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Replace these with versions built using an older toolset (so as to avoid ABI compatibilities when linking on Ubuntu 14.04 for packaging purposes)
author Chris Cannam
date Fri, 07 Feb 2020 11:51:13 +0000
parents 37bf6b4a2645
children
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Chris@10 1 <html lang="en">
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Chris@10 3 <title>Wisdom String Export/Import from Fortran - FFTW 3.3.3</title>
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Chris@10 48 <div class="node">
Chris@10 49 <a name="Wisdom-String-Export%2fImport-from-Fortran"></a>
Chris@10 50 <a name="Wisdom-String-Export_002fImport-from-Fortran"></a>
Chris@10 51 <p>
Chris@10 52 Next:&nbsp;<a rel="next" accesskey="n" href="Wisdom-Generic-Export_002fImport-from-Fortran.html#Wisdom-Generic-Export_002fImport-from-Fortran">Wisdom Generic Export/Import from Fortran</a>,
Chris@10 53 Previous:&nbsp;<a rel="previous" accesskey="p" href="Wisdom-File-Export_002fImport-from-Fortran.html#Wisdom-File-Export_002fImport-from-Fortran">Wisdom File Export/Import from Fortran</a>,
Chris@10 54 Up:&nbsp;<a rel="up" accesskey="u" href="Accessing-the-wisdom-API-from-Fortran.html#Accessing-the-wisdom-API-from-Fortran">Accessing the wisdom API from Fortran</a>
Chris@10 55 <hr>
Chris@10 56 </div>
Chris@10 57
Chris@10 58 <h4 class="subsection">7.6.2 Wisdom String Export/Import from Fortran</h4>
Chris@10 59
Chris@10 60 <p><a name="index-fftw_005fexport_005fwisdom_005fto_005fstring-568"></a>Dealing with FFTW's C string export/import is a bit more painful. In
Chris@10 61 particular, the <code>fftw_export_wisdom_to_string</code> function requires
Chris@10 62 you to deal with a dynamically allocated C string. To get its length,
Chris@10 63 you must define an interface to the C <code>strlen</code> function, and to
Chris@10 64 deallocate it you must define an interface to C <code>free</code>:
Chris@10 65
Chris@10 66 <pre class="example"> use, intrinsic :: iso_c_binding
Chris@10 67 interface
Chris@10 68 integer(C_INT) function strlen(s) bind(C, name='strlen')
Chris@10 69 import
Chris@10 70 type(C_PTR), value :: s
Chris@10 71 end function strlen
Chris@10 72 subroutine free(p) bind(C, name='free')
Chris@10 73 import
Chris@10 74 type(C_PTR), value :: p
Chris@10 75 end subroutine free
Chris@10 76 end interface
Chris@10 77 </pre>
Chris@10 78 <p>Given these definitions, you can then export wisdom to a Fortran
Chris@10 79 character array:
Chris@10 80
Chris@10 81 <pre class="example"> character(C_CHAR), pointer :: s(:)
Chris@10 82 integer(C_SIZE_T) :: slen
Chris@10 83 type(C_PTR) :: p
Chris@10 84 p = fftw_export_wisdom_to_string()
Chris@10 85 if (.not. c_associated(p)) stop 'error exporting wisdom'
Chris@10 86 slen = strlen(p)
Chris@10 87 call c_f_pointer(p, s, [slen+1])
Chris@10 88 ...
Chris@10 89 call free(p)
Chris@10 90 </pre>
Chris@10 91 <p><a name="index-c_005fassociated-569"></a><a name="index-c_005ff_005fpointer-570"></a>
Chris@10 92 Note that <code>slen</code> is the length of the C string, but the length of
Chris@10 93 the array is <code>slen+1</code> because it includes the terminating null
Chris@10 94 character. (You can omit the &lsquo;<samp><span class="samp">+1</span></samp>&rsquo; if you don't want Fortran to
Chris@10 95 know about the null character.) The standard <code>c_associated</code> function
Chris@10 96 checks whether <code>p</code> is a null pointer, which is returned by
Chris@10 97 <code>fftw_export_wisdom_to_string</code> if there was an error.
Chris@10 98
Chris@10 99 <p><a name="index-fftw_005fimport_005fwisdom_005ffrom_005fstring-571"></a>To import wisdom from a string, use
Chris@10 100 <code>fftw_import_wisdom_from_string</code> as usual; note that the argument
Chris@10 101 of this function must be a <code>character(C_CHAR)</code> that is terminated
Chris@10 102 by the <code>C_NULL_CHAR</code> character, like the <code>s</code> array above.
Chris@10 103
Chris@10 104 <!-- =========> -->
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Chris@10 106