From 26ac7e36c0710284d18d95eb0e58e21178396ffd Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 29 May 2024 11:12:21 -0400
Subject: bit: Update to match C23
Based on the latest C23 draft (N3220):
- Argument types to generic bit functions should be unsigned
- Bit functions return unsigned int
- Byte-swapping functions (stdc_memreverse8*()) weren't added
- stdc_rotate_{left,right}() weren't added
- first_leading_*() counts from the *left*
---
src/bit.h | 96 ++++++++++++++++++++++++++++++---------------------------------
1 file changed, 45 insertions(+), 51 deletions(-)
(limited to 'src')
diff --git a/src/bit.h b/src/bit.h
index 17cfbcf..880ccd6 100644
--- a/src/bit.h
+++ b/src/bit.h
@@ -173,11 +173,7 @@
# define ENDIAN_NATIVE 0
#endif
-#if __STDC_VERSION__ >= C23
-# define bswap_u16 stdc_memreverse8u16
-# define bswap_u32 stdc_memreverse8u32
-# define bswap_u64 stdc_memreverse8u64
-#elif __GNUC__
+#if __GNUC__
# define bswap_u16 __builtin_bswap16
# define bswap_u32 __builtin_bswap32
# define bswap_u64 __builtin_bswap64
@@ -222,16 +218,10 @@ static inline uint8_t bswap_u8(uint8_t n) {
// 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
@@ -239,8 +229,6 @@ static inline uint8_t bswap_u8(uint8_t n) {
#if __STDC_VERSION__ >= C23
# 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
@@ -273,31 +261,31 @@ static inline uint8_t bswap_u8(uint8_t n) {
#define BUILTIN_WIDTH(suffix) BUILTIN_WIDTH##suffix
#define COUNT_ONES(type, suffix, width) \
- static inline int count_ones##suffix(type n) { \
+ static inline unsigned 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) { \
+ static inline unsigned 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) { \
+ static inline unsigned int trailing_zeros##suffix(type n) { \
return n ? UINT_BUILTIN(ctz, suffix)(n) : (int)width; \
}
#define FIRST_TRAILING_ONE(type, suffix, width) \
- static inline int first_trailing_one##suffix(type n) { \
+ static inline unsigned 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) { \
+ static inline unsigned int count_ones##suffix(type n) { \
int ret; \
for (ret = 0; n; ++ret) { \
n &= n - 1; \
@@ -306,7 +294,7 @@ static inline uint8_t bswap_u8(uint8_t n) {
}
#define LEADING_ZEROS(type, suffix, width) \
- static inline int leading_zeros##suffix(type n) { \
+ static inline unsigned int leading_zeros##suffix(type n) { \
type bit = (type)1 << (width - 1); \
int ret; \
for (ret = 0; bit && !(n & bit); ++ret, bit >>= 1); \
@@ -314,7 +302,7 @@ static inline uint8_t bswap_u8(uint8_t n) {
}
#define TRAILING_ZEROS(type, suffix, width) \
- static inline int trailing_zeros##suffix(type n) { \
+ static inline unsigned int trailing_zeros##suffix(type n) { \
type bit = 1; \
int ret; \
for (ret = 0; bit && !(n & bit); ++ret, bit <<= 1); \
@@ -322,7 +310,7 @@ static inline uint8_t bswap_u8(uint8_t n) {
}
#define FIRST_TRAILING_ONE(type, suffix, width) \
- static inline int first_trailing_one##suffix(type n) { \
+ static inline unsigned int first_trailing_one##suffix(type n) { \
return n ? trailing_zeros##suffix(n) + 1 : 0; \
}
@@ -333,19 +321,9 @@ 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); \
+ static inline unsigned int first_leading_one##suffix(type n) { \
+ return n ? leading_zeros##suffix(n) + 1 : 0; \
}
#define HAS_SINGLE_BIT(type, suffix, width) \
@@ -354,17 +332,30 @@ UINT_OVERLOADS(FIRST_TRAILING_ONE)
return n - 1 < (n ^ (n - 1)); \
}
-UINT_OVERLOADS(ROTATE_LEFT)
-UINT_OVERLOADS(ROTATE_RIGHT)
+#define BIT_WIDTH(type, suffix, width) \
+ static inline unsigned int bit_width##suffix(type n) { \
+ return width - leading_zeros##suffix(n); \
+ }
+
+#define BIT_FLOOR(type, suffix, width) \
+ static inline type bit_floor##suffix(type n) { \
+ return n ? (type)1 << (bit_width##suffix(n) - 1) : 0; \
+ }
+
+#define BIT_CEIL(type, suffix, width) \
+ static inline type bit_ceil##suffix(type n) { \
+ return (type)1 << bit_width##suffix(n - !!n); \
+ }
+
UINT_OVERLOADS(FIRST_LEADING_ONE)
UINT_OVERLOADS(HAS_SINGLE_BIT)
+UINT_OVERLOADS(BIT_WIDTH)
+UINT_OVERLOADS(BIT_FLOOR)
+UINT_OVERLOADS(BIT_CEIL)
#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))
@@ -379,23 +370,26 @@ UINT_OVERLOADS(HAS_SINGLE_BIT)
#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_width(n) UINT_SELECT(n, bit_width)(n)
+#define bit_floor(n) UINT_SELECT(n, bit_floor)(n)
+#define bit_ceil(n) UINT_SELECT(n, bit_ceil)(n)
-#define BIT_CEIL(type, suffix, width) \
- static inline type bit_ceil##suffix(type n) { \
- return (type)1 << first_leading_one##suffix(n - !!n); \
+#endif // __STDC_VERSION__ < C23
+
+#define ROTATE_LEFT(type, suffix, width) \
+ static inline type rotate_left##suffix(type n, int c) { \
+ return (n << c) | (n >> ((width - c) % width)); \
}
-UINT_OVERLOADS(BIT_FLOOR)
-UINT_OVERLOADS(BIT_CEIL)
+#define ROTATE_RIGHT(type, suffix, width) \
+ static inline type rotate_right##suffix(type n, int c) { \
+ return (n >> c) | (n << ((width - c) % width)); \
+ }
-#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)
+UINT_OVERLOADS(ROTATE_LEFT)
+UINT_OVERLOADS(ROTATE_RIGHT)
-#endif // __STDC_VERSION__ < C23
+#define rotate_left(n, c) UINT_SELECT(n, rotate_left)(n, c)
+#define rotate_right(n, c) UINT_SELECT(n, rotate_right)(n, c)
#endif // BFS_BIT_H
--
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