63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
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#include "chash.h"
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#define mix(a,b,c) \
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{ \
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a=a-b; a=a-c; a=a^(c>>13); \
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b=b-c; b=b-a; b=b^(a<<8); \
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c=c-a; c=c-b; c=c^(b>>13); \
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a=a-b; a=a-c; a=a^(c>>12); \
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b=b-c; b=b-a; b=b^(a<<16); \
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c=c-a; c=c-b; c=c^(b>>5); \
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a=a-b; a=a-c; a=a^(c>>3); \
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b=b-c; b=b-a; b=b^(a<<10); \
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c=c-a; c=c-b; c=c^(b>>15); \
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}
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typedef unsigned int u4;
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unsigned int chash(const char *k, int length)
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{
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unsigned int a,b,c; /* the internal state */
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u4 len; /* how many key bytes still need mixing */
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/* Set up the internal state */
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len = length;
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a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
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// 'TMJR'
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c = 0x544D4A52; /* variable initialization of internal state */
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/*---------------------------------------- handle most of the key */
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while (len >= 12)
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{
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a=a+(k[0]+((u4)k[1]<<8)+((u4)k[2]<<16) +((u4)k[3]<<24));
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b=b+(k[4]+((u4)k[5]<<8)+((u4)k[6]<<16) +((u4)k[7]<<24));
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c=c+(k[8]+((u4)k[9]<<8)+((u4)k[10]<<16)+((u4)k[11]<<24));
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mix(a,b,c);
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k = k+12; len = len-12;
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}
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/*------------------------------------- handle the last 11 bytes */
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c = c+length;
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switch(len) /* all the case statements fall through */
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{
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case 11: c=c+((u4)k[10]<<24);
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case 10: c=c+((u4)k[9]<<16);
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case 9 : c=c+((u4)k[8]<<8);
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/* the first byte of c is reserved for the length */
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case 8 : b=b+((u4)k[7]<<24);
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case 7 : b=b+((u4)k[6]<<16);
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case 6 : b=b+((u4)k[5]<<8);
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case 5 : b=b+k[4];
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case 4 : a=a+((u4)k[3]<<24);
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case 3 : a=a+((u4)k[2]<<16);
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case 2 : a=a+((u4)k[1]<<8);
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case 1 : a=a+k[0];
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/* case 0: nothing left to add */
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}
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mix(a,b,c);
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/*-------------------------------------------- report the result */
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return c;
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}
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