1 files changed, 101 insertions, 0 deletions
diff --git a/common/util.c b/common/util.c
new file mode 100644
index 000000000..7e0d54299
--- /dev/null
+++ b/common/util.c
@@ -0,0 +1,101 @@
+/*
+Copyright 2011 Jun Wako <wakojun@gmail.com>
+
+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, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "util.h"
+
+// bit population - return number of on-bit
+uint8_t bitpop(uint8_t bits)
+{
+    uint8_t c;
+    for (c = 0; bits; c++)
+        bits &= bits - 1;
+    return c;
+/*
+    const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
+    return bit_count[bits>>4] + bit_count[bits&0x0F]
+*/
+}
+
+uint8_t bitpop16(uint16_t bits)
+{
+    uint8_t c;
+    for (c = 0; bits; c++)
+        bits &= bits - 1;
+    return c;
+}
+
+uint8_t bitpop32(uint32_t bits)
+{
+    uint8_t c;
+    for (c = 0; bits; c++)
+        bits &= bits - 1;
+    return c;
+}
+
+// most significant on-bit - return highest location of on-bit
+// NOTE: return 0 when bit0 is on or all bits are off
+uint8_t biton(uint8_t bits)
+{
+    uint8_t n = 0;
+    if (bits >> 4) { bits >>= 4; n += 4;}
+    if (bits >> 2) { bits >>= 2; n += 2;}
+    if (bits >> 1) { bits >>= 1; n += 1;}
+    return n;
+}
+
+uint8_t biton16(uint16_t bits)
+{
+    uint8_t n = 0;
+    if (bits >> 8) { bits >>= 8; n += 8;}
+    if (bits >> 4) { bits >>= 4; n += 4;}
+    if (bits >> 2) { bits >>= 2; n += 2;}
+    if (bits >> 1) { bits >>= 1; n += 1;}
+    return n;
+}
+
+uint8_t biton32(uint32_t bits)
+{
+    uint8_t n = 0;
+    if (bits >>16) { bits >>=16; n +=16;}
+    if (bits >> 8) { bits >>= 8; n += 8;}
+    if (bits >> 4) { bits >>= 4; n += 4;}
+    if (bits >> 2) { bits >>= 2; n += 2;}
+    if (bits >> 1) { bits >>= 1; n += 1;}
+    return n;
+}
+
+
+
+uint8_t bitrev(uint8_t bits)
+{
+    bits = (bits & 0x0f)<<4 | (bits & 0xf0)>>4;
+    bits = (bits & 0b00110011)<<2 | (bits & 0b11001100)>>2;
+    bits = (bits & 0b01010101)<<1 | (bits & 0b10101010)>>1;
+    return bits;
+}
+
+uint16_t bitrev16(uint16_t bits)
+{
+    bits = bitrev(bits & 0x00ff)<<8 | bitrev((bits & 0xff00)>>8);
+    return bits;
+}
+
+uint32_t bitrev32(uint32_t bits)
+{
+    bits = (uint32_t)bitrev16(bits & 0x0000ffff)<<16 | bitrev16((bits & 0xffff0000)>>16);
+    return bits;
+}