1 // Copyright (c) 2011 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_BASE_GZIP_FILTER_H_ 16 #define NET_BASE_GZIP_FILTER_H_ 17 18 #include "base/basictypes.h" 19 #include "base/memory/scoped_ptr.h" 20 #include "net/base/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 virtual ~GZipFilter(); 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 virtual FilterStatus ReadFilteredData(char* dest_buffer, 52 int* dest_len) OVERRIDE; 53 54 private: 55 enum DecodingStatus { 56 DECODING_UNINITIALIZED, 57 DECODING_IN_PROGRESS, 58 DECODING_DONE, 59 DECODING_ERROR 60 }; 61 62 enum DecodingMode { 63 DECODE_MODE_GZIP, 64 DECODE_MODE_DEFLATE, 65 DECODE_MODE_UNKNOWN 66 }; 67 68 enum GZipCheckHeaderState { 69 GZIP_CHECK_HEADER_IN_PROGRESS, 70 GZIP_GET_COMPLETE_HEADER, 71 GZIP_GET_INVALID_HEADER 72 }; 73 74 static const int kGZipFooterSize = 8; 75 76 // Only to be instantiated by Filter::Factory. 77 GZipFilter(); 78 friend class Filter; 79 80 // Parses and verifies the GZip header. 81 // Upon exit, the function updates gzip_header_status_ accordingly. 82 // 83 // The function returns Filter::FILTER_OK if it gets a complete header and 84 // there are more data in the pre-filter buffer. 85 // The function returns Filter::FILTER_NEED_MORE_DATA if it parses all data 86 // in the pre-filter buffer, either getting a complete header or a partial 87 // header. The caller needs to check gzip_header_status_ and call this 88 // function again for partial header. 89 // The function returns Filter::FILTER_ERROR if error occurs. 90 FilterStatus CheckGZipHeader(); 91 92 // Internal function to decode the pre-filter data and writes the output into 93 // the dest_buffer passed in. 94 // 95 // This is the internal version of ReadFilteredData. See the latter's 96 // comments for the use of function. 97 FilterStatus DoInflate(char* dest_buffer, int* dest_len); 98 99 // Inserts a zlib header to the data stream before calling zlib inflate. 100 // This is used to work around server bugs. See more comments at the place 101 // it is called in gzip_filter.cc. 102 // The function returns true on success and false otherwise. 103 bool InsertZlibHeader(); 104 105 // Skip the 8 byte GZip footer after z_stream_end 106 void SkipGZipFooter(); 107 108 // Tracks the status of decoding. 109 // This variable is initialized by InitDecoding and updated only by 110 // ReadFilteredData. 111 DecodingStatus decoding_status_; 112 113 // Indicates the type of content decoding the GZipFilter is performing. 114 // This variable is set only once by InitDecoding. 115 DecodingMode decoding_mode_; 116 117 // Used to parse the gzip header in gzip stream. 118 // It is used when the decoding_mode_ is DECODE_MODE_GZIP. 119 scoped_ptr<GZipHeader> gzip_header_; 120 121 // Tracks the progress of parsing gzip header. 122 // This variable is maintained by gzip_header_. 123 GZipCheckHeaderState gzip_header_status_; 124 125 // A flag used by InsertZlibHeader to record whether we've successfully added 126 // a zlib header to this stream. 127 bool zlib_header_added_; 128 129 // Tracks how many bytes of gzip footer have been received. 130 int gzip_footer_bytes_; 131 132 // The control block of zlib which actually does the decoding. 133 // This data structure is initialized by InitDecoding and updated only by 134 // DoInflate, with InsertZlibHeader being the exception as a workaround. 135 scoped_ptr<z_stream> zlib_stream_; 136 137 // For robustness, when we see the solo sdch filter, we chain in a gzip filter 138 // in front of it, with this flag to indicate that the gzip decoding might not 139 // be needed. This handles a strange case where "Content-Encoding: sdch,gzip" 140 // is reduced by an errant proxy to "Content-Encoding: sdch", while the 141 // content is indeed really gzipped result of sdch :-/. 142 // If this flag is set, then we will revert to being a pass through filter if 143 // we don't get a valid gzip header. 144 bool possible_sdch_pass_through_; 145 146 DISALLOW_COPY_AND_ASSIGN(GZipFilter); 147 }; 148 149 } // namespace net 150 151 #endif // NET_BASE_GZIP_FILTER_H__ 152
