97 lines
3.7 KiB
Java
97 lines
3.7 KiB
Java
/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.handler.codec.compression;
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import io.netty.buffer.ByteBuf;
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import io.netty.buffer.ByteBufAllocator;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.ByteToMessageDecoder;
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/**
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* Decompresses a {@link ByteBuf} using the deflate algorithm.
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*/
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public abstract class ZlibDecoder extends ByteToMessageDecoder {
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/**
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* Maximum allowed size of the decompression buffer.
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*/
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protected final int maxAllocation;
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/**
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* Same as {@link #ZlibDecoder(int)} with maxAllocation = 0.
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*/
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public ZlibDecoder() {
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this(0);
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}
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/**
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* Construct a new ZlibDecoder.
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* @param maxAllocation
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* Maximum size of the decompression buffer. Must be >= 0.
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* If zero, maximum size is decided by the {@link ByteBufAllocator}.
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*/
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public ZlibDecoder(int maxAllocation) {
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if (maxAllocation < 0) {
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throw new IllegalArgumentException("maxAllocation must be >= 0");
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}
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this.maxAllocation = maxAllocation;
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}
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/**
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* Returns {@code true} if and only if the end of the compressed stream
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* has been reached.
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*/
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public abstract boolean isClosed();
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/**
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* Allocate or expand the decompression buffer, without exceeding the maximum allocation.
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* Calls {@link #decompressionBufferExhausted(ByteBuf)} if the buffer is full and cannot be expanded further.
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*/
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protected ByteBuf prepareDecompressBuffer(ChannelHandlerContext ctx, ByteBuf buffer, int preferredSize) {
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if (buffer == null) {
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if (maxAllocation == 0) {
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return ctx.alloc().heapBuffer(preferredSize);
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}
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return ctx.alloc().heapBuffer(Math.min(preferredSize, maxAllocation), maxAllocation);
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}
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// this always expands the buffer if possible, even if the expansion is less than preferredSize
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// we throw the exception only if the buffer could not be expanded at all
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// this means that one final attempt to deserialize will always be made with the buffer at maxAllocation
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if (buffer.ensureWritable(preferredSize, true) == 1) {
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// buffer must be consumed so subclasses don't add it to output
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// we therefore duplicate it when calling decompressionBufferExhausted() to guarantee non-interference
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// but wait until after to consume it so the subclass can tell how much output is really in the buffer
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decompressionBufferExhausted(buffer.duplicate());
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buffer.skipBytes(buffer.readableBytes());
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throw new DecompressionException("Decompression buffer has reached maximum size: " + buffer.maxCapacity());
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}
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return buffer;
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}
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/**
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* Called when the decompression buffer cannot be expanded further.
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* Default implementation is a no-op, but subclasses can override in case they want to
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* do something before the {@link DecompressionException} is thrown, such as log the
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* data that was decompressed so far.
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*/
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protected void decompressionBufferExhausted(ByteBuf buffer) {
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}
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}
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