apps/plugins/lib/strncpy.c

   1 /*
   2 FUNCTION
   3         <<strncpy>>---counted copy string
   4
   5 INDEX
   6         strncpy
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         char *strncpy(char *<[dst]>, const char *<[src]>, size_t <[length]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         char *strncpy(<[dst]>, <[src]>, <[length]>)
  15         char *<[dst]>;
  16         char *<[src]>;
  17         size_t <[length]>;
  18
  19 DESCRIPTION
  20         <<strncpy>> copies not more than <[length]> characters from the
  21         the string pointed to by <[src]> (including the terminating
  22         null character) to the array pointed to by <[dst]>.  If the
  23         string pointed to by <[src]> is shorter than <[length]>
  24         characters, null characters are appended to the destination
  25         array until a total of <[length]> characters have been
  26         written.
  27
  28 RETURNS
  29         This function returns the initial value of <[dst]>.
  30
  31 PORTABILITY
  32 <<strncpy>> is ANSI C.
  33
  34 <<strncpy>> requires no supporting OS subroutines.
  35
  36 QUICKREF
  37         strncpy ansi pure
  38 */
  39
  40 #include <string.h>
  41 #include <limits.h>
  42 #include "plugin.h"
  43
  44 /*SUPPRESS 560*/
  45 /*SUPPRESS 530*/
  46
  47 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
  48 #define UNALIGNED(X, Y) \
  49   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
  50
  51 #if LONG_MAX == 2147483647L
  52 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
  53 #else
  54 #if LONG_MAX == 9223372036854775807L
  55 /* Nonzero if X (a long int) contains a NULL byte. */
  56 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
  57 #else
  58 #error long int is not a 32bit or 64bit type.
  59 #endif
  60 #endif
  61
  62 #ifndef DETECTNULL
  63 #error long int is not a 32bit or 64bit byte
  64 #endif
  65
  66 #define TOO_SMALL(LEN) ((LEN) < sizeof (long))
  67
  68 char *
  69 _DEFUN (strncpy, (dst0, src0),
  70         char *dst0 _AND
  71         _CONST char *src0 _AND
  72         size_t count)
  73 {
  74 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  75   char *dscan;
  76   _CONST char *sscan;
  77
  78   dscan = dst0;
  79   sscan = src0;
  80   while (count > 0)
  81     {
  82       --count;
  83       if ((*dscan++ = *sscan++) == '\0')
  84         break;
  85     }
  86   while (count-- > 0)
  87     *dscan++ = '\0';
  88
  89   return dst0;
  90 #else
  91   char *dst = dst0;
  92   _CONST char *src = src0;
  93   long *aligned_dst;
  94   _CONST long *aligned_src;
  95
  96   /* If SRC and DEST is aligned and count large enough, then copy words.  */
  97   if (!UNALIGNED (src, dst) && !TOO_SMALL (count))
  98     {
  99       aligned_dst = (long*)dst;
 100       aligned_src = (long*)src;
 101
 102       /* SRC and DEST are both "long int" aligned, try to do "long int"
 103          sized copies.  */
 104       while (count >= sizeof (long int) && !DETECTNULL(*aligned_src))
 105         {
 106           count -= sizeof (long int);
 107           *aligned_dst++ = *aligned_src++;
 108         }
 109
 110       dst = (char*)aligned_dst;
 111       src = (char*)aligned_src;
 112     }
 113
 114   while (count > 0)
 115     {
 116       --count;
 117       if ((*dst++ = *src++) == '\0')
 118         break;
 119     }
 120
 121   while (count-- > 0)
 122     *dst++ = '\0';
 123
 124   return dst0;
 125 #endif /* not PREFER_SIZE_OVER_SPEED */
 126 }