/* arm_nrv2e_d32.S -- ARM decompressor for NRV2E

   This file is part of the UPX executable compressor.

   Copyright (C) Markus Franz Xaver Johannes Oberhumer
   Copyright (C) Laszlo Molnar
   Copyright (C) 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
   <markus@oberhumer.com>               <ezerotven+github@gmail.com>

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

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

cnt  .req r1  /* overlaps 'len' while reading an offset */

#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

#ifndef PURE_THUMB
ucl_nrv2e_decompress_32: .globl ucl_nrv2e_decompress_32  @ ARM mode
        .type ucl_nrv2e_decompress_32, %function
/* error = (*)(char const *src, int len_src, char *dst, int *plen_dst) */
        adr r12,1+.thumb_nrv2e_d32; bx r12  @ enter THUMB mode
        .code 16  @ THUMB mode
        .thumb_func
#endif

.thumb_nrv2e_d32:
        add r1,len,src  @ r1= eof_src;
        push {r1,r2,r3, r4,r5,r6,r7, lr}
        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
        adr g32,get32  @ load pc-relative address
        b top_n2e

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]
        pop {r4,r5,r6,r7, pc}  @ return

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 tmp,#8
        ldrb off,[src]; add src,#1  @ low 7+1 bits
        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

        .code 32  @ ARM mode for ease of Carry manipulation
get32:  @ 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
        .code 16  @ THUMB mode

#ifndef PURE_THUMB
        .size ucl_nrv2e_decompress_32, .-ucl_nrv2e_decompress_32
#endif

    .unreq src
    .unreq len
    .unreq dst
    .unreq tmp
    .unreq bits
    .unreq off
    .unreq g32
    .unreq wrnk
    .unreq cnt

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

