New incremental SPDY header parser.

New logic to parse SPDY headers as soon as they are available,
instead of waiting to receive the entire headers block first.

No behavioural change (the new logic introduced in this CL is not yet invoked).

This lands server change 59046509 by ygi.

Chromium specific: Add SpdyHeadersBlockParserReader & tests as an
alternative to the upstream's use of Chord (not supported). The
reader has the additional advantage of not copying header block
data, unless it's part of the remainder prefix for the next
invocation.

BUG=rch@chromium.org

Review URL: https://codereview.chromium.org/130503004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247002 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 181 insertions, 0 deletions

diff --git a/net/spdy/spdy_headers_block_parser.cc b/net/spdy/spdy_headers_block_parser.cc
new file mode 100644
index 0000000..30bc00c
--- /dev/null
+++ b/net/spdy/spdy_headers_block_parser.cc
@@ -0,0 +1,181 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/spdy/spdy_headers_block_parser.h"
+
+#include <memory>
+
+#include "base/sys_byteorder.h"
+
+namespace net {
+
+SpdyHeadersBlockParserReader::SpdyHeadersBlockParserReader(
+    base::StringPiece prefix,
+    base::StringPiece suffix)
+      : prefix_(prefix),
+        suffix_(suffix),
+        in_suffix_(false),
+        offset_(0) {}
+
+size_t SpdyHeadersBlockParserReader::Available() {
+  if (in_suffix_) {
+    return suffix_.length() - offset_;
+  } else {
+    return prefix_.length() + suffix_.length() - offset_;
+  }
+}
+
+bool SpdyHeadersBlockParserReader::ReadN(size_t count, char* out) {
+  if (Available() < count)
+    return false;
+
+  if (!in_suffix_ && count > (prefix_.length() - offset_)) {
+    count -= prefix_.length() - offset_;
+    out = std::copy(prefix_.begin() + offset_, prefix_.end(), out);
+    in_suffix_ = true;
+    offset_ = 0;
+    // Fallthrough to suffix read.
+  } else if (!in_suffix_) {
+    // Read is satisfied by the prefix.
+    DCHECK_GE(prefix_.length() - offset_, count);
+    std::copy(prefix_.begin() + offset_,
+              prefix_.begin() + offset_ + count,
+              out);
+    offset_ += count;
+    return true;
+  }
+  // Read is satisfied by the suffix.
+  DCHECK(in_suffix_);
+  DCHECK_GE(suffix_.length() - offset_, count);
+  std::copy(suffix_.begin() + offset_,
+            suffix_.begin() + offset_ + count,
+            out);
+  offset_ += count;
+  return true;
+}
+
+std::vector<char> SpdyHeadersBlockParserReader::Remainder() {
+  std::vector<char> remainder(Available(), '\0');
+  if (remainder.size()) {
+    ReadN(remainder.size(), &remainder[0]);
+  }
+  DCHECK_EQ(0u, Available());
+  return remainder;
+}
+
+SpdyHeadersBlockParser::SpdyHeadersBlockParser(KeyValueHandler* handler) :
+    state_(READING_HEADER_BLOCK_LEN),
+    remaining_key_value_pairs_for_frame_(0),
+    next_field_len_(0),
+    handler_(handler) {
+}
+
+SpdyHeadersBlockParser::~SpdyHeadersBlockParser() {}
+
+bool SpdyHeadersBlockParser::ParseUInt32(Reader* reader,
+                                         uint32_t* parsed_value) {
+  // Are there enough bytes available?
+  if (reader->Available() < sizeof(uint32_t)) {
+    return false;
+  }
+
+  // Read the required bytes, convert from network to host
+  // order and return the parsed out integer.
+  char buf[sizeof(uint32_t)];
+  reader->ReadN(sizeof(uint32_t), buf);
+  *parsed_value = base::NetToHost32(*reinterpret_cast<const uint32_t *>(buf));
+  return true;
+}
+
+void SpdyHeadersBlockParser::Reset() {
+  // Clear any saved state about the last headers block.
+  headers_block_prefix_.clear();
+  state_ = READING_HEADER_BLOCK_LEN;
+}
+
+void SpdyHeadersBlockParser::HandleControlFrameHeadersData(
+    const char* headers_data, size_t len) {
+  // Only do something if we received anything new.
+  if (len == 0) {
+    return;
+  }
+
+  // Reader avoids copying data.
+  base::StringPiece prefix;
+  if (headers_block_prefix_.size()) {
+    prefix.set(&headers_block_prefix_[0], headers_block_prefix_.size());
+  }
+  Reader reader(prefix, base::StringPiece(headers_data, len));
+
+  // If we didn't parse out yet the number of key-value pairs in this
+  // headers block, try to do it now (succeeds if we received enough bytes).
+  if (state_ == READING_HEADER_BLOCK_LEN) {
+    if (ParseUInt32(&reader, &remaining_key_value_pairs_for_frame_)) {
+      state_ = READING_KEY_LEN;
+    } else {
+      headers_block_prefix_ = reader.Remainder();
+      return;
+    }
+  }
+
+  // Parse out and handle the key-value pairs.
+  while (remaining_key_value_pairs_for_frame_ > 0) {
+    // Parse the key-value length, in case we don't already have it.
+    if ((state_ == READING_KEY_LEN) || (state_ == READING_VALUE_LEN)) {
+      if (ParseUInt32(&reader, &next_field_len_)) {
+        state_ == READING_KEY_LEN ? state_ = READING_KEY :
+                                    state_ = READING_VALUE;
+      } else {
+        // Did not receive enough bytes.
+        break;
+      }
+    }
+
+    // Parse the next field if we received enough bytes.
+    if (reader.Available() >= next_field_len_) {
+      // Copy the field from the cord.
+      char* key_value_buf(new char[next_field_len_]);
+      reader.ReadN(next_field_len_, key_value_buf);
+
+      // Is this field a key?
+      if (state_ == READING_KEY) {
+        current_key.reset(key_value_buf);
+        key_len_ = next_field_len_;
+        state_ = READING_VALUE_LEN;
+
+      } else if (state_ == READING_VALUE) {
+        // We already had the key, now we got its value.
+        current_value.reset(key_value_buf);
+
+        // Call the handler for the key-value pair that we received.
+        handler_->OnKeyValuePair(
+            base::StringPiece(current_key.get(), key_len_),
+            base::StringPiece(current_value.get(), next_field_len_));
+
+        // Free allocated key and value strings.
+        current_key.reset();
+        current_value.reset();
+
+        // Finished handling a key-value pair.
+        remaining_key_value_pairs_for_frame_--;
+
+        // Finished handling a header, prepare for the next one.
+        state_ = READING_KEY_LEN;
+      }
+    } else {
+      // Did not receive enough bytes.
+      break;
+    }
+  }
+
+  // Unread suffix becomes the prefix upon next invocation.
+  headers_block_prefix_ = reader.Remainder();
+
+  // Did we finish handling the current block?
+  if (remaining_key_value_pairs_for_frame_ == 0) {
+    Reset();
+  }
+}
+
+}  // namespace net