string.c

#include "types.h"
#include "x86.h"

void *
memset (void *dst, int c, uint n)
{
    if ((int) dst % 4 == 0 && n % 4 == 0)
    {
        c &= 0xFF;
        stosl (dst, (c << 24) | (c << 16) | (c << 8) | c, n / 4);
    }
    else
        stosb (dst, c, n);
    return dst;
}

int
memcmp (const void *v1, const void *v2, uint n)
{
    const uchar *s1, *s2;

    s1 = v1;
    s2 = v2;
    while (n-- > 0)
    {
        if (*s1 != *s2)
            return *s1 - *s2;
        s1++, s2++;
    }

    return 0;
}

void *
memmove (void *dst, const void *src, uint n)
{
    const char *s;
    char *d;

    s = src;
    d = dst;
    if (s < d && s + n > d)
    {
        s += n;
        d += n;
        while (n-- > 0)
            *--d = *--s;
    }
    else
        while (n-- > 0)
            *d++ = *s++;

    return dst;
}

// memcpy exists to placate GCC.  Use memmove.
void *
memcpy (void *dst, const void *src, uint n)
{
    return memmove (dst, src, n);
}

int
strncmp (const char *p, const char *q, uint n)
{
    while (n > 0 && *p && *p == *q)
        n--, p++, q++;
    if (n == 0)
        return 0;
    return (uchar) * p - (uchar) * q;
}

char *
strncpy (char *s, const char *t, int n)
{
    char *os;

    os = s;
    while (n-- > 0 && (*s++ = *t++) != 0)
        ;
    while (n-- > 0)
        *s++ = 0;
    return os;
}

// Like strncpy but guaranteed to NUL-terminate.
char *
safestrcpy (char *s, const char *t, int n)
{
    char *os;

    os = s;
    if (n <= 0)
        return os;
    while (--n > 0 && (*s++ = *t++) != 0)
        ;
    *s = 0;
    return os;
}

int
strlen (const char *s)
{
    int n;

    for (n = 0; s[n]; n++)
        ;
    return n;
}