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<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">/* xsize.h -- Checked size_t computations.</span></div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment"></span></div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment"> Copyright (C) 2003 Free Software Foundation, Inc.</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 program is free software; you can redistribute it and/or modify it</span></div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment"> under the terms of the GNU Library General Public License as published</span></div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment"> by the Free Software Foundation; either version 2, or (at your option)</span></div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment"> any later version.</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"> This program is distributed in the hope that it will be useful,</span></div>
<div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment"> but WITHOUT ANY WARRANTY; without even the implied warranty of</span></div>
<div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment"> MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU</span></div>
<div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="comment"> Library General Public License for more details.</span></div>
<div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="comment"></span></div>
<div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="comment"> You should have received a copy of the GNU Library General Public</span></div>
<div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment"> License along with this program; if not, write to the Free Software</span></div>
<div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment"> Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,</span></div>
<div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment"> USA. */</span></div>
<div class="line"><a name="l00019"></a><span class="lineno"> 19</span> </div>
<div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="preprocessor">#ifndef _XSIZE_H</span></div>
<div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="preprocessor"></span><span class="preprocessor">#define _XSIZE_H</span></div>
<div class="line"><a name="l00022"></a><span class="lineno"> 22</span> <span class="preprocessor"></span></div>
<div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="comment">/* Get size_t. */</span></div>
<div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="preprocessor">#include <stddef.h></span></div>
<div class="line"><a name="l00025"></a><span class="lineno"> 25</span> </div>
<div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="comment">/* Get SIZE_MAX. */</span></div>
<div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="preprocessor">#include <limits.h></span></div>
<div class="line"><a name="l00028"></a><span class="lineno"> 28</span> <span class="preprocessor">#if HAVE_STDINT_H</span></div>
<div class="line"><a name="l00029"></a><span class="lineno"> 29</span> <span class="preprocessor"></span><span class="preprocessor"># include <stdint.h></span></div>
<div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00031"></a><span class="lineno"> 31</span> <span class="preprocessor"></span></div>
<div class="line"><a name="l00032"></a><span class="lineno"> 32</span> <span class="comment">/* The size of memory objects is often computed through expressions of</span></div>
<div class="line"><a name="l00033"></a><span class="lineno"> 33</span> <span class="comment"> type size_t. Example:</span></div>
<div class="line"><a name="l00034"></a><span class="lineno"> 34</span> <span class="comment"> void* p = malloc (header_size + n * element_size).</span></div>
<div class="line"><a name="l00035"></a><span class="lineno"> 35</span> <span class="comment"> These computations can lead to overflow. When this happens, malloc()</span></div>
<div class="line"><a name="l00036"></a><span class="lineno"> 36</span> <span class="comment"> returns a piece of memory that is way too small, and the program then</span></div>
<div class="line"><a name="l00037"></a><span class="lineno"> 37</span> <span class="comment"> crashes while attempting to fill the memory.</span></div>
<div class="line"><a name="l00038"></a><span class="lineno"> 38</span> <span class="comment"> To avoid this, the functions and macros in this file check for overflow.</span></div>
<div class="line"><a name="l00039"></a><span class="lineno"> 39</span> <span class="comment"> The convention is that SIZE_MAX represents overflow.</span></div>
<div class="line"><a name="l00040"></a><span class="lineno"> 40</span> <span class="comment"> malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc</span></div>
<div class="line"><a name="l00041"></a><span class="lineno"> 41</span> <span class="comment"> implementation that uses mmap --, it's recommended to use size_overflow_p()</span></div>
<div class="line"><a name="l00042"></a><span class="lineno"> 42</span> <span class="comment"> or size_in_bounds_p() before invoking malloc().</span></div>
<div class="line"><a name="l00043"></a><span class="lineno"> 43</span> <span class="comment"> The example thus becomes:</span></div>
<div class="line"><a name="l00044"></a><span class="lineno"> 44</span> <span class="comment"> size_t size = xsum (header_size, xtimes (n, element_size));</span></div>
<div class="line"><a name="l00045"></a><span class="lineno"> 45</span> <span class="comment"> void *p = (size_in_bounds_p (size) ? malloc (size) : NULL);</span></div>
<div class="line"><a name="l00046"></a><span class="lineno"> 46</span> <span class="comment">*/</span></div>
<div class="line"><a name="l00047"></a><span class="lineno"> 47</span> </div>
<div class="line"><a name="l00048"></a><span class="lineno"> 48</span> <span class="comment">/* Convert an arbitrary value >= 0 to type size_t. */</span></div>
<div class="line"><a name="l00049"></a><span class="lineno"> 49</span> <span class="preprocessor">#define xcast_size_t(N) \</span></div>
<div class="line"><a name="l00050"></a><span class="lineno"> 50</span> <span class="preprocessor"> ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX)</span></div>
<div class="line"><a name="l00051"></a><span class="lineno"> 51</span> <span class="preprocessor"></span></div>
<div class="line"><a name="l00052"></a><span class="lineno"> 52</span> <span class="comment">/* Sum of two sizes, with overflow check. */</span></div>
<div class="line"><a name="l00053"></a><span class="lineno"> 53</span> <span class="keyword">static</span> <span class="keywordtype">size_t</span></div>
<div class="line"><a name="l00054"></a><span class="lineno"> 54</span> <span class="preprocessor">#if __GNUC__ >= 3</span></div>
<div class="line"><a name="l00055"></a><span class="lineno"> 55</span> <span class="preprocessor"></span>__attribute__ ((__pure__))</div>
<div class="line"><a name="l00056"></a><span class="lineno"> 56</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00057"></a><span class="lineno"> 57</span> <span class="preprocessor"></span>xsum (<span class="keywordtype">size_t</span> size1, <span class="keywordtype">size_t</span> size2)</div>
<div class="line"><a name="l00058"></a><span class="lineno"> 58</span> {</div>
<div class="line"><a name="l00059"></a><span class="lineno"> 59</span>  <span class="keywordtype">size_t</span> sum = size1 + size2;</div>
<div class="line"><a name="l00060"></a><span class="lineno"> 60</span>  <span class="keywordflow">return</span> (sum >= size1 ? sum : SIZE_MAX);</div>
<div class="line"><a name="l00061"></a><span class="lineno"> 61</span> }</div>
<div class="line"><a name="l00062"></a><span class="lineno"> 62</span> </div>
<div class="line"><a name="l00063"></a><span class="lineno"> 63</span> <span class="comment">/* Sum of three sizes, with overflow check. */</span></div>
<div class="line"><a name="l00064"></a><span class="lineno"> 64</span> <span class="keyword">static</span> <span class="keywordtype">size_t</span></div>
<div class="line"><a name="l00065"></a><span class="lineno"> 65</span> <span class="preprocessor">#if __GNUC__ >= 3</span></div>
<div class="line"><a name="l00066"></a><span class="lineno"> 66</span> <span class="preprocessor"></span>__attribute__ ((__pure__))</div>
<div class="line"><a name="l00067"></a><span class="lineno"> 67</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00068"></a><span class="lineno"> 68</span> <span class="preprocessor"></span>xsum3 (<span class="keywordtype">size_t</span> size1, <span class="keywordtype">size_t</span> size2, <span class="keywordtype">size_t</span> size3)</div>
<div class="line"><a name="l00069"></a><span class="lineno"> 69</span> {</div>
<div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keywordflow">return</span> xsum (xsum (size1, size2), size3);</div>
<div class="line"><a name="l00071"></a><span class="lineno"> 71</span> }</div>
<div class="line"><a name="l00072"></a><span class="lineno"> 72</span> </div>
<div class="line"><a name="l00073"></a><span class="lineno"> 73</span> <span class="comment">/* Sum of four sizes, with overflow check. */</span></div>
<div class="line"><a name="l00074"></a><span class="lineno"> 74</span> <span class="keyword">static</span> <span class="keywordtype">size_t</span></div>
<div class="line"><a name="l00075"></a><span class="lineno"> 75</span> <span class="preprocessor">#if __GNUC__ >= 3</span></div>
<div class="line"><a name="l00076"></a><span class="lineno"> 76</span> <span class="preprocessor"></span>__attribute__ ((__pure__))</div>
<div class="line"><a name="l00077"></a><span class="lineno"> 77</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00078"></a><span class="lineno"> 78</span> <span class="preprocessor"></span>xsum4 (<span class="keywordtype">size_t</span> size1, <span class="keywordtype">size_t</span> size2, <span class="keywordtype">size_t</span> size3, <span class="keywordtype">size_t</span> size4)</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="keywordflow">return</span> xsum (xsum (xsum (size1, size2), size3), size4);</div>
<div class="line"><a name="l00081"></a><span class="lineno"> 81</span> }</div>
<div class="line"><a name="l00082"></a><span class="lineno"> 82</span> </div>
<div class="line"><a name="l00083"></a><span class="lineno"> 83</span> <span class="comment">/* Maximum of two sizes, with overflow check. */</span></div>
<div class="line"><a name="l00084"></a><span class="lineno"> 84</span> <span class="keyword">static</span> <span class="keywordtype">size_t</span></div>
<div class="line"><a name="l00085"></a><span class="lineno"> 85</span> <span class="preprocessor">#if __GNUC__ >= 3</span></div>
<div class="line"><a name="l00086"></a><span class="lineno"> 86</span> <span class="preprocessor"></span>__attribute__ ((__pure__))</div>
<div class="line"><a name="l00087"></a><span class="lineno"> 87</span> <span class="preprocessor">#endif</span></div>
<div class="line"><a name="l00088"></a><span class="lineno"> 88</span> <span class="preprocessor"></span>xmax (<span class="keywordtype">size_t</span> size1, <span class="keywordtype">size_t</span> size2)</div>
<div class="line"><a name="l00089"></a><span class="lineno"> 89</span> {</div>
<div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  <span class="comment">/* No explicit check is needed here, because for any n:</span></div>
<div class="line"><a name="l00091"></a><span class="lineno"> 91</span> <span class="comment"> max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX. */</span></div>
<div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  <span class="keywordflow">return</span> (size1 >= size2 ? size1 : size2);</div>
<div class="line"><a name="l00093"></a><span class="lineno"> 93</span> }</div>
<div class="line"><a name="l00094"></a><span class="lineno"> 94</span> </div>
<div class="line"><a name="l00095"></a><span class="lineno"> 95</span> <span class="comment">/* Multiplication of a count with an element size, with overflow check.</span></div>
<div class="line"><a name="l00096"></a><span class="lineno"> 96</span> <span class="comment"> The count must be >= 0 and the element size must be > 0.</span></div>
<div class="line"><a name="l00097"></a><span class="lineno"> 97</span> <span class="comment"> This is a macro, not an inline function, so that it works correctly even</span></div>
<div class="line"><a name="l00098"></a><span class="lineno"> 98</span> <span class="comment"> when N is of a wider tupe and N > SIZE_MAX. */</span></div>
<div class="line"><a name="l00099"></a><span class="lineno"> 99</span> <span class="preprocessor">#define xtimes(N, ELSIZE) \</span></div>
<div class="line"><a name="l00100"></a><span class="lineno"> 100</span> <span class="preprocessor"> ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)</span></div>
<div class="line"><a name="l00101"></a><span class="lineno"> 101</span> <span class="preprocessor"></span></div>
<div class="line"><a name="l00102"></a><span class="lineno"> 102</span> <span class="comment">/* Check for overflow. */</span></div>
<div class="line"><a name="l00103"></a><span class="lineno"> 103</span> <span class="preprocessor">#define size_overflow_p(SIZE) \</span></div>
<div class="line"><a name="l00104"></a><span class="lineno"> 104</span> <span class="preprocessor"> ((SIZE) == SIZE_MAX)</span></div>
<div class="line"><a name="l00105"></a><span class="lineno"> 105</span> <span class="preprocessor"></span><span class="comment">/* Check against overflow. */</span></div>
<div class="line"><a name="l00106"></a><span class="lineno"> 106</span> <span class="preprocessor">#define size_in_bounds_p(SIZE) \</span></div>
<div class="line"><a name="l00107"></a><span class="lineno"> 107</span> <span class="preprocessor"> ((SIZE) != SIZE_MAX)</span></div>
<div class="line"><a name="l00108"></a><span class="lineno"> 108</span> <span class="preprocessor"></span></div>
<div class="line"><a name="l00109"></a><span class="lineno"> 109</span> <span class="preprocessor">#endif </span><span class="comment">/* _XSIZE_H */</span><span class="preprocessor"></span></div>
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