xv6-cs450/string.c

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#include "types.h"
#include "defs.h"
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void *
memset(void *dst, int c, uint n)
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{
char *d = (char *) dst;
while(n-- > 0)
*d++ = c;
return dst;
}
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int
memcmp(const void *v1, const void *v2, uint n)
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{
const uint8_t *s1 = (const uint8_t *) v1;
const uint8_t *s2 = (const uint8_t *) v2;
while (n-- > 0) {
if (*s1 != *s2)
return (int) *s1 - (int) *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;
}
int
strncmp(const char *p, const char *q, uint n)
{
while (n > 0 && *p && *p == *q)
n--, p++, q++;
if (n == 0)
return 0;
else
return (int) ((uint8_t) *p - (uint8_t) *q);
}
// Memcpy is deprecated and should NOT be called.
// Use memmove instead, which has defined semantics
// when the two memory ranges overlap.
// Memcpy is here only because gcc compiles some
// structure assignments into calls to memcpy.
void *
memcpy(void *dst, void *src, uint n)
{
char *d = (char *) dst;
char *s = (char *) src;
while(n-- > 0)
*d++ = *s++;
return dst;
}