Question

Im trying to use this kind of iterators, but I have got errors for the following code:

void linearMatrix::Write_File_Matrix(const char *Path)
{
    ofstream FILE(Path, std::ios::out | std::ofstream::binary);
    FILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    FILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    ostreambuf_iterator<float> out_it (FILE);
    copy(myVector.begin(), myVector.end(), out_it);
}

void linearMatrix::Read_File_Matrix(const char *Path)
{
    ifstream FILE(Path, std::ios::in | std::ifstream::binary);

    if(!FILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    FILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));
    FILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));
    istreambuf_iterator<float> iter(FILE);
    copy(iter.begin(), iter.end(), std::back_inserter(myVector));
}

The problems are:

1- ostreambuf_iterator<float> out_it (FILE);

error: invalid conversion from ‘void*’ to
‘std::ostreambuf_iterator::streambuf_type* {aka
std::basic_streambuf >*}’
[-fpermissive]

2- FILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));

error: invalid conversion from ‘const char*’ to ‘std::basic_istream::char_type* {aka char*}’ [-fpermissive]

3- FILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));

error: invalid conversion from ‘const char*’ to
‘std::basic_istream::char_type* {aka char*}’ [-fpermissive]

4- std::ifstream FILE(Path, std::ios::in | std::ifstream::binary);

error: invalid conversion from ‘void*’ to
‘std::ostreambuf_iterator::streambuf_type* {aka
std::basic_streambuf >*}’
[-fpermissive]

5- copy(iter.begin(), iter.end(), std::back_inserter(myVector));

error: ‘class std::istreambuf_iterator’ has no member named
‘begin’

error: ‘class std::istreambuf_iterator’ has no member named
‘end’

What am I doing wrong? I’m using the nsight eclipse from CUDA, but compiling a C++ project with g++. I refer to: Reading and writing a std::vector into a file correctly

#include <iostream>
#include <algorithm>
#include <iterator>
#include <fstream>
#include <vector>

using namespace std;

void Write_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;
    v[0] = 1;
    v[1] = 2;
    v[2] = 3;
    ofstream outFILE(Path, ios::out | ofstream::binary);
    outFILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    outFILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    ostreambuf_iterator<float> out_it (outFILE);
    copy(V.begin(), V.end(), out_it);
}

void Read_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;

    ifstream inFILE(Path, ios::in | ifstream::binary);

    if(!inFILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    inFILE.read(reinterpret_cast<const char *>(&myWidth), sizeof(myWidth));
    inFILE.read(reinterpret_cast<const char *>(&myHeight), sizeof(myHeight));
    istreambuf_iterator<float> iter(inFILE);
    copy(iter.begin(), iter.end(), std::back_inserter(myVector));
}

int main() {

    Write_File_Matrix("M.dat");
    Read_File_Matrix("R.dat");

    return 0;
}

Answer 1

1- ostreambuf_iterator out_it (FILE);

error: invalid conversion from ‘void*’ to ‘std::ostreambuf_iterator::streambuf_type* {aka std::basic_streambuf >*}’ [-fpermissive]

std::ostreambuf_iterator takes as template parameter the character type of the stream, NOT the type you want to convert to. Try:

std::ostreambuf_iterator<char> out_it(FILE);

Ditto for #4.

---

EDIT: Let’s solve your big problem instead of your small ones:

Don’t bother with iterators, just write the vector data out all in one go:

void Write_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;
    v[0] = 1;
    v[1] = 2;
    v[2] = 3;
    ofstream outFILE(Path, ios::out | ofstream::binary);
    outFILE.write(reinterpret_cast<const char *>(&myWidth), sizeof(float));
    outFILE.write(reinterpret_cast<const char *>(&myHeight), sizeof(float));
    outFile.write(reinterpret_cast<const char *>(&v[0]), v.size()*sizeof(float));
}

Reading, however, still needs to be one-piece-at-a-time.

void Read_File_Matrix(const char *Path)
{
    float myWidth = 0;
    float myHeight = 0;
    vector<float> v;

    ifstream inFILE(Path, ios::in | ifstream::binary);

    if(!inFILE)
    {
        cerr << "Cannot open the file" << endl;
        exit(1);
    }
    inFILE.read(reinterpret_cast<char *>(&myWidth), sizeof(myWidth));
    inFILE.read(reinterpret_cast<char *>(&myHeight), sizeof(myHeight));
    float f;
    while( inFILE.read(reinterpret_cast<char *>(&f), sizeof(f)))
      v.push_back(f);
}