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8 <h1>bitbuf.c</h1><a href="bitbuf_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment">00001 <span class="comment">/*! \file bitbuf.c \brief Multipurpose bit buffer structure and methods. */</span>
9 00002 <span class="comment">//*****************************************************************************</span>
10 00003 <span class="comment">//</span>
11 00004 <span class="comment">// File Name : 'bitbuf.c'</span>
12 00005 <span class="comment">// Title : Multipurpose bit buffer structure and methods</span>
13 00006 <span class="comment">// Author : Pascal Stang - Copyright (C) 2001-2002</span>
14 00007 <span class="comment">// Created : 7/10/2002</span>
15 00008 <span class="comment">// Revised : 7/10/2002</span>
16 00009 <span class="comment">// Version : 0.5</span>
17 00010 <span class="comment">// Target MCU : any</span>
18 00011 <span class="comment">// Editor Tabs : 4</span>
19 00012 <span class="comment">//</span>
20 00013 <span class="comment">// This code is distributed under the GNU Public License</span>
21 00014 <span class="comment">// which can be found at http://www.gnu.org/licenses/gpl.txt</span>
22 00015 <span class="comment">//</span>
23 00016 <span class="comment">//*****************************************************************************</span>
24 00017
25 00018 <span class="preprocessor">#include "<a class="code" href="bitbuf_8h.html">bitbuf.h</a>"</span>
26 00019
27 00020 <span class="comment">// global variables</span>
28 00021 <span class="comment"></span>
29 00022 <span class="comment">//! Initialize the bit buffer</span>
30 00023 <span class="comment"></span><span class="comment">// sets the start location and size of the buffer in memory</span>
31 <a name="l00024"></a><a class="code" href="group__bitbuf.html#ga1">00024</a> <span class="keywordtype">void</span> <a class="code" href="group__bitbuf.html#ga1">bitbufInit</a>(BitBuf* bitBuffer, <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> *start, <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> bytesize)
32 00025 {
33 00026 <span class="comment">// set start pointer of the buffer</span>
34 00027 bitBuffer-&gt;dataptr = start;
35 00028 bitBuffer-&gt;size = bytesize;
36 00029 <span class="comment">// initialize indexing and length</span>
37 00030 bitBuffer-&gt;dataindex = 0;
38 00031 <a class="code" href="group__bitbuf.html#ga7">bitbufFlush</a>(bitBuffer);
39 00032 }
40 00033
41 00034 <span class="comment">// access routines</span>
42 00035 <span class="comment"></span>
43 00036 <span class="comment">//! Get a bit from the current position in the buffer</span>
44 00037 <span class="comment"></span><span class="comment">// returns the bit at the current position in the buffer</span>
45 00038 <span class="comment">// and increments the bit position</span>
46 <a name="l00039"></a><a class="code" href="group__bitbuf.html#ga2">00039</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__bitbuf.html#ga2">bitbufGet</a>(BitBuf* bitBuffer)
47 00040 {
48 00041 <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> byte;
49 00042 <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> bit;
50 00043
51 00044 <span class="comment">// get current working byte</span>
52 00045 byte = bitBuffer-&gt;dataptr[bitBuffer-&gt;bytePos];
53 00046 <span class="comment">// read data bit</span>
54 00047 bit = (byte &amp; (1&lt;&lt;bitBuffer-&gt;bitPos))?(1):(0);
55 00048
56 00049 <span class="comment">// increment bit counter</span>
57 00050 <span class="keywordflow">if</span>(bitBuffer-&gt;bitPos &lt; 7)
58 00051 {
59 00052 bitBuffer-&gt;bitPos++;
60 00053 }
61 00054 <span class="keywordflow">else</span>
62 00055 {
63 00056 <span class="comment">// increment byte counter</span>
64 00057 bitBuffer-&gt;bitPos = 0;
65 00058 bitBuffer-&gt;bytePos++;
66 00059 }
67 00060
68 00061 <span class="comment">// return bit value</span>
69 00062 <span class="keywordflow">return</span> bit;
70 00063 }
71 00064 <span class="comment"></span>
72 00065 <span class="comment">//! Get a bit from a given index into the buffer</span>
73 00066 <span class="comment"></span><span class="comment">// returns the bit at position [bitIndex] in the buffer</span>
74 <a name="l00067"></a><a class="code" href="group__bitbuf.html#ga3">00067</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__bitbuf.html#ga3">bitbufGetAtIndex</a>(BitBuf* bitBuffer, <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> bitIndex)
75 00068 {
76 00069 <span class="comment">// return bit at index in buffer</span>
77 00070 <span class="keywordflow">return</span> (bitBuffer-&gt;dataptr[bitIndex&gt;&gt;3] &amp; (1&lt;&lt;(bitIndex &amp; 0x07)))?(1):(0);
78 00071 }
79 00072 <span class="comment"></span>
80 00073 <span class="comment">//! Store a bit at the current position in the buffer</span>
81 00074 <span class="comment"></span><span class="comment">// stores the bit at the current position in the buffer</span>
82 00075 <span class="comment">// and increments the bit position</span>
83 <a name="l00076"></a><a class="code" href="group__bitbuf.html#ga4">00076</a> <span class="keywordtype">void</span> <a class="code" href="group__bitbuf.html#ga4">bitbufStore</a>(BitBuf* bitBuffer, <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> bit)
84 00077 {
85 00078 <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> byte;
86 00079 <span class="comment">// get current working byte</span>
87 00080 byte = bitBuffer-&gt;dataptr[bitBuffer-&gt;bytePos];
88 00081 <span class="comment">// apply data bit</span>
89 00082 <span class="keywordflow">if</span>(bit)
90 00083 byte |= (1&lt;&lt;bitBuffer-&gt;bitPos);
91 00084 <span class="keywordflow">else</span>
92 00085 byte &amp;= ~(1&lt;&lt;bitBuffer-&gt;bitPos);
93 00086 <span class="comment">// store data</span>
94 00087 bitBuffer-&gt;dataptr[bitBuffer-&gt;bytePos] = byte;
95 00088 bitBuffer-&gt;datalength++;
96 00089
97 00090 <span class="comment">// increment bit counter</span>
98 00091 <span class="keywordflow">if</span>(bitBuffer-&gt;bitPos &lt; 7)
99 00092 {
100 00093 bitBuffer-&gt;bitPos++;
101 00094 }
102 00095 <span class="keywordflow">else</span>
103 00096 {
104 00097 <span class="comment">// increment byte counter</span>
105 00098 bitBuffer-&gt;bitPos = 0;
106 00099 bitBuffer-&gt;bytePos++;
107 00100 }
108 00101 }
109 00102
110 <a name="l00103"></a><a class="code" href="group__bitbuf.html#ga6">00103</a> <span class="keywordtype">void</span> <a class="code" href="group__bitbuf.html#ga6">bitbufReset</a>(BitBuf* bitBuffer)
111 00104 {
112 00105 <span class="comment">// reset counters</span>
113 00106 bitBuffer-&gt;bytePos = 0;
114 00107 bitBuffer-&gt;bitPos = 0;
115 00108 }
116 00109
117 <a name="l00110"></a><a class="code" href="group__bitbuf.html#ga7">00110</a> <span class="keywordtype">void</span> <a class="code" href="group__bitbuf.html#ga7">bitbufFlush</a>(BitBuf* bitBuffer)
118 00111 {
119 00112 <span class="comment">// flush contents of the buffer</span>
120 00113 bitBuffer-&gt;datalength = 0;
121 00114 <span class="comment">// reset indexing</span>
122 00115 <a class="code" href="group__bitbuf.html#ga6">bitbufReset</a>(bitBuffer);
123 00116 }
124 00117
125 <a name="l00118"></a><a class="code" href="group__bitbuf.html#ga5">00118</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> <a class="code" href="group__bitbuf.html#ga5">bitbufGetDataLength</a>(BitBuf* bitBuffer)
126 00119 {
127 00120 <span class="keywordflow">return</span> bitBuffer-&gt;datalength;
128 00121 }
129 00122
130 00123 <span class="comment">/*</span>
131 00124 <span class="comment">unsigned char bitbufIsNotFull(cBuffer* buffer)</span>
132 00125 <span class="comment">{</span>
133 00126 <span class="comment"> // check to see if the buffer has room</span>
134 00127 <span class="comment"> // return true if there is room</span>
135 00128 <span class="comment"> return (buffer-&gt;datalength &lt; buffer-&gt;size);</span>
136 00129 <span class="comment">}</span>
137 00130 <span class="comment">*/</span>
138 00131
139 </pre></div><hr size="1"><address style="align: right;"><small>Generated on Sun Oct 29 03:41:06 2006 for Procyon AVRlib by&nbsp;
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141 <img src="doxygen.png" alt="doxygen" align="middle" border="0"></a> 1.4.2 </small></address>
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