bloom_chk_hash160.nasm

CPU X64

%macro check_bit 0             ; check whether bit rax
                               ; of the bloom filter is set
  mov   rdx, rax               ; copy hash
  shr   rax, byte 3            ; byte to check in rax
  movzx rax, byte [rdi+rax]    ; load byte to check from memory
  and   rdx, byte 7            ; mask off bit to check
  bt    rax, rdx               ; bit test against bloom filter
  jnc   bloom_miss             ; jump to return a 'miss' if bit isn't set
%endmacro                      ; rax and rdx are clobbered

global bloom_chk_hash160:function

section .text

; unsigned int bloom_chk_hash160(unsigned char *bloom, uint32_t *h);
; should compatible with the old fixed parameter bloom filter from brainflayer
bloom_chk_hash160:
  mov eax, [rsi+0x00]
  check_bit
  mov eax, [rsi+0x04]
  check_bit
  mov eax, [rsi+0x08]
  check_bit
  mov eax, [rsi+0x0c]
  check_bit
  mov eax, [rsi+0x10]
  check_bit

  mov ax,  [rsi+0x06]
  shl eax, 16
  mov ax,  [rsi+0x00]
  check_bit
  mov ax,  [rsi+0x0a]
  shl eax, 16
  mov ax,  [rsi+0x04]
  check_bit
  mov ax,  [rsi+0x0e]
  shl eax, 16
  mov ax,  [rsi+0x08]
  check_bit
  mov ax,  [rsi+0x12]
  shl eax, 16
  mov ax,  [rsi+0x0c]
  check_bit
  mov ax,  [rsi+0x02]
  shl eax, 16
  mov ax,  [rsi+0x10]
  check_bit

  mov al,  [rsi+0x07]
  shl eax, 16
  mov ax,  [rsi+0x00]
  shl eax, 8
  mov al,  [rsi+0x02]
  check_bit
  mov al,  [rsi+0x0b]
  shl eax, 16
  mov ax,  [rsi+0x04]
  shl eax, 8
  mov al,  [rsi+0x06]
  check_bit
  mov al,  [rsi+0x0f]
  shl eax, 16
  mov ax,  [rsi+0x08]
  shl eax, 8
  mov al,  [rsi+0x0a]
  check_bit
  mov al,  [rsi+0x13]
  shl eax, 16
  mov ax,  [rsi+0x0c]
  shl eax, 8
  mov al,  [rsi+0x0e]
  check_bit
  mov al,  [rsi+0x03]
  shl eax, 16
  mov ax,  [rsi+0x10]
  shl eax, 8
  mov al,  [rsi+0x12]
  check_bit

  mov eax  [rsi+0x05]
  mov al   [rsi+0x00]
  check_bit
  mov eax  [rsi+0x09]
  mov al   [rsi+0x04]
  check_bit
  mov eax  [rsi+0x0d]
  mov al   [rsi+0x08]
  check_bit
  mov ax   [rsi+0x11]
  shl eax, 16
  mov ah   [rsi+0x13]
  mov al   [rsi+0x0c]
  check_bit
  mov eax  [rsi+0x01]
  mov al   [rsi+0x10]
  check_bit

bloom_hit:
  mov eax, 1
  ret

bloom_miss:
  xor eax, eax
  ret
  

; vim:ai:sw=2:ts=2:et:syntax=nasm:filetype=nasm