blob: d6918b7c7d1954eaf5092ec161a15a33c4653c6b [file] [log] [blame]
// Copyright (c) 2012 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_frame_builder.h"
#include <limits>
#include "base/logging.h"
#include "net/spdy/spdy_bug_tracker.h"
#include "net/spdy/spdy_framer.h"
#include "net/spdy/spdy_protocol.h"
namespace net {
namespace {
// A special structure for the 8 bit flags and 24 bit length fields.
union FlagsAndLength {
uint8_t flags[4]; // 8 bits
uint32_t length; // 24 bits
};
// Creates a FlagsAndLength.
FlagsAndLength CreateFlagsAndLength(uint8_t flags, size_t length) {
DCHECK_EQ(0u, length & ~static_cast<size_t>(kLengthMask));
FlagsAndLength flags_length;
flags_length.length = base::HostToNet32(static_cast<uint32_t>(length));
DCHECK_EQ(0, flags & ~kControlFlagsMask);
flags_length.flags[0] = flags;
return flags_length;
}
} // namespace
SpdyFrameBuilder::SpdyFrameBuilder(size_t size, SpdyMajorVersion version)
: buffer_(new char[size]),
capacity_(size),
length_(0),
offset_(0),
version_(version) {
}
SpdyFrameBuilder::~SpdyFrameBuilder() {
}
char* SpdyFrameBuilder::GetWritableBuffer(size_t length) {
if (!CanWrite(length)) {
return NULL;
}
return buffer_.get() + offset_ + length_;
}
bool SpdyFrameBuilder::Seek(size_t length) {
if (!CanWrite(length)) {
return false;
}
length_ += length;
return true;
}
bool SpdyFrameBuilder::WriteControlFrameHeader(const SpdyFramer& framer,
SpdyFrameType type,
uint8_t flags) {
DCHECK_EQ(SPDY3, version_);
DCHECK(SpdyConstants::IsValidFrameType(
version_, SpdyConstants::SerializeFrameType(version_, type)));
bool success = true;
FlagsAndLength flags_length =
CreateFlagsAndLength(flags, capacity_ - framer.GetFrameHeaderSize());
success &= WriteUInt16(kControlFlagMask | kSpdy3Version);
success &= WriteUInt16(
SpdyConstants::SerializeFrameType(framer.protocol_version(), type));
success &= WriteBytes(&flags_length, sizeof(flags_length));
DCHECK_EQ(framer.GetFrameHeaderSize(), length());
return success;
}
bool SpdyFrameBuilder::WriteDataFrameHeader(const SpdyFramer& framer,
SpdyStreamId stream_id,
uint8_t flags) {
if (version_ == HTTP2) {
return BeginNewFrame(framer, DATA, flags, stream_id);
}
DCHECK_EQ(0u, stream_id & ~kStreamIdMask);
bool success = true;
success &= WriteUInt32(stream_id);
size_t length_field = capacity_ - framer.GetDataFrameMinimumSize();
DCHECK_EQ(0u, length_field & ~static_cast<size_t>(kLengthMask));
FlagsAndLength flags_length;
flags_length.length = base::HostToNet32(static_cast<uint32_t>(length_field));
DCHECK_EQ(0, flags & ~kDataFlagsMask);
flags_length.flags[0] = flags;
success &= WriteBytes(&flags_length, sizeof(flags_length));
DCHECK_EQ(framer.GetDataFrameMinimumSize(), length());
return success;
}
bool SpdyFrameBuilder::BeginNewFrame(const SpdyFramer& framer,
SpdyFrameType type,
uint8_t flags,
SpdyStreamId stream_id) {
DCHECK(SpdyConstants::IsValidFrameType(
version_, SpdyConstants::SerializeFrameType(version_, type)));
DCHECK_EQ(0u, stream_id & ~kStreamIdMask);
DCHECK_EQ(HTTP2, framer.protocol_version());
bool success = true;
size_t frame_header_length =
SpdyConstants::GetFrameHeaderSize(framer.protocol_version());
if (length_ > 0) {
// Update length field for previous frame.
OverwriteLength(framer, length_ - frame_header_length);
SPDY_BUG_IF(framer.GetFrameMaximumSize() < length_)
<< "Frame length " << length_
<< " is longer than the maximum allowed length.";
}
offset_ += length_;
length_ = 0;
// Assume all remaining capacity will be used for this frame. If not,
// the length will get overwritten when we begin the next frame.
// Don't check for length limits here because this may be larger than the
// actual frame length.
success &= WriteUInt24(capacity_ - offset_ - frame_header_length);
success &= WriteUInt8(SpdyConstants::SerializeFrameType(version_, type));
success &= WriteUInt8(flags);
success &= WriteUInt32(stream_id);
DCHECK_EQ(framer.GetDataFrameMinimumSize(), length_);
return success;
}
bool SpdyFrameBuilder::WriteStringPiece16(const base::StringPiece& value) {
if (value.size() > 0xffff) {
DCHECK(false) << "Tried to write string with length > 16bit.";
return false;
}
if (!WriteUInt16(static_cast<uint16_t>(value.size()))) {
return false;
}
return WriteBytes(value.data(), static_cast<uint16_t>(value.size()));
}
bool SpdyFrameBuilder::WriteStringPiece32(const base::StringPiece& value) {
if (!WriteUInt32(value.size())) {
return false;
}
return WriteBytes(value.data(), value.size());
}
bool SpdyFrameBuilder::WriteBytes(const void* data, uint32_t data_len) {
if (!CanWrite(data_len)) {
return false;
}
char* dest = GetWritableBuffer(data_len);
memcpy(dest, data, data_len);
Seek(data_len);
return true;
}
bool SpdyFrameBuilder::RewriteLength(const SpdyFramer& framer) {
return OverwriteLength(framer, length_ - framer.GetFrameHeaderSize());
}
bool SpdyFrameBuilder::OverwriteLength(const SpdyFramer& framer,
size_t length) {
if (version_ == SPDY3) {
DCHECK_GE(framer.GetFrameMaximumSize() - framer.GetFrameMinimumSize(),
length);
} else {
DCHECK_GE(framer.GetFrameMaximumSize(), length);
}
bool success = false;
const size_t old_length = length_;
if (version_ == SPDY3) {
FlagsAndLength flags_length = CreateFlagsAndLength(
0, // We're not writing over the flags value anyway.
length);
// Write into the correct location by temporarily faking the offset.
length_ = 5; // Offset at which the length field occurs.
success = WriteBytes(reinterpret_cast<char*>(&flags_length) + 1,
sizeof(flags_length) - 1);
} else {
length_ = 0;
success = WriteUInt24(length);
}
length_ = old_length;
return success;
}
bool SpdyFrameBuilder::OverwriteFlags(const SpdyFramer& framer, uint8_t flags) {
DCHECK_EQ(HTTP2, framer.protocol_version());
bool success = false;
const size_t old_length = length_;
// Flags are the fifth octet in the frame prefix.
length_ = 4;
success = WriteUInt8(flags);
length_ = old_length;
return success;
}
bool SpdyFrameBuilder::CanWrite(size_t length) const {
if (length > kLengthMask) {
DCHECK(false);
return false;
}
if (offset_ + length_ + length > capacity_) {
DCHECK(false);
return false;
}
return true;
}
} // namespace net