[Libclc-developers] new string functions: clc_str{n}{case}comm()

[Hallvard B F. <h.b...@us...>]

> I think you should post the nice functions as well. Never know if
> someone needs them or suddenly finds a new way of doing things. :-)

OK, here are the clc_str{n}{case}comm() functions.  Does anyone need
them?  I don't:-)

NAME
    clc_strcomm, clc_strncomm, clc_strcasecomm, clc_strncasecomm
    - find common prefix of strings

SYNOPSIS
    #include <clc_string.h>
    long clc_strcomm(const char *s1, const char *s2);
    long clc_strncomm(const char *s1, const char *s2, long len);
    long clc_strcasecomm(const char *s1, const char *s2);
    long clc_strncasecomm(const char *s1, const char *s2, long len);

DESCRIPTION
    These functions find the length of the common prefix of two strings.

    clc_strcomm() and clc_strncomm() do case-sensitive compare,
    clc_strcasecomm() and clc_strncasecomm() case-insensitive.

    clc_strcomm() and clc_strcasecomm() compare until the terminating
    null characters.  clc_strncomm() and clc_strncasecomm() also stop
    after len characters compared equal.

    If the strings are longer than LONG_MAX, the behaviors of
    clc_strncomm() and clc_strncasecomm() are undefined.

RETURN VALUES
    The functions return the common length of the strings, or -1 if the
    strings compare equal.

CAVEATS
    Note that the functions treat the size as long, not size_t.

SEE ALSO
    clc(3), strcmp(3), strncmp(3), clc_strcasecmp(3), clc_strncasecmp(3)


Implementation choices:
- I used long instead of size_t as a length parameter to emphasize that
  a long length is returned.
- I could have returned an error condition (-2?) from clc_str{case}cmp
  if the strings were equal for more than LONG_MAX characters, but
  didn't bother.  I can't imagine these functions being used on other
  than fairly short strings.

Source code for clc_strncasecomm() follows.  The others are for the time
being left as an exercise for the reader.


/* $Id$ */
/*
 * Copyright(c) 2003 Hallvard B Furuseth <h.b...@us...>
 */

#include <ctype.h>
#include <clc_assert.h>
#include <clc_string.h>

long
clc_strncasecomm(const char *s1, const char *s2, long len)
{
    const char *start = s1;

	clc_assert_arg(clc_strncasecomm, s1 != NULL && s2 != NULL);

    for (; --len >= 0; ++s1, ++s2) {
		if (tolower((unsigned char)*s1) != tolower((unsigned char)*s2))
			return s1 - start;
		if (*s1 == '\0')
			break;
    }
	return -1;
}

#ifdef CLC_TEST

#include <stdio.h>

int
main()
{
	if(clc_strncasecomm("abc", "ABD", 3) != 2 ||
	   clc_strncasecomm("abc", "ABD", 2) != -1 ||
	   clc_strncasecomm("abc", "ABD", 1) != -1 ||
	   clc_strncasecomm("ab",  "ABD", 3) != 2 ||
	   clc_strncasecomm("abc", "DEF", 3) != 0   ) {
		puts("Sorry.");
		return 1;
	}
	return 0;
}

#endif /* CLC_TEST */

-- 
Hallvard