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binaryCpp3.cc
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binaryCpp3.cc
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/*
To compile:
c++ -o binaryCpp3 binaryCpp3.c -O2 -Wall -W
Note: the -lm is implied by the C++ compiler,
but can be included.
*/
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstdio>
#include <vector>
#include <sstream> //used for buffering
#include <iostream> //for cout,cerr
#include <fstream> //use for C++ streams to files
/*
Rather than stdio.h, we
use the lower-level fcntl.h.
*/
#include <fcntl.h>
#include <unistd.h> /* Needed only on OS X */
using namespace std;
int main( int argc, char ** argv )
{
const size_t MBUFFER = 1024; //Max. buffer size in 1024*sizeof(double) bytes
vector<double> buffer;
buffer.reserve( MBUFFER );
ofstream o("testCpp4.bin",ios::out | ios::binary );
for( size_t i = 0 ; i < 1000000 ; ++i )
{
buffer.push_back(sqrt(i)/double(i));
if ( buffer.size() >= MBUFFER )
//If buffer hits our max size in memory, print it to file and clear it.
{
o.write( reinterpret_cast< char * >(&buffer[0]), buffer.size()*sizeof(double) );
buffer.clear();
}
}
//Pro tip: your amount of output % MBUFFER is probably != 0!!!
if( !buffer.empty() )
{
o.write( reinterpret_cast< char * >(&buffer[0]), buffer.size()*sizeof(double) );
buffer.clear();
}
o.close();
//read it back in
vector<double> data;
ifstream in("testCpp4.bin",ios::in | ios::binary);
double x;
do
{
in.read( reinterpret_cast<char *>(&x), sizeof(double) );
if(!in.eof() && !in.fail())
{
data.push_back(x);
}
}
while( ! in.eof() && !in.fail() );
cerr << data.size() << " doubles read from file\n";
for( size_t i = 0 ; i < 10 ; ++i )
{
cout << "Element " << i << " = " << buffer[i] << " and " << data[i] << '\n';
}
}