string.s

Intel x86处理器的汇编器

.text

//------------------------------------------
// unsigned int str_len(const char *s)
//
//     return value:
//     unsigned int: the length of strings
//-----------------------------------------

.global str_len
str_len:
	xor %eax, %eax
	movl 4(%esp), %edx
loop:
	movb (%edx), %bl
	inc %eax
	inc %edx
	test %bl,%bl
	jnz loop
	dec %eax
	ret


//-------------------------------------
// char get_char(const char *s)
// 
// return value:
// 	   char: get char of string[ith]
//--------------------------------------

.global get_char
get_char:
	movl 4(%esp), %edx
	movl 8(%esp), %ecx
		
loop1:
	movb (%edx), %al
	test %al, %al
	jz out
	inc %edx
	dec %ecx
	test %ecx, %ecx
	jnz loop1
out:

	ret

//----------------------------------
//  int str_ch(const char *d, char c)
//
// return: 0: no found
//	value: found & postion;
//---------------------------
.global str_ch
str_ch:
	xor %eax, %eax
	movl 4(%esp), %edx
	movl 8(%esp), %ecx

loop2:
	inc  %eax
	movb (%edx), %bl
	test %bl, %bl
	jz out1
	inc %edx
	cmpb %bl, %cl
	jnz loop2
	jmp out2

out1:
	xor %eax, %eax

out2:
	ret


//--------------------------------------------------------------
//     unsigned int str_str(const char *dest, const char* source)
//
//    reture value:
//               0:    no found
//    unsigned int:    found & get postion
//--------------------------------------------------------------

.global str_str
str_str:
	movl 4(%esp), %edi
	movl 8(%esp), %esi
	
// set tmp var
	sub $8, %esp
	movl %edi, 4(%esp)	
	movl %esi, (%esp)

	mov $1, %eax

loop3:
	mov %esi, %ebx
	mov %edi, %edx

	inc %esi
	inc %edi
	movb (%ebx), %cl

//-----------
// found & no found
	test %cl,%cl
	jz result	
	cmpb $0, (%edx)
	jz no		
//-----------

	cmpb (%edx), %cl
	jz loop3		
yes:
	incl 4(%esp)
	movl 4(%esp), %edi
	movl (%esp), %esi
	inc %eax
	jmp loop3
no:
	xor %eax, %eax
result:
	add $8, %esp
	ret

//----------------------------
// ungisgned get_c_sum(char *s, char c)
//
// return char c sum in string s
//
//------------------------------------
.global get_c_sum
get_c_sum:
	movl 4(%esp), %edx
	movb 8(%esp), %bl
	xor %eax, %eax
	
	test %edx, %edx
	jz out_get_c

loop_get_c:	
	inc %edx
	movb -1(%edx), %cl
	test %cl, %cl
	jz out_get_c

	cmp %bl, %cl
	jnz loop_get_c
	inc %eax
	jmp loop_get_c
	
out_get_c:
	ret


//
//--------------------------
.global get_pc
get_pc:
	call next
next:	pop %eax
	ret


//-----------------------------------------

.global dump_banry

dump_banry:
	push %ebp
	mov %esp, %ebp

	movl 8(%ebp), %edx
	movb 12(%ebp), %al

	movl $9, %ecx

loop5:

	dec %ecx
	jz out5
	shl $1, %al
	jc one

zero: 
	movb $48, (%edx)
	inc %edx
	jmp loop5

one:	
	movb  $49, (%edx)
	inc %edx
	jmp loop5

out5:
	pop %ebp
	ret