Question

I have an array of a large structure that I am trying to output to hard drive. I seem to be able to write to hard drive just fine (though it’s difficult to verify by looking at the binary data), however when I try to read it back, I always end up with a garbled mess. Any ideas what I’m doing wrong?

here’s the structure configuration:

class xyz
{
public:
    double x, y, z;
};
class trianglePackage
{
public:

    int score;
    int position;

    xyz contactCoordinates;
    xyz normalVector;
    xyz locatorOffset;

};
class quadanglesOutput
{
public:

    int locator1position, locator2position, locator3position, locator4position;

    xyz centroid;

    int surfaceAreaScore;
    int centroidDifferance1Score;
    int centroidDifferance2Score;
    int minDistance1Score;
    int minDistance2Score;

    int totalLocatorScore;
    int totalHullScore;
    int totalScore;

    double surfaceArea;
    double centroidDifferance1;
    double centroidDifferance2;
    double minDistance1;
    double minDistance2;

    int hull;

    trianglePackage locator1, locator2, locator3, locator4;
};

and here are the read/write functions I’m using:

void outputQuadangleOutput(quadanglesOutput* output, string description, param parameters)
{

    string outputName = parameters.fileName + " " + description + ".bin";
    cout << "Output " << outputName.c_str() << "...";
    ofstream output2;
    output2.open(outputName.c_str());
    output2.write(reinterpret_cast<char*>(output), streamsize(parameters.topXlist * sizeof(quadanglesOutput)));
    output2.close();
    cout << "done" << endl;

}
void readIn(quadanglesOutput* pointer, param parameters, string description)
{
    string fileName = parameters.fileName + " " + description + ".bin";
    cout << "openining " << fileName << "...";
    ifstream readFile;
    readFile.open(fileName.c_str());
    readFile.read(reinterpret_cast<char*>(pointer), (parameters.topXlist * sizeof(quadanglesOutput)));
    readFile.close();
    cout << "done" << endl;
}

Typically the arrays of structures are about 100 in length, but usually only about the first 25 read back correctly, everything else is default uninitialized data.

I’m 99% sure that it’s something wrong with my code, however is there a possibility it has something to do with four byte alignment?

Thanks.

Answer 1

It may be an issue with byte alignment, use pragma.
try wrap classes around with

#PRAGMA PACK PUSH(1)
....
#PRAGMA PACK POP

or

#PRAGMA PACK(1)
struct{
..
}

Try those as well:
Force binary flag for the stream.

ios_base::binary

readFile.open(fileName.c_str(), ios_base::binary);

Try to flush the the stream.

stream.write(...)
stream.flush()

//i know that close() should flush it.

UPDATE:
Everything works for me:

#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>

using namespace std;
#pragma pack(1)
class xyz
{
public:
    double x, y, z;
};

#pragma pack(1)
class trianglePackage
{
public:

    int score;
    int position;

    xyz contactCoordinates;
    xyz normalVector;
    xyz locatorOffset;

};

#pragma pack(1)
class quadanglesOutput
{
public:

    int locator1position, locator2position, locator3position, locator4position;

    xyz centroid;

    int surfaceAreaScore;
    int centroidDifferance1Score;
    int centroidDifferance2Score;
    int minDistance1Score;
    int minDistance2Score;

    int totalLocatorScore;
    int totalHullScore;
    int totalScore;

    double surfaceArea;
    double centroidDifferance1;
    double centroidDifferance2;
    double minDistance1;
    double minDistance2;

    int hull;

    trianglePackage locator1, locator2, locator3, locator4;
};

class param
{
public:
    string fileName;
    int topXlist;
};


void outputQuadangleOutput(quadanglesOutput* output, string description, param parameters)
{

    string outputName = parameters.fileName + " " + description + ".bin";
    cout << "Output " << outputName.c_str() << "...";
    ofstream output2;
    output2.open(outputName.c_str());
    output2.write(reinterpret_cast<char*>(output), streamsize(parameters.topXlist * sizeof(quadanglesOutput)));
    output2.close();
    cout << "done" << endl;

}
void readIn(quadanglesOutput* pointer, param parameters, string description)
{
    string fileName = parameters.fileName + " " + description + ".bin";
    cout << "openining " << fileName << "...";
    ifstream readFile;
    readFile.open(fileName.c_str());
    readFile.read(reinterpret_cast<char*>(pointer), (parameters.topXlist * sizeof(quadanglesOutput)));
    readFile.close();
    cout << "done" << endl;
}



int main(int argc, char *argv[])
{

    quadanglesOutput a = {0};
    cout<<"total score:"<<a.totalScore<<endl;
    cout<<"locator position:"<<a.totalScore<<endl;
    cout<<"locator position:"<<a.locator1.position<<endl;
    cout<<"locator position:"<<a.locator2.normalVector.y <<endl;
    cout<<"sizeof quadangsomething:"<<sizeof(quadanglesOutput)<<endl;
    a.totalScore=1;
    a.locator1.position=333445;
    a.locator2.normalVector.y = 999.3224;
    cout<<"total score:"<<a.totalScore<<endl;
    cout<<"locator position:"<<a.locator1.position<<endl;
    cout<<"locator position:"<<a.locator2.normalVector.y <<endl;
    param p = {"C:/", 1};
    outputQuadangleOutput(&a, "file1", p);

    quadanglesOutput *b = new quadanglesOutput();
    readIn(b, p, "file1");
    cout<<"new total score:"<<b->totalScore<<endl;
    cout<<"new locator position:"<<b->locator1.position<<endl;
    cout<<"new locator position:"<<b->locator2.normalVector.y <<endl;

    delete b;





    string asdf;
    cin>>asdf;

};

OUTPUT:
total score:0
locator position:0
locator2.normalVector.y :0
sizeof quadangsomething:436
total score:1
locator position:333445
locator2.normalVector.y :999.322
Output C:/ file1.bin…done
openining C:/ file1.bin…done
new total score:1
new locator position:333445
new locator2.normalVector.y :999.322

without pragma it’s still correct but you can see the difference in size:

sizeof quadangsomething:440

But packing it is good when sending structures over network.
Because here system alligns it always in the same fashion.