root/library/string.c

DEFINITIONS

1. strchr
2. strlen
3. strncmp
4. strcpy
5. strcmp
6. strcat

//==================================================================
// Finds first occurrence of c in string.
// Returns pointer to that occurrence or 0 if not found
//==================================================================
unsigned char *strchr(unsigned char *string, unsigned char c)
{
    long i = 0;
    while (string[i]) {
        if (string[i] == c)
            return string + i;
        i++;
    }
    return 0;
}

//================================================================
// Returns the length of string
//================================================================
long strlen(unsigned char *string)
{
    int i = 0;
    while (string[i++]) ;
    return i - 1;
}

//===============================================================
// Compares s1 and s2 up to length characters.
// Returns 0 if they are equal, non-zero otherwise.
//===============================================================
long strncmp(unsigned char *s1, unsigned char *s2, long length)
{
    long count;
    short done = 0;

    for (count = 1; count < length; count++) {
        if (s1[count] != s2[count]) {
            done = 1;
            break;
        }
    }
    if (done)
        return (1);
    else
        return (0);
}

//=======================================================
// Copy null-terminates string s1 to s2
//=======================================================
unsigned char *strcpy(unsigned char *destination, unsigned char *source)
{
    unsigned char *retval = destination;
    while (*source) {
        *destination++ = *source++;
    }
    *destination = 0;
    return retval;
}

//===============================================================
// Compares s1 and s2.
// Returns 0 if they are equal, non-zero otherwise.
//===============================================================
long strcmp(unsigned char *s1, unsigned char *s2)
{
    long retval = 1;
    int count = 0;
    while (s1[count] == s2[count]) {
        if (s1[count++] == 0)
            retval = 0;
    }
    return retval;
}

//===========================================================
// Concatenates s2 to the end of s1.
// Returns s1
//===========================================================
unsigned char *strcat(unsigned char *s1, unsigned char *s2)
{
    int n = strlen(s1);
    strcpy(s1 + n, s2);
    return s1;
}