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// Copyright (c) 2020 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/common/quiche_data_reader.h"
#include <cstring>
#include <string>
#include "absl/strings/numbers.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "quiche/common/platform/api/quiche_bug_tracker.h"
#include "quiche/common/platform/api/quiche_logging.h"
#include "quiche/common/quiche_endian.h"
namespace quiche {
QuicheDataReader::QuicheDataReader(absl::string_view data)
: QuicheDataReader(data.data(), data.length(), quiche::NETWORK_BYTE_ORDER) {
}
QuicheDataReader::QuicheDataReader(const char* data, const size_t len)
: QuicheDataReader(data, len, quiche::NETWORK_BYTE_ORDER) {}
QuicheDataReader::QuicheDataReader(const char* data, const size_t len,
quiche::Endianness endianness)
: data_(data), len_(len), pos_(0), endianness_(endianness) {}
bool QuicheDataReader::ReadUInt8(uint8_t* result) {
return ReadBytes(result, sizeof(*result));
}
bool QuicheDataReader::ReadUInt16(uint16_t* result) {
if (!ReadBytes(result, sizeof(*result))) {
return false;
}
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
*result = quiche::QuicheEndian::NetToHost16(*result);
}
return true;
}
bool QuicheDataReader::ReadUInt24(uint32_t* result) {
if (endianness_ != quiche::NETWORK_BYTE_ORDER) {
// TODO(b/214573190): Implement and test HOST_BYTE_ORDER case.
QUICHE_BUG(QuicheDataReader_ReadUInt24_NotImplemented);
return false;
}
*result = 0;
if (!ReadBytes(reinterpret_cast<char*>(result) + 1, 3u)) {
return false;
}
*result = quiche::QuicheEndian::NetToHost32(*result);
return true;
}
bool QuicheDataReader::ReadUInt32(uint32_t* result) {
if (!ReadBytes(result, sizeof(*result))) {
return false;
}
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
*result = quiche::QuicheEndian::NetToHost32(*result);
}
return true;
}
bool QuicheDataReader::ReadUInt64(uint64_t* result) {
if (!ReadBytes(result, sizeof(*result))) {
return false;
}
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
*result = quiche::QuicheEndian::NetToHost64(*result);
}
return true;
}
bool QuicheDataReader::ReadBytesToUInt64(size_t num_bytes, uint64_t* result) {
*result = 0u;
if (num_bytes > sizeof(*result)) {
return false;
}
if (endianness_ == quiche::HOST_BYTE_ORDER) {
return ReadBytes(result, num_bytes);
}
if (!ReadBytes(reinterpret_cast<char*>(result) + sizeof(*result) - num_bytes,
num_bytes)) {
return false;
}
*result = quiche::QuicheEndian::NetToHost64(*result);
return true;
}
bool QuicheDataReader::ReadStringPiece16(absl::string_view* result) {
// Read resultant length.
uint16_t result_len;
if (!ReadUInt16(&result_len)) {
// OnFailure() already called.
return false;
}
return ReadStringPiece(result, result_len);
}
bool QuicheDataReader::ReadStringPiece8(absl::string_view* result) {
// Read resultant length.
uint8_t result_len;
if (!ReadUInt8(&result_len)) {
// OnFailure() already called.
return false;
}
return ReadStringPiece(result, result_len);
}
bool QuicheDataReader::ReadStringPiece(absl::string_view* result, size_t size) {
// Make sure that we have enough data to read.
if (!CanRead(size)) {
OnFailure();
return false;
}
// Set result.
*result = absl::string_view(data_ + pos_, size);
// Iterate.
pos_ += size;
return true;
}
bool QuicheDataReader::ReadTag(uint32_t* tag) {
return ReadBytes(tag, sizeof(*tag));
}
bool QuicheDataReader::ReadDecimal64(size_t num_digits, uint64_t* result) {
absl::string_view digits;
if (!ReadStringPiece(&digits, num_digits)) {
return false;
}
return absl::SimpleAtoi(digits, result);
}
QuicheVariableLengthIntegerLength QuicheDataReader::PeekVarInt62Length() {
QUICHE_DCHECK_EQ(endianness(), NETWORK_BYTE_ORDER);
const unsigned char* next =
reinterpret_cast<const unsigned char*>(data() + pos());
if (BytesRemaining() == 0) {
return VARIABLE_LENGTH_INTEGER_LENGTH_0;
}
return static_cast<QuicheVariableLengthIntegerLength>(
1 << ((*next & 0b11000000) >> 6));
}
// Read an RFC 9000 62-bit Variable Length Integer.
//
// Performance notes
//
// Measurements and experiments showed that unrolling the four cases
// like this and dereferencing next_ as we do (*(next_+n) --- and then
// doing a single pos_+=x at the end) gains about 10% over making a
// loop and dereferencing next_ such as *(next_++)
//
// Using a register for pos_ was not helpful.
//
// Branches are ordered to increase the likelihood of the first being
// taken.
//
// Low-level optimization is useful here because this function will be
// called frequently, leading to outsize benefits.
bool QuicheDataReader::ReadVarInt62(uint64_t* result) {
QUICHE_DCHECK_EQ(endianness(), quiche::NETWORK_BYTE_ORDER);
size_t remaining = BytesRemaining();
const unsigned char* next =
reinterpret_cast<const unsigned char*>(data() + pos());
if (remaining != 0) {
switch (*next & 0xc0) {
case 0xc0:
// Leading 0b11...... is 8 byte encoding
if (remaining >= 8) {
*result = (static_cast<uint64_t>((*(next)) & 0x3f) << 56) +
(static_cast<uint64_t>(*(next + 1)) << 48) +
(static_cast<uint64_t>(*(next + 2)) << 40) +
(static_cast<uint64_t>(*(next + 3)) << 32) +
(static_cast<uint64_t>(*(next + 4)) << 24) +
(static_cast<uint64_t>(*(next + 5)) << 16) +
(static_cast<uint64_t>(*(next + 6)) << 8) +
(static_cast<uint64_t>(*(next + 7)) << 0);
AdvancePos(8);
return true;
}
return false;
case 0x80:
// Leading 0b10...... is 4 byte encoding
if (remaining >= 4) {
*result = (((*(next)) & 0x3f) << 24) + (((*(next + 1)) << 16)) +
(((*(next + 2)) << 8)) + (((*(next + 3)) << 0));
AdvancePos(4);
return true;
}
return false;
case 0x40:
// Leading 0b01...... is 2 byte encoding
if (remaining >= 2) {
*result = (((*(next)) & 0x3f) << 8) + (*(next + 1));
AdvancePos(2);
return true;
}
return false;
case 0x00:
// Leading 0b00...... is 1 byte encoding
*result = (*next) & 0x3f;
AdvancePos(1);
return true;
}
}
return false;
}
bool QuicheDataReader::ReadStringPieceVarInt62(absl::string_view* result) {
uint64_t result_length;
if (!ReadVarInt62(&result_length)) {
return false;
}
return ReadStringPiece(result, result_length);
}
bool QuicheDataReader::ReadStringVarInt62(std::string& result) {
absl::string_view result_view;
bool success = ReadStringPieceVarInt62(&result_view);
result = std::string(result_view);
return success;
}
absl::string_view QuicheDataReader::ReadRemainingPayload() {
absl::string_view payload = PeekRemainingPayload();
pos_ = len_;
return payload;
}
absl::string_view QuicheDataReader::PeekRemainingPayload() const {
return absl::string_view(data_ + pos_, len_ - pos_);
}
absl::string_view QuicheDataReader::FullPayload() const {
return absl::string_view(data_, len_);
}
absl::string_view QuicheDataReader::PreviouslyReadPayload() const {
return absl::string_view(data_, pos_);
}
bool QuicheDataReader::ReadBytes(void* result, size_t size) {
// Make sure that we have enough data to read.
if (!CanRead(size)) {
OnFailure();
return false;
}
// Read into result.
memcpy(result, data_ + pos_, size);
// Iterate.
pos_ += size;
return true;
}
bool QuicheDataReader::Seek(size_t size) {
if (!CanRead(size)) {
OnFailure();
return false;
}
pos_ += size;
return true;
}
bool QuicheDataReader::IsDoneReading() const { return len_ == pos_; }
size_t QuicheDataReader::BytesRemaining() const {
if (pos_ > len_) {
QUICHE_BUG(quiche_reader_pos_out_of_bound)
<< "QUIC reader pos out of bound: " << pos_ << ", len: " << len_;
return 0;
}
return len_ - pos_;
}
bool QuicheDataReader::TruncateRemaining(size_t truncation_length) {
if (truncation_length > BytesRemaining()) {
return false;
}
len_ = pos_ + truncation_length;
return true;
}
bool QuicheDataReader::CanRead(size_t bytes) const {
return bytes <= (len_ - pos_);
}
void QuicheDataReader::OnFailure() {
// Set our iterator to the end of the buffer so that further reads fail
// immediately.
pos_ = len_;
}
uint8_t QuicheDataReader::PeekByte() const {
if (pos_ >= len_) {
QUICHE_LOG(FATAL)
<< "Reading is done, cannot peek next byte. Tried to read pos = "
<< pos_ << " buffer length = " << len_;
return 0;
}
return data_[pos_];
}
std::string QuicheDataReader::DebugString() const {
return absl::StrCat(" { length: ", len_, ", position: ", pos_, " }");
}
#undef ENDPOINT // undef for jumbo builds
} // namespace quiche