github.com/afumu/libc@v0.0.6/musl/src/locale/__mo_lookup.c (about)

     1  #include <stdint.h>
     2  #include <string.h>
     3  
     4  static inline uint32_t swapc(uint32_t x, int c)
     5  {
     6  	return c ? x>>24 | x>>8&0xff00 | x<<8&0xff0000 | x<<24 : x;
     7  }
     8  
     9  const char *__mo_lookup(const void *p, size_t size, const char *s)
    10  {
    11  	const uint32_t *mo = p;
    12  	int sw = *mo - 0x950412de;
    13  	uint32_t b = 0, n = swapc(mo[2], sw);
    14  	uint32_t o = swapc(mo[3], sw);
    15  	uint32_t t = swapc(mo[4], sw);
    16  	if (n>=size/4 || o>=size-4*n || t>=size-4*n || ((o|t)%4))
    17  		return 0;
    18  	o/=4;
    19  	t/=4;
    20  	for (;;) {
    21  		uint32_t ol = swapc(mo[o+2*(b+n/2)], sw);
    22  		uint32_t os = swapc(mo[o+2*(b+n/2)+1], sw);
    23  		if (os >= size || ol >= size-os || ((char *)p)[os+ol])
    24  			return 0;
    25  		int sign = strcmp(s, (char *)p + os);
    26  		if (!sign) {
    27  			uint32_t tl = swapc(mo[t+2*(b+n/2)], sw);
    28  			uint32_t ts = swapc(mo[t+2*(b+n/2)+1], sw);
    29  			if (ts >= size || tl >= size-ts || ((char *)p)[ts+tl])
    30  				return 0;
    31  			return (char *)p + ts;
    32  		}
    33  		else if (n == 1) return 0;
    34  		else if (sign < 0)
    35  			n /= 2;
    36  		else {
    37  			b += n/2;
    38  			n -= n/2;
    39  		}
    40  	}
    41  	return 0;
    42  }