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/*
 * 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 io.netty.handler.codec;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufProcessor;
import io.netty.channel.ChannelHandlerContext;

import java.util.List;

/**
 * A decoder that splits the received {@link ByteBuf}s on line endings.
 * 

* Both {@code "\n"} and {@code "\r\n"} are handled. * For a more general delimiter-based decoder, see {@link DelimiterBasedFrameDecoder}. */ public class LineBasedFrameDecoder extends ByteToMessageDecoder { /** 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 true, a {@link TooLongFrameException} is * thrown as soon as the decoder notices the length of the * frame will exceed maxFrameLength regardless of * whether the entire frame has been read. * If false, a {@link TooLongFrameException} is * thrown after the entire frame that exceeds * maxFrameLength 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 final void decode(ChannelHandlerContext ctx, ByteBuf in, List out) throws Exception { Object decoded = decode(ctx, in); if (decoded != null) { out.add(decoded); } } /** * Create a frame out of the {@link ByteBuf} and return it. * * @param ctx the {@link ChannelHandlerContext} which this {@link ByteToMessageDecoder} belongs to * @param buffer the {@link ByteBuf} from which to read data * @return frame the {@link ByteBuf} which represent the frame or {@code null} if no frame could * be created. */ protected Object decode(ChannelHandlerContext ctx, ByteBuf buffer) throws Exception { final int eol = findEndOfLine(buffer); if (!discarding) { if (eol >= 0) { final ByteBuf 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; } if (stripDelimiter) { frame = buffer.readSlice(length); buffer.skipBytes(delimLength); } else { frame = buffer.readSlice(length + delimLength); } return frame.retain(); } 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) { ctx.fireExceptionCaught( 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 ByteBuf buffer) { int i = buffer.forEachByte(ByteBufProcessor.FIND_LF); if (i > 0 && buffer.getByte(i - 1) == '\r') { i--; } return i; } }