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Diffstat (limited to 'firmware/common/memchr.c')
-rw-r--r-- | firmware/common/memchr.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/firmware/common/memchr.c b/firmware/common/memchr.c new file mode 100644 index 0000000000..a7ff222a61 --- /dev/null +++ b/firmware/common/memchr.c @@ -0,0 +1,116 @@ +/* +FUNCTION + <<memchr>>---search for character in memory + +INDEX + memchr + +ANSI_SYNOPSIS + #include <string.h> + void * memchr(const void *<[s1]>, int <[c]>, size_t <[n]>); + +TRAD_SYNOPSIS + #include <string.h> + void * memchr(<[s1]>, <[c]>, <[n]>); + void *<[string]>; + int *<[c]>; + size_t *<[n]>; + +DESCRIPTION + This function scans the first <[n]> bytes of the memory pointed + to by <[s1]> for the character <[c]> (converted to a char). + +RETURNS + Returns a pointer to the matching byte, or a null pointer if + <[c]> does not occur in <[s1]>. + +PORTABILITY +<<memchr>> is ANSI C. + +<<memchr>> requires no supporting OS subroutines. + +QUICKREF + memchr ansi pure +*/ + +#include <string.h> +#include <limits.h> + +/* Nonzero if X is not aligned on a "long" boundary. */ +#define UNALIGNED(X) ((long)X & (sizeof (long) - 1)) + +/* How many bytes are loaded each iteration of the word copy loop. */ +#define LBLOCKSIZE (sizeof (long)) + +#if LONG_MAX == 2147483647L +#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) +#else +#if LONG_MAX == 9223372036854775807L +/* Nonzero if X (a long int) contains a NULL byte. */ +#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) +#else +#error long int is not a 32bit or 64bit type. +#endif +#endif + +/* DETECTCHAR returns nonzero if (long)X contains the byte used + to fill (long)MASK. */ +#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK)) + +void * +_DEFUN (memchr, (s1, i, n), + _CONST void *s1 _AND + int i _AND size_t n) +{ + _CONST unsigned char *s = (_CONST unsigned char *)s1; +#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) + unsigned char c = (unsigned char)i; + + while (n-- > 0) + { + if (*s == c) + { + return (void *)s; + } + s++; + } + + return NULL; +#else + unsigned char c = (unsigned char)i; + unsigned long mask,j; + unsigned long *aligned_addr; + + if (!UNALIGNED (s)) + { + mask = 0; + for (j = 0; j < LBLOCKSIZE; j++) + mask = (mask << 8) | c; + + aligned_addr = (unsigned long*)s; + while ((!DETECTCHAR (*aligned_addr, mask)) && (n>LBLOCKSIZE)) + { + aligned_addr++; + n -= LBLOCKSIZE; + } + + /* The block of bytes currently pointed to by aligned_addr + may contain the target character or there may be less than + LBLOCKSIZE bytes left to search. We check the last few + bytes using the bytewise search. */ + + s = (unsigned char*)aligned_addr; + } + + while (n-- > 0) + { + if (*s == c) + { + return (void *)s; + } + s++; + } + + return NULL; +#endif /* not PREFER_SIZE_OVER_SPEED */ +} |