| // Copyright 2017 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 "components/zucchini/buffer_source.h" |
| |
| #include <algorithm> |
| |
| #include "components/zucchini/algorithm.h" |
| |
| namespace zucchini { |
| |
| BufferSource::BufferSource(ConstBufferView buffer) : ConstBufferView(buffer) {} |
| |
| BufferSource& BufferSource::Skip(size_type n) { |
| remove_prefix(std::min(n, Remaining())); |
| return *this; |
| } |
| |
| bool BufferSource::CheckNextBytes(std::initializer_list<uint8_t> bytes) const { |
| if (Remaining() < bytes.size()) |
| return false; |
| return std::mismatch(bytes.begin(), bytes.end(), begin()).first == |
| bytes.end(); |
| } |
| |
| bool BufferSource::ConsumeBytes(std::initializer_list<uint8_t> bytes) { |
| if (!CheckNextBytes(bytes)) |
| return false; |
| remove_prefix(bytes.size()); |
| return true; |
| } |
| |
| bool BufferSource::GetRegion(size_type count, ConstBufferView* buffer) { |
| DCHECK_NE(begin(), nullptr); |
| if (Remaining() < count) |
| return false; |
| *buffer = ConstBufferView(begin(), count); |
| remove_prefix(count); |
| return true; |
| } |
| |
| // [0aaaaaaa] => 00000000'00000000'00000000'0aaaaaaa |
| // [1aaaaaaa 0bbbbbbb] => 00000000'00000000'00bbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 0ccccccc] => 00000000'000ccccc'ccbbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 1ccccccc 0ddddddd] => 0000dddd'dddccccc'ccbbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 1ccccccc 1ddddddd 0???eeee] |
| // => eeeedddd'dddccccc'ccbbbbbb'baaaaaaa |
| // Note that "???" is discarded. Meanwhile, 1???eeee is invalid. |
| bool BufferSource::GetUleb128(uint32_t* ret) { |
| int shift_lim = |
| static_cast<int>(std::min<size_type>(kMaxLeb128Size, size())) * 7; |
| const_iterator cur = cbegin(); |
| uint32_t value = 0U; |
| for (int shift = 0; shift < shift_lim; shift += 7, ++cur) { |
| uint32_t b = *cur; |
| // When |shift == 28|, |(b & 0x7F) << shift| discards the "???" bits. |
| value |= static_cast<uint32_t>(b & 0x7F) << shift; |
| if (!(b & 0x80)) { |
| *ret = value; |
| seek(cur + 1); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| // [0Saaaaaa] => SSSSSSSS'SSSSSSSS'SSSSSSSS'SSaaaaaa |
| // [1aaaaaaa 0Sbbbbbb] => SSSSSSSS'SSSSSSSS'SSSbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 0Scccccc] => SSSSSSSS'SSSScccc'ccbbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 1ccccccc 0Sdddddd] => SSSSSddd'dddccccc'ccbbbbbb'baaaaaaa |
| // [1aaaaaaa 1bbbbbbb 1ccccccc 1ddddddd 0???Seee] |
| // => Seeedddd'dddccccc'ccbbbbbb'baaaaaaa |
| // Note that "???" is discarded. Meanwhile, 1???eeee is invalid. |
| bool BufferSource::GetSleb128(int32_t* ret) { |
| int shift_lim = |
| static_cast<int>(std::min<size_type>(kMaxLeb128Size, size())) * 7; |
| const_iterator cur = cbegin(); |
| int32_t value = 0; |
| for (int shift = 0; shift < shift_lim; shift += 7, ++cur) { |
| uint32_t b = *cur; |
| // When |shift == 28|, |(b & 0x7F) << shift| discards the "???" bits. |
| value |= static_cast<int32_t>(static_cast<uint32_t>(b & 0x7F) << shift); |
| if (!(b & 0x80)) { |
| *ret = (shift == 28) ? value : SignExtend(shift + 6, value); |
| seek(cur + 1); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| bool BufferSource::SkipLeb128() { |
| int lim = static_cast<int>(std::min<size_type>(kMaxLeb128Size, size())); |
| const_iterator cur = cbegin(); |
| for (int i = 0; i < lim; ++i, ++cur) { |
| if (!(*cur & 0x80)) { |
| seek(cur + 1); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| } // namespace zucchini |