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@ ScummVM - Graphic Adventure Engine
@
@ ScummVM is the legal property of its developers, whose names
@ are too numerous to list here. Please refer to the COPYRIGHT
@ file distributed with this source distribution.
@
@ 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@ 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@ if not, write to the Free Software
@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
@
@ @author Robin Watts (robin@wss.co.uk)
.global ARM_adpcm
.section .itcm,"ax", %progbits
.align 2
.code 32
@ ARM implementation of inner ADPCM decoding loop
@
@ C prototype would be:
@
@ extern "C" void ARM_adpcm(int *block,
@ int len,
@ int stepTableIndex,
@ int firstSample,
@ s16 *decompressionBuffer)
ARM_adpcm
@ r0 = block
@ r1 = len
@ r2 = stepTableIndex
@ r3 = firstSample
@ <> = decompressionBuffer
STMFD r13!,{r4-r11,r14}
LDR r4,[r13,#4*9]
LDR r12,[r0],#4 @ r12 = word = block[r>>3]
MOV r14,#0
ADR r11,stepTab
ADR r7, indexTab
MOV r2, r2, LSL #1 @ r2 = stepTableIndex*2 - hold it doubled
STR r3, [r4],#2 @ decompBuff[0] = firstSample
MOV r3, r3, LSL #16 @ r3 = firstSample<<16 (for saturated maths)
SUBS r1, r1, #1
BLE end
loop:
LDRH r10,[r11,r2] @ r10 = stepTab[stepTableIndex]
TST r12,#4 @ if ((offset & 4) == 0)
MOVEQ r9, #0 @ r9 = diff = 0
MOVNE r9, r10 @ else r9 = diff = stepTab[stepTableIndex]
TST r12,#2 @ if (offset & 2)
ADDNE r9, r9, r10,ASR #1 @ diff += r10>>1
TST r12,#1 @ if (offset & 1)
ADDNE r9, r9, r10,ASR #2 @ diff += r10>>2
ADD r9, r9, r10,ASR #3 @ diff += r10>>3
TST r12,#8 @ if (offset & 8
RSBNE r9, r9, r10
ADDS r3, r3, r9 @ r3 = newSample = prevSample+diff
RSCVS r3, r3, #1<<31 @ r3 = clip(newSample)
MOV r8, r3, LSR #16
AND r6, r12,#4 @ r6 = offset
LDRB r6, [r7,r6] @ r6 = indexTab[offset]
MOV r12,r12,LSR #4
STRH r8, [r4],#2
ADDS r2,r2,r6,LSL #1 @ r2 = stepTableIndex += indexTab[offset]
MOVLT r2,#0
CMP r2,#88*2
MOVGT r2,#88*2
SUBS r1,r1,#1
BEQ end
SUBS r14,r14,#0x10000000
LDREQ r12,[r0],#4
B loop
end:
LDMFD r13!,{r4-r11,PC}
stepTab:
DCW 7, 8, 9, 10, 11, 12, 13, 14,
DCW 16, 17, 19, 21, 23, 25, 28, 31,
DCW 34, 37, 41, 45, 50, 55, 60, 66,
DCW 73, 80, 88, 97, 107, 118, 130, 143,
DCW 157, 173, 190, 209, 230, 253, 279, 307,
DCW 337, 371, 408, 449, 494, 544, 598, 658,
DCW 724, 796, 876, 963, 1060, 1166, 1282, 1411,
DCW 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
DCW 3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
DCW 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
DCW 15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
DCW 32767
indexTab:
DCB -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8
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