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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 19 Nov 2019 14:52:55 +0000
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3 <!-- This manual is for FFTW
4 (version 3.3.8, 24 May 2018).
5
6 Copyright (C) 2003 Matteo Frigo.
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8 Copyright (C) 2003 Massachusetts Institute of Technology.
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25 <title>FFTW 3.3.8: Wisdom String Export/Import from Fortran</title>
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35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
36 <link href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" rel="up" title="Accessing the wisdom API from Fortran">
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71 <a name="Wisdom-String-Export_002fImport-from-Fortran"></a>
72 <div class="header">
73 <p>
74 Next: <a href="Wisdom-Generic-Export_002fImport-from-Fortran.html#Wisdom-Generic-Export_002fImport-from-Fortran" accesskey="n" rel="next">Wisdom Generic Export/Import from Fortran</a>, Previous: <a href="Wisdom-File-Export_002fImport-from-Fortran.html#Wisdom-File-Export_002fImport-from-Fortran" accesskey="p" rel="prev">Wisdom File Export/Import from Fortran</a>, Up: <a href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran" accesskey="u" rel="up">Accessing the wisdom API from Fortran</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
75 </div>
76 <hr>
77 <a name="Wisdom-String-Export_002fImport-from-Fortran-1"></a>
78 <h4 class="subsection">7.6.2 Wisdom String Export/Import from Fortran</h4>
79
80 <a name="index-fftw_005fexport_005fwisdom_005fto_005fstring-1"></a>
81 <p>Dealing with FFTW&rsquo;s C string export/import is a bit more painful. In
82 particular, the <code>fftw_export_wisdom_to_string</code> function requires
83 you to deal with a dynamically allocated C string. To get its length,
84 you must define an interface to the C <code>strlen</code> function, and to
85 deallocate it you must define an interface to C <code>free</code>:
86 </p>
87 <div class="example">
88 <pre class="example"> use, intrinsic :: iso_c_binding
89 interface
90 integer(C_INT) function strlen(s) bind(C, name='strlen')
91 import
92 type(C_PTR), value :: s
93 end function strlen
94 subroutine free(p) bind(C, name='free')
95 import
96 type(C_PTR), value :: p
97 end subroutine free
98 end interface
99 </pre></div>
100
101 <p>Given these definitions, you can then export wisdom to a Fortran
102 character array:
103 </p>
104 <div class="example">
105 <pre class="example"> character(C_CHAR), pointer :: s(:)
106 integer(C_SIZE_T) :: slen
107 type(C_PTR) :: p
108 p = fftw_export_wisdom_to_string()
109 if (.not. c_associated(p)) stop 'error exporting wisdom'
110 slen = strlen(p)
111 call c_f_pointer(p, s, [slen+1])
112 ...
113 call free(p)
114 </pre></div>
115 <a name="index-c_005fassociated"></a>
116 <a name="index-c_005ff_005fpointer-3"></a>
117
118 <p>Note that <code>slen</code> is the length of the C string, but the length of
119 the array is <code>slen+1</code> because it includes the terminating null
120 character. (You can omit the &lsquo;<samp>+1</samp>&rsquo; if you don&rsquo;t want Fortran to
121 know about the null character.) The standard <code>c_associated</code> function
122 checks whether <code>p</code> is a null pointer, which is returned by
123 <code>fftw_export_wisdom_to_string</code> if there was an error.
124 </p>
125 <a name="index-fftw_005fimport_005fwisdom_005ffrom_005fstring-1"></a>
126 <p>To import wisdom from a string, use
127 <code>fftw_import_wisdom_from_string</code> as usual; note that the argument
128 of this function must be a <code>character(C_CHAR)</code> that is terminated
129 by the <code>C_NULL_CHAR</code> character, like the <code>s</code> array above.
130 </p>
131
132
133
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135 </html>