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Diffstat (limited to 'src/bit.h')
| -rw-r--r-- | src/bit.h | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/src/bit.h b/src/bit.h new file mode 100644 index 0000000..efd7d27 --- /dev/null +++ b/src/bit.h @@ -0,0 +1,355 @@ +// Copyright © Tavian Barnes <tavianator@tavianator.com> +// SPDX-License-Identifier: 0BSD + +/** + * Bits & bytes. + */ + +#ifndef BFS_BIT_H +#define BFS_BIT_H + +#include "config.h" +#include <limits.h> +#include <stdint.h> + +#if __STDC_VERSION__ >= 202311L +# include <stdbit.h> +#endif + +// C23 polyfill: _WIDTH macros + +// The U*_MAX macros are of the form 2**n - 1, and we want to extract the n. +// One way would be *_WIDTH = popcount(*_MAX). Alternatively, we can use +// Hallvard B. Furuseth's technique from [1], which is shorter. +// +// [1]: https://groups.google.com/g/comp.lang.c/c/NfedEFBFJ0k + +// Let mask be of the form 2**m - 1, e.g. 0b111, and let n range over +// [0b0, 0b1, 0b11, 0b111, 0b1111, ...]. Then we have +// +// n % 0b111 +// == [0b0, 0b1, 0b11, 0b0, 0b1, 0b11, ...] +// n / (n % 0b111 + 1) +// == [0b0 (x3), 0b111 (x3), 0b111111 (x3), ...] +// n / (n % 0b111 + 1) / 0b111 +// == [0b0 (x3), 0b1 (x3), 0b1001 (x3), 0b1001001 (x3), ...] +// n / (n % 0b111 + 1) / 0b111 % 0b111 +// == [0 (x3), 1 (x3), 2 (x3), ...] +// == UMAX_CHUNK(n, 0b111) +#define UMAX_CHUNK(n, mask) (n / (n % mask + 1) / mask % mask) + +// 8 * UMAX_CHUNK(n, 255) gives [0 (x8), 8 (x8), 16 (x8), ...]. To that we add +// [0, 1, 2, ..., 6, 7, 0, 1, ...], which we get from a linear interpolation on +// n % 255: +// +// n % 255 +// == [0, 1, 3, 7, 15, 31, 63, 127, 0, ...] +// 86 / (n % 255 + 12) +// == [7, 6, 5, 4, 3, 2, 1, 0, 7, ...] +#define UMAX_INTERP(n) (7 - 86 / (n % 255 + 12)) + +#define UMAX_WIDTH(n) (8 * UMAX_CHUNK(n, 255) + UMAX_INTERP(n)) + +#ifndef CHAR_WIDTH +# define CHAR_WIDTH CHAR_BIT +#endif +#ifndef UCHAR_WIDTH +# define UCHAR_WIDTH CHAR_WIDTH +#endif +#ifndef SCHAR_WIDTH +# define SCHAR_WIDTH CHAR_WIDTH +#endif +#ifndef USHRT_WIDTH +# define USHRT_WIDTH UMAX_WIDTH(USHRT_MAX) +#endif +#ifndef SHRT_WIDTH +# define SHRT_WIDTH USHRT_WIDTH +#endif +#ifndef UINT_WIDTH +# define UINT_WIDTH UMAX_WIDTH(UINT_MAX) +#endif +#ifndef INT_WIDTH +# define INT_WIDTH UINT_WIDTH +#endif +#ifndef ULONG_WIDTH +# define ULONG_WIDTH UMAX_WIDTH(ULONG_MAX) +#endif +#ifndef LONG_WIDTH +# define LONG_WIDTH ULONG_WIDTH +#endif +#ifndef ULLONG_WIDTH +# define ULLONG_WIDTH UMAX_WIDTH(ULLONG_MAX) +#endif +#ifndef LLONG_WIDTH +# define LLONG_WIDTH ULLONG_WIDTH +#endif +#ifndef SIZE_WIDTH +# define SIZE_WIDTH UMAX_WIDTH(SIZE_MAX) +#endif +#ifndef PTRDIFF_WIDTH +# define PTRDIFF_WIDTH (UMAX_WIDTH(PTRDIFF_MAX) + 1) +#endif +#ifndef UINTPTR_WIDTH +# define UINTPTR_WIDTH UMAX_WIDTH(UINTPTR_MAX) +#endif +#ifndef INTPTR_WIDTH +# define INTPTR_WIDTH UINTPTR_WIDTH +#endif +#ifndef UINTMAX_WIDTH +# define UINTMAX_WIDTH UMAX_WIDTH(UINTMAX_MAX) +#endif +#ifndef INTMAX_WIDTH +# define INTMAX_WIDTH UINTMAX_WIDTH +#endif + +// C23 polyfill: byte order + +#ifdef __STDC_ENDIAN_LITTLE__ +# define ENDIAN_LITTLE __STDC_ENDIAN_LITTLE__ +#elif defined(__ORDER_LITTLE_ENDIAN__) +# define ENDIAN_LITTLE __ORDER_LITTLE_ENDIAN__ +#else +# define ENDIAN_LITTLE 1234 +#endif + +#ifdef __STDC_ENDIAN_BIG__ +# define ENDIAN_BIG __STDC_ENDIAN_BIG__ +#elif defined(__ORDER_BIG_ENDIAN__) +# define ENDIAN_BIG __ORDER_BIG_ENDIAN__ +#else +# define ENDIAN_BIG 4321 +#endif + +#ifdef __STDC_ENDIAN_NATIVE__ +# define ENDIAN_NATIVE __STDC_ENDIAN_NATIVE__ +#elif defined(__ORDER_NATIVE_ENDIAN__) +# define ENDIAN_NATIVE __ORDER_NATIVE_ENDIAN__ +#else +# define ENDIAN_NATIVE 0 +#endif + +#if __STDC_VERSION__ >= 202311L +# define bswap16 stdc_memreverse8u16 +# define bswap32 stdc_memreverse8u32 +# define bswap64 stdc_memreverse8u64 +#elif __GNUC__ +# define bswap16 __builtin_bswap16 +# define bswap32 __builtin_bswap32 +# define bswap64 __builtin_bswap64 +#else + +static inline uint16_t bswap16(uint16_t n) { + return (n << 8) | (n >> 8); +} + +static inline uint32_t bswap32(uint32_t n) { + return ((uint32_t)bswap16(n) << 16) | bswap16(n >> 16); +} + +static inline uint64_t bswap64(uint64_t n) { + return ((uint64_t)bswap32(n) << 32) | bswap32(n >> 32); +} + +#endif + +static inline uint8_t bswap8(uint8_t n) { + return n; +} + +/** + * Reverse the byte order of an integer. + */ +#define bswap(n) \ + _Generic((n), \ + uint8_t: bswap8, \ + uint16_t: bswap16, \ + uint32_t: bswap32, \ + uint64_t: bswap64)(n) + +// Define an overload for each unsigned type +#define UINT_OVERLOADS(macro) \ + macro(unsigned char, _uc, UCHAR_WIDTH) \ + macro(unsigned short, _us, USHRT_WIDTH) \ + macro(unsigned int, _ui, UINT_WIDTH) \ + macro(unsigned long, _ul, ULONG_WIDTH) \ + macro(unsigned long long, _ull, ULLONG_WIDTH) + +// Select an overload based on an unsigned integer type +#define UINT_SELECT(n, name) \ + _Generic((n), \ + char: name##_uc, \ + signed char: name##_uc, \ + unsigned char: name##_uc, \ + signed short: name##_us, \ + unsigned short: name##_us, \ + signed int: name##_ui, \ + unsigned int: name##_ui, \ + signed long: name##_ul, \ + unsigned long: name##_ul, \ + signed long long: name##_ull, \ + unsigned long long: name##_ull) + +// C23 polyfill: bit utilities + +#if __STDC_VERSION__ >= 202311L +# define count_ones stdc_count_ones +# define count_zeros stdc_count_zeros +# define rotate_left stdc_rotate_left +# define rotate_right stdc_rotate_right +# define leading_zeros stdc_leading_zeros +# define leading_ones stdc_leading_ones +# define trailing_zeros stdc_trailing_zeros +# define trailing_ones stdc_trailing_ones +# define first_leading_zero stdc_first_leading_zero +# define first_leading_one stdc_first_leading_one +# define first_trailing_zero stdc_first_trailing_zero +# define first_trailing_one stdc_first_trailing_one +# define has_single_bit stdc_has_single_bit +# define bit_width stdc_bit_width +# define bit_ceil stdc_bit_ceil +# define bit_floor stdc_bit_floor +#else + +#if __GNUC__ + +// GCC provides builtins for unsigned {int,long,long long}, so promote char/short +#define UINT_BUILTIN_uc(name) __builtin_##name +#define UINT_BUILTIN_us(name) __builtin_##name +#define UINT_BUILTIN_ui(name) __builtin_##name +#define UINT_BUILTIN_ul(name) __builtin_##name##l +#define UINT_BUILTIN_ull(name) __builtin_##name##ll +#define UINT_BUILTIN(name, suffix) UINT_BUILTIN##suffix(name) + +#define BUILTIN_WIDTH_uc UINT_WIDTH +#define BUILTIN_WIDTH_us UINT_WIDTH +#define BUILTIN_WIDTH_ui UINT_WIDTH +#define BUILTIN_WIDTH_ul ULONG_WIDTH +#define BUILTIN_WIDTH_ull ULLONG_WIDTH +#define BUILTIN_WIDTH(suffix) BUILTIN_WIDTH##suffix + +#define COUNT_ONES(type, suffix, width) \ + static inline int count_ones##suffix(type n) { \ + return UINT_BUILTIN(popcount, suffix)(n); \ + } + +#define LEADING_ZEROS(type, suffix, width) \ + static inline int leading_zeros##suffix(type n) { \ + return n \ + ? UINT_BUILTIN(clz, suffix)(n) - (BUILTIN_WIDTH(suffix) - width) \ + : width; \ + } + +#define TRAILING_ZEROS(type, suffix, width) \ + static inline int trailing_zeros##suffix(type n) { \ + return n ? UINT_BUILTIN(ctz, suffix)(n) : width; \ + } + +#define FIRST_TRAILING_ONE(type, suffix, width) \ + static inline int first_trailing_one##suffix(type n) { \ + return UINT_BUILTIN(ffs, suffix)(n); \ + } + +#else // !__GNUC__ + +#define COUNT_ONES(type, suffix, width) \ + static inline int count_ones##suffix(type n) { \ + int ret; \ + for (ret = 0; n; ++ret) { \ + n &= n - 1; \ + } \ + return ret; \ + } + +#define LEADING_ZEROS(type, suffix, width) \ + static inline int leading_zeros##suffix(type n) { \ + type bit = (type)1 << (width - 1); \ + int ret; \ + for (ret = 0; bit && !(n & bit); ++ret, bit >>= 1); \ + return ret; \ + } + +#define TRAILING_ZEROS(type, suffix, width) \ + static inline int trailing_zeros##suffix(type n) { \ + type bit = 1; \ + int ret; \ + for (ret = 0; bit && !(n & bit); ++ret, bit <<= 1); \ + return ret; \ + } + +#define FIRST_TRAILING_ONE(type, suffix, width) \ + static inline int first_trailing_one##suffix(type n) { \ + return n ? trailing_zeros##suffix(n) + 1 : 0; \ + } + +#endif // !__GNUC__ + +UINT_OVERLOADS(COUNT_ONES) +UINT_OVERLOADS(LEADING_ZEROS) +UINT_OVERLOADS(TRAILING_ZEROS) +UINT_OVERLOADS(FIRST_TRAILING_ONE) + +#define ROTATE_LEFT(type, suffix, width) \ + static inline type rotate_left##suffix(type n, int c) { \ + return (n << c) | (n >> ((width - c) % width)); \ + } + +#define ROTATE_RIGHT(type, suffix, width) \ + static inline type rotate_right##suffix(type n, int c) { \ + return (n >> c) | (n << ((width - c) % width)); \ + } + +#define FIRST_LEADING_ONE(type, suffix, width) \ + static inline int first_leading_one##suffix(type n) { \ + return width - leading_zeros##suffix(n); \ + } + +#define HAS_SINGLE_BIT(type, suffix, width) \ + static inline bool has_single_bit##suffix(type n) { \ + return n && !(n & (n - 1)); \ + } + +UINT_OVERLOADS(ROTATE_LEFT) +UINT_OVERLOADS(ROTATE_RIGHT) +UINT_OVERLOADS(FIRST_LEADING_ONE) +UINT_OVERLOADS(HAS_SINGLE_BIT) + +#define count_ones(n) UINT_SELECT(n, count_ones)(n) +#define count_zeros(n) UINT_SELECT(n, count_ones)(~(n)) + +#define rotate_left(n, c) UINT_SELECT(n, rotate_left)(n, c) +#define rotate_right(n, c) UINT_SELECT(n, rotate_right)(n, c) + +#define leading_zeros(n) UINT_SELECT(n, leading_zeros)(n) +#define leading_ones(n) UINT_SELECT(n, leading_zeros)(~(n)) + +#define trailing_zeros(n) UINT_SELECT(n, trailing_zeros)(n) +#define trailing_ones(n) UINT_SELECT(n, trailing_zeros)(~(n)) + +#define first_leading_one(n) UINT_SELECT(n, first_leading_one)(n) +#define first_leading_zero(n) UINT_SELECT(n, first_leading_one)(~(n)) + +#define first_trailing_one(n) UINT_SELECT(n, first_trailing_one)(n) +#define first_trailing_zero(n) UINT_SELECT(n, first_trailing_one)(~(n)) + +#define has_single_bit(n) UINT_SELECT(n, has_single_bit)(n) + +#define BIT_FLOOR(type, suffix, width) \ + static inline type bit_floor##suffix(type n) { \ + return n ? (type)1 << (first_leading_one##suffix(n) - 1) : 0; \ + } + +#define BIT_CEIL(type, suffix, width) \ + static inline type bit_ceil##suffix(type n) { \ + return (type)1 << first_leading_one##suffix(n - !!n); \ + } + +UINT_OVERLOADS(BIT_FLOOR) +UINT_OVERLOADS(BIT_CEIL) + +#define bit_width(n) first_leading_one(n) +#define bit_floor(n) UINT_SELECT(n, bit_floor)(n) +#define bit_ceil(n) UINT_SELECT(n, bit_ceil)(n) + +#endif // __STDC_VERSION__ < 202311L + +#endif // BFS_BIT_H |