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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 <memory> | |
19 | |
20 #include "base/macros.h" | |
21 #include "net/filter/filter.h" | |
22 | |
23 typedef struct z_stream_s z_stream; | |
24 | |
25 namespace net { | |
26 | |
27 class GZipHeader; | |
28 | |
29 class GZipFilter : public Filter { | |
30 public: | |
31 ~GZipFilter() override; | |
32 | |
33 // Initializes filter decoding mode and internal control blocks. | |
34 // Parameter filter_type specifies the type of filter, which corresponds to | |
35 // either gzip or deflate decoding. The function returns true if success and | |
36 // false otherwise. | |
37 // The filter can only be initialized once. | |
38 bool InitDecoding(Filter::FilterType filter_type); | |
39 | |
40 // Decodes the pre-filter data and writes the output into the dest_buffer | |
41 // passed in. | |
42 // The function returns FilterStatus. See filter.h for its description. | |
43 // | |
44 // Upon entry, *dest_len is the total size (in number of chars) of the | |
45 // destination buffer. Upon exit, *dest_len is the actual number of chars | |
46 // written into the destination buffer. | |
47 // | |
48 // This function will fail if there is no pre-filter data in the | |
49 // stream_buffer_. On the other hand, *dest_len can be 0 upon successful | |
50 // return. For example, the internal zlib may process some pre-filter data | |
51 // but not produce output yet. | |
52 FilterStatus ReadFilteredData(char* dest_buffer, 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 explicit GZipFilter(FilterType type); | |
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 std::unique_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 std::unique_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_FILTER_GZIP_FILTER_H__ | |
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