Source code of Windows XP (NT5)
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#include "mbrmake.h"
WORD HashAtomStr (char *pStr) {
WORD hash = 0; while (*pStr) hash += (hash << 5) + *pStr++;
return (hash % (MAXSYMPTRTBLSIZ-1));}
#if rjsa
HashAtomStr PROC NEAR USES DS SI, npsz:DWORD xor ax,ax ; (ax) = byte-extended-to-word mov cx,ax ; (cx) = hash mov dx,ax ; (dx) = high part for later div cld lds si,npsz ; (si) = pointer to string align 4hfs1: lodsb ; get next byte or al,al ; are we at end of string? jz hfs2 ; yes, compute div and we're done mov bx,cx shl bx,1 shl bx,1 shl bx,1 shl bx,1 shl bx,1 add cx,bx ; (newcx) = (oldcx) + (oldcx) << 5 add cx,ax ; (cx) += (cx) << 5 + (ax) jmp hfs1
hfs2: mov ax,4094 ; magic divider xchg ax,cx ; (dx:ax) = number, (cx) = dividend div cx mov ax,dx retHashAtomStr ENDP
end
#endif
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