# dlib C++ Library - mnist.cpp

    // Copyright (C) 2015  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_MNIST_CPp_
    #define DLIB_MNIST_CPp_

    #include "mnist.h"
    #include <fstream>
    #include "../byte_orderer.h"
    #include "../uintn.h"

    // ----------------------------------------------------------------------------------------

    namespace dlib
    {
        void load_mnist_dataset (
            const std::string& folder_name,
            std::vector<matrix<unsigned char> >& training_images,
            std::vector<unsigned long>& training_labels,
            std::vector<matrix<unsigned char> >& testing_images,
            std::vector<unsigned long>& testing_labels
        )
        {
            using namespace std;
            ifstream fin1((folder_name+"/train-images-idx3-ubyte").c_str(), ios::binary);
            if (!fin1)
            {
                fin1.open((folder_name + "/train-images.idx3-ubyte").c_str(), ios::binary);
            }

            ifstream fin2((folder_name+"/train-labels-idx1-ubyte").c_str(), ios::binary);
            if (!fin2)
            {
                fin2.open((folder_name + "/train-labels.idx1-ubyte").c_str(), ios::binary);
            }

            ifstream fin3((folder_name+"/t10k-images-idx3-ubyte").c_str(), ios::binary);
            if (!fin3)
            {
                fin3.open((folder_name + "/t10k-images.idx3-ubyte").c_str(), ios::binary);
            }

            ifstream fin4((folder_name+"/t10k-labels-idx1-ubyte").c_str(), ios::binary);
            if (!fin4)
            {
                fin4.open((folder_name + "/t10k-labels.idx1-ubyte").c_str(), ios::binary);
            }

            if (!fin1) throw error("Unable to open file train-images-idx3-ubyte or train-images.idx3-ubyte");
            if (!fin2) throw error("Unable to open file train-labels-idx1-ubyte or train-labels.idx1-ubyte");
            if (!fin3) throw error("Unable to open file t10k-images-idx3-ubyte or t10k-images.idx3-ubyte");
            if (!fin4) throw error("Unable to open file t10k-labels-idx1-ubyte or t10k-labels.idx1-ubyte");

            byte_orderer bo;

            // make sure the files have the contents we expect.
            uint32 magic, num, nr, nc, num2, num3, num4;
            fin1.read((char*)&magic, sizeof(magic));  bo.big_to_host(magic);
            fin1.read((char*)&num, sizeof(num));  bo.big_to_host(num);
            fin1.read((char*)&nr, sizeof(nr));  bo.big_to_host(nr);
            fin1.read((char*)&nc, sizeof(nc));  bo.big_to_host(nc);
            if (magic != 2051 || num != 60000 || nr != 28 || nc != 28)
                throw error("mnist dat files are corrupted.");

            fin2.read((char*)&magic, sizeof(magic));  bo.big_to_host(magic);
            fin2.read((char*)&num2, sizeof(num2));  bo.big_to_host(num2);
            if (magic != 2049 || num2 != 60000)
                throw error("mnist dat files are corrupted.");

            fin3.read((char*)&magic, sizeof(magic));  bo.big_to_host(magic);
            fin3.read((char*)&num3, sizeof(num3));  bo.big_to_host(num3);
            fin3.read((char*)&nr, sizeof(nr));  bo.big_to_host(nr);
            fin3.read((char*)&nc, sizeof(nc));  bo.big_to_host(nc);
            if (magic != 2051 || num3 != 10000 || nr != 28 || nc != 28)
                throw error("mnist dat files are corrupted.");

            fin4.read((char*)&magic, sizeof(magic));  bo.big_to_host(magic);
            fin4.read((char*)&num4, sizeof(num4));  bo.big_to_host(num4);
            if (magic != 2049 || num4 != 10000)
                throw error("mnist dat files are corrupted.");

            if (!fin1) throw error("Unable to read train-images-idx3-ubyte");
            if (!fin2) throw error("Unable to read train-labels-idx1-ubyte");
            if (!fin3) throw error("Unable to read t10k-images-idx3-ubyte");
            if (!fin4) throw error("Unable to read t10k-labels-idx1-ubyte");

            training_images.resize(60000);
            training_labels.resize(60000);
            testing_images.resize(10000);
            testing_labels.resize(10000);

            for (size_t i = 0; i < training_images.size(); ++i)
            {
                training_images[i].set_size(nr,nc);
                fin1.read((char*)&training_images[i](0,0), nr*nc);
            }
            for (size_t i = 0; i < training_labels.size(); ++i)
            {
                char l;
                fin2.read(&l, 1);
                training_labels[i] = l;
            }

            for (size_t i = 0; i < testing_images.size(); ++i)
            {
                testing_images[i].set_size(nr,nc);
                fin3.read((char*)&testing_images[i](0,0), nr*nc);
            }
            for (size_t i = 0; i < testing_labels.size(); ++i)
            {
                char l;
                fin4.read(&l, 1);
                testing_labels[i] = l;
            }

            if (!fin1) throw error("Unable to read train-images-idx3-ubyte");
            if (!fin2) throw error("Unable to read train-labels-idx1-ubyte");
            if (!fin3) throw error("Unable to read t10k-images-idx3-ubyte");
            if (!fin4) throw error("Unable to read t10k-labels-idx1-ubyte");

            if (fin1.get() != EOF) throw error("Unexpected bytes at end of train-images-idx3-ubyte");
            if (fin2.get() != EOF) throw error("Unexpected bytes at end of train-labels-idx1-ubyte");
            if (fin3.get() != EOF) throw error("Unexpected bytes at end of t10k-images-idx3-ubyte");
            if (fin4.get() != EOF) throw error("Unexpected bytes at end of t10k-labels-idx1-ubyte");
        }
    }

    // ----------------------------------------------------------------------------------------

    #endif // DLIB_MNIST_CPp_