xv6/string.c

104 lines
1.7 KiB
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;
}