You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
166 lines
8.5 KiB
HTML
166 lines
8.5 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- This manual describes how to install and use the GNU multiple precision
|
||
|
|
arithmetic library, version 6.1.0.
|
||
|
|
|
||
|
|
Copyright 1991, 1993-2015 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 no Invariant Sections,
|
||
|
|
with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
|
||
|
|
Texts being "You have freedom to copy and modify this GNU Manual, like GNU
|
||
|
|
software". A copy of the license is included in
|
||
|
|
GNU Free Documentation License. -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Integer Import and Export (GNU MP 6.1.0)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
|
||
|
|
<meta name="keywords" content="Integer Import and Export (GNU MP 6.1.0)">
|
||
|
|
<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=iso-8859-1">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
|
||
|
|
<link href="Integer-Functions.html#Integer-Functions" rel="up" title="Integer Functions">
|
||
|
|
<link href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" rel="next" title="Miscellaneous Integer Functions">
|
||
|
|
<link href="Integer-Random-Numbers.html#Integer-Random-Numbers" rel="prev" title="Integer Random Numbers">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
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.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Integer-Import-and-Export"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" accesskey="n" rel="next">Miscellaneous Integer Functions</a>, Previous: <a href="Integer-Random-Numbers.html#Integer-Random-Numbers" accesskey="p" rel="prev">Integer Random Numbers</a>, Up: <a href="Integer-Functions.html#Integer-Functions" accesskey="u" rel="up">Integer Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Integer-Import-and-Export-1"></a>
|
||
|
|
<h3 class="section">5.14 Integer Import and Export</h3>
|
||
|
|
|
||
|
|
<p><code>mpz_t</code> variables can be converted to and from arbitrary words of binary
|
||
|
|
data with the following functions.
|
||
|
|
</p>
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-mpz_005fimport"></a>Function: <em>void</em> <strong>mpz_import</strong> <em>(mpz_t <var>rop</var>, size_t <var>count</var>, int <var>order</var>, size_t <var>size</var>, int <var>endian</var>, size_t <var>nails</var>, const void *<var>op</var>)</em></dt>
|
||
|
|
<dd><a name="index-Integer-import"></a>
|
||
|
|
<a name="index-Import"></a>
|
||
|
|
<p>Set <var>rop</var> from an array of word data at <var>op</var>.
|
||
|
|
</p>
|
||
|
|
<p>The parameters specify the format of the data. <var>count</var> many words are
|
||
|
|
read, each <var>size</var> bytes. <var>order</var> can be 1 for most significant word
|
||
|
|
first or -1 for least significant first. Within each word <var>endian</var> can be
|
||
|
|
1 for most significant byte first, -1 for least significant first, or 0 for
|
||
|
|
the native endianness of the host CPU. The most significant <var>nails</var> bits
|
||
|
|
of each word are skipped, this can be 0 to use the full words.
|
||
|
|
</p>
|
||
|
|
<p>There is no sign taken from the data, <var>rop</var> will simply be a positive
|
||
|
|
integer. An application can handle any sign itself, and apply it for instance
|
||
|
|
with <code>mpz_neg</code>.
|
||
|
|
</p>
|
||
|
|
<p>There are no data alignment restrictions on <var>op</var>, any address is allowed.
|
||
|
|
</p>
|
||
|
|
<p>Here’s an example converting an array of <code>unsigned long</code> data, most
|
||
|
|
significant element first, and host byte order within each value.
|
||
|
|
</p>
|
||
|
|
<div class="example">
|
||
|
|
<pre class="example">unsigned long a[20];
|
||
|
|
/* Initialize <var>z</var> and <var>a</var> */
|
||
|
|
mpz_import (z, 20, 1, sizeof(a[0]), 0, 0, a);
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>This example assumes the full <code>sizeof</code> bytes are used for data in the
|
||
|
|
given type, which is usually true, and certainly true for <code>unsigned long</code>
|
||
|
|
everywhere we know of. However on Cray vector systems it may be noted that
|
||
|
|
<code>short</code> and <code>int</code> are always stored in 8 bytes (and with
|
||
|
|
<code>sizeof</code> indicating that) but use only 32 or 46 bits. The <var>nails</var>
|
||
|
|
feature can account for this, by passing for instance
|
||
|
|
<code>8*sizeof(int)-INT_BIT</code>.
|
||
|
|
</p></dd></dl>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><a name="index-mpz_005fexport"></a>Function: <em>void *</em> <strong>mpz_export</strong> <em>(void *<var>rop</var>, size_t *<var>countp</var>, int <var>order</var>, size_t <var>size</var>, int <var>endian</var>, size_t <var>nails</var>, const mpz_t <var>op</var>)</em></dt>
|
||
|
|
<dd><a name="index-Integer-export"></a>
|
||
|
|
<a name="index-Export"></a>
|
||
|
|
<p>Fill <var>rop</var> with word data from <var>op</var>.
|
||
|
|
</p>
|
||
|
|
<p>The parameters specify the format of the data produced. Each word will be
|
||
|
|
<var>size</var> bytes and <var>order</var> can be 1 for most significant word first or
|
||
|
|
-1 for least significant first. Within each word <var>endian</var> can be 1 for
|
||
|
|
most significant byte first, -1 for least significant first, or 0 for the
|
||
|
|
native endianness of the host CPU. The most significant <var>nails</var> bits of
|
||
|
|
each word are unused and set to zero, this can be 0 to produce full words.
|
||
|
|
</p>
|
||
|
|
<p>The number of words produced is written to <code>*<var>countp</var></code>, or
|
||
|
|
<var>countp</var> can be <code>NULL</code> to discard the count. <var>rop</var> must have
|
||
|
|
enough space for the data, or if <var>rop</var> is <code>NULL</code> then a result array
|
||
|
|
of the necessary size is allocated using the current GMP allocation function
|
||
|
|
(see <a href="Custom-Allocation.html#Custom-Allocation">Custom Allocation</a>). In either case the return value is the
|
||
|
|
destination used, either <var>rop</var> or the allocated block.
|
||
|
|
</p>
|
||
|
|
<p>If <var>op</var> is non-zero then the most significant word produced will be
|
||
|
|
non-zero. If <var>op</var> is zero then the count returned will be zero and
|
||
|
|
nothing written to <var>rop</var>. If <var>rop</var> is <code>NULL</code> in this case, no
|
||
|
|
block is allocated, just <code>NULL</code> is returned.
|
||
|
|
</p>
|
||
|
|
<p>The sign of <var>op</var> is ignored, just the absolute value is exported. An
|
||
|
|
application can use <code>mpz_sgn</code> to get the sign and handle it as desired.
|
||
|
|
(see <a href="Integer-Comparisons.html#Integer-Comparisons">Integer Comparisons</a>)
|
||
|
|
</p>
|
||
|
|
<p>There are no data alignment restrictions on <var>rop</var>, any address is allowed.
|
||
|
|
</p>
|
||
|
|
<p>When an application is allocating space itself the required size can be
|
||
|
|
determined with a calculation like the following. Since <code>mpz_sizeinbase</code>
|
||
|
|
always returns at least 1, <code>count</code> here will be at least one, which
|
||
|
|
avoids any portability problems with <code>malloc(0)</code>, though if <code>z</code> is
|
||
|
|
zero no space at all is actually needed (or written).
|
||
|
|
</p>
|
||
|
|
<div class="example">
|
||
|
|
<pre class="example">numb = 8*size - nail;
|
||
|
|
count = (mpz_sizeinbase (z, 2) + numb-1) / numb;
|
||
|
|
p = malloc (count * size);
|
||
|
|
</pre></div>
|
||
|
|
</dd></dl>
|
||
|
|
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Miscellaneous-Integer-Functions.html#Miscellaneous-Integer-Functions" accesskey="n" rel="next">Miscellaneous Integer Functions</a>, Previous: <a href="Integer-Random-Numbers.html#Integer-Random-Numbers" accesskey="p" rel="prev">Integer Random Numbers</a>, Up: <a href="Integer-Functions.html#Integer-Functions" accesskey="u" rel="up">Integer Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|