HashMap/xor_hash.s at master · InversionSpaces/HashMap · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
	global __xor_hash

	section .text
__xor_hash:
	xor rax, rax 		; rax = 0

	mov rcx, rsi 		; rcx = len
	shr rcx, 0x3 		; rcx = len / 8

	test rcx, rcx
	je .process_back 	; if rcx == 0 - skip

.process_front_loop:
	xor rax, [rdi] 		; rax ^= [rdi] (64 bits)
	add rdi, 0x8 		; rdi += 8

	loop .process_front_loop

.process_back:
	mov rcx, rsi 		; rcx = len
	and rcx, 0b111 		; rcx = len % 8

	test rcx, rcx
	je .end 		; if rcx == 0 - return

	add rdi, rcx
	dec rdi 		; rdi += rcx - 1

	xor rdx, rdx 		; rdx = 0

.process_back_loop:
	shl rdx, 0x8 		; rdx <<= 8
	or dl, [rdi] 		; rdx |= *rdi
	dec rdi 		; --rdi

	loop .process_back_loop

	xor rax, rdx 		; rax ^= rdx
.end:
	ret