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Add FFTW 3.3.8 source, and a Linux build
author Chris Cannam
date Tue, 19 Nov 2019 14:52:55 +0000
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Chris@82 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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Chris@82 3 <!-- This manual is for FFTW
Chris@82 4 (version 3.3.8, 24 May 2018).
Chris@82 5
Chris@82 6 Copyright (C) 2003 Matteo Frigo.
Chris@82 7
Chris@82 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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Chris@82 10 Permission is granted to make and distribute verbatim copies of this
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Chris@82 24 <head>
Chris@82 25 <title>FFTW 3.3.8: Wisdom String Export/Import from Fortran</title>
Chris@82 26
Chris@82 27 <meta name="description" content="FFTW 3.3.8: Wisdom String Export/Import from Fortran">
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Chris@82 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
Chris@82 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">
Chris@82 37 <link href="Wisdom-Generic-Export_002fImport-from-Fortran.html#Wisdom-Generic-Export_002fImport-from-Fortran" rel="next" title="Wisdom Generic Export/Import from Fortran">
Chris@82 38 <link href="Wisdom-File-Export_002fImport-from-Fortran.html#Wisdom-File-Export_002fImport-from-Fortran" rel="prev" title="Wisdom File Export/Import from Fortran">
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Chris@82 68 </head>
Chris@82 69
Chris@82 70 <body lang="en">
Chris@82 71 <a name="Wisdom-String-Export_002fImport-from-Fortran"></a>
Chris@82 72 <div class="header">
Chris@82 73 <p>
Chris@82 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>
Chris@82 75 </div>
Chris@82 76 <hr>
Chris@82 77 <a name="Wisdom-String-Export_002fImport-from-Fortran-1"></a>
Chris@82 78 <h4 class="subsection">7.6.2 Wisdom String Export/Import from Fortran</h4>
Chris@82 79
Chris@82 80 <a name="index-fftw_005fexport_005fwisdom_005fto_005fstring-1"></a>
Chris@82 81 <p>Dealing with FFTW&rsquo;s C string export/import is a bit more painful. In
Chris@82 82 particular, the <code>fftw_export_wisdom_to_string</code> function requires
Chris@82 83 you to deal with a dynamically allocated C string. To get its length,
Chris@82 84 you must define an interface to the C <code>strlen</code> function, and to
Chris@82 85 deallocate it you must define an interface to C <code>free</code>:
Chris@82 86 </p>
Chris@82 87 <div class="example">
Chris@82 88 <pre class="example"> use, intrinsic :: iso_c_binding
Chris@82 89 interface
Chris@82 90 integer(C_INT) function strlen(s) bind(C, name='strlen')
Chris@82 91 import
Chris@82 92 type(C_PTR), value :: s
Chris@82 93 end function strlen
Chris@82 94 subroutine free(p) bind(C, name='free')
Chris@82 95 import
Chris@82 96 type(C_PTR), value :: p
Chris@82 97 end subroutine free
Chris@82 98 end interface
Chris@82 99 </pre></div>
Chris@82 100
Chris@82 101 <p>Given these definitions, you can then export wisdom to a Fortran
Chris@82 102 character array:
Chris@82 103 </p>
Chris@82 104 <div class="example">
Chris@82 105 <pre class="example"> character(C_CHAR), pointer :: s(:)
Chris@82 106 integer(C_SIZE_T) :: slen
Chris@82 107 type(C_PTR) :: p
Chris@82 108 p = fftw_export_wisdom_to_string()
Chris@82 109 if (.not. c_associated(p)) stop 'error exporting wisdom'
Chris@82 110 slen = strlen(p)
Chris@82 111 call c_f_pointer(p, s, [slen+1])
Chris@82 112 ...
Chris@82 113 call free(p)
Chris@82 114 </pre></div>
Chris@82 115 <a name="index-c_005fassociated"></a>
Chris@82 116 <a name="index-c_005ff_005fpointer-3"></a>
Chris@82 117
Chris@82 118 <p>Note that <code>slen</code> is the length of the C string, but the length of
Chris@82 119 the array is <code>slen+1</code> because it includes the terminating null
Chris@82 120 character. (You can omit the &lsquo;<samp>+1</samp>&rsquo; if you don&rsquo;t want Fortran to
Chris@82 121 know about the null character.) The standard <code>c_associated</code> function
Chris@82 122 checks whether <code>p</code> is a null pointer, which is returned by
Chris@82 123 <code>fftw_export_wisdom_to_string</code> if there was an error.
Chris@82 124 </p>
Chris@82 125 <a name="index-fftw_005fimport_005fwisdom_005ffrom_005fstring-1"></a>
Chris@82 126 <p>To import wisdom from a string, use
Chris@82 127 <code>fftw_import_wisdom_from_string</code> as usual; note that the argument
Chris@82 128 of this function must be a <code>character(C_CHAR)</code> that is terminated
Chris@82 129 by the <code>C_NULL_CHAR</code> character, like the <code>s</code> array above.
Chris@82 130 </p>
Chris@82 131
Chris@82 132
Chris@82 133
Chris@82 134 </body>
Chris@82 135 </html>