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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// GZipFilter applies gzip and deflate content encoding/decoding to a data
// stream. As specified by HTTP 1.1, with gzip encoding the content is
// wrapped with a gzip header, and with deflate encoding the content is in
// a raw, headerless DEFLATE stream.
// Internally GZipFilter uses zlib inflate to do decoding.
// GZipFilter is a subclass of Filter. See the latter's header file filter.h
// for sample usage.
#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "net/filter/filter.h"
typedef struct z_stream_s z_stream;
namespace net {
class GZipHeader;
class GZipFilter : public Filter {
~GZipFilter() override;
// Initializes filter decoding mode and internal control blocks.
// Parameter filter_type specifies the type of filter, which corresponds to
// either gzip or deflate decoding. The function returns true if success and
// false otherwise.
// The filter can only be initialized once.
bool InitDecoding(Filter::FilterType filter_type);
// Decodes the pre-filter data and writes the output into the dest_buffer
// passed in.
// The function returns FilterStatus. See filter.h for its description.
// Upon entry, *dest_len is the total size (in number of chars) of the
// destination buffer. Upon exit, *dest_len is the actual number of chars
// written into the destination buffer.
// This function will fail if there is no pre-filter data in the
// stream_buffer_. On the other hand, *dest_len can be 0 upon successful
// return. For example, the internal zlib may process some pre-filter data
// but not produce output yet.
FilterStatus ReadFilteredData(char* dest_buffer, int* dest_len) override;
enum DecodingStatus {
enum DecodingMode {
enum GZipCheckHeaderState {
static const int kGZipFooterSize = 8;
// Only to be instantiated by Filter::Factory.
friend class Filter;
// Parses and verifies the GZip header.
// Upon exit, the function updates gzip_header_status_ accordingly.
// The function returns Filter::FILTER_OK if it gets a complete header and
// there are more data in the pre-filter buffer.
// The function returns Filter::FILTER_NEED_MORE_DATA if it parses all data
// in the pre-filter buffer, either getting a complete header or a partial
// header. The caller needs to check gzip_header_status_ and call this
// function again for partial header.
// The function returns Filter::FILTER_ERROR if error occurs.
FilterStatus CheckGZipHeader();
// Internal function to decode the pre-filter data and writes the output into
// the dest_buffer passed in.
// This is the internal version of ReadFilteredData. See the latter's
// comments for the use of function.
FilterStatus DoInflate(char* dest_buffer, int* dest_len);
// Inserts a zlib header to the data stream before calling zlib inflate.
// This is used to work around server bugs. See more comments at the place
// it is called in
// The function returns true on success and false otherwise.
bool InsertZlibHeader();
// Skip the 8 byte GZip footer after z_stream_end
void SkipGZipFooter();
// Tracks the status of decoding.
// This variable is initialized by InitDecoding and updated only by
// ReadFilteredData.
DecodingStatus decoding_status_;
// Indicates the type of content decoding the GZipFilter is performing.
// This variable is set only once by InitDecoding.
DecodingMode decoding_mode_;
// Used to parse the gzip header in gzip stream.
// It is used when the decoding_mode_ is DECODE_MODE_GZIP.
scoped_ptr<GZipHeader> gzip_header_;
// Tracks the progress of parsing gzip header.
// This variable is maintained by gzip_header_.
GZipCheckHeaderState gzip_header_status_;
// A flag used by InsertZlibHeader to record whether we've successfully added
// a zlib header to this stream.
bool zlib_header_added_;
// Tracks how many bytes of gzip footer have been received.
int gzip_footer_bytes_;
// The control block of zlib which actually does the decoding.
// This data structure is initialized by InitDecoding and updated only by
// DoInflate, with InsertZlibHeader being the exception as a workaround.
scoped_ptr<z_stream> zlib_stream_;
// For robustness, when we see the solo sdch filter, we chain in a gzip filter
// in front of it, with this flag to indicate that the gzip decoding might not
// be needed. This handles a strange case where "Content-Encoding: sdch,gzip"
// is reduced by an errant proxy to "Content-Encoding: sdch", while the
// content is indeed really gzipped result of sdch :-/.
// If this flag is set, then we will revert to being a pass through filter if
// we don't get a valid gzip header.
bool possible_sdch_pass_through_;
} // namespace net