kolibrios/drivers/ddk/string/_strncmp.S
Sergey Semyonov (Serge) 1402c59305 ddk: tiny libc and kernel imports library
git-svn-id: svn://kolibrios.org@1408 a494cfbc-eb01-0410-851d-a64ba20cac60
2010-02-12 20:11:35 +00:00

45 lines
1.0 KiB
ArmAsm

# strncmp() Author: Kees J. Bot 1 Jan 1994
# int strncmp(const char *s1, const char *s2, size_t ecx)
# Compare two strings.
#
.intel_syntax
.globl __strncmp
.text
.align 16
__strncmp:
push ebp
mov ebp, esp
push esi
push edi
test ecx, ecx # Max length is zero?
je done
mov esi, [ebp+8] # esi = string s1
mov edi, [ebp+12] # edi = string s2
cld
compare:
cmpsb # Compare two bytes
jne done
cmpb [esi-1], 0 # End of string?
je done
dec ecx # Length limit reached?
jne compare
done:
seta al # al = (s1 > s2)
setb ah # ah = (s1 < s2)
subb al, ah
movsx eax, al # eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1
pop edi
pop esi
pop ebp
ret