mnist_read.c

struct mnist_images
{
	unsigned char *data;
	float *dataf;
	int count;
	int w, h;
};

struct mnist_labels
{
	unsigned char *data;
	int count;
};

int32_t endian_swap32(int32_t val)
{
    val = ((val << 8) & 0xFF00FF00) | ((val >> 8) & 0xFF00FF); 
    return (val << 16) | ((val >> 16) & 0xFFFF);
}

void mnist_labels_destroy(struct mnist_labels *dest)
{
	free(dest->data);
}

void mnist_images_destroy(struct mnist_images *dest)
{
	free(dest->data);
	free(dest->dataf);
}

int mnist_labels_read(struct mnist_labels *dest, const char *filename)
{
	FILE *file = fopen(filename, "rb");
	int header;

	if(! file) {
		printf("MNIST ERROR: can't read file %s\n", filename);
		return 0;
	}

	fread(&header, sizeof(int), 1, file);
	fread(&dest->count, sizeof(int), 1, file);

	dest->count = endian_swap32(dest->count);

	dest->data = (unsigned char *)malloc(dest->count * sizeof(char));
	fread(dest->data, sizeof(char), dest->count, file);

	fclose(file);
	return 1;
}

int mnist_images_read(struct mnist_images *dest, const char *filename)
{
	FILE *file = fopen(filename, "rb");
	int header, size, i;

	if(! file) {
		printf("MNIST ERROR: can't read file %s\n", filename);
		return 0;
	}

	fread(&header, sizeof(int), 1, file);
	fread(&dest->count, sizeof(int), 1, file);
	fread(&dest->w, sizeof(int), 1, file);
	fread(&dest->h, sizeof(int), 1, file);

	dest->count = endian_swap32(dest->count);
	dest->w = endian_swap32(dest->w);
	dest->h = endian_swap32(dest->h);
	size = dest->count * dest->w * dest->h;

	dest->data = (unsigned char *)malloc(size * sizeof(char));
	dest->dataf = (float *)malloc(size * sizeof(float));
	fread(dest->data, sizeof(char), size, file);

	for (i = 0; i < size; i++)
		dest->dataf[i] = (dest->data[i] / 255.0) * 2.0 - 1.0;

	fclose(file);
	return 1;
}