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175 lines
6.2 KiB
Java
175 lines
6.2 KiB
Java
/*
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* ====================================================================
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* 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,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*
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*/
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package ch.boye.httpclientandroidlib.client.entity;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.PushbackInputStream;
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import java.util.zip.DataFormatException;
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import java.util.zip.Inflater;
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import java.util.zip.InflaterInputStream;
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import ch.boye.httpclientandroidlib.Header;
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import ch.boye.httpclientandroidlib.HttpEntity;
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import ch.boye.httpclientandroidlib.entity.HttpEntityWrapper;
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/**
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* {@link HttpEntityWrapper} responsible for handling deflate Content Coded responses. In RFC2616
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* terms, <code>deflate</code> means a <code>zlib</code> stream as defined in RFC1950. Some server
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* implementations have misinterpreted RFC2616 to mean that a <code>deflate</code> stream as
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* defined in RFC1951 should be used (or maybe they did that since that's how IE behaves?). It's
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* confusing that <code>deflate</code> in HTTP 1.1 means <code>zlib</code> streams rather than
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* <code>deflate</code> streams. We handle both types in here, since that's what is seen on the
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* internet. Moral - prefer <code>gzip</code>!
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*
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* @see GzipDecompressingEntity
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*
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* @since 4.1
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*/
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public class DeflateDecompressingEntity extends DecompressingEntity {
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/**
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* Creates a new {@link DeflateDecompressingEntity} which will wrap the specified
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* {@link HttpEntity}.
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*
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* @param entity
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* a non-null {@link HttpEntity} to be wrapped
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*/
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public DeflateDecompressingEntity(final HttpEntity entity) {
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super(entity);
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}
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/**
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* Returns the non-null InputStream that should be returned to by all requests to
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* {@link #getContent()}.
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*
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* @return a non-null InputStream
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* @throws IOException if there was a problem
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*/
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@Override
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InputStream getDecompressingInputStream(final InputStream wrapped) throws IOException {
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/*
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* A zlib stream will have a header.
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*
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* CMF | FLG [| DICTID ] | ...compressed data | ADLER32 |
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*
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* * CMF is one byte.
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*
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* * FLG is one byte.
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*
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* * DICTID is four bytes, and only present if FLG.FDICT is set.
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*
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* Sniff the content. Does it look like a zlib stream, with a CMF, etc? c.f. RFC1950,
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* section 2.2. http://tools.ietf.org/html/rfc1950#page-4
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*
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* We need to see if it looks like a proper zlib stream, or whether it is just a deflate
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* stream. RFC2616 calls zlib streams deflate. Confusing, isn't it? That's why some servers
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* implement deflate Content-Encoding using deflate streams, rather than zlib streams.
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*
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* We could start looking at the bytes, but to be honest, someone else has already read
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* the RFCs and implemented that for us. So we'll just use the JDK libraries and exception
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* handling to do this. If that proves slow, then we could potentially change this to check
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* the first byte - does it look like a CMF? What about the second byte - does it look like
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* a FLG, etc.
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*/
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/* We read a small buffer to sniff the content. */
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byte[] peeked = new byte[6];
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PushbackInputStream pushback = new PushbackInputStream(wrapped, peeked.length);
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int headerLength = pushback.read(peeked);
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if (headerLength == -1) {
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throw new IOException("Unable to read the response");
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}
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/* We try to read the first uncompressed byte. */
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byte[] dummy = new byte[1];
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Inflater inf = new Inflater();
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try {
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int n;
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while ((n = inf.inflate(dummy)) == 0) {
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if (inf.finished()) {
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/* Not expecting this, so fail loudly. */
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throw new IOException("Unable to read the response");
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}
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if (inf.needsDictionary()) {
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/* Need dictionary - then it must be zlib stream with DICTID part? */
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break;
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}
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if (inf.needsInput()) {
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inf.setInput(peeked);
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}
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}
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if (n == -1) {
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throw new IOException("Unable to read the response");
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}
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/*
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* We read something without a problem, so it's a valid zlib stream. Just need to reset
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* and return an unused InputStream now.
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*/
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pushback.unread(peeked, 0, headerLength);
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return new InflaterInputStream(pushback);
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} catch (DataFormatException e) {
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/* Presume that it's an RFC1951 deflate stream rather than RFC1950 zlib stream and try
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* again. */
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pushback.unread(peeked, 0, headerLength);
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return new InflaterInputStream(pushback, new Inflater(true));
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}
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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public Header getContentEncoding() {
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/* This HttpEntityWrapper has dealt with the Content-Encoding. */
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return null;
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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public long getContentLength() {
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/* Length of inflated content is unknown. */
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return -1;
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}
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}
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