bit: Rename int.h to bit.h

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