mkinitrd-magellan/isolinux/rllpack.inc

; -*- fundamental -*-
; -----------------------------------------------------------------------
;   
;   Copyright 2004 H. Peter Anvin - All Rights Reserved
;
;   This program is free software; you can redistribute it and/or modify
;   it under the terms of the GNU General Public License as published by
;   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
;   Boston MA 02111-1307, USA; either version 2 of the License, or
;   (at your option) any later version; incorporated herein by reference.
;
; -----------------------------------------------------------------------
; $Id: rllpack.inc,v 1.1 2007-09-01 22:44:05 niro Exp $

;
; rllpack.inc
;
; Very simple RLL compressor/decompressor, used to pack binary structures
; together.
;
; Format of leading byte
; 1-128		= x verbatim bytes follow
; 129-255 	= (x-126) times subsequent byte
; 0		= end of data
;

		section .text

;
; rllpack:
;	Pack CX bytes from DS:SI into ES:DI
;	Returns updated SI, DI and CX = number of bytes output
;
rllpack:
		push ax
		push bx
		push cx
		push bp
		push di
.startseq:
		xor ax,ax		; Zero byte
		xor bx,bx		; Run length zero
		mov bp,di		; Pointer to header byte
		stosb			; Store header byte (might be zero)
		jcxz .done_null
.stdbyte:
		lodsb
		stosb
		dec cx
		cmp ah,al
		je .same
.diff:
		mov ah,al
		xor bx,bx
.plainbyte:
		inc bx
		inc byte [es:bp]
		jcxz .done
		jns .stdbyte
		jmp .startseq
.same:
		cmp bl,2
		jb .plainbyte
		; 3 bytes or more in a row, time to convert sequence
		sub byte [es:bp],bl
		jnz .normal
		dec di			; We killed a whole stretch, remove start byte
.normal:
		inc bx	
		sub di,bx
		mov bp,di
		mov al,bl
		add al,126
		stosb
		mov al,ah
		stosb
.getrun:
		jcxz .done
		cmp bl,255-126
		jae .startseq
		lodsb
		cmp al,ah
		jne .nomatch
		inc bx
		inc byte [es:bp]
		dec cx
		jmp .getrun
.nomatch:
		dec si
		jmp .startseq
.done:
		xor al,al
		stosb
.done_null:
		pop dx
		sub dx,di
		neg dx
		pop bp
		pop cx
		pop bx
		pop ax
		ret
;
; rllunpack:
;	Unpack bytes from DS:SI into ES:DI
;	On return SI, DI are updated and CX contains number of bytes output
;	
rllunpack:
		push ax
		push di
		xor cx,cx
.header:
		lodsb
		and al,al
		jz .done
		cmp al,129
		jae .isrun
		; Not a run
		mov cl,al
		rep movsb
		jmp .header
.isrun:
		sub al,126
		mov cl,al
		lodsb
		rep stosb
		jmp .header
.done:
		pop cx
		sub cx,di
		neg cx
		pop ax
		ret
1	niro	532	; -- fundamental --
2			; -----------------------------------------------------------------------
3			;
4			; Copyright 2004 H. Peter Anvin - All Rights Reserved
5			;
6			; This program is free software; you can redistribute it and/or modify
7			; it under the terms of the GNU General Public License as published by
8			; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
9			; Boston MA 02111-1307, USA; either version 2 of the License, or
10			; (at your option) any later version; incorporated herein by reference.
11			;
12			; -----------------------------------------------------------------------
13			; $Id: rllpack.inc,v 1.1 2007-09-01 22:44:05 niro Exp $
14
15			;
16			; rllpack.inc
17			;
18			; Very simple RLL compressor/decompressor, used to pack binary structures
19			; together.
20			;
21			; Format of leading byte
22			; 1-128 = x verbatim bytes follow
23			; 129-255 = (x-126) times subsequent byte
24			; 0 = end of data
25			;
26
27			section .text
28
29			;
30			; rllpack:
31			; Pack CX bytes from DS:SI into ES:DI
32			; Returns updated SI, DI and CX = number of bytes output
33			;
34			rllpack:
35			push ax
36			push bx
37			push cx
38			push bp
39			push di
40			.startseq:
41			xor ax,ax ; Zero byte
42			xor bx,bx ; Run length zero
43			mov bp,di ; Pointer to header byte
44			stosb ; Store header byte (might be zero)
45			jcxz .done_null
46			.stdbyte:
47			lodsb
48			stosb
49			dec cx
50			cmp ah,al
51			je .same
52			.diff:
53			mov ah,al
54			xor bx,bx
55			.plainbyte:
56			inc bx
57			inc byte [es:bp]
58			jcxz .done
59			jns .stdbyte
60			jmp .startseq
61			.same:
62			cmp bl,2
63			jb .plainbyte
64			; 3 bytes or more in a row, time to convert sequence
65			sub byte [es:bp],bl
66			jnz .normal
67			dec di ; We killed a whole stretch, remove start byte
68			.normal:
69			inc bx
70			sub di,bx
71			mov bp,di
72			mov al,bl
73			add al,126
74			stosb
75			mov al,ah
76			stosb
77			.getrun:
78			jcxz .done
79			cmp bl,255-126
80			jae .startseq
81			lodsb
82			cmp al,ah
83			jne .nomatch
84			inc bx
85			inc byte [es:bp]
86			dec cx
87			jmp .getrun
88			.nomatch:
89			dec si
90			jmp .startseq
91			.done:
92			xor al,al
93			stosb
94			.done_null:
95			pop dx
96			sub dx,di
97			neg dx
98			pop bp
99			pop cx
100			pop bx
101			pop ax
102			ret
103			;
104			; rllunpack:
105			; Unpack bytes from DS:SI into ES:DI
106			; On return SI, DI are updated and CX contains number of bytes output
107			;
108			rllunpack:
109			push ax
110			push di
111			xor cx,cx
112			.header:
113			lodsb
114			and al,al
115			jz .done
116			cmp al,129
117			jae .isrun
118			; Not a run
119			mov cl,al
120			rep movsb
121			jmp .header
122			.isrun:
123			sub al,126
124			mov cl,al
125			lodsb
126			rep stosb
127			jmp .header
128			.done:
129			pop cx
130			sub cx,di
131			neg cx
132			pop ax
133			ret