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Side by Side Diff: net/filter/sdch_filter.h

Issue 992733002: Remove //net (except for Android test stuff) and sdch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 9 months ago
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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 // SdchFilter applies open_vcdiff content decoding to a datastream.
6 // This decoding uses a pre-cached dictionary of text fragments to decode
7 // (expand) the stream back to its original contents.
8 //
9 // This SdchFilter internally uses open_vcdiff/vcdec library to do decoding.
10 //
11 // SdchFilter is also a subclass of Filter. See the latter's header file
12 // filter.h for sample usage.
13
14 #ifndef NET_FILTER_SDCH_FILTER_H_
15 #define NET_FILTER_SDCH_FILTER_H_
16
17 #include <string>
18
19 #include "base/memory/scoped_ptr.h"
20 #include "net/base/net_export.h"
21 #include "net/base/sdch_manager.h"
22 #include "net/filter/filter.h"
23
24 namespace open_vcdiff {
25 class VCDiffStreamingDecoder;
26 }
27
28 namespace net {
29
30 class NET_EXPORT_PRIVATE SdchFilter : public Filter {
31 public:
32 ~SdchFilter() override;
33
34 // Initializes filter decoding mode and internal control blocks.
35 bool InitDecoding(Filter::FilterType filter_type);
36
37 // Decode the pre-filter data and writes the output into |dest_buffer|
38 // The function returns FilterStatus. See filter.h for its description.
39 //
40 // Upon entry, *dest_len is the total size (in number of chars) of the
41 // destination buffer. Upon exit, *dest_len is the actual number of chars
42 // written into the destination buffer.
43 FilterStatus ReadFilteredData(char* dest_buffer, int* dest_len) override;
44
45 private:
46 // Internal status. Once we enter an error state, we stop processing data.
47 enum DecodingStatus {
48 DECODING_UNINITIALIZED,
49 WAITING_FOR_DICTIONARY_SELECTION,
50 DECODING_IN_PROGRESS,
51 DECODING_ERROR,
52 META_REFRESH_RECOVERY, // Decoding error being handled by a meta-refresh.
53 PASS_THROUGH, // Non-sdch content being passed without alteration.
54 };
55
56 // Only to be instantiated by Filter::Factory.
57 SdchFilter(FilterType type, const FilterContext& filter_context);
58 friend class Filter;
59
60 // Identify the suggested dictionary, and initialize underlying decompressor.
61 Filter::FilterStatus InitializeDictionary();
62
63 // Move data that was internally buffered (after decompression) to the
64 // specified dest_buffer.
65 int OutputBufferExcess(char* const dest_buffer, size_t available_space);
66
67 // Add SDCH Problem to net-log and record histogram.
68 void LogSdchProblem(SdchProblemCode problem);
69
70 // Context data from the owner of this filter.
71 const FilterContext& filter_context_;
72
73 // Tracks the status of decoding.
74 // This variable is initialized by InitDecoding and updated only by
75 // ReadFilteredData.
76 DecodingStatus decoding_status_;
77
78 // The underlying decoder that processes data.
79 // This data structure is initialized by InitDecoding and updated in
80 // ReadFilteredData.
81 scoped_ptr<open_vcdiff::VCDiffStreamingDecoder> vcdiff_streaming_decoder_;
82
83 // In case we need to assemble the hash piecemeal, we have a place to store
84 // a part of the hash until we "get all 8 bytes plus a null."
85 std::string dictionary_hash_;
86
87 // After assembling an entire dictionary hash (the first 9 bytes of the
88 // sdch payload, we check to see if it is plausible, meaning it has a null
89 // termination, and has 8 characters that are possible in a net-safe base64
90 // encoding. If the hash is not plausible, then the payload is probably not
91 // an SDCH encoded bundle, and various error recovery strategies can be
92 // attempted.
93 bool dictionary_hash_is_plausible_;
94
95 // Validity of this pointer is guaranteed by either the FilterContext holding
96 // a containing SdchManager::DictionarySet, or this object holding a
97 // container in |unexpected_dictionary_handle_| below.
98 const SdchManager::Dictionary *dictionary_;
99
100 // We keep a copy of the URLRequestContext for use in the destructor, (at
101 // which point GetURLRequestContext() will likely return null because of
102 // the disassociation of the URLRequest from the URLRequestJob). This is
103 // safe because the URLRequestJob (and any filters) are guaranteed to be
104 // deleted before the URLRequestContext is destroyed.
105 const URLRequestContext* const url_request_context_;
106
107 // The decoder may demand a larger output buffer than the target of
108 // ReadFilteredData so we buffer the excess output between calls.
109 std::string dest_buffer_excess_;
110 // To avoid moving strings around too much, we save the index into
111 // dest_buffer_excess_ that has the next byte to output.
112 size_t dest_buffer_excess_index_;
113
114 // To get stats on activities, we keep track of source and target bytes.
115 // Visit about:histograms/Sdch to see histogram data.
116 size_t source_bytes_;
117 size_t output_bytes_;
118
119 // Error recovery in content type may add an sdch filter type, in which case
120 // we should gracefully perform pass through if the format is incorrect, or
121 // an applicable dictionary can't be found.
122 bool possible_pass_through_;
123
124 // The URL that is currently being filtered.
125 // This is used to restrict use of a dictionary to a specific URL or path.
126 GURL url_;
127
128 // To facilitate error recovery, allow filter to know if content is text/html
129 // by checking within this mime type (we may do a meta-refresh via html).
130 std::string mime_type_;
131
132 // If the response was encoded with a dictionary different than those
133 // advertised (e.g. a cached response using an old dictionary), this
134 // variable preserves that dictionary from deletion during decoding.
135 scoped_ptr<SdchManager::DictionarySet> unexpected_dictionary_handle_;
136
137 DISALLOW_COPY_AND_ASSIGN(SdchFilter);
138 };
139
140 } // namespace net
141
142 #endif // NET_FILTER_SDCH_FILTER_H_
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