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authorMax Kellermann <max@duempel.org>2012-03-21 08:44:43 +0100
committerMax Kellermann <max@duempel.org>2012-03-21 08:44:43 +0100
commitc1d0a8b5ce93c4b70b00b14f2015fb6a57681dbe (patch)
treeacae564b851d4c799dd3bd635e25a18531770b94 /src/util/bit_reverse.c
parent08ce24ec3fb094f653b3f3421388edec02f1dced (diff)
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dsd2pcm: move the bit reversing code to a generic library
Instead of doing run-time initialisation, use a constant lookup table.
Diffstat (limited to 'src/util/bit_reverse.c')
-rw-r--r--src/util/bit_reverse.c31
1 files changed, 31 insertions, 0 deletions
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)
+};