Orion

/*
 * This file contains a few routines for the manipulation of memory and strings.
 * The functions would normally be part of a C library, but this is for the
 * Kernel.  The functions are standalone, and have no dependencies - they can be
 * called immediately after boot.
 */

#include <stdint.h>
#include <stddef.h>

/* Fill a region of memory with the specified byte */
void *
memset(void *s, int c, size_t n)
{
	unsigned char *a = s;
	if (n > 0) {
		while (n-- > 0)
			*a++ = c;
	}
	return s;
}

/* Copy one region of memory to another */
void *
memcpy(void *dest, void *src, size_t n)
{
	unsigned char *a = (unsigned char *) dest,
	              *b = (unsigned char *) src;
	while (n-- > 0)
		*a++ = *b++;
	return dest;
}

/* Compare two regions of memory */
int
memcmp(void *s1, void *s2, size_t n)
{
	unsigned char *a = (unsigned char *) s1,
	              *b = (unsigned char *) s2;
	while (n-- > 0)
		if (*a++ != *b++)
			return a[-1] - b[-1];
	return 0;
}

/* Find the length of a string */
size_t
strlen(char *s)
{
	if (!s)
		return 0;
	size_t i;
	for (i = 0; s[i]; i++);
	return i;
}

/* Find the length of a string up to maximum */
size_t
strnlen(char *s, size_t maxlen)
{
	if (!s)
		return 0;
	size_t i;
	for (i = 0; s[i] && i <= maxlen; i++);
	return i;
}

/* Compare two strings */
int
strcmp(char *s1, char *s2)
{
	for (; *s1 == *s2 && *s1 && *s2; s1++, s2++);
	return *(unsigned char *) s1 - *(unsigned char *) s2;
}

/* Compare two limited strings */
int
strncmp(char *s1, char *s2, size_t n)
{
	if (!n--) return 0;
	for (; *s1 == *s2 && *s1 && *s2 && n; s1++, s2++, n--);
	return *(unsigned char *) s1 - *(unsigned char *) s2;
}

/* Copy a string */
char *
strcpy(char *dest, const char *src)
{
	char *ret = dest;
	while (*src)
		*dest++ = *src++;
	*dest = '\0';
	return ret;
}

/* Copy a limited string */
char *
strncpy(char *dest, const char *src, size_t n)
{
	char *ret = dest;
	while (*src && n--)
		*dest++ = *src++;
	*dest = '\0';
	return ret;
}