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103 lines
4.4 KiB
HTML
103 lines
4.4 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Raw Output Internals (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Raw Output Internals (GNU MP 6.1.0)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Internals.html#Internals" rel="up" title="Internals">
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<link href="C_002b_002b-Interface-Internals.html#C_002b_002b-Interface-Internals" rel="next" title="C++ Interface Internals">
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<link href="Float-Internals.html#Float-Internals" rel="prev" title="Float Internals">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Raw-Output-Internals"></a>
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<div class="header">
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<p>
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Next: <a href="C_002b_002b-Interface-Internals.html#C_002b_002b-Interface-Internals" accesskey="n" rel="next">C++ Interface Internals</a>, Previous: <a href="Float-Internals.html#Float-Internals" accesskey="p" rel="prev">Float Internals</a>, Up: <a href="Internals.html#Internals" accesskey="u" rel="up">Internals</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Raw-Output-Internals-1"></a>
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<h3 class="section">16.4 Raw Output Internals</h3>
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<a name="index-Raw-output-internals"></a>
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<p><code>mpz_out_raw</code> uses the following format.
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</p>
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<div class="example">
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<pre class="example">+------+------------------------+
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| size | data bytes |
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+------+------------------------+
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</pre></div>
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<p>The size is 4 bytes written most significant byte first, being the number of
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subsequent data bytes, or the twos complement negative of that when a negative
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integer is represented. The data bytes are the absolute value of the integer,
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written most significant byte first.
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</p>
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<p>The most significant data byte is always non-zero, so the output is the same
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on all systems, irrespective of limb size.
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</p>
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<p>In GMP 1, leading zero bytes were written to pad the data bytes to a multiple
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of the limb size. <code>mpz_inp_raw</code> will still accept this, for
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compatibility.
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</p>
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<p>The use of “big endian” for both the size and data fields is deliberate, it
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makes the data easy to read in a hex dump of a file. Unfortunately it also
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means that the limb data must be reversed when reading or writing, so neither
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a big endian nor little endian system can just read and write <code>_mp_d</code>.
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</p>
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</body>
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</html>
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