/* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause *//* * Copyright (c) Meta Platforms, Inc. and affiliates. * All rights reserved. * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses. */ #ifndef ZSTD_BITS_H#define ZSTD_BITS_H #include "mem.h" MEM_STATIC unsigned ZSTD_countTrailingZeros32_fallback(U32 val){    assert(val != 0);    {        static const U32 DeBruijnBytePos[32] = {0, 1, 28, 2, 29, 14, 24, 3,                                                30, 22, 20, 15, 25, 17, 4, 8,                                                31, 27, 13, 23, 21, 19, 16, 7,                                                26, 12, 18, 6, 11, 5, 10, 9};        return DeBruijnBytePos[((U32) ((val & -(S32) val) * 0x077CB531U)) >> 27];    }} MEM_STATIC unsigned ZSTD_countTrailingZeros32(U32 val){    assert(val != 0);#if (__GNUC__ >= 4)    return (unsigned)__builtin_ctz(val);#else    return ZSTD_countTrailingZeros32_fallback(val);#endif} MEM_STATIC unsigned ZSTD_countLeadingZeros32_fallback(U32 val){    assert(val != 0);    {        static const U32 DeBruijnClz[32] = {0, 9, 1, 10, 13, 21, 2, 29,                                            11, 14, 16, 18, 22, 25, 3, 30,                                            8, 12, 20, 28, 15, 17, 24, 7,                                            19, 27, 23, 6, 26, 5, 4, 31};        val |= val >> 1;        val |= val >> 2;        val |= val >> 4;        val |= val >> 8;        val |= val >> 16;        return 31 - DeBruijnClz[(val * 0x07C4ACDDU) >> 27];    }} MEM_STATIC unsigned ZSTD_countLeadingZeros32(U32 val){    assert(val != 0);#if (__GNUC__ >= 4)    return (unsigned)__builtin_clz(val);#else    return ZSTD_countLeadingZeros32_fallback(val);#endif} MEM_STATIC unsigned ZSTD_countTrailingZeros64(U64 val){    assert(val != 0);#if (__GNUC__ >= 4) && defined(__LP64__)    return (unsigned)__builtin_ctzll(val);#else    {        U32 mostSignificantWord = (U32)(val >> 32);        U32 leastSignificantWord = (U32)val;        if (leastSignificantWord == 0) {            return 32 + ZSTD_countTrailingZeros32(mostSignificantWord);        } else {            return ZSTD_countTrailingZeros32(leastSignificantWord);        }    }#endif} MEM_STATIC unsigned ZSTD_countLeadingZeros64(U64 val){    assert(val != 0);#if (__GNUC__ >= 4)    return (unsigned)(__builtin_clzll(val));#else    {        U32 mostSignificantWord = (U32)(val >> 32);        U32 leastSignificantWord = (U32)val;        if (mostSignificantWord == 0) {            return 32 + ZSTD_countLeadingZeros32(leastSignificantWord);        } else {            return ZSTD_countLeadingZeros32(mostSignificantWord);        }    }#endif} MEM_STATIC unsigned ZSTD_NbCommonBytes(size_t val){    if (MEM_isLittleEndian()) {        if (MEM_64bits()) {            return ZSTD_countTrailingZeros64((U64)val) >> 3;        } else {            return ZSTD_countTrailingZeros32((U32)val) >> 3;        }    } else {  /* Big Endian CPU */        if (MEM_64bits()) {            return ZSTD_countLeadingZeros64((U64)val) >> 3;        } else {            return ZSTD_countLeadingZeros32((U32)val) >> 3;        }    }} MEM_STATIC unsigned ZSTD_highbit32(U32 val)   /* compress, dictBuilder, decodeCorpus */{    assert(val != 0);    return 31 - ZSTD_countLeadingZeros32(val);} /* ZSTD_rotateRight_*(): * Rotates a bitfield to the right by "count" bits. * https://en.wikipedia.org/w/index.php?title=Circular_shift&oldid=991635599#Implementing_circular_shifts */MEM_STATICU64 ZSTD_rotateRight_U64(U64 const value, U32 count) {    assert(count < 64);    count &= 0x3F; /* for fickle pattern recognition */    return (value >> count) | (U64)(value << ((0U - count) & 0x3F));} MEM_STATICU32 ZSTD_rotateRight_U32(U32 const value, U32 count) {    assert(count < 32);    count &= 0x1F; /* for fickle pattern recognition */    return (value >> count) | (U32)(value << ((0U - count) & 0x1F));} MEM_STATICU16 ZSTD_rotateRight_U16(U16 const value, U32 count) {    assert(count < 16);    count &= 0x0F; /* for fickle pattern recognition */    return (value >> count) | (U16)(value << ((0U - count) & 0x0F));} #endif /* ZSTD_BITS_H */