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diff --git a/share/doc/gfortran/CONVERT-specifier.html b/share/doc/gfortran/CONVERT-specifier.html new file mode 100644 index 0000000..e98a9ea --- /dev/null +++ b/share/doc/gfortran/CONVERT-specifier.html @@ -0,0 +1,144 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1999-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). 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Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The GNU Fortran Compiler: CONVERT specifier</title> + +<meta name="description" content="The GNU Fortran Compiler: CONVERT specifier"> +<meta name="keywords" content="The GNU Fortran Compiler: CONVERT specifier"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" rel="up" title="Extensions implemented in GNU Fortran"> +<link href="OpenMP.html#OpenMP" rel="next" title="OpenMP"> +<link href="Cray-pointers.html#Cray-pointers" rel="previous" title="Cray pointers"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="CONVERT-specifier"></a> +<div class="header"> +<p> +Next: <a href="OpenMP.html#OpenMP" accesskey="n" rel="next">OpenMP</a>, Previous: <a href="Cray-pointers.html#Cray-pointers" accesskey="p" rel="previous">Cray pointers</a>, Up: <a href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" accesskey="u" rel="up">Extensions implemented in GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="CONVERT-specifier-1"></a> +<h4 class="subsection">5.1.17 <code>CONVERT</code> specifier</h4> +<a name="index-CONVERT-specifier"></a> + +<p>GNU Fortran allows the conversion of unformatted data between little- +and big-endian representation to facilitate moving of data +between different systems. The conversion can be indicated with +the <code>CONVERT</code> specifier on the <code>OPEN</code> statement. +See <a href="GFORTRAN_005fCONVERT_005fUNIT.html#GFORTRAN_005fCONVERT_005fUNIT">GFORTRAN_CONVERT_UNIT</a>, for an alternative way of specifying +the data format via an environment variable. +</p> +<p>Valid values for <code>CONVERT</code> on most systems are: +</p><ul class="no-bullet"> +<li><!-- /@w --> <code>CONVERT='NATIVE'</code> Use the native format. This is the default. +</li><li><!-- /@w --> <code>CONVERT='SWAP'</code> Swap between little- and big-endian. +</li><li><!-- /@w --> <code>CONVERT='LITTLE_ENDIAN'</code> Use the little-endian representation +for unformatted files. +</li><li><!-- /@w --> <code>CONVERT='BIG_ENDIAN'</code> Use the big-endian representation for +unformatted files. +</li></ul> +<p>On POWER systems which support <samp>-mabi=ieeelongdouble</samp>, +there are additional options, which can be combined with the others +with commas. Those are +</p><ul class="no-bullet"> +<li><!-- /@w --> <code>CONVERT='R16_IEEE'</code> Use IEEE 128-bit format for +<code>REAL(KIND=16)</code>. +</li><li><!-- /@w --> <code>CONVERT='R16_IBM'</code> Use IBM <code>long double</code> format for +real<code>REAL(KIND=16)</code>. +</li></ul> + +<p>Using the option could look like this: +</p><div class="smallexample"> +<pre class="smallexample"> open(file='big.dat',form='unformatted',access='sequential', & + convert='big_endian') +</pre></div> + +<p>The value of the conversion can be queried by using +<code>INQUIRE(CONVERT=ch)</code>. The values returned are +<code>'BIG_ENDIAN'</code> and <code>'LITTLE_ENDIAN'</code>. +</p> +<p><code>CONVERT</code> works between big- and little-endian for +<code>INTEGER</code> values of all supported kinds and for <code>REAL</code> +on IEEE systems of kinds 4 and 8. Conversion between different +“extended double” types on different architectures such as +m68k and x86_64, which GNU Fortran +supports as <code>REAL(KIND=10)</code> and <code>REAL(KIND=16)</code>, will +probably not work. +</p> +<p><em>Note that the values specified via the GFORTRAN_CONVERT_UNIT +environment variable will override the CONVERT specifier in the +open statement</em>. This is to give control over data formats to +users who do not have the source code of their program available. +</p> +<p>Using anything but the native representation for unformatted data +carries a significant speed overhead. If speed in this area matters +to you, it is best if you use this only for data that needs to be +portable. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="OpenMP.html#OpenMP" accesskey="n" rel="next">OpenMP</a>, Previous: <a href="Cray-pointers.html#Cray-pointers" accesskey="p" rel="previous">Cray pointers</a>, Up: <a href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" accesskey="u" rel="up">Extensions implemented in GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |