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Add null config files
author Chris Cannam <cannam@all-day-breakfast.com>
date Mon, 02 Mar 2020 14:03:47 +0000
parents bd3cc4d1df30
children
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cannam@167 3 <!-- This manual is for FFTW
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cannam@167 6 Copyright (C) 2003 Matteo Frigo.
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cannam@167 24 <head>
cannam@167 25 <title>FFTW 3.3.8: Wisdom Generic Export/Import from Fortran</title>
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cannam@167 70 <body lang="en">
cannam@167 71 <a name="Wisdom-Generic-Export_002fImport-from-Fortran"></a>
cannam@167 72 <div class="header">
cannam@167 73 <p>
cannam@167 74 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@167 75 </div>
cannam@167 76 <hr>
cannam@167 77 <a name="Wisdom-Generic-Export_002fImport-from-Fortran-1"></a>
cannam@167 78 <h4 class="subsection">7.6.3 Wisdom Generic Export/Import from Fortran</h4>
cannam@167 79
cannam@167 80 <p>The most generic wisdom export/import functions allow you to provide
cannam@167 81 an arbitrary callback function to read/write one character at a time
cannam@167 82 in any way you want. However, your callback function must be written
cannam@167 83 in a special way, using the <code>bind(C)</code> attribute to be passed to a
cannam@167 84 C interface.
cannam@167 85 </p>
cannam@167 86 <a name="index-fftw_005fexport_005fwisdom-1"></a>
cannam@167 87 <p>In particular, to call the generic wisdom export function
cannam@167 88 <code>fftw_export_wisdom</code>, you would write a callback subroutine of the form:
cannam@167 89 </p>
cannam@167 90 <div class="example">
cannam@167 91 <pre class="example"> subroutine my_write_char(c, p) bind(C)
cannam@167 92 use, intrinsic :: iso_c_binding
cannam@167 93 character(C_CHAR), value :: c
cannam@167 94 type(C_PTR), value :: p
cannam@167 95 <em>...write c...</em>
cannam@167 96 end subroutine my_write_char
cannam@167 97 </pre></div>
cannam@167 98
cannam@167 99 <p>Given such a subroutine (along with the corresponding interface definition), you could then export wisdom using:
cannam@167 100 </p>
cannam@167 101 <a name="index-c_005ffunloc"></a>
cannam@167 102 <div class="example">
cannam@167 103 <pre class="example"> call fftw_export_wisdom(c_funloc(my_write_char), p)
cannam@167 104 </pre></div>
cannam@167 105
cannam@167 106 <a name="index-c_005floc"></a>
cannam@167 107 <a name="index-c_005ff_005fpointer-4"></a>
cannam@167 108 <p>The standard <code>c_funloc</code> intrinsic converts a Fortran
cannam@167 109 <code>bind(C)</code> subroutine into a C function pointer. The parameter
cannam@167 110 <code>p</code> is a <code>type(C_PTR)</code> to any arbitrary data that you want
cannam@167 111 to pass to <code>my_write_char</code> (or <code>C_NULL_PTR</code> if none). (Note
cannam@167 112 that you can get a C pointer to Fortran data using the intrinsic
cannam@167 113 <code>c_loc</code>, and convert it back to a Fortran pointer in
cannam@167 114 <code>my_write_char</code> using <code>c_f_pointer</code>.)
cannam@167 115 </p>
cannam@167 116 <p>Similarly, to use the generic <code>fftw_import_wisdom</code>, you would
cannam@167 117 define a callback function of the form:
cannam@167 118 </p>
cannam@167 119 <a name="index-fftw_005fimport_005fwisdom-1"></a>
cannam@167 120 <div class="example">
cannam@167 121 <pre class="example"> integer(C_INT) function my_read_char(p) bind(C)
cannam@167 122 use, intrinsic :: iso_c_binding
cannam@167 123 type(C_PTR), value :: p
cannam@167 124 character :: c
cannam@167 125 <em>...read a character c...</em>
cannam@167 126 my_read_char = ichar(c, C_INT)
cannam@167 127 end function my_read_char
cannam@167 128
cannam@167 129 ....
cannam@167 130
cannam@167 131 integer(C_INT) :: ret
cannam@167 132 ret = fftw_import_wisdom(c_funloc(my_read_char), p)
cannam@167 133 if (ret .eq. 0) stop 'error importing wisdom'
cannam@167 134 </pre></div>
cannam@167 135
cannam@167 136 <p>Your function can return <code>-1</code> if the end of the input is reached.
cannam@167 137 Again, <code>p</code> is an arbitrary <code>type(C_PTR</code> that is passed
cannam@167 138 through to your function. <code>fftw_import_wisdom</code> returns <code>0</code>
cannam@167 139 if an error occurred and nonzero otherwise.
cannam@167 140 </p>
cannam@167 141 <hr>
cannam@167 142 <div class="header">
cannam@167 143 <p>
cannam@167 144 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@167 145 </div>
cannam@167 146
cannam@167 147
cannam@167 148
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cannam@167 150 </html>