几个 GetHashCode 函数

几个 GetHashCode 函数：

DBTables.pas

   function GetHashCode(Str: PChar): Integer;
   var
     Off, Len, Skip, I: Integer;
   begin
     Result := 0;
     Off := 1;
     Len := StrLen(Str);
     if Len < 16 then
       for I := (Len - 1) downto 0 do
       begin
         Result := (Result * 37) + Ord(Str[Off]);
         Inc(Off);
       end
     else
     begin
       { Only sample some characters }
       Skip := Len div 8;
       I := Len - 1;
       while I >= 0 do
       begin
         Result := (Result * 39) + Ord(Str[Off]);
         Dec(I, Skip);
         Inc(Off, Skip);
       end;
     end;
   end;

Graphics.pas

function GetHashCode(const Buffer; Count: Integer): Word; assembler;
asm
       MOV     ECX,EDX
       MOV     EDX,EAX
       XOR     EAX,EAX
@@1:    ROL     AX,5
       XOR     AL,[EDX]
       INC     EDX
       DEC     ECX
       JNE     @@1
end;

SysUtils.pas

function HashName(Name: PChar): Cardinal;
asm
 PUSH  ESI
 PUSH  EBX
 MOV   ESI, Name
 XOR   EAX, EAX

@@loop:
 ROL   EAX, 5
 MOV   BL, [ESI]
 CMP   BL, 0
 JE    @@done
 CMP   BL, 'A'
 JL    @@LowerCased
 CMP   BL, 'Z'
 JG    @@LowerCased
 OR    BL, 20H // make lower case
@@LowerCased:
 XOR   AL, BL
 INC   ESI
 JMP   @@loop
@@done:
 POP   EBX
 POP   ESI
 RET
end;

HTTPParse.pas

function GetHashCode(Ident: PChar; Length: Integer): Word;
asm
     PUSH ESI
{$IFNDEF PIC}
   PUSH    EBX
   XOR    EBX,EBX
{$ENDIF}
     MOV  ESI, EAX
     XOR  EAX, EAX
     XOR  ECX, ECX
@@1:  MOV   AL,[ESI]
     ROL    CX,5
     XOR    CL,CharValue.Byte[EBX + EAX]
     INC    ESI
     DEC    EDX
   JNE    @@1
     MOV    EAX,ECX
{$IFNDEF PIC}
   POP    EBX
{$ENDIF}
     POP   ESI
end;

转载于:https://www.cnblogs.com/bjxsky/p/4620101.html