strings.h and wrapping this macro with a macro check of whether

Question

I infer from Google search results that strings.h (from here) is for UNIX systems. I would like to wrap the following line with a macro check of whether the host's operating system is Linux/UNIX. It would be much appreciated to hear suggestions about it. Thanks in advance.

#include <strings.h>

Answer 1

strings.h contains only a few functions, most of which are simply different names for functions that are in the standard library (such as bcmp() <--> memcmp()). If your code uses these functions, instead of throwing #ifdefs around why not just write your own set?

Then everyone gets to use them and be happily conditional-compilation free.

Here's a not-fully-tested set of functions in the public domain that you can use at your own risk:

#include <string.h>
#include <ctype.h>

int bcmp(const void * p1, const void * p2, size_t n)
{
    return memcmp( p1, p2, n);
}

void   bcopy(const void * src, void * dst, size_t n)
{
    memmove( dst, src, n);  /* note different order of args - yuck */
}

void   bzero(void * p, size_t n)
{
    memset( p, 0, n);
}

char   *index(const char * s, int c)
{
    return strchr( s, c);
}

char   *rindex(const char * s, int c)
{
    return strrchr( s, c);
}

int    strcasecmp(const char* s1, const char* s2)
{
    for (;;) {
        int c1 = tolower( *((unsigned char*) s1++));
        int c2 = tolower( *((unsigned char*) s2++));

        if ((c1 != c2) || (c1 == '\0')) {
            return( c1 - c2);
        }
    }
}

int    strncasecmp(const char* s1, const char* s2, size_t n)
{
    for (; n != 0; --n) {
        int c1 = tolower( *((unsigned char*) s1++));
        int c2 = tolower( *((unsigned char*) s2++));

        if ((c1 != c2) || (c1 == '\0')) {
            return( c1 - c2);
        }
    }

    return( 0);
}


int    ffs(int v)
{
    unsigned int x = v;
    int c = 1;

    /* 
     * adapted from from 
     *      http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightBinSearch
     *
     * a modified binary search algorithm to count 0 bits from 
     *  the right (lsb).  This algorithm should work regardless 
     *  of the size of ints on the platform.
     *
     */

    /* a couple special cases */
    if (x == 0) return 0;
    if (x & 1)  return 1;   /* probably pretty common */

    c = 1;
    while ((x & 0xffff) == 0) {
        x >>= 16;
        c +=  16;
    }
    if ((x & 0xff) == 0) {
        x >>= 8;
        c +=  8;
    }
    if ((x & 0x0f) == 0) {
        x >>= 4;
        c +=  4;
    }
    if ((x & 0x03) == 0) {
        x >>= 2;
        c +=  2;
    }

    c -= (x & 1);
    c += 1;     /* ffs() requires indexing bits from 1 */
                /*   ie., the lsb is bit 1, not bit 0  */
    return c;
}

Answer 2

One option would be:

#ifndef _WIN32
#include <strings.h>
#endif

Per MSDN, _WIN32 is "defined for applications for Win32 and Win64. Always defined."

A compiler or standard library for an operating system other than Windows is, of course, free to define _WIN32, but that would be... most unusual.