net/spdy/spdy_headers_block_parser.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/spdy_headers_block_parser.h"
   6
   7 #include <memory>
   8
   9 #include "base/sys_byteorder.h"
  10
  11 namespace net {
  12
  13 SpdyHeadersBlockParserReader::SpdyHeadersBlockParserReader(
  14     base::StringPiece prefix,
  15     base::StringPiece suffix)
  16       : prefix_(prefix),
  17         suffix_(suffix),
  18         in_suffix_(false),
  19         offset_(0) {}
  20
  21 size_t SpdyHeadersBlockParserReader::Available() {
  22   if (in_suffix_) {
  23     return suffix_.length() - offset_;
  24   } else {
  25     return prefix_.length() + suffix_.length() - offset_;
  26   }
  27 }
  28
  29 bool SpdyHeadersBlockParserReader::ReadN(size_t count, char* out) {
  30   if (Available() < count)
  31     return false;
  32
  33   if (!in_suffix_ && count > (prefix_.length() - offset_)) {
  34     count -= prefix_.length() - offset_;
  35     out = std::copy(prefix_.begin() + offset_, prefix_.end(), out);
  36     in_suffix_ = true;
  37     offset_ = 0;
  38     // Fallthrough to suffix read.
  39   } else if (!in_suffix_) {
  40     // Read is satisfied by the prefix.
  41     DCHECK_GE(prefix_.length() - offset_, count);
  42     std::copy(prefix_.begin() + offset_,
  43               prefix_.begin() + offset_ + count,
  44               out);
  45     offset_ += count;
  46     return true;
  47   }
  48   // Read is satisfied by the suffix.
  49   DCHECK(in_suffix_);
  50   DCHECK_GE(suffix_.length() - offset_, count);
  51   std::copy(suffix_.begin() + offset_,
  52             suffix_.begin() + offset_ + count,
  53             out);
  54   offset_ += count;
  55   return true;
  56 }
  57
  58 std::vector<char> SpdyHeadersBlockParserReader::Remainder() {
  59   std::vector<char> remainder(Available(), '\0');
  60   if (remainder.size()) {
  61     ReadN(remainder.size(), &remainder[0]);
  62   }
  63   DCHECK_EQ(0u, Available());
  64   return remainder;
  65 }
  66
  67 SpdyHeadersBlockParser::SpdyHeadersBlockParser(
  68     SpdyHeadersHandlerInterface* handler) : state_(READING_HEADER_BLOCK_LEN),
  69     remaining_key_value_pairs_for_frame_(0), next_field_len_(0),
  70     handler_(handler) {
  71 }
  72
  73 SpdyHeadersBlockParser::~SpdyHeadersBlockParser() {}
  74
  75 bool SpdyHeadersBlockParser::ParseUInt32(Reader* reader,
  76                                          uint32_t* parsed_value) {
  77   // Are there enough bytes available?
  78   if (reader->Available() < sizeof(uint32_t)) {
  79     return false;
  80   }
  81
  82   // Read the required bytes, convert from network to host
  83   // order and return the parsed out integer.
  84   char buf[sizeof(uint32_t)];
  85   reader->ReadN(sizeof(uint32_t), buf);
  86   *parsed_value = base::NetToHost32(*reinterpret_cast<const uint32_t *>(buf));
  87   return true;
  88 }
  89
  90 void SpdyHeadersBlockParser::Reset() {
  91   // Clear any saved state about the last headers block.
  92   headers_block_prefix_.clear();
  93   state_ = READING_HEADER_BLOCK_LEN;
  94 }
  95
  96 void SpdyHeadersBlockParser::HandleControlFrameHeadersData(
  97     const char* headers_data, size_t len) {
  98   // Only do something if we received anything new.
  99   if (len == 0) {
 100     return;
 101   }
 102
 103   // Reader avoids copying data.
 104   base::StringPiece prefix;
 105   if (headers_block_prefix_.size()) {
 106     prefix.set(&headers_block_prefix_[0], headers_block_prefix_.size());
 107   }
 108   Reader reader(prefix, base::StringPiece(headers_data, len));
 109
 110   // If we didn't parse out yet the number of key-value pairs in this
 111   // headers block, try to do it now (succeeds if we received enough bytes).
 112   if (state_ == READING_HEADER_BLOCK_LEN) {
 113     if (ParseUInt32(&reader, &remaining_key_value_pairs_for_frame_)) {
 114       handler_->OnHeaderBlock(remaining_key_value_pairs_for_frame_);
 115       state_ = READING_KEY_LEN;
 116     } else {
 117       headers_block_prefix_ = reader.Remainder();
 118       return;
 119     }
 120   }
 121
 122   // Parse out and handle the key-value pairs.
 123   while (remaining_key_value_pairs_for_frame_ > 0) {
 124     // Parse the key-value length, in case we don't already have it.
 125     if ((state_ == READING_KEY_LEN) || (state_ == READING_VALUE_LEN)) {
 126       if (ParseUInt32(&reader, &next_field_len_)) {
 127         state_ == READING_KEY_LEN ? state_ = READING_KEY :
 128                                     state_ = READING_VALUE;
 129       } else {
 130         // Did not receive enough bytes.
 131         break;
 132       }
 133     }
 134
 135     // Parse the next field if we received enough bytes.
 136     if (reader.Available() >= next_field_len_) {
 137       // Copy the field from the cord.
 138       char* key_value_buf(new char[next_field_len_]);
 139       reader.ReadN(next_field_len_, key_value_buf);
 140
 141       // Is this field a key?
 142       if (state_ == READING_KEY) {
 143         current_key.reset(key_value_buf);
 144         key_len_ = next_field_len_;
 145         state_ = READING_VALUE_LEN;
 146
 147       } else if (state_ == READING_VALUE) {
 148         // We already had the key, now we got its value.
 149         current_value.reset(key_value_buf);
 150
 151         // Call the handler for the key-value pair that we received.
 152         handler_->OnKeyValuePair(
 153             base::StringPiece(current_key.get(), key_len_),
 154             base::StringPiece(current_value.get(), next_field_len_));
 155
 156         // Free allocated key and value strings.
 157         current_key.reset();
 158         current_value.reset();
 159
 160         // Finished handling a key-value pair.
 161         remaining_key_value_pairs_for_frame_--;
 162
 163         // Finished handling a header, prepare for the next one.
 164         state_ = READING_KEY_LEN;
 165       }
 166     } else {
 167       // Did not receive enough bytes.
 168       break;
 169     }
 170   }
 171
 172   // Unread suffix becomes the prefix upon next invocation.
 173   headers_block_prefix_ = reader.Remainder();
 174
 175   // Did we finish handling the current block?
 176   if (remaining_key_value_pairs_for_frame_ == 0) {
 177     handler_->OnHeaderBlockEnd();
 178     Reset();
 179   }
 180 }
 181
 182 }  // namespace net