forked from boostorg/endian
78 lines
2.1 KiB
C++
78 lines
2.1 KiB
C++
// endian_example.cpp -------------------------------------------------------//
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// Copyright Beman Dawes, 2006
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// Distributed under the Boost Software License, Version 1.0.
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// See http://www.boost.org/LICENSE_1_0.txt
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// See library home page at http://www.boost.org/libs/endian
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//----------------------------------------------------------------------------//
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#define _CRT_SECURE_NO_DEPRECATE // quiet VC++ 8.0 foolishness
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#include <boost/endian/detail/disable_warnings.hpp>
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#include <iostream>
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#include <cstdio>
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#include <boost/endian/integers.hpp>
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#include <boost/static_assert.hpp>
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using namespace boost::endian;
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namespace
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{
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// This is an extract from a very widely used GIS file format. I have no idea
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// why a designer would mix big and little endians in the same file - but
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// this is a real-world format and users wishing to write low level code
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// manipulating these files have to deal with the mixed endianness.
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struct header
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{
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big32_t file_code;
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big32_t file_length;
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little32_t version;
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little32_t shape_type;
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};
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const char * filename = "test.dat";
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}
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int main(int, char * [])
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{
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BOOST_STATIC_ASSERT( sizeof( header ) == 16U ); // check requirement
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header h;
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h.file_code = 0x01020304;
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h.file_length = sizeof( header );
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h.version = -1;
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h.shape_type = 0x01020304;
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// Low-level I/O such as POSIX read/write or <cstdio> fread/fwrite is sometimes
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// used for binary file operations when ultimate efficiency is important.
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// Such I/O is often performed in some C++ wrapper class, but to drive home the
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// point that endian integers are often used in fairly low-level code that
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// does bulk I/O operations, <cstdio> fopen/fwrite is used for I/O in this example.
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std::FILE * fi = std::fopen( filename, "wb" ); // MUST BE BINARY
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if ( !fi )
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{
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std::cout << "could not open " << filename << '\n';
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return 1;
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}
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if ( std::fwrite( &h, sizeof( header ), 1, fi ) != 1 )
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{
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std::cout << "write failure for " << filename << '\n';
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return 1;
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}
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std::fclose( fi );
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std::cout << "created file " << filename << '\n';
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return 0;
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}
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