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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 // GZipFilter applies gzip and deflate content encoding/decoding to a data | |
| 6 // stream. As specified by HTTP 1.1, with gzip encoding the content is | |
| 7 // wrapped with a gzip header, and with deflate encoding the content is in | |
| 8 // a raw, headerless DEFLATE stream. | |
| 9 // | |
| 10 // Internally GZipFilter uses zlib inflate to do decoding. | |
| 11 // | |
| 12 // GZipFilter is a subclass of Filter. See the latter's header file filter.h | |
| 13 // for sample usage. | |
| 14 | |
| 15 #ifndef NET_FILTER_GZIP_FILTER_H_ | |
| 16 #define NET_FILTER_GZIP_FILTER_H_ | |
| 17 | |
| 18 #include "base/basictypes.h" | |
| 19 #include "base/memory/scoped_ptr.h" | |
| 20 #include "net/filter/filter.h" | |
| 21 | |
| 22 typedef struct z_stream_s z_stream; | |
| 23 | |
| 24 namespace net { | |
| 25 | |
| 26 class GZipHeader; | |
| 27 | |
| 28 class GZipFilter : public Filter { | |
| 29 public: | |
| 30 ~GZipFilter() override; | |
| 31 | |
| 32 // Initializes filter decoding mode and internal control blocks. | |
| 33 // Parameter filter_type specifies the type of filter, which corresponds to | |
| 34 // either gzip or deflate decoding. The function returns true if success and | |
| 35 // false otherwise. | |
| 36 // The filter can only be initialized once. | |
| 37 bool InitDecoding(Filter::FilterType filter_type); | |
| 38 | |
| 39 // Decodes the pre-filter data and writes the output into the dest_buffer | |
| 40 // passed in. | |
| 41 // The function returns FilterStatus. See filter.h for its description. | |
| 42 // | |
| 43 // Upon entry, *dest_len is the total size (in number of chars) of the | |
| 44 // destination buffer. Upon exit, *dest_len is the actual number of chars | |
| 45 // written into the destination buffer. | |
| 46 // | |
| 47 // This function will fail if there is no pre-filter data in the | |
| 48 // stream_buffer_. On the other hand, *dest_len can be 0 upon successful | |
| 49 // return. For example, the internal zlib may process some pre-filter data | |
| 50 // but not produce output yet. | |
| 51 FilterStatus ReadFilteredData(char* dest_buffer, int* dest_len) override; | |
| 52 | |
| 53 private: | |
| 54 enum DecodingStatus { | |
| 55 DECODING_UNINITIALIZED, | |
| 56 DECODING_IN_PROGRESS, | |
| 57 DECODING_DONE, | |
| 58 DECODING_ERROR | |
| 59 }; | |
| 60 | |
| 61 enum DecodingMode { | |
| 62 DECODE_MODE_GZIP, | |
| 63 DECODE_MODE_DEFLATE, | |
| 64 DECODE_MODE_UNKNOWN | |
| 65 }; | |
| 66 | |
| 67 enum GZipCheckHeaderState { | |
| 68 GZIP_CHECK_HEADER_IN_PROGRESS, | |
| 69 GZIP_GET_COMPLETE_HEADER, | |
| 70 GZIP_GET_INVALID_HEADER | |
| 71 }; | |
| 72 | |
| 73 static const int kGZipFooterSize = 8; | |
| 74 | |
| 75 // Only to be instantiated by Filter::Factory. | |
| 76 GZipFilter(FilterType type); | |
| 77 friend class Filter; | |
| 78 | |
| 79 // Parses and verifies the GZip header. | |
| 80 // Upon exit, the function updates gzip_header_status_ accordingly. | |
| 81 // | |
| 82 // The function returns Filter::FILTER_OK if it gets a complete header and | |
| 83 // there are more data in the pre-filter buffer. | |
| 84 // The function returns Filter::FILTER_NEED_MORE_DATA if it parses all data | |
| 85 // in the pre-filter buffer, either getting a complete header or a partial | |
| 86 // header. The caller needs to check gzip_header_status_ and call this | |
| 87 // function again for partial header. | |
| 88 // The function returns Filter::FILTER_ERROR if error occurs. | |
| 89 FilterStatus CheckGZipHeader(); | |
| 90 | |
| 91 // Internal function to decode the pre-filter data and writes the output into | |
| 92 // the dest_buffer passed in. | |
| 93 // | |
| 94 // This is the internal version of ReadFilteredData. See the latter's | |
| 95 // comments for the use of function. | |
| 96 FilterStatus DoInflate(char* dest_buffer, int* dest_len); | |
| 97 | |
| 98 // Inserts a zlib header to the data stream before calling zlib inflate. | |
| 99 // This is used to work around server bugs. See more comments at the place | |
| 100 // it is called in gzip_filter.cc. | |
| 101 // The function returns true on success and false otherwise. | |
| 102 bool InsertZlibHeader(); | |
| 103 | |
| 104 // Skip the 8 byte GZip footer after z_stream_end | |
| 105 void SkipGZipFooter(); | |
| 106 | |
| 107 // Tracks the status of decoding. | |
| 108 // This variable is initialized by InitDecoding and updated only by | |
| 109 // ReadFilteredData. | |
| 110 DecodingStatus decoding_status_; | |
| 111 | |
| 112 // Indicates the type of content decoding the GZipFilter is performing. | |
| 113 // This variable is set only once by InitDecoding. | |
| 114 DecodingMode decoding_mode_; | |
| 115 | |
| 116 // Used to parse the gzip header in gzip stream. | |
| 117 // It is used when the decoding_mode_ is DECODE_MODE_GZIP. | |
| 118 scoped_ptr<GZipHeader> gzip_header_; | |
| 119 | |
| 120 // Tracks the progress of parsing gzip header. | |
| 121 // This variable is maintained by gzip_header_. | |
| 122 GZipCheckHeaderState gzip_header_status_; | |
| 123 | |
| 124 // A flag used by InsertZlibHeader to record whether we've successfully added | |
| 125 // a zlib header to this stream. | |
| 126 bool zlib_header_added_; | |
| 127 | |
| 128 // Tracks how many bytes of gzip footer have been received. | |
| 129 int gzip_footer_bytes_; | |
| 130 | |
| 131 // The control block of zlib which actually does the decoding. | |
| 132 // This data structure is initialized by InitDecoding and updated only by | |
| 133 // DoInflate, with InsertZlibHeader being the exception as a workaround. | |
| 134 scoped_ptr<z_stream> zlib_stream_; | |
| 135 | |
| 136 // For robustness, when we see the solo sdch filter, we chain in a gzip filter | |
| 137 // in front of it, with this flag to indicate that the gzip decoding might not | |
| 138 // be needed. This handles a strange case where "Content-Encoding: sdch,gzip" | |
| 139 // is reduced by an errant proxy to "Content-Encoding: sdch", while the | |
| 140 // content is indeed really gzipped result of sdch :-/. | |
| 141 // If this flag is set, then we will revert to being a pass through filter if | |
| 142 // we don't get a valid gzip header. | |
| 143 bool possible_sdch_pass_through_; | |
| 144 | |
| 145 DISALLOW_COPY_AND_ASSIGN(GZipFilter); | |
| 146 }; | |
| 147 | |
| 148 } // namespace net | |
| 149 | |
| 150 #endif // NET_FILTER_GZIP_FILTER_H__ | |
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