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Current fftw source
author Chris Cannam <cannam@all-day-breakfast.com>
date Tue, 18 Oct 2016 13:40:26 +0100
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cannam@127 3 <!-- This manual is for FFTW
cannam@127 4 (version 3.3.5, 30 July 2016).
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cannam@127 6 Copyright (C) 2003 Matteo Frigo.
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cannam@127 24 <head>
cannam@127 25 <title>FFTW 3.3.5: Wisdom Generic Export/Import from Fortran</title>
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cannam@127 71 <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
cannam@127 72 <a name="Wisdom-Generic-Export_002fImport-from-Fortran"></a>
cannam@127 73 <div class="header">
cannam@127 74 <p>
cannam@127 75 Previous: <a href="Wisdom-String-Export_002fImport-from-Fortran.html#Wisdom-String-Export_002fImport-from-Fortran" accesskey="p" rel="prev">Wisdom String 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@127 76 </div>
cannam@127 77 <hr>
cannam@127 78 <a name="Wisdom-Generic-Export_002fImport-from-Fortran-1"></a>
cannam@127 79 <h4 class="subsection">7.6.3 Wisdom Generic Export/Import from Fortran</h4>
cannam@127 80
cannam@127 81 <p>The most generic wisdom export/import functions allow you to provide
cannam@127 82 an arbitrary callback function to read/write one character at a time
cannam@127 83 in any way you want. However, your callback function must be written
cannam@127 84 in a special way, using the <code>bind(C)</code> attribute to be passed to a
cannam@127 85 C interface.
cannam@127 86 </p>
cannam@127 87 <a name="index-fftw_005fexport_005fwisdom-1"></a>
cannam@127 88 <p>In particular, to call the generic wisdom export function
cannam@127 89 <code>fftw_export_wisdom</code>, you would write a callback subroutine of the form:
cannam@127 90 </p>
cannam@127 91 <div class="example">
cannam@127 92 <pre class="example"> subroutine my_write_char(c, p) bind(C)
cannam@127 93 use, intrinsic :: iso_c_binding
cannam@127 94 character(C_CHAR), value :: c
cannam@127 95 type(C_PTR), value :: p
cannam@127 96 <em>...write c...</em>
cannam@127 97 end subroutine my_write_char
cannam@127 98 </pre></div>
cannam@127 99
cannam@127 100 <p>Given such a subroutine (along with the corresponding interface definition), you could then export wisdom using:
cannam@127 101 </p>
cannam@127 102 <a name="index-c_005ffunloc"></a>
cannam@127 103 <div class="example">
cannam@127 104 <pre class="example"> call fftw_export_wisdom(c_funloc(my_write_char), p)
cannam@127 105 </pre></div>
cannam@127 106
cannam@127 107 <a name="index-c_005floc"></a>
cannam@127 108 <a name="index-c_005ff_005fpointer-4"></a>
cannam@127 109 <p>The standard <code>c_funloc</code> intrinsic converts a Fortran
cannam@127 110 <code>bind(C)</code> subroutine into a C function pointer. The parameter
cannam@127 111 <code>p</code> is a <code>type(C_PTR)</code> to any arbitrary data that you want
cannam@127 112 to pass to <code>my_write_char</code> (or <code>C_NULL_PTR</code> if none). (Note
cannam@127 113 that you can get a C pointer to Fortran data using the intrinsic
cannam@127 114 <code>c_loc</code>, and convert it back to a Fortran pointer in
cannam@127 115 <code>my_write_char</code> using <code>c_f_pointer</code>.)
cannam@127 116 </p>
cannam@127 117 <p>Similarly, to use the generic <code>fftw_import_wisdom</code>, you would
cannam@127 118 define a callback function of the form:
cannam@127 119 </p>
cannam@127 120 <a name="index-fftw_005fimport_005fwisdom-1"></a>
cannam@127 121 <div class="example">
cannam@127 122 <pre class="example"> integer(C_INT) function my_read_char(p) bind(C)
cannam@127 123 use, intrinsic :: iso_c_binding
cannam@127 124 type(C_PTR), value :: p
cannam@127 125 character :: c
cannam@127 126 <em>...read a character c...</em>
cannam@127 127 my_read_char = ichar(c, C_INT)
cannam@127 128 end function my_read_char
cannam@127 129
cannam@127 130 ....
cannam@127 131
cannam@127 132 integer(C_INT) :: ret
cannam@127 133 ret = fftw_import_wisdom(c_funloc(my_read_char), p)
cannam@127 134 if (ret .eq. 0) stop 'error importing wisdom'
cannam@127 135 </pre></div>
cannam@127 136
cannam@127 137 <p>Your function can return <code>-1</code> if the end of the input is reached.
cannam@127 138 Again, <code>p</code> is an arbitrary <code>type(C_PTR</code> that is passed
cannam@127 139 through to your function. <code>fftw_import_wisdom</code> returns <code>0</code>
cannam@127 140 if an error occurred and nonzero otherwise.
cannam@127 141 </p>
cannam@127 142 <hr>
cannam@127 143 <div class="header">
cannam@127 144 <p>
cannam@127 145 Previous: <a href="Wisdom-String-Export_002fImport-from-Fortran.html#Wisdom-String-Export_002fImport-from-Fortran" accesskey="p" rel="prev">Wisdom String 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>
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