1 /* Copyright (C) 2011 Wildfire Games.
2  *
3  * Permission is hereby granted, free of charge, to any person obtaining
4  * a copy of this software and associated documentation files (the
5  * "Software"), to deal in the Software without restriction, including
6  * without limitation the rights to use, copy, modify, merge, publish,
7  * distribute, sublicense, and/or sell copies of the Software, and to
8  * permit persons to whom the Software is furnished to do so, subject to
9  * the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included
12  * in all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
15  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
17  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
18  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
19  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
20  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21  */
22 
23 /*
24  * FIFO bit queue
25  */
26 
27 #ifndef INCLUDED_ADTS_BIT_BUF
28 #define INCLUDED_ADTS_BIT_BUF
29 
30 #include "lib/bits.h"
31 
32 struct BitBuf
33 {
34 	uintptr_t buf;
35 	uintptr_t cur;	// bit to be appended (toggled by add())
36 	size_t len;	// |buf| [bits]
37 
resetBitBuf38 	void reset()
39 	{
40 		buf = 0;
41 		cur = 0;
42 		len = 0;
43 	}
44 
45 	// toggle current bit if desired, and add to buffer (new bit is LSB)
addBitBuf46 	void add(uintptr_t toggle)
47 	{
48 		cur ^= toggle;
49 		buf <<= 1;
50 		buf |= cur;
51 		len++;
52 	}
53 
54 	// extract LS n bits
extractBitBuf55 	size_t extract(uintptr_t n)
56 	{
57 		const uintptr_t bits = buf & bit_mask<uintptr_t>(n);
58 		buf >>= n;
59 
60 		return bits;
61 	}
62 };
63 
64 #endif	// #ifndef INCLUDED_ADTS_BIT_BUF
65