45 lines
1,015 B
ArmAsm
Executable file
45 lines
1,015 B
ArmAsm
Executable file
! memset() Author: Kees J. Bot
|
|
! 2 Jan 1994
|
|
.sect .text; .sect .rom; .sect .data; .sect .bss
|
|
|
|
! void *memset(void *s, int c, size_t n)
|
|
! Set a chunk of memory to the same byte value.
|
|
!
|
|
.sect .text
|
|
.define _memset
|
|
.align 16
|
|
_memset:
|
|
push ebp
|
|
mov ebp, esp
|
|
push edi
|
|
mov edi, 8(ebp) ! The string
|
|
movzxb eax, 12(ebp) ! The fill byte
|
|
mov ecx, 16(ebp) ! Length
|
|
cld
|
|
cmp ecx, 16
|
|
jb sbyte ! Don't bother being smart with short arrays
|
|
test edi, 1
|
|
jnz sbyte ! Bit 0 set, use byte store
|
|
test edi, 2
|
|
jnz sword ! Bit 1 set, use word store
|
|
slword: movb ah, al
|
|
mov edx, eax
|
|
sal edx, 16
|
|
or eax, edx ! One byte to four bytes
|
|
shrd edx, ecx, 2 ! Save low two bits of ecx in edx
|
|
shr ecx, 2
|
|
rep
|
|
stos ! Store longwords.
|
|
shld ecx, edx, 2 ! Restore low two bits
|
|
sword: movb ah, al ! One byte to two bytes
|
|
shr ecx, 1
|
|
rep
|
|
o16 stos ! Store words
|
|
adc ecx, ecx ! One more byte?
|
|
sbyte: rep
|
|
stosb ! Store bytes
|
|
done: mov eax, 8(ebp) ! Return some value you have no need for
|
|
pop edi
|
|
pop ebp
|
|
ret
|