goofing off

gistfile1.c

/*
 * strkittens
 *
 * Conceptually, strcat() is a sequence of strlen() followed by a
 * strcpy() using the offset derived from strlen().
 * These functions build on that idea.
 *
 * None of the FreeBSD, OpenBSD, nor Linux/glibc implementations
 * of strcat() use this delegation to strcpy(), presumably because
 * the pointer-based strcpy() algorithm, when used with short strings,
 * is sufficiently simple and efficient that an additional procedure
 * call was considered unnecessary.
 */

#include <cstdio>
#include <cstdlib>
#include <cstring>

char *strkitten(char *s1, char *s2);
char *charArrayKitten(char s1[], char s2[]);

int main()
{
    char buffer1[80] = {};
    char buffer2[80] = {};
    char *foo = "Foo";
    char *bar = " Bar";

    strkitten(buffer1, foo);          // buffer1 => "Foo"
    charArrayKitten(buffer2, foo);    // buffer2 => "Foo"

    printf("buffer1 => \"%s\"\nbuffer2 => \"%s\"\n\n", buffer1, buffer2);

    strkitten(buffer1, bar);          // buffer1 => "Foo Bar"
    charArrayKitten(buffer2, bar);    // buffer2 => "Foo Bar"

    printf("buffer1 => \"%s\"\nbuffer2 => \"%s\"\n\n", buffer1, buffer2);

    strkitten(buffer1, bar);          // buffer1 => "Foo Bar Bar"
    charArrayKitten(buffer2, bar);    // buffer2 => "Foo Bar Bar"

    printf("buffer1 => \"%s\"\nbuffer2 => \"%s\"\n\n", buffer1, buffer2);

    system("pause");
    return (0);
}

/*
 * Ironically, I think the pointer-based version of this function
 * provides greater clarity of purpose. Especially given the common
 * C idiom of "typeptr + int * sizeof(type)".
 */
char *
strkitten(char *s1, char *s2)
{
    strcpy(s1 + strlen(s1), s2);

    return s1;
}

/*
 * Mostly to prove I could do it using array indicies.
 * This method appears more cluttered, probably due to the
 * additional requirement of the & operator to turn the
 * element access back into a char*.
 */
char *
charArrayKitten(char s1[], char s2[])
{
    strcpy(&s1[strlen(s1)], s2);

    return s1;
}