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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.io;
import com.yahoo.text.AbstractUtf8Array;
import java.io.IOException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.util.ArrayList;
import java.util.List;
/**
* Data store for AbstractByteWriter. Tested in unit tests for ByteWriter.
*
* @author Steinar Knutsen
*/
public final class BufferChain {
// refer to the revision history of ByteWriter for more information about
// the reasons behind the sizing of BUFFERSIZE, WATERMARK and MAXBUFFERS
static final int BUFFERSIZE = 4096;
static final int WATERMARK = 1024;
static final int MAXBUFFERS = 50;
static {
//noinspection ConstantConditions
assert BUFFERSIZE > WATERMARK;
}
private final List<ByteBuffer> buffers = new ArrayList<>();
private final WritableByteTransmitter endpoint;
private ByteBuffer current = ByteBuffer.allocate(BUFFERSIZE);
private long appended = 0L;
public BufferChain(final WritableByteTransmitter endpoint) {
this.endpoint = endpoint;
}
public void append(final byte b) throws IOException {
makeRoom(1);
current.put(b);
}
private final boolean shouldCopy(int length) {
return (length < WATERMARK);
}
private final void makeRoom(int length) throws IOException {
if (current.remaining() < length) {
scratch();
}
}
public void append(AbstractUtf8Array v) throws IOException {
final int length = v.getByteLength();
if (shouldCopy(length)) {
makeRoom(length);
v.writeTo(current);
} else {
append(v.wrap());
}
}
public void append(final byte[] alreadyEncoded) throws java.io.IOException {
if (alreadyEncoded.length > 0) {
append(alreadyEncoded, 0, alreadyEncoded.length);
}
}
public void append(final byte[] alreadyEncoded, final int offset, final int length) throws java.io.IOException {
if (shouldCopy(length)) {
makeRoom(length);
current.put(alreadyEncoded, offset, length);
} else {
append(ByteBuffer.wrap(alreadyEncoded, offset, length));
}
}
public void append(final ByteBuffer alreadyEncoded) throws java.io.IOException {
if (alreadyEncoded.remaining() == 0) {
return;
}
final int length = alreadyEncoded.limit() - alreadyEncoded.position();
if (shouldCopy(length)) {
makeRoom(length);
current.put(alreadyEncoded);
} else {
scratch();
add(alreadyEncoded);
}
}
private final void add(final ByteBuffer buf) {
buffers.add(buf);
appended += buf.limit();
}
public void append(final CharBuffer toEncode, final CharsetEncoder encoder)
throws java.io.IOException {
CoderResult overflow;
do {
overflow = encoder.encode(toEncode, current, true);
if (overflow.isOverflow()) {
scratch();
} else if (overflow.isError()) {
try {
toEncode.get();
} catch (final BufferUnderflowException e) {
// Give up if we can't discard some presumptively malformed
// or unmappable data
break;
}
}
} while (!overflow.isUnderflow());
}
private void scratch() throws java.io.IOException {
if (!possibleFlush() && current.position() != 0) {
current.flip();
add(current);
current = ByteBuffer.allocate(BUFFERSIZE);
}
}
private boolean possibleFlush() throws java.io.IOException {
if (buffers.size() > MAXBUFFERS) {
flush();
return true;
}
return false;
}
public void flush() throws IOException {
for (ByteBuffer b : buffers) {
endpoint.send(b);
}
buffers.clear();
if (current.position() > 0) {
current.flip();
appended += current.limit();
endpoint.send(current);
current = ByteBuffer.allocate(BUFFERSIZE);
}
}
/**
* @return number of bytes written to this buffer
*/
public long appended() {
return appended + current.position();
}
}
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