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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 1.4.1 --><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_000003.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">00001 00025 <span class="preprocessor">#include "<a class="code" href="common_8h.html">common.h</a>"</span>00026 <span class="preprocessor">#include "<a class="code" href="fix_8h.html">fix.h</a>"</span>00027 00028 00029 <span class="comment">/*</span>00030 <span class="comment">Helper functions</span>00031 <span class="comment">*/</span>00032 00033 00034 <span class="keyword">static</span> <span class="keyword">inline</span> <span class="keywordtype">int</span> Interpolate(<span class="keyword">const</span> <span class="keywordtype">int</span>* table,<span class="keywordtype">int</span> value,<span class="keywordtype">int</span> shift)00035 {00036 <span class="comment">// get values from table (required value lies between b and c)</span>00037 <span class="keywordtype">int</span> i = value>>shift;00038 <span class="keywordtype">int</span> a = table[i+0];00039 <span class="keywordtype">int</span> b = table[i+1];00040 <span class="keywordtype">int</span> c = table[i+2];00041 <span class="keywordtype">int</span> d = table[i+3];00042 00043 <span class="comment">// interpolate</span>00044 <span class="keywordtype">int</span> f = value&((1<<shift)-1);00045 <span class="keywordtype">int</span> cadb = ( (c-a) - (d-b) ) >> 2;00046 <span class="keywordtype">int</span> r = (c-b) + cadb - (cadb*f>>shift);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>00048 r += b;00049 00050 <span class="keywordflow">return</span> r;00051 }00052 00053 00054 <span class="comment">/*</span>00055 <span class="comment">Members of class Fix</span>00056 <span class="comment">*/</span>00057 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>(fix a,fix b)00060 {00061 <a class="code" href="group__fix.html#ga0">fix</a> r = a+b;00062 <span class="keywordflow">if</span>((~(a^b) & (a^r)) < 0)00063 r = (r>>31)^0x80000000; <span class="comment">// produce saturated result if overflow</span>00064 <span class="keywordflow">return</span> r;00065 }00066 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>(fix a,fix b)00069 {00070 <a class="code" href="group__fix.html#ga0">fix</a> r = a-b;00071 <span class="keywordflow">if</span>(((a^b) & (a^r)) < 0)00072 r = (r>>31)^0x80000000; <span class="comment">// produce saturated result if overflow</span>00073 <span class="keywordflow">return</span> r;00074 }00075 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>(fix a,fix b)00078 {00079 <span class="comment">// calculate sign result</span>00080 <span class="keywordtype">int</span> sign = a^b;00081 00082 <span class="comment">// calculate absolute values</span>00083 <span class="keywordflow">if</span>(a<0) a=-a;00084 <span class="keywordflow">if</span>(b<0) b=-b;00085 00086 <span class="comment">// do the multiply in four parts</span>00087 <a class="code" href="group__integers.html#ga2">uint32</a> al = a&0xFFFF;00088 <a class="code" href="group__integers.html#ga2">uint32</a> bl = b&0xFFFF;00089 <a class="code" href="group__integers.html#ga2">uint32</a> c = al*bl;00090 c += 0x8000;00091 c >>= 16;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);00093 c += c1;00094 <span class="keywordflow">if</span>(c>=c1) <span class="comment">// No carry from addition</span>00095 {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);00097 c += c2;00098 <span class="keywordflow">if</span>(c>=c2) <span class="comment">// No carry from addition</span>00099 {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);00101 <span class="keywordflow">if</span>(d<0x10000) <span class="comment">// No overflow from multiply</span>00102 {00103 <a class="code" href="group__integers.html#ga6">uint</a> dl = d<<16;00104 c += dl;00105 <span class="keywordflow">if</span>(c>=dl) <span class="comment">// No carry from addition</span>00106 {00107 <span class="keywordflow">if</span>(sign<0)00108 {00109 <span class="keywordflow">if</span>(c<=0x80000000)00110 <span class="keywordflow">return</span> -(<a class="code" href="group__integers.html#ga5">int32</a>)c;00111 }00112 <span class="keywordflow">else</span>00113 {00114 <span class="keywordflow">if</span>(c<=0x7fffffff)00115 <span class="keywordflow">return</span> c;00116 }00117 }00118 }00119 }00120 }00121 00122 <span class="comment">// produce saturated result</span>00123 <span class="keywordflow">return</span> (sign<0) ? 0x80000000 : 0x7fffffff;00124 }00125 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>(fix a,fix b)00128 {00129 <a class="code" href="group__integers.html#ga2">uint32</a> al = a&0xFFFF;00130 <a class="code" href="group__integers.html#ga2">uint32</a> bl = b&0xFFFF;00131 <a class="code" href="group__integers.html#ga2">uint32</a> r = al*bl;00132 r += 0x8000;00133 r >>= 16;00134 r += bl*(a>>16);00135 r += al*(b>>16);00136 r += ((a>>16)*(b>>16))<<16;00137 <span class="keywordflow">return</span> r;00138 }00139 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>(fix a,fix b)00142 {00143 <span class="comment">// calculate sign bit of result</span>00144 <a class="code" href="group__integers.html#ga5">int32</a> r = a^b;00145 r &= (1<<31);00146 00147 <span class="comment">// calculate absolute values</span>00148 <span class="keywordflow">if</span>(a<0) a = -a;00149 <span class="keywordflow">if</span>(b<0) b = -b;00150 00151 <span class="comment">// calculate the number of integer bits is the result</span>00152 <a class="code" href="group__integers.html#ga5">int32</a> intBits = 0;00153 <a class="code" href="group__integers.html#ga2">uint32</a> q = a;00154 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>16))00155 intBits += 16, q >>= 16;00156 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>8))00157 intBits += 8, q >>= 8;00158 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>4))00159 intBits += 4, q >>= 4;00160 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>2))00161 intBits += 2, q >>= 2;00162 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)b<=((uint32)q>>1))00163 intBits += 1, q >>= 1;00164 00165 <span class="preprocessor">#if 0 // set true to use loops rather than inline code</span>00166 <span class="preprocessor"></span>00167 <span class="keywordflow">if</span>(intBits>14)00168 <span class="keywordflow">return</span> (r<0) ? 0x80000000 : 0x7fffffff; <span class="comment">// saturated result</span>00169 00170 <span class="comment">// calculate the integer part of result (bits 31 to 16)</span>00171 b <<= intBits;00172 <a class="code" href="group__integers.html#ga5">int32</a> bit = 1<<(intBits+16);00173 <span class="keywordflow">while</span>(bit>0x10000)00174 {00175 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)a>=(<a class="code" href="group__integers.html#ga2">uint32</a>)b)00176 {00177 a -= b;00178 r += bit;00179 }00180 b >>= 1;00181 bit >>= 1;00182 }00183 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)a>=(<a class="code" href="group__integers.html#ga2">uint32</a>)b)00184 {00185 a -= b;00186 r += bit;00187 }00188 bit >>= 1;00189 00190 <span class="comment">// calculate the fractional part of result (bits 15 to 0)</span>00191 <span class="keywordflow">do</span>00192 {00193 a <<= 1;00194 <span class="keywordflow">if</span>((<a class="code" href="group__integers.html#ga2">uint32</a>)a>=(<a class="code" href="group__integers.html#ga2">uint32</a>)b)00195 {00196 a -= b;00197 r += bit;⌨️ 快捷键说明
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