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 #include "_ansi.h"
  44
  45 /*SUPPRESS 560*/
  46 /*SUPPRESS 530*/
  47
  48 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
  49 #define UNALIGNED(X, Y) \
  50   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
  51
  52 #if LONG_MAX == 2147483647L
  53 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
  54 #else
  55 #if LONG_MAX == 9223372036854775807L
  56 /* Nonzero if X (a long int) contains a NULL byte. */
  57 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
  58 #else
  59 #error long int is not a 32bit or 64bit type.
  60 #endif
  61 #endif
  62
  63 #ifndef DETECTNULL
  64 #error long int is not a 32bit or 64bit byte
  65 #endif
  66
  67 #define TOO_SMALL(LEN) ((LEN) < sizeof (long))
  68
  69 char *
  70 _DEFUN (strncpy, (dst0, src0),
  71         char *dst0 _AND
  72         _CONST char *src0 _AND
  73         size_t count)
  74 {
  75 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  76   char *dscan;
  77   _CONST char *sscan;
  78
  79   dscan = dst0;
  80   sscan = src0;
  81   while (count > 0)
  82     {
  83       --count;
  84       if ((*dscan++ = *sscan++) == '\0')
  85         break;
  86     }
  87   while (count-- > 0)
  88     *dscan++ = '\0';
  89
  90   return dst0;
  91 #else
  92   char *dst = dst0;
  93   _CONST char *src = src0;
  94   long *aligned_dst;
  95   _CONST long *aligned_src;
  96
  97   /* If SRC and DEST is aligned and count large enough, then copy words.  */
  98   if (!UNALIGNED (src, dst) && !TOO_SMALL (count))
  99     {
 100       aligned_dst = (long*)dst;
 101       aligned_src = (long*)src;
 102
 103       /* SRC and DEST are both "long int" aligned, try to do "long int"
 104          sized copies.  */
 105       while (count >= sizeof (long int) && !DETECTNULL(*aligned_src))
 106         {
 107           count -= sizeof (long int);
 108           *aligned_dst++ = *aligned_src++;
 109         }
 110
 111       dst = (char*)aligned_dst;
 112       src = (char*)aligned_src;
 113     }
 114
 115   while (count > 0)
 116     {
 117       --count;
 118       if ((*dst++ = *src++) == '\0')
 119         break;
 120     }
 121
 122   while (count-- > 0)
 123     *dst++ = '\0';
 124
 125   return dst0;
 126 #endif /* not PREFER_SIZE_OVER_SPEED */
 127 }