| // 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 |