diff options
Diffstat (limited to 'cpukit/libc/string/strchr.c')
-rw-r--r-- | cpukit/libc/string/strchr.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/cpukit/libc/string/strchr.c b/cpukit/libc/string/strchr.c new file mode 100644 index 0000000000..96f30be044 --- /dev/null +++ b/cpukit/libc/string/strchr.c @@ -0,0 +1,116 @@ +/* +FUNCTION + <<strchr>>---search for character in string + +INDEX + strchr + +SYNOPSIS + #include <string.h> + char * strchr(const char *<[string]>, int <[c]>); + +DESCRIPTION + This function finds the first occurence of <[c]> (converted to + a char) in the string pointed to by <[string]> (including the + terminating null character). + +RETURNS + Returns a pointer to the located character, or a null pointer + if <[c]> does not occur in <[string]>. + +PORTABILITY +<<strchr>> is ANSI C. + +<<strchr>> requires no supporting OS subroutines. + +QUICKREF + strchr 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)) + +char * +strchr (const char *s1, + int i) +{ + const unsigned char *s = (const unsigned char *)s1; + unsigned char c = i; + +#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__) + unsigned long mask,j; + unsigned long *aligned_addr; + + /* Special case for finding 0. */ + if (!c) + { + while (UNALIGNED (s)) + { + if (!*s) + return (char *) s; + s++; + } + /* Operate a word at a time. */ + aligned_addr = (unsigned long *) s; + while (!DETECTNULL (*aligned_addr)) + aligned_addr++; + /* Found the end of string. */ + s = (const unsigned char *) aligned_addr; + while (*s) + s++; + return (char *) s; + } + + /* All other bytes. Align the pointer, then search a long at a time. */ + while (UNALIGNED (s)) + { + if (!*s) + return NULL; + if (*s == c) + return (char *) s; + s++; + } + + mask = c; + for (j = 8; j < LBLOCKSIZE * 8; j <<= 1) + mask = (mask << j) | mask; + + aligned_addr = (unsigned long *) s; + while (!DETECTNULL (*aligned_addr) && !DETECTCHAR (*aligned_addr, mask)) + aligned_addr++; + + /* The block of bytes currently pointed to by aligned_addr + contains either a null or the target char, or both. We + catch it using the bytewise search. */ + + s = (unsigned char *) aligned_addr; + +#endif /* not PREFER_SIZE_OVER_SPEED */ + + while (*s && *s != c) + s++; + if (*s == c) + return (char *)s; + return NULL; +} |