Related Blog Items

• Bad Standard APIs
• C++ Basics Tutorial - Lesson 4
• const correctness
• Differences between new, malloc; delete, free
• i64toa - Converts a 64 bit integer to string

I’d covered bad standard APIs in my previous article, here I’ve attempted to overcome those defects in standard APIs, please check these fucntions.. I’ll post more functions later..

Strcpy:
1)copy src to string dst of size size
2)At most size-1 characters will be copied
3)Returns strlen(src); if retval >= size, truncation occurred
4)Always NUL terminates (unless size is 0)

size_t safe_strcpy(char *dst, const char *src, size_t size)
{
  const char *s = src;
  size_t n = size;

  if (size != 0)
  {
    while (--size != 0)
    {
      if ((*dst++ = *src++) == 0)
      break;
    }
  }

  if (size == 0)
  {
    if (n)
      *dst = 0;
    while (*src++);
  }

  //count does not include ''
  return(src-s-1);
}

strcat:
1)Appends src to string dst of size size, unlike strncat size is the full size of dst
2)At most size-1 characters will be copied
3)Always NUL terminates (unless size = siz, truncation occurred.

size_t safe_strcat(char *dst, const char *src, size_t size)
{
  char *d = dst;
  const char *s = src;
  size_t n = size;
  size_t dstlen;
 
  while (n-- != 0 && *d != 0)
  {
    d++;
  }
 
  dstlen = d - dst;
  n = size - dstlen;
 
  if (n == 0)
  {
    return(dstlen + strlen(s));
  }
 
  while (*s != 0)
  {
    if (n != 1)
    {
      *d++ = *s;
      n--;
    }
    s++;
  }
  *d = 0;
 
  return(dstlen + (s - src));
}

download src safe string operations

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Related Blog Items

• Bad Standard APIs
• C++ Basics Tutorial - Lesson 4
• const correctness
• Differences between new, malloc; delete, free
• i64toa - Converts a 64 bit integer to string

This entry was written by ponnada and posted on December 4, 2007 at 9:57 pm and filed under C Tidbits. Bookmark the permalink. Follow any comments here with the RSS feed for this post. Trackbacks are closed, but you can post a comment.