cfile_sink_src.cpp

This is an example on how to use C++ devices for C FILE*.

// cfile_sink_src.cpp
// 
// Copyright (c) 2009 - Michele De Stefano (micdestefano@users.sourceforge.net)
// 
// Distributed under the MIT License (See accompanying file LICENSE)

#include <iostream>
#include <mds_utils/file_utils/cfile_stream.hpp>
#include <boost/iostreams/stream_buffer.hpp>

namespace bios = boost::iostreams;
namespace mds_fu = mds_utils::file_utils;

int main(int argc,char *argv[]) {
    
    using namespace std;
    
    if (argc != 2) {
        cerr << "\nSyntax:\n\t" << argv[0] << " <file name>\n" << endl;
        return EXIT_FAILURE;
    }
    
    FILE *fp(NULL);
    
    // Open a file with fopen
    fp = fopen(argv[1],"w");
    
    // Instantiate the sink
    mds_fu::cFile_Sink      fsink(fp);
    
    // Instantiate the stream_buffer
    bios::stream_buffer<mds_fu::cFile_Sink>     sbuf;
    
    // Instantiate an std output stream, connecting it to the buffer
    ostream         ofs(&sbuf);
    
    // Connect the buffer to the file sink
    // (you could do this also before the ofs instantiation)
    sbuf.open(fsink);
    
    // Activate stream exceptions
    ofs.exceptions(ios::failbit | ios::badbit);
    
    double      val = 45.6;
    
    // Write a binary value
    ofs.write(reinterpret_cast<char*>(&val),sizeof(double));
    
    // Flush the value to the file
    ofs.flush();
    
    // Try to disconnect the buffer from the sink
    sbuf.close();
    
    // Re-connect the buffer to the sink
    sbuf.open(fsink);
    
    // Write something to file
    ofs << "This is a test string" << endl;
    
    // Flush before next operations
    ofs.flush();
    
    // Try the seekp function
    ofs.seekp(-5,ios::cur);
    
    // Overwrite from the current position
    ofs << "word" << endl;
    
    // Close the file
    fclose(fp); fp = NULL;
    
    // Disconnect the buffer
    sbuf.close();
    
    // Re-open the file in append mode
    fp = fopen(argv[1],"ab");
    
    // Re-set the file pointer into the sink
    fsink.set_FILEp(fp);
    
    // Re-connect the buffer to the sink
    sbuf.open(fsink);
    
    // Write something
    ofs << "Mic" << endl;
    
    // Remember to flush
    ofs.flush();
    
    // Try to seek in a file in append mode
    ofs.seekp(-3,ios::end);
    
    ofs << "Des" << std::endl;  // It is written at the end, because the file is opened
                                // in append mode
    
    // Close the file
    fclose(fp); fp = NULL;
    
    // Disconnect the buffer
    sbuf.close();
    
    
    // Re-open in read-binary
    fp = fopen(argv[1],"rb");
    
    // Instantiate a source device
    mds_fu::cFile_Source        fsource(fp);
    
    // Instantiate a new buffer for the source
    bios::stream_buffer<mds_fu::cFile_Source>       sbuf2;
    
    // Connect the buffer to the source device
    sbuf2.open(fsource);
    
    // Instantiate an input stream and connect it to
    // the prepared buffer
    istream                     ifs(&sbuf2);
    
    // Activate stream exceptions
    ifs.exceptions(ios::badbit | ios::failbit);
    
    // Try to seek
    ifs.seekg(-4,ios::end);
    
    string      str;
    
    // Extract a string
    ifs >> str;
    
    cout << "Read string: " << str << endl;
    
    // Seek again
    ifs.seekg(0,ios::beg);
    
    // Read a double
    ifs.read(reinterpret_cast<char*>(&val),sizeof(double));
    
    cout << "Value read: " << val << endl;
    
    fclose(fp); fp = NULL;
    
    return EXIT_SUCCESS;
}