xv6-cs450/string.c

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#include "types.h"
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#include "x86.h"
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void*
memset(void *dst, int c, uint n)
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{
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stosb(dst, c, n);
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return dst;
}
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int
memcmp(const void *v1, const void *v2, uint n)
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{
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const uchar *s1, *s2;
s1 = v1;
s2 = v2;
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while(n-- > 0){
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if(*s1 != *s2)
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return *s1 - *s2;
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s1++, s2++;
}
return 0;
}
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void*
memmove(void *dst, const void *src, uint n)
{
const char *s;
char *d;
s = src;
d = dst;
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if(s < d && s + n > d){
s += n;
d += n;
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while(n-- > 0)
*--d = *--s;
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} else
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while(n-- > 0)
*d++ = *s++;
return dst;
}
int
strncmp(const char *p, const char *q, uint n)
{
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while(n > 0 && *p && *p == *q)
n--, p++, q++;
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if(n == 0)
return 0;
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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;
}
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// 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;
}