fix_8cpp-source.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"><title>maths/fix.cpp Source File</title><link href="doxygen.css" rel="stylesheet" type="text/css"></head><body><!-- Generated by Doxygen 1.4.4 --><div class="qindex"><a class="qindex" href="index.html">Main Page</a> | <a class="qindex" href="modules.html">Modules</a> | <a class="qindex" href="hierarchy.html">Class Hierarchy</a> | <a class="qindex" href="annotated.html">Class List</a> | <a class="qindex" href="dirs.html">Directories</a> | <a class="qindex" href="files.html">File List</a> | <a class="qindex" href="functions.html">Class Members</a> | <a class="qindex" href="globals.html">File Members</a></div><div class="nav"><a class="el" href="dir_000004.html">maths</a></div><h1>fix.cpp</h1><a href="fix_8cpp.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <a name="l00025"></a>00025 <span class="preprocessor">#include "<a class="code" href="common_8h.html">common.h</a>"</span><a name="l00026"></a>00026 <span class="preprocessor">#include "<a class="code" href="fix_8h.html">fix.h</a>"</span><a name="l00027"></a>00027 <a name="l00028"></a>00028 <a name="l00029"></a>00029 <span class="comment">/*</span><a name="l00030"></a>00030 <span class="comment">Helper functions</span><a name="l00031"></a>00031 <span class="comment">*/</span><a name="l00032"></a>00032 <a name="l00033"></a>00033 <a name="l00034"></a><a class="code" href="fix_8cpp.html#a0">00034</a> <span class="keyword">static</span> <span class="keyword">inline</span> <span class="keywordtype">int</span> <a class="code" href="fix_8cpp.html#a0">Interpolate</a>(<span class="keyword">const</span> <span class="keywordtype">int</span>* table,<span class="keywordtype">int</span> value,<span class="keywordtype">int</span> shift)<a name="l00035"></a>00035 {<a name="l00036"></a>00036 <span class="comment">// get values from table (required value lies between b and c)</span><a name="l00037"></a>00037 <span class="keywordtype">int</span> i = value>>shift;<a name="l00038"></a>00038 <span class="keywordtype">int</span> a = table[i+0];<a name="l00039"></a>00039 <span class="keywordtype">int</span> b = table[i+1];<a name="l00040"></a>00040 <span class="keywordtype">int</span> c = table[i+2];<a name="l00041"></a>00041 <span class="keywordtype">int</span> d = table[i+3];<a name="l00042"></a>00042 <a name="l00043"></a>00043 <span class="comment">// interpolate</span><a name="l00044"></a>00044 <span class="keywordtype">int</span> f = value&((1<<shift)-1);<a name="l00045"></a>00045 <span class="keywordtype">int</span> cadb = ( (c-a) - (d-b) ) >> 2;<a name="l00046"></a>00046 <span class="keywordtype">int</span> r = (c-b) + cadb - (cadb*f>>shift);<a name="l00047"></a>00047 r = (<a class="code" href="group__integers.html#ga6">uint</a>)(r*f)>>shift; <span class="comment">// cast to uint assumes table only contains increasing values (and gains us 1 more bit headroom)</span><a name="l00048"></a>00048 r += b;<a name="l00049"></a>00049 <a name="l00050"></a>00050 <span class="keywordflow">return</span> r;<a name="l00051"></a>00051 }<a name="l00052"></a>00052 <a name="l00053"></a>00053 <a name="l00054"></a>00054 <span class="comment">/*</span><a name="l00055"></a>00055 <span class="comment">Members of class Fix</span><a name="l00056"></a>00056 <span class="comment">*/</span><a name="l00057"></a>00057 <a name="l00058"></a>00058 <a name="l00059"></a><a class="code" href="classFix.html#e0">00059</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__fix.html#ga0">fix</a> <a class="code" href="classFix.html#e0">Fix::Add</a>(<a class="code" href="group__fix.html#ga0">fix</a> a,<a class="code" href="group__fix.html#ga0">fix</a> b)<a name="l00060"></a>00060 {<a name="l00061"></a>00061 <a class="code" href="group__fix.html#ga0">fix</a> r = a+b;<a name="l00062"></a>00062 <span class="keywordflow">if</span>((~(a^b) & (a^r)) < 0)<a name="l00063"></a>00063 r = (r>>31)^0x80000000; <span class="comment">// produce saturated result if overflow</span><a name="l00064"></a>00064 <span class="keywordflow">return</span> r;<a name="l00065"></a>00065 }<a name="l00066"></a>00066 <a name="l00067"></a>00067 <a name="l00068"></a><a class="code" href="classFix.html#e1">00068</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__fix.html#ga0">fix</a> <a class="code" href="classFix.html#e1">Fix::Sub</a>(<a class="code" href="group__fix.html#ga0">fix</a> a,<a class="code" href="group__fix.html#ga0">fix</a> b)<a name="l00069"></a>00069 {<a name="l00070"></a>00070 <a class="code" href="group__fix.html#ga0">fix</a> r = a-b;<a name="l00071"></a>00071 <span class="keywordflow">if</span>(((a^b) & (a^r)) < 0)<a name="l00072"></a>00072 r = (r>>31)^0x80000000; <span class="comment">// produce saturated result if overflow</span><a name="l00073"></a>00073 <span class="keywordflow">return</span> r;<a name="l00074"></a>00074 }<a name="l00075"></a>00075 <a name="l00076"></a>00076 <a name="l00077"></a><a class="code" href="classFix.html#e2">00077</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__fix.html#ga0">fix</a> <a class="code" href="classFix.html#e2">Fix::Mul</a>(<a class="code" href="group__fix.html#ga0">fix</a> a,<a class="code" href="group__fix.html#ga0">fix</a> b)<a name="l00078"></a>00078 {<a name="l00079"></a>00079 <span class="comment">// calculate sign result</span><a name="l00080"></a>00080 <span class="keywordtype">int</span> sign = a^b;<a name="l00081"></a>00081 <a name="l00082"></a>00082 <span class="comment">// calculate absolute values</span><a name="l00083"></a>00083 <span class="keywordflow">if</span>(a<0) a=-a;<a name="l00084"></a>00084 <span class="keywordflow">if</span>(b<0) b=-b;<a name="l00085"></a>00085 <a name="l00086"></a>00086 <span class="comment">// do the multiply in four parts</span><a name="l00087"></a>00087 <a class="code" href="group__integers.html#ga2">uint32</a> al = a&0xFFFF;<a name="l00088"></a>00088 <a class="code" href="group__integers.html#ga2">uint32</a> bl = b&0xFFFF;<a name="l00089"></a>00089 <a class="code" href="group__integers.html#ga2">uint32</a> c = al*bl;<a name="l00090"></a>00090 c += 0x8000;<a name="l00091"></a>00091 c >>= 16;<a name="l00092"></a>00092 <a class="code" href="group__integers.html#ga2">uint32</a> c1 = bl*((<a class="code" href="group__integers.html#ga6">uint</a>)a>>16);<a name="l00093"></a>00093 c += c1;<a name="l00094"></a>00094 <span class="keywordflow">if</span>(c>=c1) <span class="comment">// No carry from addition</span><a name="l00095"></a>00095 {<a name="l00096"></a>00096 <a class="code" href="group__integers.html#ga2">uint32</a> c2 = al*((<a class="code" href="group__integers.html#ga6">uint</a>)b>>16);<a name="l00097"></a>00097 c += c2;<a name="l00098"></a>00098 <span class="keywordflow">if</span>(c>=c2) <span class="comment">// No carry from addition</span><a name="l00099"></a>00099 {<a name="l00100"></a>00100 <a class="code" href="group__integers.html#ga2">uint32</a> d = ((<a class="code" href="group__integers.html#ga6">uint</a>)a>>16)*((<a class="code" href="group__integers.html#ga6">uint</a>)b>>16);<a name="l00101"></a>00101 <span class="keywordflow">if</span>(d<0x10000) <span class="comment">// No overflow from multiply</span><a name="l00102"></a>00102 {<a name="l00103"></a>00103 <a class="code" href="group__integers.html#ga6">uint</a> dl = d<<16;<a name="l00104"></a>00104 c += dl;<a name="l00105"></a>00105 <span class="keywordflow">if</span>(c>=dl) <span class="comment">// No carry from addition</span><a name="l00106"></a>00106 {<a name="l00107"></a>00107 <span class="keywordflow">if</span>(sign<0)<a name="l00108"></a>00108 {<a name="l00109"></a>00109 <span class="keywordflow">if</span>(c<=0x80000000)<a name="l00110"></a>00110 <span class="keywordflow">return</span> -(<a class="code" href="group__integers.html#ga5">int32</a>)c;<a name="l00111"></a>00111 }<a name="l00112"></a>00112 <span class="keywordflow">else</span><a name="l00113"></a>00113 {<a name="l00114"></a>00114 <span class="keywordflow">if</span>(c<=0x7fffffff)<a name="l00115"></a>00115 <span class="keywordflow">return</span> c;<a name="l00116"></a>00116 }<a name="l00117"></a>00117 }<a name="l00118"></a>00118 }<a name="l00119"></a>00119 }<a name="l00120"></a>00120 }<a name="l00121"></a>00121 <a name="l00122"></a>00122 <span class="comment">// produce saturated result</span><a name="l00123"></a>00123 <span class="keywordflow">return</span> (sign<0) ? 0x80000000 : 0x7fffffff;<a name="l00124"></a>00124 }<a name="l00125"></a>00125 <a name="l00126"></a>00126 <a name="l00127"></a><a class="code" href="classFix.html#e3">00127</a> <a class="code" href="common_8h.html#a2">EXPORT</a> <a class="code" href="group__fix.html#ga0">fix</a> <a class="code" href="classFix.html#e3">Fix::MulNS</a>(<a class="code" href="group__fix.html#ga0">fix</a> a,<a class="code" href="group__fix.html#ga0">fix</a> b)<a name="l00128"></a>00128 {<a name="l00129"></a>00129 <a class="code" href="group__integers.html#ga2">uint32</a> al = a&0xFFFF;<a name="l00130"></a>00130 <a class="code" href="group__integers.html#ga2">uint32</a> bl = b&0xFFFF;<a name="l00131"></a>00131 <a class="code" href="group__integers.html#ga2">uint32</a> r = al*bl;<a name="l00132"></a>00132 r += 0x8000;<a name="l00133"></a>00133 r >>= 16;<a name="l00134"></a>00134 r += bl*(a>>16);<a name="l00135"></a>00135 r += al*(b>>16);<a name="l00136"></a>00136 r += ((a>>16)*(b>>16))<<16;<a name="l00137"></a>00137 <span class="keywordflow">return</span> r;<a name="l00138"></a>00138 }<a name="l00139"></a>00139 <a name="l00140"></a>00140 <a name="l00141"></a><a class="code" href="classFix.html#e4">00141</a> <a class="code" href="group__fix.html#ga0">fix</a> <a class="code" href="classFix.html#e4">Fix::Div</a>(<a class="code" href="group__fix.html#ga0">fix</a> a,<a class="code" href="group__fix.html#ga0">fix</a> b)<a name="l00142"></a>00142 {<a name="l00143"></a>00143 <span class="comment">// calculate sign bit of result</span><a name="l00144"></a>00144 <a class="code" href="group__integers.html#ga5">int32</a> r = a^b;<a name="l00145"></a>00145 r &= (1<<31);<a name="l00146"></a>00146 <a name="l00147"></a>00147 <span class="comment">// calculate absolute values</span><a name="l00148"></a>00148 <span class="keywordflow">if</span>(a<0) a = -a;<a name="l00149"></a>00149 <span class="keywordflow">if</span>(b<0) b = -b;<a name="l00150"></a>00150 <a name="l00151"></a>00151 <span class="comment">// calculate the number of integer bits is the result</span><a name="l00152"></a>00152 <a class="code" href="group__integers.html#ga5">int32</a> intBits = 0;<a name="l00153"></a>00153 <a class="code" href="group__integers.html#ga2">uint32</a> q = a;<a name="l00154"></a>00154 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>16))<a name="l00155"></a>00155 intBits += 16, q >>= 16;<a name="l00156"></a>00156 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>8))⌨️ 快捷键说明
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