net/spdy/hpack_decoder.cc

   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 #include "net/spdy/hpack_decoder.h"
   6
   7 #include "base/basictypes.h"
   8 #include "base/logging.h"
   9 #include "net/spdy/hpack_constants.h"
  10 #include "net/spdy/hpack_output_stream.h"
  11
  12 namespace net {
  13
  14 using base::StringPiece;
  15 using std::string;
  16
  17 namespace {
  18
  19 const uint8 kNoState = 0;
  20 // Set on entries added to the reference set during this decoding.
  21 const uint8 kReferencedThisEncoding = 1;
  22
  23 const char kCookieKey[] = "cookie";
  24
  25 }  // namespace
  26
  27 HpackDecoder::HpackDecoder(const HpackHuffmanTable& table)
  28     : max_string_literal_size_(kDefaultMaxStringLiteralSize),
  29       huffman_table_(table) {}
  30
  31 HpackDecoder::~HpackDecoder() {}
  32
  33 bool HpackDecoder::HandleControlFrameHeadersData(SpdyStreamId id,
  34                                                  const char* headers_data,
  35                                                  size_t headers_data_length) {
  36   decoded_block_.clear();
  37
  38   size_t new_size = headers_block_buffer_.size() + headers_data_length;
  39   if (new_size > kMaxDecodeBufferSize) {
  40     return false;
  41   }
  42   headers_block_buffer_.insert(headers_block_buffer_.end(),
  43                                headers_data,
  44                                headers_data + headers_data_length);
  45   return true;
  46 }
  47
  48 bool HpackDecoder::HandleControlFrameHeadersComplete(SpdyStreamId id) {
  49   HpackInputStream input_stream(max_string_literal_size_,
  50                                 headers_block_buffer_);
  51   while (input_stream.HasMoreData()) {
  52     if (!DecodeNextOpcode(&input_stream)) {
  53       headers_block_buffer_.clear();
  54       return false;
  55     }
  56   }
  57   headers_block_buffer_.clear();
  58
  59   // Emit everything in the reference set that hasn't already been emitted.
  60   // Also clear entry state for the next decoded headers block.
  61   // TODO(jgraettinger): We may need to revisit the order in which headers
  62   // are emitted (b/14051713).
  63   for (HpackHeaderTable::OrderedEntrySet::const_iterator it =
  64           header_table_.reference_set().begin();
  65        it != header_table_.reference_set().end(); ++it) {
  66     HpackEntry* entry = *it;
  67
  68     if (entry->state() == kNoState) {
  69       HandleHeaderRepresentation(entry->name(), entry->value());
  70     } else {
  71       entry->set_state(kNoState);
  72     }
  73   }
  74   // Emit the Cookie header, if any crumbles were encountered.
  75   if (!cookie_value_.empty()) {
  76     decoded_block_[kCookieKey] = cookie_value_;
  77     cookie_value_.clear();
  78   }
  79   return true;
  80 }
  81
  82 void HpackDecoder::HandleHeaderRepresentation(StringPiece name,
  83                                               StringPiece value) {
  84   typedef std::pair<std::map<string, string>::iterator, bool> InsertResult;
  85
  86   if (name == kCookieKey) {
  87     if (cookie_value_.empty()) {
  88       cookie_value_.assign(value.data(), value.size());
  89     } else {
  90       cookie_value_ += "; ";
  91       cookie_value_.insert(cookie_value_.end(), value.begin(), value.end());
  92     }
  93   } else {
  94     InsertResult result = decoded_block_.insert(
  95         std::make_pair(name.as_string(), value.as_string()));
  96     if (!result.second) {
  97       result.first->second.push_back('\0');
  98       result.first->second.insert(result.first->second.end(),
  99                                   value.begin(),
 100                                   value.end());
 101     }
 102   }
 103 }
 104
 105 bool HpackDecoder::DecodeNextOpcode(HpackInputStream* input_stream) {
 106   // Implements 4.2: Indexed Header Field Representation.
 107   if (input_stream->MatchPrefixAndConsume(kIndexedOpcode)) {
 108     return DecodeNextIndexedHeader(input_stream);
 109   }
 110   // Implements 4.3.1: Literal Header Field without Indexing.
 111   if (input_stream->MatchPrefixAndConsume(kLiteralNoIndexOpcode)) {
 112     return DecodeNextLiteralHeader(input_stream, false);
 113   }
 114   // Implements 4.3.2: Literal Header Field with Incremental Indexing.
 115   if (input_stream->MatchPrefixAndConsume(kLiteralIncrementalIndexOpcode)) {
 116     return DecodeNextLiteralHeader(input_stream, true);
 117   }
 118   // Implements 4.3.3: Literal Header Field never Indexed.
 119   // TODO(jgraettinger): Preserve the never-indexed bit.
 120   if (input_stream->MatchPrefixAndConsume(kLiteralNeverIndexOpcode)) {
 121     return DecodeNextLiteralHeader(input_stream, false);
 122   }
 123   // Implements 4.4: Encoding context update.
 124   if (input_stream->MatchPrefixAndConsume(kEncodingContextOpcode)) {
 125     return DecodeNextContextUpdate(input_stream);
 126   }
 127   // Unrecognized opcode.
 128   return false;
 129 }
 130
 131 bool HpackDecoder::DecodeNextContextUpdate(HpackInputStream* input_stream) {
 132   if (input_stream->MatchPrefixAndConsume(kEncodingContextEmptyReferenceSet)) {
 133     header_table_.ClearReferenceSet();
 134     return true;
 135   }
 136   if (input_stream->MatchPrefixAndConsume(kEncodingContextNewMaximumSize)) {
 137     uint32 size = 0;
 138     if (!input_stream->DecodeNextUint32(&size)) {
 139       return false;
 140     }
 141     if (size > header_table_.settings_size_bound()) {
 142       return false;
 143     }
 144     header_table_.SetMaxSize(size);
 145     return true;
 146   }
 147   // Unrecognized encoding context update.
 148   return false;
 149 }
 150
 151 bool HpackDecoder::DecodeNextIndexedHeader(HpackInputStream* input_stream) {
 152   uint32 index = 0;
 153   if (!input_stream->DecodeNextUint32(&index))
 154     return false;
 155
 156   HpackEntry* entry = header_table_.GetByIndex(index);
 157   if (entry == NULL)
 158     return false;
 159
 160   if (entry->IsStatic()) {
 161     HandleHeaderRepresentation(entry->name(), entry->value());
 162
 163     HpackEntry* new_entry = header_table_.TryAddEntry(
 164         entry->name(), entry->value());
 165     if (new_entry) {
 166       header_table_.Toggle(new_entry);
 167       new_entry->set_state(kReferencedThisEncoding);
 168     }
 169   } else {
 170     entry->set_state(kNoState);
 171     if (header_table_.Toggle(entry)) {
 172       HandleHeaderRepresentation(entry->name(), entry->value());
 173       entry->set_state(kReferencedThisEncoding);
 174     }
 175   }
 176   return true;
 177 }
 178
 179 bool HpackDecoder::DecodeNextLiteralHeader(HpackInputStream* input_stream,
 180                                            bool should_index) {
 181   StringPiece name;
 182   if (!DecodeNextName(input_stream, &name))
 183     return false;
 184
 185   StringPiece value;
 186   if (!DecodeNextStringLiteral(input_stream, false, &value))
 187     return false;
 188
 189   HandleHeaderRepresentation(name, value);
 190
 191   if (!should_index)
 192     return true;
 193
 194   HpackEntry* new_entry = header_table_.TryAddEntry(name, value);
 195   if (new_entry) {
 196     header_table_.Toggle(new_entry);
 197     new_entry->set_state(kReferencedThisEncoding);
 198   }
 199   return true;
 200 }
 201
 202 bool HpackDecoder::DecodeNextName(
 203     HpackInputStream* input_stream, StringPiece* next_name) {
 204   uint32 index_or_zero = 0;
 205   if (!input_stream->DecodeNextUint32(&index_or_zero))
 206     return false;
 207
 208   if (index_or_zero == 0)
 209     return DecodeNextStringLiteral(input_stream, true, next_name);
 210
 211   const HpackEntry* entry = header_table_.GetByIndex(index_or_zero);
 212   if (entry == NULL) {
 213     return false;
 214   } else if (entry->IsStatic()) {
 215     *next_name = entry->name();
 216   } else {
 217     // |entry| could be evicted as part of this insertion. Preemptively copy.
 218     key_buffer_.assign(entry->name());
 219     *next_name = key_buffer_;
 220   }
 221   return true;
 222 }
 223
 224 bool HpackDecoder::DecodeNextStringLiteral(HpackInputStream* input_stream,
 225                                            bool is_key,
 226                                            StringPiece* output) {
 227   if (input_stream->MatchPrefixAndConsume(kStringLiteralHuffmanEncoded)) {
 228     string* buffer = is_key ? &key_buffer_ : &value_buffer_;
 229     bool result = input_stream->DecodeNextHuffmanString(huffman_table_, buffer);
 230     *output = StringPiece(*buffer);
 231     return result;
 232   } else if (input_stream->MatchPrefixAndConsume(
 233       kStringLiteralIdentityEncoded)) {
 234     return input_stream->DecodeNextIdentityString(output);
 235   } else {
 236     return false;
 237   }
 238 }
 239
 240 }  // namespace net