MAT_T_STRING not correctly recognized?

[BruhGreg]

I wrote a little snippet to parse .mat file:

void _printProperties(matvar_t *mat_var);

int main()
{
	Log::Init();

	std::string filepath;
	std::cout << "Please enter the path to your .mat file: ";
	std::getline(std::cin, filepath);

	mat_t *mat = Mat_Open(filepath.c_str(), MAT_ACC_RDONLY);
	if (mat == nullptr) {
		LOG_ERROR("Failed to open .mat file: {0}", filepath);
		return 1;
	}

	matvar_t *matVar = nullptr;
	while ((matVar = Mat_VarReadNext(mat)) != nullptr) {
		_printProperties(matVar);

		if (matVar->data) {
			unsigned size = matVar->nbytes / matVar->data_size;
			if (matVar->data_type == MAT_T_DOUBLE) {
				const double *data = static_cast<const double *>(matVar->data);

				for (size_t i = 0; i < matVar->dims[0]; ++i) {
					for (size_t j = 0; j < matVar->dims[1]; ++j) {
						LOG_INFO("\t[{0}][{1}] = {2}", i, j, data[i + j * matVar->dims[0]]);
					}
				}
			}
			else if (matVar->data_type == MAT_T_UTF8) {
				const char *data = static_cast<const char *>(matVar->data);
				LOG_INFO("Char: {0}", std::string(data, matVar->nbytes));
			}
			else if (matVar->data_type == MAT_T_STRING) {
				const std::string *data = static_cast<const std::string *>(matVar->data);
				LOG_INFO("String: {0}", data->c_str());
			}
		}
		else {
			LOG_INFO("Data: (null)");
		}
		LOG_INFO("");

		Mat_VarFree(matVar);
	}

	Mat_Close(mat);

	return 0;
}

std::string _getType(matio_types type)
{
	switch (type) {
		case MAT_T_UNKNOWN:
			return "Unknown";
		case MAT_T_INT8:
			return "Int8";
		case MAT_T_UINT8:
			return "UInt8";
		case MAT_T_INT16:
			return "Int16";
		case MAT_T_UINT16:
			return "UInt16";
		case MAT_T_INT32:
			return "Int32";
		case MAT_T_UINT32:
			return "UInt32";
		case MAT_T_SINGLE:
			return "Single";
		case MAT_T_DOUBLE:
			return "Double";
		case MAT_T_INT64:
			return "Int64";
		case MAT_T_UINT64:
			return "UInt64";
		case MAT_T_MATRIX:
			return "Matrix";
		case MAT_T_COMPRESSED:
			return "Compressed";
		case MAT_T_UTF8:
			return "UTF8";
		case MAT_T_UTF16:
			return "UTF16";
		case MAT_T_UTF32:
			return "UTF32";
		case MAT_T_STRING:
			return "String";
		case MAT_T_CELL:
			return "Cell";
		case MAT_T_STRUCT:
			return "Struct";
		case MAT_T_ARRAY:
			return "Array";
		case MAT_T_FUNCTION:
			return "Function";
		default:
			return "Unknown Default";
	}
}

void _printProperties(matvar_t *mat_var)
{
	std::string msg;
	std::string var_name = mat_var->name ? mat_var->name : "(unnamed)";

	msg += fmt::format("---\nVariable: {0}, Type: {1}, Rank: {2}\n",
		var_name,
		_getType(mat_var->data_type),
		mat_var->rank);

	msg += fmt::format("Dimension: ");
	for (int i = 0; i < mat_var->rank; ++i) {
		msg += fmt::format("{0} x ", mat_var->dims[i]);
	}
	msg = msg.substr(0, msg.length() - 3); // Remove last " x "
	msg += "\n";
	LOG_INFO(msg);
}

When i feed in my .mat file

Note: the last variable str_last is actually char typed, it is named so to be placed at the last of the list, and used as an indicatior to show the list has come to the end.

The output is as follows:

Please enter the path to your .mat file: c:\Users\xxx\Desktop\test.mat
---
Variable: a, Type: Double, Rank: 2
Dimension: 3 x 3

        [0][0] = 1
        [0][1] = 2.2
        [0][2] = 3
        [1][0] = 4
        [1][1] = 5
        [1][2] = 6
        [2][0] = 7
        [2][1] = 0
        [2][2] = 0

---
Variable: b, Type: Int8, Rank: 2
Dimension: 1 x 1


---
Variable: c, Type: Double, Rank: 2
Dimension: 1 x 1

        [0][0] = 2

---
Variable: cell, Type: Cell, Rank: 2
Dimension: 2 x 3


---
Variable: char, Type: UTF8, Rank: 2
Dimension: 1 x 10

Char: char_value

---
Variable: ee, Type: Double, Rank: 2
Dimension: 1 x 3

        [0][0] = 1
        [0][1] = 2
        [0][2] = 3

---
Variable: (unnamed), Type: Unknown, Rank: 0
Dimensio

Data: (null)

---
Variable: (unnamed), Type: Unknown, Rank: 0
Dimensio

Data: (null)

---
Variable: str_last, Type: UTF8, Rank: 2
Dimension: 1 x 3

Char: end

---
Variable: , Type: UInt8, Rank: 2
Dimension: 1 x 1304

As is shown, string data in .mat file are not recognized, as in the type is treated as MAT_T_UNKNOWN, and the weird thing is, if there's a string in the .mat file, there will be an extra Variable typed UInt8

[tbeu]

Can you please provide the MAT file?

[BruhGreg]

yes, the mat file is attached.
test_mat.zip

[tbeu]

Duplicate of #98.