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// Copyright (C) 2018-2022 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
//
// clang-format off
#include <fstream>
#include <iostream>
#include <string>
#include "MnistUbyte.h"
// clang-format on
using namespace FormatReader;
int MnistUbyte::reverseInt(int i) {
unsigned char ch1, ch2, ch3, ch4;
ch1 = (unsigned char)(i & 255);
ch2 = (unsigned char)((i >> 8) & 255);
ch3 = (unsigned char)((i >> 16) & 255);
ch4 = (unsigned char)((i >> 24) & 255);
return (static_cast<int>(ch1) << 24) + (static_cast<int>(ch2) << 16) + (static_cast<int>(ch3) << 8) + ch4;
}
MnistUbyte::MnistUbyte(const std::string& filename) {
std::ifstream file(filename, std::ios::binary);
if (!file.is_open()) {
return;
}
int magic_number = 0;
int number_of_images = 0;
int n_rows = 0;
int n_cols = 0;
file.read(reinterpret_cast<char*>(&magic_number), sizeof(magic_number));
magic_number = reverseInt(magic_number);
if (magic_number != 2051) {
return;
}
file.read(reinterpret_cast<char*>(&number_of_images), sizeof(number_of_images));
number_of_images = reverseInt(number_of_images);
file.read(reinterpret_cast<char*>(&n_rows), sizeof(n_rows));
n_rows = reverseInt(n_rows);
_height = (size_t)n_rows;
file.read(reinterpret_cast<char*>(&n_cols), sizeof(n_cols));
n_cols = reverseInt(n_cols);
_width = (size_t)n_cols;
if (number_of_images > 1) {
std::cout << "[MNIST] Warning: number_of_images in mnist file equals " << number_of_images
<< ". Only a first image will be read." << std::endl;
}
size_t size = _width * _height * 1;
_data.reset(new unsigned char[size], std::default_delete<unsigned char[]>());
size_t count = 0;
if (0 < number_of_images) {
for (int r = 0; r < n_rows; ++r) {
for (int c = 0; c < n_cols; ++c) {
unsigned char temp = 0;
file.read(reinterpret_cast<char*>(&temp), sizeof(temp));
_data.get()[count++] = temp;
}
}
}
file.close();
}
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