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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 09:22:09 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 09:22:09 +0000 |
commit | 43a97878ce14b72f0981164f87f2e35e14151312 (patch) | |
tree | 620249daf56c0258faa40cbdcf9cfba06de2a846 /toolkit/components/url-classifier/RiceDeltaDecoder.cpp | |
parent | Initial commit. (diff) | |
download | firefox-43a97878ce14b72f0981164f87f2e35e14151312.tar.xz firefox-43a97878ce14b72f0981164f87f2e35e14151312.zip |
Adding upstream version 110.0.1.upstream/110.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'toolkit/components/url-classifier/RiceDeltaDecoder.cpp')
-rw-r--r-- | toolkit/components/url-classifier/RiceDeltaDecoder.cpp | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/toolkit/components/url-classifier/RiceDeltaDecoder.cpp b/toolkit/components/url-classifier/RiceDeltaDecoder.cpp new file mode 100644 index 0000000000..acef610f49 --- /dev/null +++ b/toolkit/components/url-classifier/RiceDeltaDecoder.cpp @@ -0,0 +1,220 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "RiceDeltaDecoder.h" + +namespace { + +//////////////////////////////////////////////////////////////////////// +// BitBuffer is copied and modified from webrtc/base/bitbuffer.h +// + +/* + * Copyright 2015 The WebRTC Project Authors. All rights reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree (webrtc/base/bitbuffer.h/cc). An additional intellectual property + * rights grant can be found in the file PATENTS. All contributing + * project authors may be found in the AUTHORS file in the root of + * the source tree. + */ + +class BitBuffer { + public: + BitBuffer(const uint8_t* bytes, size_t byte_count); + + // The remaining bits in the byte buffer. + uint64_t RemainingBitCount() const; + + // Reads bit-sized values from the buffer. Returns false if there isn't enough + // data left for the specified bit count.. + bool ReadBits(uint32_t* val, size_t bit_count); + + // Peeks bit-sized values from the buffer. Returns false if there isn't enough + // data left for the specified number of bits. Doesn't move the current + // offset. + bool PeekBits(uint32_t* val, size_t bit_count); + + // Reads the exponential golomb encoded value at the current offset. + // Exponential golomb values are encoded as: + // 1) x = source val + 1 + // 2) In binary, write [countbits(x) - 1] 1s, then x + // To decode, we count the number of leading 1 bits, read that many + 1 bits, + // and increment the result by 1. + // Returns false if there isn't enough data left for the specified type, or if + // the value wouldn't fit in a uint32_t. + bool ReadExponentialGolomb(uint32_t* val); + + // Moves current position |bit_count| bits forward. Returns false if + // there aren't enough bits left in the buffer. + bool ConsumeBits(size_t bit_count); + + protected: + const uint8_t* const bytes_; + // The total size of |bytes_|. + size_t byte_count_; + // The current offset, in bytes, from the start of |bytes_|. + size_t byte_offset_; + // The current offset, in bits, into the current byte. + size_t bit_offset_; +}; + +} // end of unnamed namespace + +static void ReverseByte(uint8_t& b) { + b = (b & 0xF0) >> 4 | (b & 0x0F) << 4; + b = (b & 0xCC) >> 2 | (b & 0x33) << 2; + b = (b & 0xAA) >> 1 | (b & 0x55) << 1; +} + +namespace mozilla { +namespace safebrowsing { + +RiceDeltaDecoder::RiceDeltaDecoder(uint8_t* aEncodedData, + size_t aEncodedDataSize) + : mEncodedData(aEncodedData), mEncodedDataSize(aEncodedDataSize) {} + +bool RiceDeltaDecoder::Decode(uint32_t aRiceParameter, uint32_t aFirstValue, + uint32_t aNumEntries, uint32_t* aDecodedData) { + // Reverse each byte before reading bits from the byte buffer. + for (size_t i = 0; i < mEncodedDataSize; i++) { + ReverseByte(mEncodedData[i]); + } + + BitBuffer bitBuffer(mEncodedData, mEncodedDataSize); + + // q = quotient + // r = remainder + // k = RICE parameter + const uint32_t k = aRiceParameter; + aDecodedData[0] = aFirstValue; + for (uint32_t i = 0; i < aNumEntries; i++) { + // Read the quotient of N. + uint32_t q; + if (!bitBuffer.ReadExponentialGolomb(&q)) { + LOG(("Encoded data underflow!")); + return false; + } + + // Read the remainder of N, one bit at a time. + uint32_t r = 0; + for (uint32_t j = 0; j < k; j++) { + uint32_t b = 0; + if (!bitBuffer.ReadBits(&b, 1)) { + // Insufficient bits. Just leave them as zeros. + break; + } + // Add the bit to the right position so that it's in Little Endian order. + r |= b << j; + } + + // Caculate N from q,r,k. + uint32_t N = (q << k) + r; + + // We start filling aDecodedData from [1]. + aDecodedData[i + 1] = N + aDecodedData[i]; + } + + return true; +} + +} // namespace safebrowsing +} // namespace mozilla + +namespace { +////////////////////////////////////////////////////////////////////////// +// The BitBuffer impl is copied and modified from webrtc/base/bitbuffer.cc +// + +// Returns the lowest (right-most) |bit_count| bits in |byte|. +uint8_t LowestBits(uint8_t byte, size_t bit_count) { + return byte & ((1 << bit_count) - 1); +} + +// Returns the highest (left-most) |bit_count| bits in |byte|, shifted to the +// lowest bits (to the right). +uint8_t HighestBits(uint8_t byte, size_t bit_count) { + MOZ_ASSERT(bit_count < 8u); + uint8_t shift = 8 - static_cast<uint8_t>(bit_count); + uint8_t mask = 0xFF << shift; + return (byte & mask) >> shift; +} + +BitBuffer::BitBuffer(const uint8_t* bytes, size_t byte_count) + : bytes_(bytes), byte_count_(byte_count), byte_offset_(), bit_offset_() { + MOZ_ASSERT(static_cast<uint64_t>(byte_count_) <= + std::numeric_limits<uint32_t>::max()); +} + +uint64_t BitBuffer::RemainingBitCount() const { + return (static_cast<uint64_t>(byte_count_) - byte_offset_) * 8 - bit_offset_; +} + +bool BitBuffer::PeekBits(uint32_t* val, size_t bit_count) { + if (!val || bit_count > RemainingBitCount() || bit_count > 32) { + return false; + } + const uint8_t* bytes = bytes_ + byte_offset_; + size_t remaining_bits_in_current_byte = 8 - bit_offset_; + uint32_t bits = LowestBits(*bytes++, remaining_bits_in_current_byte); + // If we're reading fewer bits than what's left in the current byte, just + // return the portion of this byte that we need. + if (bit_count < remaining_bits_in_current_byte) { + *val = HighestBits(bits, bit_offset_ + bit_count); + return true; + } + // Otherwise, subtract what we've read from the bit count and read as many + // full bytes as we can into bits. + bit_count -= remaining_bits_in_current_byte; + while (bit_count >= 8) { + bits = (bits << 8) | *bytes++; + bit_count -= 8; + } + // Whatever we have left is smaller than a byte, so grab just the bits we need + // and shift them into the lowest bits. + if (bit_count > 0) { + bits <<= bit_count; + bits |= HighestBits(*bytes, bit_count); + } + *val = bits; + return true; +} + +bool BitBuffer::ReadBits(uint32_t* val, size_t bit_count) { + return PeekBits(val, bit_count) && ConsumeBits(bit_count); +} + +bool BitBuffer::ConsumeBits(size_t bit_count) { + if (bit_count > RemainingBitCount()) { + return false; + } + + byte_offset_ += (bit_offset_ + bit_count) / 8; + bit_offset_ = (bit_offset_ + bit_count) % 8; + return true; +} + +bool BitBuffer::ReadExponentialGolomb(uint32_t* val) { + if (!val) { + return false; + } + + *val = 0; + + // Count the number of leading 0 bits by peeking/consuming them one at a time. + size_t one_bit_count = 0; + uint32_t peeked_bit; + while (PeekBits(&peeked_bit, 1) && peeked_bit == 1) { + one_bit_count++; + ConsumeBits(1); + } + if (!ConsumeBits(1)) { + return false; // The stream is incorrectly terminated at '1'. + } + + *val = one_bit_count; + return true; +} +} // namespace |