/*
* Copyright 2012 The Netty Project
*
* The Netty Project 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 com.facebook.presto.jdbc.internal.netty.handler.codec.frame;
import com.facebook.presto.jdbc.internal.netty.buffer.ChannelBuffer;
import com.facebook.presto.jdbc.internal.netty.channel.Channel;
import com.facebook.presto.jdbc.internal.netty.channel.ChannelHandlerContext;
import com.facebook.presto.jdbc.internal.netty.channel.Channels;
/**
* A decoder that splits the received {@link ChannelBuffer}s on line endings.
* <p>
* Both {@code "\n"} and {@code "\r\n"} are handled.
* For a more general delimiter-based decoder, see {@link DelimiterBasedFrameDecoder}.
*/
public class LineBasedFrameDecoder extends FrameDecoder {
/** Maximum length of a frame we're willing to decode. */
private final int maxLength;
/** Whether or not to throw an exception as soon as we exceed maxLength. */
private final boolean failFast;
private final boolean stripDelimiter;
/** True if we're discarding input because we're already over maxLength. */
private boolean discarding;
private int discardedBytes;
/**
* Creates a new decoder.
* @param maxLength the maximum length of the decoded frame.
* A {@link TooLongFrameException} is thrown if
* the length of the frame exceeds this value.
*/
public LineBasedFrameDecoder(final int maxLength) {
this(maxLength, true, false);
}
/**
* Creates a new decoder.
* @param maxLength the maximum length of the decoded frame.
* A {@link TooLongFrameException} is thrown if
* the length of the frame exceeds this value.
* @param stripDelimiter whether the decoded frame should strip out the
* delimiter or not
* @param failFast If <tt>true</tt>, a {@link TooLongFrameException} is
* thrown as soon as the decoder notices the length of the
* frame will exceed <tt>maxFrameLength</tt> regardless of
* whether the entire frame has been read.
* If <tt>false</tt>, a {@link TooLongFrameException} is
* thrown after the entire frame that exceeds
* <tt>maxFrameLength</tt> has been read.
*/
public LineBasedFrameDecoder(final int maxLength, final boolean stripDelimiter, final boolean failFast) {
this.maxLength = maxLength;
this.failFast = failFast;
this.stripDelimiter = stripDelimiter;
}
@Override
protected Object decode(final ChannelHandlerContext ctx,
final Channel channel,
final ChannelBuffer buffer) throws Exception {
final int eol = findEndOfLine(buffer);
if (!discarding) {
if (eol >= 0) {
final ChannelBuffer frame;
final int length = eol - buffer.readerIndex();
final int delimLength = buffer.getByte(eol) == '\r'? 2 : 1;
if (length > maxLength) {
buffer.readerIndex(eol + delimLength);
fail(ctx, length);
return null;
}
try {
if (stripDelimiter) {
frame = extractFrame(buffer, buffer.readerIndex(), length);
} else {
frame = extractFrame(buffer, buffer.readerIndex(), length + delimLength);
}
} finally {
buffer.skipBytes(length + delimLength);
}
return frame;
} else {
final int length = buffer.readableBytes();
if (length > maxLength) {
discardedBytes = length;
buffer.readerIndex(buffer.writerIndex());
discarding = true;
if (failFast) {
fail(ctx, "over " + discardedBytes);
}
}
return null;
}
} else {
if (eol >= 0) {
final int length = discardedBytes + eol - buffer.readerIndex();
final int delimLength = buffer.getByte(eol) == '\r'? 2 : 1;
buffer.readerIndex(eol + delimLength);
discardedBytes = 0;
discarding = false;
if (!failFast) {
fail(ctx, length);
}
} else {
discardedBytes = buffer.readableBytes();
buffer.readerIndex(buffer.writerIndex());
}
return null;
}
}
private void fail(final ChannelHandlerContext ctx, int length) {
fail(ctx, String.valueOf(length));
}
private void fail(final ChannelHandlerContext ctx, String length) {
Channels.fireExceptionCaught(
ctx.getChannel(),
new TooLongFrameException(
"frame length (" + length + ") exceeds the allowed maximum (" + maxLength + ')'));
}
/**
* Returns the index in the buffer of the end of line found.
* Returns -1 if no end of line was found in the buffer.
*/
private static int findEndOfLine(final ChannelBuffer buffer) {
final int n = buffer.writerIndex();
for (int i = buffer.readerIndex(); i < n; i ++) {
final byte b = buffer.getByte(i);
if (b == '\n') {
return i;
} else if (b == '\r' && i < n - 1 && buffer.getByte(i + 1) == '\n') {
return i; // \r\n
}
}
return -1; // Not found.
}
}