() {
return (readMode)
? (writePos - buf.position())
: (buf.position() - readPos);
}
public ByteBuffer getReadable() {
setReadMode();
return buf;
}
public ByteBuffer getWritable(int minFree) {
setWriteMode();
ensureFree(minFree);
return buf;
}
public ByteBuffer getChannelReadable() {
ByteBuffer bb = getReadable();
if (bb.remaining() > MAX_IO) {
bb.limit(bb.position() + MAX_IO);
}
return bb;
}
public ByteBuffer getChannelWritable(int minFree) {
ByteBuffer bb = getWritable(minFree);
if (bb.remaining() > MAX_IO) {
bb.limit(bb.position() + MAX_IO);
}
return bb;
}
}
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