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https://github.com/darlinghq/darling-WTF.git
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108 lines
3.9 KiB
C++
108 lines
3.9 KiB
C++
/*
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* Copyright (C) 2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "Compiler.h"
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#include <algorithm>
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// This file contains a bunch of helper functions for decoding LEB numbers.
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// See https://en.wikipedia.org/wiki/LEB128 for more information about the
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// LEB format.
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namespace WTF { namespace LEBDecoder {
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template<typename T>
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inline bool WARN_UNUSED_RETURN decodeUInt(const uint8_t* bytes, size_t length, size_t& offset, T& result)
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{
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const size_t numBits = sizeof(T) * CHAR_BIT;
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const size_t maxByteLength = (numBits - 1) / 7 + 1; // numBits / 7 rounding up.
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if (length <= offset)
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return false;
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result = 0;
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unsigned shift = 0;
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size_t last = std::min(maxByteLength, length - offset) - 1;
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for (unsigned i = 0; true; ++i) {
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uint8_t byte = bytes[offset++];
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result |= static_cast<T>(byte & 0x7f) << shift;
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shift += 7;
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if (!(byte & 0x80))
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return true;
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if (i == last)
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return false;
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}
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RELEASE_ASSERT_NOT_REACHED();
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return true;
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}
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template<typename T>
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inline bool WARN_UNUSED_RETURN decodeInt(const uint8_t* bytes, size_t length, size_t& offset, T& result)
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{
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const size_t numBits = sizeof(T) * CHAR_BIT;
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const size_t maxByteLength = (numBits - 1) / 7 + 1; // numBits / 7 rounding up.
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if (length <= offset)
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return false;
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result = 0;
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unsigned shift = 0;
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size_t last = std::min(maxByteLength, length - offset) - 1;
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uint8_t byte;
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for (unsigned i = 0; true; ++i) {
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byte = bytes[offset++];
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result |= static_cast<T>(byte & 0x7f) << shift;
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shift += 7;
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if (!(byte & 0x80))
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break;
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if (i == last)
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return false;
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}
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using UnsignedT = typename std::make_unsigned<T>::type;
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if (shift < numBits && (byte & 0x40))
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result = static_cast<T>(static_cast<UnsignedT>(result) | (static_cast<UnsignedT>(-1) << shift));
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return true;
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}
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inline bool WARN_UNUSED_RETURN decodeUInt32(const uint8_t* bytes, size_t length, size_t& offset, uint32_t& result)
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{
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return decodeUInt<uint32_t>(bytes, length, offset, result);
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}
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inline bool WARN_UNUSED_RETURN decodeUInt64(const uint8_t* bytes, size_t length, size_t& offset, uint64_t& result)
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{
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return decodeUInt<uint64_t>(bytes, length, offset, result);
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}
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inline bool WARN_UNUSED_RETURN decodeInt32(const uint8_t* bytes, size_t length, size_t& offset, int32_t& result)
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{
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return decodeInt<int32_t>(bytes, length, offset, result);
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}
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inline bool WARN_UNUSED_RETURN decodeInt64(const uint8_t* bytes, size_t length, size_t& offset, int64_t& result)
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{
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return decodeInt<int64_t>(bytes, length, offset, result);
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}
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} } // WTF::LEBDecoder
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