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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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cannam@167 1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
cannam@167 2 <html>
cannam@167 3 <!-- This manual is for FFTW
cannam@167 4 (version 3.3.8, 24 May 2018).
cannam@167 5
cannam@167 6 Copyright (C) 2003 Matteo Frigo.
cannam@167 7
cannam@167 8 Copyright (C) 2003 Massachusetts Institute of Technology.
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cannam@167 10 Permission is granted to make and distribute verbatim copies of this
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cannam@167 24 <head>
cannam@167 25 <title>FFTW 3.3.8: Wisdom String Export/Import from Fortran</title>
cannam@167 26
cannam@167 27 <meta name="description" content="FFTW 3.3.8: Wisdom String Export/Import from Fortran">
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cannam@167 35 <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
cannam@167 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">
cannam@167 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">
cannam@167 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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cannam@167 69
cannam@167 70 <body lang="en">
cannam@167 71 <a name="Wisdom-String-Export_002fImport-from-Fortran"></a>
cannam@167 72 <div class="header">
cannam@167 73 <p>
cannam@167 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>
cannam@167 75 </div>
cannam@167 76 <hr>
cannam@167 77 <a name="Wisdom-String-Export_002fImport-from-Fortran-1"></a>
cannam@167 78 <h4 class="subsection">7.6.2 Wisdom String Export/Import from Fortran</h4>
cannam@167 79
cannam@167 80 <a name="index-fftw_005fexport_005fwisdom_005fto_005fstring-1"></a>
cannam@167 81 <p>Dealing with FFTW&rsquo;s C string export/import is a bit more painful. In
cannam@167 82 particular, the <code>fftw_export_wisdom_to_string</code> function requires
cannam@167 83 you to deal with a dynamically allocated C string. To get its length,
cannam@167 84 you must define an interface to the C <code>strlen</code> function, and to
cannam@167 85 deallocate it you must define an interface to C <code>free</code>:
cannam@167 86 </p>
cannam@167 87 <div class="example">
cannam@167 88 <pre class="example"> use, intrinsic :: iso_c_binding
cannam@167 89 interface
cannam@167 90 integer(C_INT) function strlen(s) bind(C, name='strlen')
cannam@167 91 import
cannam@167 92 type(C_PTR), value :: s
cannam@167 93 end function strlen
cannam@167 94 subroutine free(p) bind(C, name='free')
cannam@167 95 import
cannam@167 96 type(C_PTR), value :: p
cannam@167 97 end subroutine free
cannam@167 98 end interface
cannam@167 99 </pre></div>
cannam@167 100
cannam@167 101 <p>Given these definitions, you can then export wisdom to a Fortran
cannam@167 102 character array:
cannam@167 103 </p>
cannam@167 104 <div class="example">
cannam@167 105 <pre class="example"> character(C_CHAR), pointer :: s(:)
cannam@167 106 integer(C_SIZE_T) :: slen
cannam@167 107 type(C_PTR) :: p
cannam@167 108 p = fftw_export_wisdom_to_string()
cannam@167 109 if (.not. c_associated(p)) stop 'error exporting wisdom'
cannam@167 110 slen = strlen(p)
cannam@167 111 call c_f_pointer(p, s, [slen+1])
cannam@167 112 ...
cannam@167 113 call free(p)
cannam@167 114 </pre></div>
cannam@167 115 <a name="index-c_005fassociated"></a>
cannam@167 116 <a name="index-c_005ff_005fpointer-3"></a>
cannam@167 117
cannam@167 118 <p>Note that <code>slen</code> is the length of the C string, but the length of
cannam@167 119 the array is <code>slen+1</code> because it includes the terminating null
cannam@167 120 character. (You can omit the &lsquo;<samp>+1</samp>&rsquo; if you don&rsquo;t want Fortran to
cannam@167 121 know about the null character.) The standard <code>c_associated</code> function
cannam@167 122 checks whether <code>p</code> is a null pointer, which is returned by
cannam@167 123 <code>fftw_export_wisdom_to_string</code> if there was an error.
cannam@167 124 </p>
cannam@167 125 <a name="index-fftw_005fimport_005fwisdom_005ffrom_005fstring-1"></a>
cannam@167 126 <p>To import wisdom from a string, use
cannam@167 127 <code>fftw_import_wisdom_from_string</code> as usual; note that the argument
cannam@167 128 of this function must be a <code>character(C_CHAR)</code> that is terminated
cannam@167 129 by the <code>C_NULL_CHAR</code> character, like the <code>s</code> array above.
cannam@167 130 </p>
cannam@167 131
cannam@167 132
cannam@167 133
cannam@167 134 </body>
cannam@167 135 </html>