34 lines
1,020 B
C++
34 lines
1,020 B
C++
// Copyright (c) the JPEG XL Project Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#ifndef LIB_JXL_PACK_H_
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#define LIB_JXL_PACK_H_
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// Pack/UnpackSigned utilities.
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#include <cstddef>
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#include <cstdint>
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#include "lib/jxl/base/compiler_specific.h"
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namespace jxl {
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// Encodes non-negative (X) into (2 * X), negative (-X) into (2 * X - 1)
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constexpr uint32_t PackSigned(int32_t value)
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JXL_NO_SANITIZE("unsigned-integer-overflow") {
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return (static_cast<uint32_t>(value) << 1) ^
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((static_cast<uint32_t>(~value) >> 31) - 1);
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}
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// Reverse to PackSigned, i.e. UnpackSigned(PackSigned(X)) == X.
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// (((~value) & 1) - 1) is either 0 or 0xFF...FF and it will have an expected
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// unsigned-integer-overflow.
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constexpr intptr_t UnpackSigned(size_t value)
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JXL_NO_SANITIZE("unsigned-integer-overflow") {
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return static_cast<intptr_t>((value >> 1) ^ (((~value) & 1) - 1));
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}
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} // namespace jxl
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#endif // LIB_JXL_PACK_H_
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