minix/lib/i386/string/strchr.s
2005-04-21 14:53:53 +00:00

41 lines
884 B
ArmAsm
Executable file

! strchr() Author: Kees J. Bot
! 1 Jan 1994
.sect .text; .sect .rom; .sect .data; .sect .bss
! char *strchr(const char *s, int c)
! Look for a character in a string.
!
.sect .text
.define _strchr
.align 16
_strchr:
push ebp
mov ebp, esp
push edi
cld
mov edi, 8(ebp) ! edi = string
mov edx, 16 ! Look at small chunks of the string
next: shl edx, 1 ! Chunks become bigger each time
mov ecx, edx
xorb al, al ! Look for the zero at the end
repne
scasb
pushf ! Remember the flags
sub ecx, edx
neg ecx ! Some or all of the chunk
sub edi, ecx ! Step back
movb al, 12(ebp) ! The character to look for
repne
scasb
je found
popf ! Did we find the end of string earlier?
jne next ! No, try again
xor eax, eax ! Return NULL
pop edi
pop ebp
ret
found: pop eax ! Get rid of those flags
lea eax, -1(edi) ! Address of byte found
pop edi
pop ebp
ret