StupidOS/lib/lzp/lzp.asm

	;; File: lzp.asm
	;; *Lempel-Ziv + Prediction* (a fast, efficient, and memory-use
	;; conservative compression algorithm)
	;;
	;; (paper: https://ieeexplore.ieee.org/document/488353)

	format COFF
	use32

	;; https://hugi.scene.org/online/coding/hugi%2012%20-%20colzp.htm

LZP_HASH_ORDER = 16
LZP_HASH_SIZE  = (1 shl LZP_HASH_ORDER)

	public lzp_compress
	public lzp_decompress

	; hash(h, x) (h = (h << 4) ^ x)

	section '.code' code

	; xor hash, hash
	; xor mask, mask
	; j = 1
	; while (insz > 0)
	; {
	;    if (ecx == 8)
	;    {
	;       mov [out], mask
	;       xor ecx, ecx
	;       xor mask, mask
	;       j = 1;
	;    }
	;    c = in[inpos++]
	;    if (c == table[hash])
	;    {
	;        mask |= 1 << ecx
	;    }
	;    else
	;    {
	;        table[hash] = c
	;        out[j] = c;
	;    }
	;    HASH(hash, c)
	;    ecx++;
	; }

	;; Function: lzp_compress
	;; 
	;; Parameters:
	;;
	;;     [esp+8]  - output buffer (can be NULL)
	;;     [esp+12] - input buffer
	;;     [esp+16] - size of the input buffer
	;;
	;; Returns:
	;; 
	;;     eax - size of compressed data
	;;
	param_out   equ [ebp+8]
	param_in    equ [ebp+12]
	param_insz  equ [ebp+16]
	local_buff  equ [ebp-10]
	local_inpos equ [ebp-14]
lzp_compress:
	push ebp
	mov ebp, esp
	sub esp, 14

	push ebx
	push esi
	push edi

	mov edi, param_insz
	test edi, edi
	je .exit

	mov ebx, 0
	mov esi, 0
	mov edi, 0
.loop:
	xor ecx, ecx

	cmp esi, param_insz
	je .end

	
	xor ecx, ecx
	;; fetch data
	mov eax, param_in
	movzx eax, byte [eax+esi]
	inc esi

	cmp al, byte [table + ebx]
	jne .not_in_table
	mov edx, 1
	sal edx, cl
	or ebx, edx
	
.not_in_table:
	mov byte [table + ebx], al

	inc ecx
.check:
	cmp esi, param_insz
	jb .loop
.end:
.exit:
	mov eax, edi				; return compressed data size
	;; restore esi, edi
	pop edi
	pop esi

	leave
	ret

	;; Function: lzp_decompress
	;; 
	;; Parameters:
	;;
	;;     [esp+8]  - output buffer (can be null)
	;;     [esp+12] - input buffer
	;;     [esp+16] - size of the input buffer
	;;
	;; Returns:
	;; 
	;;     eax - size of uncompressed data
	;;
lzp_decompress:
	push ebp
	mov ebp, esp
	mov eax, [esp+8]	; in
	mov edx, [esp+12]	; size
	xor ecx, ecx
.loop:
	cmp ecx, edx
	je .end

	inc ecx
	jmp .loop
.end:
	mov eax, ecx
	leave
	ret

	section '.data' data

table db LZP_HASH_SIZE dup(0)