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<a href="../../d3/d67/strlen_8c.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">/*-</span></div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment"> * Copyright (c) 2002-2018 The UbixOS Project.</span></div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment"> * All rights reserved.</span></div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment"> *</span></div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment"> * This was developed by Christopher W. Olsen for the UbixOS Project.</span></div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment"> *</span></div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment"> * Redistribution and use in source and binary forms, with or without modification, are permitted</span></div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment"> * provided that the following conditions are met:</span></div>
<div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="comment"> *</span></div>
<div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="comment"> * 1) Redistributions of source code must retain the above copyright notice, this list of</span></div>
<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment"> * conditions, the following disclaimer and the list of authors.</span></div>
<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment"> * 2) Redistributions in binary form must reproduce the above copyright notice, this list of</span></div>
<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="comment"> * conditions, the following disclaimer and the list of authors in the documentation and/or</span></div>
<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="comment"> * other materials provided with the distribution.</span></div>
<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="comment"> * 3) Neither the name of the UbixOS Project nor the names of its contributors may be used to</span></div>
<div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment"> * endorse or promote products derived from this software without specific prior written</span></div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment"> * permission.</span></div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment"> *</span></div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="comment"> * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED</span></div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="comment"> * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS</span></div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="comment"> * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS</span></div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <span class="comment"> * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES</span></div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="comment"> * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,</span></div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="comment"> * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN</span></div>
<div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="comment"> * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT</span></div>
<div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="comment"> * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.</span></div>
<div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="comment"> */</span></div>
<div class="line"><a name="l00028"></a><span class="lineno"> 28</span>  </div>
<div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="preprocessor">#include <<a class="code" href="../../dd/d97/sys_2limits_8h.html">sys/limits.h</a>></span></div>
<div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="preprocessor">#include <<a class="code" href="../../d0/d27/include_2sys_2types_8h.html">sys/types.h</a>></span></div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span>  </div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span> <span class="comment">/* Magic numbers for the algorithm */</span></div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span> <span class="preprocessor">#if LONG_BIT == 32</span></div>
<div class="line"><a name="l00034"></a><span class="lineno"> 34</span> <span class="keyword">static</span> <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> mask01 = 0x01010101;</div>
<div class="line"><a name="l00035"></a><span class="lineno"> 35</span> <span class="keyword">static</span> <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> mask80 = 0x80808080;</div>
<div class="line"><a name="l00036"></a><span class="lineno"> 36</span> <span class="preprocessor">#elif LONG_BIT == 64</span></div>
<div class="line"><a name="l00037"></a><span class="lineno"> 37</span> <span class="keyword">static</span> <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> mask01 = 0x0101010101010101;</div>
<div class="line"><a name="l00038"></a><span class="lineno"> 38</span> <span class="keyword">static</span> <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> mask80 = 0x8080808080808080;</div>
<div class="line"><a name="l00039"></a><span class="lineno"> 39</span> <span class="preprocessor">#else</span></div>
<div class="line"><a name="l00040"></a><span class="lineno"> 40</span> <span class="preprocessor">#error Unsupported word size</span></div>
<div class="line"><a name="l00041"></a><span class="lineno"> 41</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00042"></a><span class="lineno"> 42</span>  </div>
<div class="line"><a name="l00043"></a><span class="lineno"><a class="line" href="../../d3/d67/strlen_8c.html#ae33e2dfb5c1456c17782ba1e0894d783"> 43</a></span> <span class="preprocessor">#define LONGPTR_MASK (sizeof(long) - 1)</span></div>
<div class="line"><a name="l00044"></a><span class="lineno"> 44</span>  </div>
<div class="line"><a name="l00045"></a><span class="lineno"> 45</span> <span class="comment">/*</span></div>
<div class="line"><a name="l00046"></a><span class="lineno"> 46</span> <span class="comment"> * Helper macro to return string length if we caught the zero</span></div>
<div class="line"><a name="l00047"></a><span class="lineno"> 47</span> <span class="comment"> * byte.</span></div>
<div class="line"><a name="l00048"></a><span class="lineno"> 48</span> <span class="comment"> */</span></div>
<div class="line"><a name="l00049"></a><span class="lineno"><a class="line" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32"> 49</a></span> <span class="preprocessor">#define testbyte(x) \</span></div>
<div class="line"><a name="l00050"></a><span class="lineno"> 50</span> <span class="preprocessor"> do { \</span></div>
<div class="line"><a name="l00051"></a><span class="lineno"> 51</span> <span class="preprocessor"> if (p[x] == '\0') \</span></div>
<div class="line"><a name="l00052"></a><span class="lineno"> 52</span> <span class="preprocessor"> return (p - str + x); \</span></div>
<div class="line"><a name="l00053"></a><span class="lineno"> 53</span> <span class="preprocessor"> } while (0)</span></div>
<div class="line"><a name="l00054"></a><span class="lineno"> 54</span>  </div>
<div class="line"><a name="l00055"></a><span class="lineno"><a class="line" href="../../d3/d67/strlen_8c.html#a008e171a518fe0e0352f31b245e03875"> 55</a></span> <span class="keywordtype">size_t</span> <a class="code" href="../../d3/d67/strlen_8c.html#a008e171a518fe0e0352f31b245e03875">strlen</a>(<span class="keyword">const</span> <span class="keywordtype">char</span> *str) {</div>
<div class="line"><a name="l00056"></a><span class="lineno"> 56</span>  <span class="keyword">const</span> <span class="keywordtype">char</span> *p;</div>
<div class="line"><a name="l00057"></a><span class="lineno"> 57</span>  <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> *lp;</div>
<div class="line"><a name="l00058"></a><span class="lineno"> 58</span>  <span class="keywordtype">long</span> va, vb;</div>
<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  </div>
<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  <span class="comment">/*</span></div>
<div class="line"><a name="l00061"></a><span class="lineno"> 61</span> <span class="comment"> * Before trying the hard (unaligned byte-by-byte access) way</span></div>
<div class="line"><a name="l00062"></a><span class="lineno"> 62</span> <span class="comment"> * to figure out whether there is a nul character, try to see</span></div>
<div class="line"><a name="l00063"></a><span class="lineno"> 63</span> <span class="comment"> * if there is a nul character is within this accessible word</span></div>
<div class="line"><a name="l00064"></a><span class="lineno"> 64</span> <span class="comment"> * first.</span></div>
<div class="line"><a name="l00065"></a><span class="lineno"> 65</span> <span class="comment"> *</span></div>
<div class="line"><a name="l00066"></a><span class="lineno"> 66</span> <span class="comment"> * p and (p & ~LONGPTR_MASK) must be equally accessible since</span></div>
<div class="line"><a name="l00067"></a><span class="lineno"> 67</span> <span class="comment"> * they always fall in the same memory page, as long as page</span></div>
<div class="line"><a name="l00068"></a><span class="lineno"> 68</span> <span class="comment"> * boundaries is integral multiple of word size.</span></div>
<div class="line"><a name="l00069"></a><span class="lineno"> 69</span> <span class="comment"> */</span></div>
<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  lp = (<span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> *) ((<a class="code" href="../../d0/d27/include_2sys_2types_8h.html#a09674b9e56fd7a93a2169aa9210deec7">uintptr_t</a>) str & ~<a class="code" href="../../d3/d67/strlen_8c.html#ae33e2dfb5c1456c17782ba1e0894d783">LONGPTR_MASK</a>);</div>
<div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  va = (*lp - mask01);</div>
<div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  vb = ((~*lp) & mask80);</div>
<div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  lp++;</div>
<div class="line"><a name="l00074"></a><span class="lineno"> 74</span>  <span class="keywordflow">if</span> (va & vb)</div>
<div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <span class="comment">/* Check if we have \0 in the first part */</span></div>
<div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="keywordflow">for</span> (p = str; p < (<span class="keyword">const</span> <span class="keywordtype">char</span> *) lp; p++)</div>
<div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  <span class="keywordflow">if</span> (*p == <span class="charliteral">'\0'</span>)</div>
<div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="keywordflow">return</span> (p - str);</div>
<div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  </div>
<div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="comment">/* Scan the rest of the string using word sized operation */</span></div>
<div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  <span class="keywordflow">for</span> (;; lp++) {</div>
<div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  va = (*lp - mask01);</div>
<div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  vb = ((~*lp) & mask80);</div>
<div class="line"><a name="l00084"></a><span class="lineno"> 84</span>  <span class="keywordflow">if</span> (va & vb) {</div>
<div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  p = (<span class="keyword">const</span> <span class="keywordtype">char</span> *) (lp);</div>
<div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(0);</div>
<div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(1);</div>
<div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(2);</div>
<div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(3);</div>
<div class="line"><a name="l00090"></a><span class="lineno"> 90</span> <span class="preprocessor">#if (LONG_BIT >= 64)</span></div>
<div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(4);</div>
<div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(5);</div>
<div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(6);</div>
<div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  <a class="code" href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a>(7);</div>
<div class="line"><a name="l00095"></a><span class="lineno"> 95</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  }</div>
<div class="line"><a name="l00097"></a><span class="lineno"> 97</span>  }</div>
<div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  </div>
<div class="line"><a name="l00099"></a><span class="lineno"> 99</span>  <span class="comment">/* NOTREACHED */</span></div>
<div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  <span class="keywordflow">return</span> (0);</div>
<div class="line"><a name="l00101"></a><span class="lineno"> 101</span> }</div>
</div><!-- fragment --></div><!-- contents -->
</div><!-- doc-content -->
<div class="ttc" id="asys_2limits_8h_html"><div class="ttname"><a href="../../dd/d97/sys_2limits_8h.html">limits.h</a></div></div>
<div class="ttc" id="ainclude_2sys_2types_8h_html"><div class="ttname"><a href="../../d0/d27/include_2sys_2types_8h.html">types.h</a></div></div>
<div class="ttc" id="astrlen_8c_html_ae33e2dfb5c1456c17782ba1e0894d783"><div class="ttname"><a href="../../d3/d67/strlen_8c.html#ae33e2dfb5c1456c17782ba1e0894d783">LONGPTR_MASK</a></div><div class="ttdeci">#define LONGPTR_MASK</div><div class="ttdef"><b>Definition:</b> <a href="../../d3/d67/strlen_8c_source.html#l00043">strlen.c:43</a></div></div>
<div class="ttc" id="astrlen_8c_html_a008e171a518fe0e0352f31b245e03875"><div class="ttname"><a href="../../d3/d67/strlen_8c.html#a008e171a518fe0e0352f31b245e03875">strlen</a></div><div class="ttdeci">size_t strlen(const char *str)</div><div class="ttdef"><b>Definition:</b> <a href="../../d3/d67/strlen_8c_source.html#l00055">strlen.c:55</a></div></div>
<div class="ttc" id="astrlen_8c_html_a57c8d92afd27a2061de282ec221f8c32"><div class="ttname"><a href="../../d3/d67/strlen_8c.html#a57c8d92afd27a2061de282ec221f8c32">testbyte</a></div><div class="ttdeci">#define testbyte(x)</div><div class="ttdef"><b>Definition:</b> <a href="../../d3/d67/strlen_8c_source.html#l00049">strlen.c:49</a></div></div>
<div class="ttc" id="ainclude_2sys_2types_8h_html_a09674b9e56fd7a93a2169aa9210deec7"><div class="ttname"><a href="../../d0/d27/include_2sys_2types_8h.html#a09674b9e56fd7a93a2169aa9210deec7">uintptr_t</a></div><div class="ttdeci">uint32_t uintptr_t</div><div class="ttdef"><b>Definition:</b> <a href="../../d0/d27/include_2sys_2types_8h_source.html#l00136">types.h:136</a></div></div>
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