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https://github.com/Z3Prover/z3
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86 lines
2 KiB
C++
86 lines
2 KiB
C++
/*++
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Copyright (c) 2006 Microsoft Corporation
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Module Name:
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hash.cpp
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Abstract:
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Basic hash computation support.
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Author:
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Leonardo de Moura (leonardo) 2006-09-11.
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Revision History:
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--*/
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#include"debug.h"
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#include"hash.h"
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// I'm using Bob Jenkin's hash function.
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// http://burtleburtle.net/bob/hash/doobs.html
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unsigned string_hash(const char * str, unsigned length, unsigned init_value) {
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register unsigned a, b, c, len;
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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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c = init_value; /* the previous hash value */
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/*---------------------------------------- handle most of the key */
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while (len >= 12) {
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a += reinterpret_cast<const unsigned *>(str)[0];
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b += reinterpret_cast<const unsigned *>(str)[1];
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c += reinterpret_cast<const unsigned *>(str)[2];
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mix(a,b,c);
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str += 12; len -= 12;
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}
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/*------------------------------------- handle the last 11 bytes */
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c += length;
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switch(len) { /* all the case statements fall through */
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case 11:
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c+=((unsigned)str[10]<<24);
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__fallthrough;
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case 10:
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c+=((unsigned)str[9]<<16);
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__fallthrough;
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case 9 :
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c+=((unsigned)str[8]<<8);
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__fallthrough;
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/* the first byte of c is reserved for the length */
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case 8 :
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b+=((unsigned)str[7]<<24);
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__fallthrough;
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case 7 :
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b+=((unsigned)str[6]<<16);
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__fallthrough;
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case 6 :
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b+=((unsigned)str[5]<<8);
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__fallthrough;
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case 5 :
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b+=str[4];
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__fallthrough;
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case 4 :
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a+=((unsigned)str[3]<<24);
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__fallthrough;
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case 3 :
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a+=((unsigned)str[2]<<16);
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__fallthrough;
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case 2 :
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a+=((unsigned)str[1]<<8);
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__fallthrough;
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case 1 :
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a+=str[0];
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__fallthrough;
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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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