/*
* Copyright 2011 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.http;
import io.netty.buffer.ChannelBuffer;
import io.netty.handler.codec.compression.ZlibEncoder;
import io.netty.handler.codec.compression.ZlibWrapper;
import io.netty.handler.codec.embedder.EncoderEmbedder;
/**
* Compresses an {@link HttpMessage} and an {@link HttpChunk} in {@code gzip} or
* {@code deflate} encoding while respecting the {@code "Accept-Encoding"} header.
* If there is no matching encoding, no compression is done. For more
* information on how this handler modifies the message, please refer to
* {@link HttpContentEncoder}.
*/
public class HttpContentCompressor extends HttpContentEncoder {
private final int compressionLevel;
private final int windowBits;
private final int memLevel;
/**
* Creates a new handler with the default compression level (<tt>6</tt>),
* default window size (<tt>15</tt>) and default memory level (<tt>8</tt>).
*/
public HttpContentCompressor() {
this(6);
}
/**
* Creates a new handler with the specified compression level, default
* window size (<tt>15</tt>) and default memory level (<tt>8</tt>).
*
* @param compressionLevel
* {@code 1} yields the fastest compression and {@code 9} yields the
* best compression. {@code 0} means no compression. The default
* compression level is {@code 6}.
*/
public HttpContentCompressor(int compressionLevel) {
this(compressionLevel, 15, 8);
}
/**
* Creates a new handler with the specified compression level, window size,
* and memory level..
*
* @param compressionLevel
* {@code 1} yields the fastest compression and {@code 9} yields the
* best compression. {@code 0} means no compression. The default
* compression level is {@code 6}.
* @param windowBits
* The base two logarithm of the size of the history buffer. The
* value should be in the range {@code 9} to {@code 15} inclusive.
* Larger values result in better compression at the expense of
* memory usage. The default value is {@code 15}.
* @param memLevel
* How much memory should be allocated for the internal compression
* state. {@code 1} uses minimum memory and {@code 9} uses maximum
* memory. Larger values result in better and faster compression
* at the expense of memory usage. The default value is {@code 8}
*/
public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel) {
if (compressionLevel < 0 || compressionLevel > 9) {
throw new IllegalArgumentException(
"compressionLevel: " + compressionLevel +
" (expected: 0-9)");
}
if (windowBits < 9 || windowBits > 15) {
throw new IllegalArgumentException(
"windowBits: " + windowBits + " (expected: 9-15)");
}
if (memLevel < 1 || memLevel > 9) {
throw new IllegalArgumentException(
"memLevel: " + memLevel + " (expected: 1-9)");
}
this.compressionLevel = compressionLevel;
this.windowBits = windowBits;
this.memLevel = memLevel;
}
@Override
protected Result beginEncode(HttpMessage msg, String acceptEncoding) throws Exception {
String contentEncoding = msg.getHeader(HttpHeaders.Names.CONTENT_ENCODING);
if (contentEncoding != null &&
!HttpHeaders.Values.IDENTITY.equalsIgnoreCase(contentEncoding)) {
return null;
}
ZlibWrapper wrapper = determineWrapper(acceptEncoding);
if (wrapper == null) {
return null;
}
String targetContentEncoding;
switch (wrapper) {
case GZIP:
targetContentEncoding = "gzip";
break;
case ZLIB:
targetContentEncoding = "deflate";
break;
default:
throw new Error();
}
return new Result(
targetContentEncoding,
new EncoderEmbedder<ChannelBuffer>(
new ZlibEncoder(wrapper, compressionLevel, windowBits, memLevel)));
}
protected ZlibWrapper determineWrapper(String acceptEncoding) {
float starQ = -1.0f;
float gzipQ = -1.0f;
float deflateQ = -1.0f;
for (String encoding : acceptEncoding.split(",")) {
float q = 1.0f;
int equalsPos = encoding.indexOf('=');
if (equalsPos != -1) {
try {
q = Float.valueOf(encoding.substring(equalsPos + 1));
} catch (NumberFormatException e) {
// Ignore encoding
q = 0.0f;
}
}
if (encoding.indexOf("*") >= 0) {
starQ = q;
} else if (encoding.indexOf("gzip") >= 0 && q > gzipQ) {
gzipQ = q;
} else if (encoding.indexOf("deflate") >= 0 && q > deflateQ) {
deflateQ = q;
}
}
if (gzipQ > 0.0f || deflateQ > 0.0f) {
if (gzipQ >= deflateQ) {
return ZlibWrapper.GZIP;
} else {
return ZlibWrapper.ZLIB;
}
}
if (starQ > 0.0f) {
if (gzipQ == -1.0f) {
return ZlibWrapper.GZIP;
}
if (deflateQ == -1.0f) {
return ZlibWrapper.ZLIB;
}
}
return null;
}
}