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/* arm_nrv2e_d8.S -- ARM decompressor for NRV2E
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This file is part of the UPX executable compressor.
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Copyright (C) 1996-2008 Markus Franz Xaver Johannes Oberhumer
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Copyright (C) 1996-2008 Laszlo Molnar
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Copyright (C) 2000-2008 John F. Reiser
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All Rights Reserved.
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UPX and the UCL library are free software; you can redistribute them
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and/or modify them under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; see the file COPYING.
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If not, write to the Free Software Foundation, Inc.,
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59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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Markus F.X.J. Oberhumer Laszlo Molnar
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<markus@oberhumer.com> <ml1050@users.sourceforge.net>
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John F. Reiser
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<jreiser@users.sourceforge.net>
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*/
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#define src r0
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#define len r1 /* overlaps 'cnt' */
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#define dst r2
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#define tmp r3
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#define bits r4
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#define off r5
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#define wrnk r6 /* 0x500 M2_MAX_OFFSET before "wrinkle" */
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#define srclim r7
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#define cnt r1 /* overlaps 'len' while reading an offset */
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/* "mov lr,pc; bxx ..." implements conditional subroutine call */
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#define GETBIT add bits,bits; mov lr,pc; beq get1_n2e
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#define getnextb(reg) GETBIT; adc reg,reg
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#define jnextb0 GETBIT; bcc
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#define jnextb1 GETBIT; bcs
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.section .icode.ucl_decompress, "ax", %progbits
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.align 2
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theseven |
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ucl_decompress: .globl ucl_decompress @ ARM mode
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.type ucl_decompress, %function
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/* error = (*)(char const *src, int len_src, char *dst, int *plen_dst)
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Actual decompressed length is stored through plen_dst.
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*/
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adr r12,1+.thumb_nrv2e_d8; bx r12 @ enter THUMB mode
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.code 16 @ THUMB mode
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.thumb_func
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.thumb_nrv2e_d8:
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push {r2,r3,r4,r5,r6,r7,lr}
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add srclim,len,src @ srclim= eof_src;
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mov bits,#1; neg off,bits @ off= -1 initial condition
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lsl bits,#31 @ 1<<31: refill next time
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mov wrnk,#5
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lsl wrnk,#8 @ 0x500 @ nrv2e M2_MAX_OFFSET
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b top_n2e
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eof_n2e:
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pop {r3,r4} @ r3= orig_dst; r4= plen_dst
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sub src,srclim @ 0 if actual src length equals expected length
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sub dst,r3 @ actual dst length
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str dst,[r4]
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pop {r4,r5,r6,r7}
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pop {r1}
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bx r1
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get1_n2e: @ In: Carry set [from adding 0x80000000 (1<<31) to itself]
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ldrb bits,[src] @ zero-extend next byte
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adc bits,bits @ double and insert CarryIn as low bit
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add src,#1
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lsl bits,#24 @ move to top byte, and set CarryOut from old bit 8
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mov pc,lr @ return, stay in current (THUMB) mode
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lit_n2e:
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ldrb tmp,[src]; add src,#1
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strb tmp,[dst]; add dst,#1
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top_n2e:
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jnextb1 lit_n2e
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mov cnt,#1; b getoff_n2e
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off_n2e:
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sub cnt,#1
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getnextb(cnt)
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getoff_n2e:
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getnextb(cnt)
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jnextb0 off_n2e
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sub tmp,cnt,#3 @ set Carry
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mov len,#0 @ Carry unaffected
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blo offprev_n2e @ cnt was 2; tests Carry only
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lsl tmp,#8
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ldrb off,[src]; add src,#1 @ low 7+1 bits
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orr off,tmp
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mvn off,off; beq eof_n2e @ off= ~off
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asr off,#1; bcs lenlast_n2e
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b lenmore_n2e
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offprev_n2e:
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jnextb1 lenlast_n2e
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lenmore_n2e:
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mov len,#1
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jnextb1 lenlast_n2e
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len_n2e:
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getnextb(len)
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jnextb0 len_n2e
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add len,#6-2
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b gotlen_n2e
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lenlast_n2e:
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getnextb(len) @ 0,1,2,3
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add len,#2
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gotlen_n2e: @ 'cmn': add the inputs, set condition codes, discard the sum
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cmn wrnk,off; bcs near_n2e @ within M2_MAX_OFFSET
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add len,#1 @ too far away, so minimum match length is 3
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near_n2e:
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ldrb tmp,[dst] @ force cacheline allocate
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copy_n2e:
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ldrb tmp,[dst,off]
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strb tmp,[dst]; add dst,#1
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sub len,#1; bne copy_n2e
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b top_n2e
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.size ucl_decompress, .-ucl_decompress
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