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Accumulator factory: Difference between revisions
Create x86 Assembly entry for "Accumulator factory"
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(Create x86 Assembly entry for "Accumulator factory") |
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=={{header|x86 Assembly}}==
{{works with|NASM}}
{{works with|Linux}}
32 bit
The accumulator function that is returned uses a section of its instruction space to store the accumulated sum.
This way it works without having to keep track of any addresses external to the function itself.
The only deviation from the spec is that this only works with integer values.
With some extra work, floating point numbers can be incorporated, but outputting would be trickier.
<lang asm>
; Accumulator factory
; Returns a function that returns the sum of all numbers ever passed in
; Build:
; nasm -felf32 af.asm
; ld -m elf32_i386 af.o -o af
global _start
section .text
_start:
mov eax, 0x2D ; sys_brk(unsigned long brk)
xor ebx, ebx ; Returns current break on an error
int 0x80 ; syscall
push eax ; Save the initial program break
push 2 ; Get an accumulator initialized to 2
call factory
mov [acc1], eax ; Save the pointer in acc1
push 5 ; Get an accumulator initialized to 5
call factory
mov [acc2], eax ; Save the pointer in acc2
push 4 ; Call acc1 with 4
lea eax, [acc1]
call [eax]
push 4 ; Call acc2 with 4
lea eax, [acc2]
call [eax]
push -9 ; Call acc1 with -9
lea eax, [acc1]
call [eax]
push 13 ; Call acc1 with 13
lea eax, [acc1]
call [eax]
push eax ; Print the number, should be 10
call print_num
push -5 ; Call acc2 with -5
lea eax, [acc2]
call [eax]
push eax ; Print the number, should be 4
call print_num
mov eax, 0x2D ; Reset the program break
pop ebx
int 0x80
mov eax, 0x01 ; sys_exit(int error)
xor ebx, ebx ; error = 0 (success)
int 0x80
; int (*function)(int) factory (int n)
; Returns a pointer to a function that returns the sum of all numbers passed
; in to it, including the initial parameter n;
factory:
push ebp ; Create stack frame
mov ebp, esp
push ebx
push edi
push esi
mov eax, 0x2D ; Allocate memory for the accumulator
xor ebx, ebx
int 0x80
push eax ; Save the current program break
mov ebx, .acc_end ; Calculate the new program break
sub ebx, .acc
push ebx ; Save the length
add ebx, eax
mov eax, 0x2D
int 0x80
pop ecx ; Copy the accumulator code into memory
pop eax ; Set the returned address
mov edi, eax
mov esi, .acc
rep movsb
lea edi, [eax + 10] ; Copy the parameter to initialize accumulator
lea esi, [ebp + 8]
movsd
pop esi ; Tear down stack frame
pop edi
pop ebx
mov esp, ebp
pop ebp
ret 4 ; Return and remove parameter from stack
.acc: ; Start of the returned accumulator
push ebp
mov ebp, esp
push edi
push esi
call .acc_skip ; Jumps over storage, pushing address to stack
dd 0 ; The accumulator storage (32 bits)
.acc_skip:
pop esi ; Retrieve the accumulator using address on stack
lodsd
add eax, [ebp + 8] ; Add the parameter
lea edi, [esi - 4]
stosd ; Save the new value
pop esi
pop edi
mov esp, ebp
pop ebp
ret 4
.acc_end: ; End of accumulator
; void print_num (int n)
; Prints a positive integer and a newline
print_num:
push ebp
mov ebp, esp
mov eax, [ebp + 8] ; Get the number
lea ecx, [output + 10] ; Put a newline at the end
mov BYTE [ecx], 0x0A
mov ebx, 10 ; Divisor
.loop:
dec ecx ; Move backwards in string
xor edx, edx
div ebx
add edx, 0x30 ; Store ASCII digit
mov [ecx], dl
cmp eax, 0 ; Loop until all digits removed
jnz .loop
mov eax, 0x04 ; sys_write(int fd, char *buf, int len)
mov ebx, 0x01 ; stdout
lea edx, [output + 11] ; Calulate length
sub edx, ecx
int 0x80
mov esp, ebp
pop ebp
ret 4
section .bss
acc1: ; Variable that stores the first accumulator
resd 1
acc2: ; Variable that stores the second accumulator
resd 1
output: ; Holds the output buffer
resb 11
</lang>
Output
<pre>
10
4
</pre>
=={{header|XLISP}}==
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