20 lines
567 B
C
20 lines
567 B
C
#include <string.h>
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#include <stdint.h>
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#include <limits.h>
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#define ALIGN (sizeof(size_t))
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#define ONES ((size_t)-1/UCHAR_MAX)
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#define HIGHS (ONES * (UCHAR_MAX/2+1))
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#define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
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size_t strnlen(const char *s, size_t maxlen)
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{
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const char *a = s;
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const size_t *w;
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size_t over = maxlen;
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for (; ((uintptr_t)s % ALIGN) && over; s++, over--) if (!*s) return s-a;
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for (w = (const void *)s; over>ALIGN && !HASZERO(*w); w++,over-=ALIGN);
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for (s = (const void *)w; *s && over; s++, over--);
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if (over) return s-a;
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else return maxlen;
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}
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