upx/src/stub/arm_nrv2e_d32.S

/* arm_nrv2e_d32.S -- ARM decompressor for NRV2E

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2004 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2004 Laszlo Molnar
   Copyright (C) 2000-2006 John F. Reiser
   All Rights Reserved.

   UPX and the UCL library are free software; you can redistribute them
   and/or modify them under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer              Laszlo Molnar
   <mfx@users.sourceforge.net>          <ml1050@users.sourceforge.net>

   John F. Reiser
   <jreiser@users.sourceforge.net>
*/

#define src  r0
#define len  r1  /* overlaps 'cnt' */
#define dst  r2
#define tmp  r3
#define bits r4
#define off  r5
#define g32  r6
#define wrnk r7  /* 0x500  M2_MAX_OFFSET before "wrinkle" */

#define cnt  r1  /* overlaps 'len' while reading an offset */

ucl_nrv2e_decompress_32: .globl ucl_nrv2e_decompress_32  @ ARM mode
/* error = (*)(char const *src, int len_src, char *dst, int *plen_dst) */
	add r1,len,src  @ r1= eof_src;
	stmfd sp!,{r1,r2,r3, r4,r5,r6,r7,lr}
	blx hitch_n2e
hitch_n2e_r:
	ldmfd sp!,{r4,r5,r6,r7,pc}

get32:  @ ARM mode; In: Carry set (unchanged until final adcs)
	ldrb bits,[src],#1
	ldrb tmp, [src],#1; orr bits,bits,tmp,lsl #1*8
	ldrb tmp, [src],#1; orr bits,bits,tmp,lsl #2*8
	ldrb tmp, [src],#1; orr bits,bits,tmp,lsl #3*8
	adcs bits,bits,bits  @ Set Carry out
	bx lr

#define GETBIT \
   add bits,bits; beq 1f; 0: \
   .subsection 1; \
1: blx g32; b 0b; \
   .subsection 0

#define getnextb(reg) GETBIT; adc reg,reg
#define   jnextb0     GETBIT; bcc
#define   jnextb1     GETBIT; bcs

	.code 16  @ THUMB mode
eof_n2e:
	pop {r1,r3,r4}  @ r1= eof_src; r3= orig_dst; r4= plen_dst
	sub src,r1  @ 0 if actual src length equals expected length
	sub dst,r3  @ actual dst length
	str dst,[r4]
	sub g32,#get32 - hitch_n2e_r  @ g32= &hitch_n2e_r
	bx g32

hitch_n2e:
	mov g32,lr  @ return address
	add g32,#get32 - hitch_n2e_r  @ g32= &get32
	mov bits,#1; neg off,bits  @ off= -1 initial condition
        lsl bits,#31  @ 1<<31; refill next time
        mov wrnk,#5
        lsl wrnk,#8  @ 0x500
	b top_n2e

lit_n2e:
	ldrb tmp,[src]; add src,#1
	strb tmp,[dst]; add dst,#1
top_n2e:
        jnextb1 lit_n2e
        mov cnt,#1; b getoff_n2e

off_n2e:
        sub cnt,#1
        getnextb(cnt)
getoff_n2e:
        getnextb(cnt)
        jnextb0 off_n2e

        sub tmp,cnt,#3  @ set Carry
        mov len,#0  @ Carry unaffected
        blo offprev_n2e  @ cnt was 2; tests Carry only
        lsl off,tmp,#8
        ldrb tmp,[src]; add src,#1
        orr off,tmp
        mvn off,off; beq eof_n2e  @ off= ~off
        asr off,#1; bcs lenlast_n2e
        b lenmore_n2e

offprev_n2e:
        jnextb1 lenlast_n2e
lenmore_n2e:
        mov len,#1
        jnextb1 lenlast_n2e
len_n2e:
        getnextb(len)
        jnextb0 len_n2e
        add len,#6-2
        b gotlen_n2e

lenlast_n2e:
        getnextb(len)  @ 0,1,2,3
        add len,#2
gotlen_n2e:  @ 'cmn': add the inputs, set condition codes, discard the sum
        cmn off,wrnk; bcs near_n2e  @ within M2_MAX_OFFSET
        add len,#1  @ too far away, so minimum match length is 3
near_n2e:
	ldrb tmp,[dst]  @ force cacheline allocate
copy_n2e:
	ldrb tmp,[dst,off]
	strb tmp,[dst]; add dst,#1
	sub len,#1; bne copy_n2e
	b top_n2e

/*
vi:ts=8:et:nowrap
 */