firmware/libc/strchr.c

   1 /*
   2 FUNCTION
   3         <<strchr>>---search for character in string
   4
   5 INDEX
   6         strchr
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         char * strchr(const char *<[string]>, int <[c]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         char * strchr(<[string]>, <[c]>);
  15         char *<[string]>;
  16         int *<[c]>;
  17
  18 DESCRIPTION
  19         This function finds the first occurence of <[c]> (converted to
  20         a char) in the string pointed to by <[string]> (including the
  21         terminating null character).
  22
  23 RETURNS
  24         Returns a pointer to the located character, or a null pointer
  25         if <[c]> does not occur in <[string]>.
  26
  27 PORTABILITY
  28 <<strchr>> is ANSI C.
  29
  30 <<strchr>> requires no supporting OS subroutines.
  31
  32 QUICKREF
  33         strchr ansi pure
  34 */
  35
  36 #include <string.h>
  37 #include <limits.h>
  38
  39 /* Nonzero if X is not aligned on a "long" boundary.  */
  40 #define UNALIGNED(X) ((long)X & (sizeof (long) - 1))
  41
  42 /* How many bytes are loaded each iteration of the word copy loop.  */
  43 #define LBLOCKSIZE (sizeof (long))
  44
  45 #if LONG_MAX == 2147483647L
  46 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
  47 #else
  48 #if LONG_MAX == 9223372036854775807L
  49 /* Nonzero if X (a long int) contains a NULL byte. */
  50 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
  51 #else
  52 #error long int is not a 32bit or 64bit type.
  53 #endif
  54 #endif
  55
  56 /* DETECTCHAR returns nonzero if (long)X contains the byte used
  57    to fill (long)MASK. */
  58 #define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
  59
  60 char *
  61 _DEFUN (strchr, (s1, i),
  62         _CONST char *s1 _AND
  63         int i)
  64 {
  65   _CONST unsigned char *s = (_CONST unsigned char *)s1;
  66 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  67   unsigned char c = (unsigned int)i;
  68
  69   while (*s && *s != c)
  70     {
  71       s++;
  72     }
  73
  74   if (*s != c)
  75     {
  76       s = NULL;
  77     }
  78
  79   return (char *) s;
  80 #else
  81   unsigned char c = (unsigned char)i;
  82   unsigned long mask,j;
  83   unsigned long *aligned_addr;
  84
  85   if (!UNALIGNED (s))
  86     {
  87       mask = 0;
  88       for (j = 0; j < LBLOCKSIZE; j++)
  89         mask = (mask << 8) | c;
  90
  91       aligned_addr = (unsigned long*)s;
  92       while (!DETECTNULL (*aligned_addr) && !DETECTCHAR (*aligned_addr, mask))
  93         aligned_addr++;
  94
  95       /* The block of bytes currently pointed to by aligned_addr
  96          contains either a null or the target char, or both.  We
  97          catch it using the bytewise search.  */
  98
  99       s = (unsigned char*)aligned_addr;
 100     }
 101
 102   while (*s && *s != c)
 103       s++;
 104   if (*s == c)
 105     return (char *)s;
 106   return NULL;
 107 #endif /* not PREFER_SIZE_OVER_SPEED */
 108 }