From c1d0a8b5ce93c4b70b00b14f2015fb6a57681dbe Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Wed, 21 Mar 2012 08:44:43 +0100 Subject: dsd2pcm: move the bit reversing code to a generic library Instead of doing run-time initialisation, use a constant lookup table. --- src/dsd2pcm/dsd2pcm.c | 12 ++++-------- src/util/bit_reverse.c | 31 +++++++++++++++++++++++++++++++ src/util/bit_reverse.h | 35 +++++++++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+), 8 deletions(-) create mode 100644 src/util/bit_reverse.c create mode 100644 src/util/bit_reverse.h (limited to 'src') diff --git a/src/dsd2pcm/dsd2pcm.c b/src/dsd2pcm/dsd2pcm.c index 315820f60..4c7640853 100644 --- a/src/dsd2pcm/dsd2pcm.c +++ b/src/dsd2pcm/dsd2pcm.c @@ -1,3 +1,5 @@ +#include "util/bit_reverse.h" + #include #include @@ -84,7 +86,6 @@ static const double htaps[HTAPS] = { }; static float ctables[CTABLES][256]; -static unsigned char bitreverse[256]; static int precalculated = 0; static void precalc(void) @@ -92,11 +93,6 @@ static void precalc(void) int t, e, m, k; double acc; if (precalculated) return; - for (t=0, e=0; t<256; ++t) { - bitreverse[t] = e; - for (m=128; m && !((e^=m)&m); m>>=1) - ; - } for (t=0; t8) k=8; @@ -170,10 +166,10 @@ extern void dsd2pcm_translate( lsbf = lsbf ? 1 : 0; while (samples-- > 0) { bite1 = *src & 0xFFu; - if (lsbf) bite1 = bitreverse[bite1]; + if (lsbf) bite1 = bit_reverse(bite1); ptr->fifo[ffp] = bite1; src += src_stride; p = ptr->fifo + ((ffp-CTABLES) & FIFOMASK); - *p = bitreverse[*p & 0xFF]; + *p = bit_reverse(*p); acc = 0; for (i=0; ififo[(ffp -i) & FIFOMASK] & 0xFF; diff --git a/src/util/bit_reverse.c b/src/util/bit_reverse.c new file mode 100644 index 000000000..ba8a23ef1 --- /dev/null +++ b/src/util/bit_reverse.c @@ -0,0 +1,31 @@ +/* + * Copyright (C) 2003-2012 The Music Player Daemon Project + * http://www.musicpd.org + * + * 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. + */ + +#include "bit_reverse.h" + +/** + * @see http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable + */ +const uint8_t bit_reverse_table[256] = +{ +#define R2(n) n, n + 2*64, n + 1*64, n + 3*64 +#define R4(n) R2(n), R2(n + 2*16), R2(n + 1*16), R2(n + 3*16) +#define R6(n) R4(n), R4(n + 2*4 ), R4(n + 1*4 ), R4(n + 3*4 ) + R6(0), R6(2), R6(1), R6(3) +}; diff --git a/src/util/bit_reverse.h b/src/util/bit_reverse.h new file mode 100644 index 000000000..e44693b1d --- /dev/null +++ b/src/util/bit_reverse.h @@ -0,0 +1,35 @@ +/* + * Copyright (C) 2003-2012 The Music Player Daemon Project + * http://www.musicpd.org + * + * 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. + */ + +#ifndef MPD_BIT_REVERSE_H +#define MPD_BIT_REVERSE_H + +#include +#include + +extern const uint8_t bit_reverse_table[256]; + +G_GNUC_CONST +static inline uint8_t +bit_reverse(uint8_t x) +{ + return bit_reverse_table[x]; +} + +#endif -- cgit v1.2.3