diff options
Diffstat (limited to 'nuttx/lib/string/lib_memset.c')
| -rw-r--r-- | nuttx/lib/string/lib_memset.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/nuttx/lib/string/lib_memset.c b/nuttx/lib/string/lib_memset.c index 916351b97..c910d2ce0 100644 --- a/nuttx/lib/string/lib_memset.c +++ b/nuttx/lib/string/lib_memset.c @@ -42,8 +42,12 @@ ************************************************************/ #include <nuttx/config.h> + #include <sys/types.h> + +#include <stdint.h> #include <string.h> +#include <assert.h> /************************************************************ * Global Functions @@ -52,8 +56,88 @@ #ifndef CONFIG_ARCH_MEMSET void *memset(void *s, int c, size_t n) { +#ifdef CONFIG_MEMSET_OPTSPEED + /* This version is optimized for speed (you could do better + * still by exploiting processor caching or memory burst + * knowledge. 64-bit support might improve performance as + * well. + */ + + uintptr_t addr = (uintptr_t)s; + uint16_t val16 = ((uint16_t)c << 8) | (uint16_t)c; + uint32_t val32 = ((uint32_t)val16 << 16) | (uint32_t)val16; + + /* Make sure that there is something to be cleared */ + + if (n > 0) + { + /* Align to a 16-bit boundary */ + + if ((addr & 1) != 0) + { + *(uint8_t*)addr = (uint8_t)c; + addr += 1; + n -= 1; + } + + /* Check if there are at least 16-bits left to be zeroed */ + + if (n >= 2) + { + /* Align to a 32-bit boundary (we know that the destination + * address is already aligned to at least a 16-bit boundary). + */ + + if ((addr & 3) != 0) + { + *(uint16_t*)addr = val16; + addr += 2; + n -= 2; + } + + /* Loop while there are at least 32-bits left to be zeroed */ + + while (n >= 4) + { + *(uint32_t*)addr = val32; + addr += 4; + n -= 4; + } + } + + /* We may get here under the following conditions: + * + * n = 0, addr may or may not be aligned + * n = 1, addr may or may not be aligned + * n = 2, addr is aligned to a 32-bit boundary + * n = 3, addr is aligned to a 32-bit boundary + */ + + switch (n) + { + default: + case 0: + DEBUGASSERT(n == 0); + break; + + case 2: + *(uint16_t*)addr = val16; + break; + + case 3: + *(uint16_t*)addr = val16; + addr += 2; + case 1: + *(uint8_t*)addr = (uint8_t)c; + break; + } + } +#else + /* This version is optimized for size */ + unsigned char *p = (unsigned char*)s; while (n-- > 0) *p++ = c; +#endif return s; } #endif |