rulimine/common/lib/mem.asm64

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section .text
global memcpy
memcpy:
mov rcx, rdx
mov rax, rdi
rep movsb
ret
global memset
memset:
push rdi
mov rax, rsi
mov rcx, rdx
rep stosb
pop rax
ret
global memmove
memmove:
mov rcx, rdx
mov rax, rdi
cmp rdi, rsi
ja .copy_backwards
rep movsb
jmp .done
.copy_backwards:
lea rdi, [rdi+rcx-1]
lea rsi, [rsi+rcx-1]
std
rep movsb
cld
.done:
ret
global memcmp
memcmp:
mov rcx, rdx
repe cmpsb
jecxz .equal
mov al, byte [rdi-1]
sub al, byte [rsi-1]
movsx rax, al
jmp .done
.equal:
xor eax, eax
.done:
ret