/src/libjxl/lib/jxl/pack_signed.h
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1 | | // Copyright (c) the JPEG XL Project Authors. All rights reserved. |
2 | | // |
3 | | // Use of this source code is governed by a BSD-style |
4 | | // license that can be found in the LICENSE file. |
5 | | |
6 | | #ifndef LIB_JXL_PACK_H_ |
7 | | #define LIB_JXL_PACK_H_ |
8 | | |
9 | | // Pack/UnpackSigned utilities. |
10 | | |
11 | | #include <cstddef> |
12 | | #include <cstdint> |
13 | | |
14 | | #include "lib/jxl/base/compiler_specific.h" |
15 | | |
16 | | namespace jxl { |
17 | | // Encodes non-negative (X) into (2 * X), negative (-X) into (2 * X - 1) |
18 | | constexpr uint32_t PackSigned(int32_t value) |
19 | 4.55M | JXL_NO_SANITIZE("unsigned-integer-overflow") { |
20 | 4.55M | return (static_cast<uint32_t>(value) << 1) ^ |
21 | 4.55M | ((static_cast<uint32_t>(~value) >> 31) - 1); |
22 | 4.55M | } |
23 | | |
24 | | // Reverse to PackSigned, i.e. UnpackSigned(PackSigned(X)) == X. |
25 | | // (((~value) & 1) - 1) is either 0 or 0xFF...FF and it will have an expected |
26 | | // unsigned-integer-overflow. |
27 | | constexpr intptr_t UnpackSigned(size_t value) |
28 | 720M | JXL_NO_SANITIZE("unsigned-integer-overflow") { |
29 | 720M | return static_cast<intptr_t>((value >> 1) ^ (((~value) & 1) - 1)); |
30 | 720M | } |
31 | | |
32 | | } // namespace jxl |
33 | | |
34 | | #endif // LIB_JXL_PACK_H_ |