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// 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 "quiche/common/quiche_data_writer.h"
#include <algorithm>
#include <limits>
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "quiche/common/platform/api/quiche_bug_tracker.h"
#include "quiche/common/quiche_endian.h"
namespace quiche {
QuicheDataWriter::QuicheDataWriter(size_t size, char* buffer)
: QuicheDataWriter(size, buffer, quiche::NETWORK_BYTE_ORDER) {}
QuicheDataWriter::QuicheDataWriter(size_t size, char* buffer,
quiche::Endianness endianness)
: buffer_(buffer), capacity_(size), length_(0), endianness_(endianness) {}
QuicheDataWriter::~QuicheDataWriter() {}
char* QuicheDataWriter::data() { return buffer_; }
bool QuicheDataWriter::WriteUInt8(uint8_t value) {
return WriteBytes(&value, sizeof(value));
}
bool QuicheDataWriter::WriteUInt16(uint16_t value) {
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
value = quiche::QuicheEndian::HostToNet16(value);
}
return WriteBytes(&value, sizeof(value));
}
bool QuicheDataWriter::WriteUInt32(uint32_t value) {
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
value = quiche::QuicheEndian::HostToNet32(value);
}
return WriteBytes(&value, sizeof(value));
}
bool QuicheDataWriter::WriteUInt64(uint64_t value) {
if (endianness_ == quiche::NETWORK_BYTE_ORDER) {
value = quiche::QuicheEndian::HostToNet64(value);
}
return WriteBytes(&value, sizeof(value));
}
bool QuicheDataWriter::WriteBytesToUInt64(size_t num_bytes, uint64_t value) {
if (num_bytes > sizeof(value)) {
return false;
}
if (endianness_ == quiche::HOST_BYTE_ORDER) {
return WriteBytes(&value, num_bytes);
}
value = quiche::QuicheEndian::HostToNet64(value);
return WriteBytes(reinterpret_cast<char*>(&value) + sizeof(value) - num_bytes,
num_bytes);
}
bool QuicheDataWriter::WriteStringPiece16(absl::string_view val) {
if (val.size() > std::numeric_limits<uint16_t>::max()) {
return false;
}
if (!WriteUInt16(static_cast<uint16_t>(val.size()))) {
return false;
}
return WriteBytes(val.data(), val.size());
}
bool QuicheDataWriter::WriteStringPiece(absl::string_view val) {
return WriteBytes(val.data(), val.size());
}
char* QuicheDataWriter::BeginWrite(size_t length) {
if (length_ > capacity_) {
return nullptr;
}
if (capacity_ - length_ < length) {
return nullptr;
}
#ifdef ARCH_CPU_64_BITS
QUICHE_DCHECK_LE(length, std::numeric_limits<uint32_t>::max());
#endif
return buffer_ + length_;
}
bool QuicheDataWriter::WriteBytes(const void* data, size_t data_len) {
char* dest = BeginWrite(data_len);
if (!dest) {
return false;
}
std::copy(static_cast<const char*>(data),
static_cast<const char*>(data) + data_len, dest);
length_ += data_len;
return true;
}
bool QuicheDataWriter::WriteRepeatedByte(uint8_t byte, size_t count) {
char* dest = BeginWrite(count);
if (!dest) {
return false;
}
std::fill(dest, dest + count, byte);
length_ += count;
return true;
}
void QuicheDataWriter::WritePadding() {
QUICHE_DCHECK_LE(length_, capacity_);
if (length_ > capacity_) {
return;
}
std::fill(buffer_ + length_, buffer_ + capacity_, 0x00);
length_ = capacity_;
}
bool QuicheDataWriter::WritePaddingBytes(size_t count) {
return WriteRepeatedByte(0x00, count);
}
bool QuicheDataWriter::WriteTag(uint32_t tag) {
return WriteBytes(&tag, sizeof(tag));
}
// Converts a uint64_t into a 62-bit RFC 9000 Variable Length Integer.
//
// Performance notes
//
// Measurements and experiments showed that unrolling the four cases
// like this and dereferencing next_ as we do (*(next_+n)) gains about
// 10% over making a loop and dereferencing it as *(next_++)
//
// Using a register for next didn't help.
//
// 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 QuicheDataWriter::WriteVarInt62(uint64_t value) {
QUICHE_DCHECK_EQ(endianness(), quiche::NETWORK_BYTE_ORDER);
size_t remaining_bytes = remaining();
char* next = buffer() + length();
if ((value & kVarInt62ErrorMask) == 0) {
// We know the high 2 bits are 0 so |value| is legal.
// We can do the encoding.
if ((value & kVarInt62Mask8Bytes) != 0) {
// Someplace in the high-4 bytes is a 1-bit. Do an 8-byte
// encoding.
if (remaining_bytes >= 8) {
*(next + 0) = ((value >> 56) & 0x3f) + 0xc0;
*(next + 1) = (value >> 48) & 0xff;
*(next + 2) = (value >> 40) & 0xff;
*(next + 3) = (value >> 32) & 0xff;
*(next + 4) = (value >> 24) & 0xff;
*(next + 5) = (value >> 16) & 0xff;
*(next + 6) = (value >> 8) & 0xff;
*(next + 7) = value & 0xff;
IncreaseLength(8);
return true;
}
return false;
}
// The high-order-4 bytes are all 0, check for a 1, 2, or 4-byte
// encoding
if ((value & kVarInt62Mask4Bytes) != 0) {
// The encoding will not fit into 2 bytes, Do a 4-byte
// encoding.
if (remaining_bytes >= 4) {
*(next + 0) = ((value >> 24) & 0x3f) + 0x80;
*(next + 1) = (value >> 16) & 0xff;
*(next + 2) = (value >> 8) & 0xff;
*(next + 3) = value & 0xff;
IncreaseLength(4);
return true;
}
return false;
}
// The high-order bits are all 0. Check to see if the number
// can be encoded as one or two bytes. One byte encoding has
// only 6 significant bits (bits 0xffffffff ffffffc0 are all 0).
// Two byte encoding has more than 6, but 14 or less significant
// bits (bits 0xffffffff ffffc000 are 0 and 0x00000000 00003fc0
// are not 0)
if ((value & kVarInt62Mask2Bytes) != 0) {
// Do 2-byte encoding
if (remaining_bytes >= 2) {
*(next + 0) = ((value >> 8) & 0x3f) + 0x40;
*(next + 1) = (value)&0xff;
IncreaseLength(2);
return true;
}
return false;
}
if (remaining_bytes >= 1) {
// Do 1-byte encoding
*next = (value & 0x3f);
IncreaseLength(1);
return true;
}
return false;
}
// Can not encode, high 2 bits not 0
return false;
}
bool QuicheDataWriter::WriteStringPieceVarInt62(
const absl::string_view& string_piece) {
if (!WriteVarInt62(string_piece.size())) {
return false;
}
if (!string_piece.empty()) {
if (!WriteBytes(string_piece.data(), string_piece.size())) {
return false;
}
}
return true;
}
// static
QuicheVariableLengthIntegerLength QuicheDataWriter::GetVarInt62Len(
uint64_t value) {
if ((value & kVarInt62ErrorMask) != 0) {
QUICHE_BUG(invalid_varint) << "Attempted to encode a value, " << value
<< ", that is too big for VarInt62";
return VARIABLE_LENGTH_INTEGER_LENGTH_0;
}
if ((value & kVarInt62Mask8Bytes) != 0) {
return VARIABLE_LENGTH_INTEGER_LENGTH_8;
}
if ((value & kVarInt62Mask4Bytes) != 0) {
return VARIABLE_LENGTH_INTEGER_LENGTH_4;
}
if ((value & kVarInt62Mask2Bytes) != 0) {
return VARIABLE_LENGTH_INTEGER_LENGTH_2;
}
return VARIABLE_LENGTH_INTEGER_LENGTH_1;
}
bool QuicheDataWriter::WriteVarInt62WithForcedLength(
uint64_t value, QuicheVariableLengthIntegerLength write_length) {
QUICHE_DCHECK_EQ(endianness(), NETWORK_BYTE_ORDER);
size_t remaining_bytes = remaining();
if (remaining_bytes < write_length) {
return false;
}
const QuicheVariableLengthIntegerLength min_length = GetVarInt62Len(value);
if (write_length < min_length) {
QUICHE_BUG(invalid_varint_forced) << "Cannot write value " << value
<< " with write_length " << write_length;
return false;
}
if (write_length == min_length) {
return WriteVarInt62(value);
}
if (write_length == VARIABLE_LENGTH_INTEGER_LENGTH_2) {
return WriteUInt8(0b01000000) && WriteUInt8(value);
}
if (write_length == VARIABLE_LENGTH_INTEGER_LENGTH_4) {
return WriteUInt8(0b10000000) && WriteUInt8(0) && WriteUInt16(value);
}
if (write_length == VARIABLE_LENGTH_INTEGER_LENGTH_8) {
return WriteUInt8(0b11000000) && WriteUInt8(0) && WriteUInt16(0) &&
WriteUInt32(value);
}
QUICHE_BUG(invalid_write_length)
<< "Invalid write_length " << static_cast<int>(write_length);
return false;
}
bool QuicheDataWriter::Seek(size_t length) {
if (!BeginWrite(length)) {
return false;
}
length_ += length;
return true;
}
std::string QuicheDataWriter::DebugString() const {
return absl::StrCat(" { capacity: ", capacity_, ", length: ", length_, " }");
}
} // namespace quiche