CRC32C calculation utility (standalone x86 32bit nasm version).

crc32c_32bit.asm

%define BUFSIZE 4096

bits 32

section .text

extern fdopen
extern fprintf
extern printf

extern open
extern close
extern read

%macro fail 1+
	push dword %%str
	push dword [stderr]
	call fprintf
	add esp, 8
	popad
	pop ebp
	mov eax, 1
	ret
	%%str: db %1, 10, 0
%endmacro

global main
align 16
main:
	; Set up stack frame.
	push ebp
	mov ebp, esp
	pushad
	; Get command line arguments in an easy place.
	mov eax, [ebp+8] ; argc
	mov [argc], eax
	mov eax, [ebp+12] ; argv
	mov [argv], eax
	; Get a FILE* for stderr.
	push dword .s_w
	push dword 2
	call fdopen
	add esp, 8
	mov [stderr], eax
	; Check if we got the right amount of arguments (1).
	cmp dword [argc], 2
	je .argc_ok
	; If we reach here we have more or less than 1 argument.
	mov eax, [argv]
	push dword [eax]
	push dword .err_args
	push dword [stderr]
	call fprintf
	add esp, 12
	popad
	pop ebp
	mov eax, 1
	ret
	.err_args: db "usage: %s <filename>", 10, 0
.argc_ok:
	; Try to open the specified file.
	mov eax, [argv]
	add eax, 4
	push dword 0 | 0o00100000 ; O_RDONLY | O_LARGEFILE
	push dword [eax]
	call open
	add esp, 8
	mov [fd], eax
	test eax, eax
	jns .open_ok
	fail "error: can't open file"
.open_ok:
	; EBX will hold the sum here.
	mov ebx, 0xFFFFFFFF
align 16
.doblock:
	; Read a bit of the file.
	push dword BUFSIZE
	push dword buf
	push dword [fd]
	call read
	add esp, 12
	; Count the length while we're at it.
	add dword [len], eax
	adc dword [len+4], 0
	; Calculate CRC of that bit.
	mov edx, buf
.crc32c: ; eax = length, ebx = sum, edx = buf
	; Do 4-byte blocks.
	mov ecx, eax
	shr ecx, 2
	test ecx, ecx
	jz .end32
	align 16
.step32:
	crc32 ebx, dword [edx] ; Doesn't seem to matter much wether aligned.
	add edx, 4
	loop .step32
.end32:
	; Finish.
	mov ecx, eax
	and ecx, 3
	test ecx, ecx
	jz .end
	align 16
.step8:
	crc32 ebx, byte [edx]
	inc edx
	loop .step8
.end:
	cmp eax, BUFSIZE
	je .doblock
	xor ebx, 0xFFFFFFFF
	; Close the file.
	push dword [fd]
	call close
	add esp, 4
	; Print out the result.
	push dword [len+4]
	push dword [len]
	push ebx
	push dword .format
	call printf
	add esp, 16
	; The end.
	popad
	pop ebp
	xor eax, eax
	ret

.format: db "%08X %llu", 10, 0
.s_w: db "w", 0

section .bss
	stderr: resd 1
	argc: resd 1
	argv: resd 1
	fd: resd 1
	len: resq 1
	buf: resb BUFSIZE