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AK: Move the LEB128 logic to AK and make it usable with InputStream
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2 changed files with 88 additions and 51 deletions
85
AK/LEB128.h
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85
AK/LEB128.h
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/*
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* Copyright (c) 2020-2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Stream.h>
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#include <AK/Types.h>
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namespace AK {
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struct LEB128 {
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template<typename StreamT>
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static bool read_unsigned(StreamT& stream, size_t& result)
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{
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[[maybe_unused]] size_t backup_offset = 0;
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if constexpr (requires { stream.offset(); })
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backup_offset = stream.offset();
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InputStream& input_stream { stream };
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result = 0;
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size_t num_bytes = 0;
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while (true) {
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if (input_stream.unreliable_eof()) {
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if constexpr (requires { stream.seek(backup_offset); })
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stream.seek(backup_offset);
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input_stream.set_fatal_error();
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return false;
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}
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u8 byte = 0;
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input_stream >> byte;
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if (input_stream.has_any_error())
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return false;
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result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
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if (!(byte & (1 << 7)))
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break;
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++num_bytes;
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}
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return true;
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}
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template<typename StreamT>
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static bool read_signed(StreamT& stream, ssize_t& result)
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{
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[[maybe_unused]] size_t backup_offset = 0;
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if constexpr (requires { stream.offset(); })
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backup_offset = stream.offset();
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InputStream& input_stream { stream };
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result = 0;
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size_t num_bytes = 0;
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u8 byte = 0;
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do {
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if (input_stream.unreliable_eof()) {
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if constexpr (requires { stream.seek(backup_offset); })
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stream.seek(backup_offset);
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input_stream.set_fatal_error();
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return false;
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}
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input_stream >> byte;
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if (input_stream.has_any_error())
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return false;
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result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
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++num_bytes;
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} while (byte & (1 << 7));
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if (num_bytes * 7 < sizeof(size_t) * 4 && (byte & 0x40)) {
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// sign extend
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result |= ((size_t)(-1) << (num_bytes * 7));
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}
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return true;
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}
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};
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}
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using AK::LEB128;
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