最佳化的兩款串Hash函數

對以下兩種hash函數(FNV BKDR)做了點最佳化，方便用於以0結尾的短字串進行hash，得到32位的hash值

----------------- By G-Spider

 FNV hash

Fnv32_t__stdcall fnv_32a_str_c(char *str){    unsigned char *s = (unsigned char *)str;/* unsigned string */    Fnv32_t hval= 2166136261;       /*     * FNV-1a hash each octet in the buffer     */    do {/* xor the bottom with the current octet */hval ^= (Fnv32_t)*s;/* multiply by the 32 bit FNV magic prime mod 2^32 */hval *= 0x01000193;    }while(*s++);    return hval;}

彙編1:

__declspec(naked)  Fnv32_t __stdcall fnv_32a_str_asm1(char *str){  __asm{           mov     edx,[esp + 4]       ;str           mov     eax,2166136261      ;FNV1_32A_INIT        ;---------------------------        A00:           movzx   ecx,byte ptr [edx]           xor     eax,ecx           inc     edx           imul    eax,16777619       ;fnv_32_prime           test    ecx,ecx           jnz     A00        ;---------------------------           retn    4        }}

彙編2:

__declspec(naked)  Fnv32_t __stdcall fnv_32a_str_asm4(char *str){  __asm{    mov   eax,2166136261      //;FNV1_32A_INIT    mov   edx,[esp + 4]       //;str    push  esi    push  edi//;---------------------------   //;hval ^= (Fnv32_t)*s;//;hval *= 0x01000193;//;hval =hval * (0x01000000  +256+128+16+2+1)//;hval + = (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);//;---------------------------A00:    movzx ecx,byte ptr [edx]    xor   eax,ecx            //;hval ^= (Fnv32_t)*s;    lea   esi,[eax+eax*2]    //;(hval)+(hval<<1)    shl   eax,4              //;(hval<<4)    inc   edx    lea   edi,[eax+eax*8]    //;(hval<<4) + (hval<<7)    shl   eax,4    add   esi,eax            //;(hval)+(hval<<1) +(hval<<8)    shl   eax,16             //;(hval<<24)    add   edi,eax            //;(hval<<24) +(hval<<4) + (hval<<7)    test  ecx,ecx    lea   eax,[esi+edi]     jnz   A00;---------------------------        pop     edi    pop     esi;---------------------------        retn    4   }} 

BKDR Hash

unsigned int __stdcall BKDRHash(unsigned char *str) {    unsigned int seed = 131; // 31 131 1313 13131 131313 etc..    unsigned int hash = 0;    do    {        hash = hash * seed + (*str);    }while(*str++);        return hash; }

彙編1:

__declspec(naked) unsigned int __stdcall BKDRHash1(unsigned char *str){__asm{        xor    eax, eax        mov    edx, [4+esp]A00:        imul   eax,131        movzx  ecx, BYTE ptr [edx]        inc    edx        add    eax, ecx                test   ecx, ecx        jne    A00;---------------------------        retn   4      }}

彙編2:

__declspec(naked) unsigned int __stdcall BKDRHash2(unsigned char *str){__asm{        xor    eax, eax        mov    edx, [esp+4]    A00:         mov    ecx, eax        shl    ecx, 6        add    ecx, eax        lea    eax, [eax+ecx*2]        movzx  ecx ,byte ptr [edx]        inc    edx        add    eax, ecx        test   ecx, ecx        jnz A00;---------------------------        retn    4      }}