blob: f41007ec1e9b1153fba039fa41d0fc52503e298c [file] [log] [blame]
// 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 "quiche/spdy/core/hpack/hpack_output_stream.h"
#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>
#include "absl/strings/string_view.h"
#include "quiche/common/platform/api/quiche_logging.h"
#include "quiche/spdy/core/hpack/hpack_constants.h"
namespace spdy {
HpackOutputStream::HpackOutputStream() : bit_offset_(0) {}
HpackOutputStream::~HpackOutputStream() = default;
void HpackOutputStream::AppendBits(uint8_t bits, size_t bit_size) {
QUICHE_DCHECK_GT(bit_size, 0u);
QUICHE_DCHECK_LE(bit_size, 8u);
QUICHE_DCHECK_EQ(bits >> bit_size, 0);
size_t new_bit_offset = bit_offset_ + bit_size;
if (bit_offset_ == 0) {
// Buffer ends on a byte boundary.
QUICHE_DCHECK_LE(bit_size, 8u);
buffer_.append(1, bits << (8 - bit_size));
} else if (new_bit_offset <= 8) {
// Buffer does not end on a byte boundary but the given bits fit
// in the remainder of the last byte.
buffer_.back() |= bits << (8 - new_bit_offset);
} else {
// Buffer does not end on a byte boundary and the given bits do
// not fit in the remainder of the last byte.
buffer_.back() |= bits >> (new_bit_offset - 8);
buffer_.append(1, bits << (16 - new_bit_offset));
}
bit_offset_ = new_bit_offset % 8;
}
void HpackOutputStream::AppendPrefix(HpackPrefix prefix) {
AppendBits(prefix.bits, prefix.bit_size);
}
void HpackOutputStream::AppendBytes(absl::string_view buffer) {
QUICHE_DCHECK_EQ(bit_offset_, 0u);
buffer_.append(buffer.data(), buffer.size());
}
void HpackOutputStream::AppendUint32(uint32_t I) {
// The algorithm below is adapted from the pseudocode in 6.1.
size_t N = 8 - bit_offset_;
uint8_t max_first_byte = static_cast<uint8_t>((1 << N) - 1);
if (I < max_first_byte) {
AppendBits(static_cast<uint8_t>(I), N);
} else {
AppendBits(max_first_byte, N);
I -= max_first_byte;
while ((I & ~0x7f) != 0) {
buffer_.append(1, (I & 0x7f) | 0x80);
I >>= 7;
}
AppendBits(static_cast<uint8_t>(I), 8);
}
QUICHE_DCHECK_EQ(bit_offset_, 0u);
}
std::string* HpackOutputStream::MutableString() {
QUICHE_DCHECK_EQ(bit_offset_, 0u);
return &buffer_;
}
std::string HpackOutputStream::TakeString() {
// This must hold, since all public functions cause the buffer to
// end on a byte boundary.
QUICHE_DCHECK_EQ(bit_offset_, 0u);
std::string out = std::move(buffer_);
buffer_ = {};
bit_offset_ = 0;
return out;
}
std::string HpackOutputStream::BoundedTakeString(size_t max_size) {
if (buffer_.size() > max_size) {
// Save off overflow bytes to temporary string (causes a copy).
std::string overflow = buffer_.substr(max_size);
// Resize buffer down to the given limit.
buffer_.resize(max_size);
// Give buffer to output string.
std::string out = std::move(buffer_);
// Reset to contain overflow.
buffer_ = std::move(overflow);
return out;
} else {
return TakeString();
}
}
} // namespace spdy