lab7-fix2023/lib/string.c
2023-11-22 16:16:24 +08:00

110 lines
1.4 KiB
C

#include "string.h"
int
strlen(const char *s)
{
int n;
for (n = 0; *s != '\0'; s++)
n++;
return n;
}
int
strnlen(const char *s, size_t size)
{
int n;
for (n = 0; size > 0 && *s != '\0'; s++, size--)
n++;
return n;
}
char *
strcpy(char *dst, const char *src)
{
char *ret;
ret = dst;
while ((*dst++ = *src++) != '\0')
/* do nothing */;
return ret;
}
char *
strcat(char *dst, const char *src)
{
int len = strlen(dst);
strcpy(dst + len, src);
return dst;
}
char *
strncpy(char *dst, const char *src, size_t size) {
size_t i;
char *ret;
ret = dst;
for (i = 0; i < size; i++) {
*dst++ = *src;
// If strlen(src) < size, null-pad 'dst' out to 'size' chars
if (*src != '\0')
src++;
}
return ret;
}
int
strcmp(const char *p, const char *q)
{
while (*p && *p == *q)
p++, q++;
return (int) ((unsigned char) *p - (unsigned char) *q);
}
int
strncmp(const char *p, const char *q, size_t n)
{
while (n > 0 && *p && *p == *q)
n--, p++, q++;
if (n == 0)
return 0;
else
return (int) ((unsigned char) *p - (unsigned char) *q);
}
void *
memset(void *v, int c, size_t n)
{
char *p;
int m;
p = v;
m = n;
while (--m >= 0)
*p++ = c;
return v;
}
void *
memcpy(void *dst, const void *src, size_t 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;
}