get media metadata from a file

main.cpp

#include <iostream>
#include <Windows.h>
#include <filesystem>
#include <array>
#include <string>
#include <string_view>
#include <vector>
#include <variant>
#include <Wmsdk.h>
#include <stdexcept>

#pragma comment(lib, "Wmvcore.lib")

using std::filesystem::path, std::wcout;

void writeHelp(std::wstring_view message = {})
{
	wcout << message << std::endl;
	std::array<wchar_t, MAX_PATH> buffer;
	const auto actualLength = GetModuleFileNameW(nullptr, buffer.data(), buffer.size());
	std::wstring_view exePath(buffer.data(), actualLength);
	wcout << exePath << L" <filePath>" << std::endl;
}
struct MetadataName
{
	WORD languageIndex;
	std::wstring name;
};
using Attribute = std::variant<DWORD, QWORD, BOOL, std::vector<BYTE>, std::wstring>;
using Metadata = std::pair < MetadataName, Attribute>;
std::vector<Metadata> getFileMetadata(path fileName)
{
	auto result = CoInitialize(nullptr);
	if (result != S_OK)
		throw std::runtime_error{ "error in CoInitialize" };
	IWMMetadataEditor* editor{ nullptr };
	result = WMCreateEditor(&editor);
	if (result != S_OK)
		throw std::runtime_error("error in WMCreateEditor");
	IWMHeaderInfo3* headerinfo{ nullptr };
	result = editor->QueryInterface(&headerinfo);
	if (result != S_OK)
		throw std::runtime_error("error in QueryInterface<IWMHeaderInfo3>");
	result = editor->Open(fileName.wstring().c_str());
	if (result != S_OK)
		throw std::runtime_error{ "error in IWMMetadataEditor::Open" };
	constexpr DWORD streamNumber{0xFFFF};
	WORD attributeCount{ 0 };
	result = headerinfo->GetAttributeCount(streamNumber, &attributeCount);
	if (result != S_OK)
		throw std::runtime_error{ "error in IWMHeaderInfo3::GetAttributeCount" };
	std::vector<Metadata> fileMetadata;
	fileMetadata.reserve(attributeCount);
	for (int i{0}; i < attributeCount; i++)
	{
		WORD nameLen{ 0 };
		DWORD dataLen{ 0 };
		result = headerinfo->GetAttributeByIndexEx(streamNumber, i, nullptr, &nameLen, nullptr, nullptr, nullptr, &dataLen);
		if (result != S_OK)
		{
			throw std::runtime_error{ "error in IWMHeaderInfo3::GetAttributeByIndexEx" };

		}
		thread_local std::vector<wchar_t> name;
		name.resize(nameLen);
		thread_local std::vector<BYTE> data;
		data.resize(dataLen);
		WMT_ATTR_DATATYPE attType{};
		WORD langIndex{ 0 };
		result = headerinfo->GetAttributeByIndexEx(streamNumber, i, name.data(), &nameLen, &attType, &langIndex, data.data(), &dataLen);
		if (result != S_OK)
		{
			throw std::runtime_error{ "error in IWMHeaderInfo3::GetAttributeByIndexEx" };

		}
		MetadataName metaName{langIndex, std::wstring(name.begin(), name.end())};
		const auto attribute{
			[&]
			{
				switch (attType)
				{
				case WMT_TYPE_WORD:
					return Attribute{ static_cast<WORD>(*data.data()) };
				case WMT_TYPE_DWORD:
					return Attribute{ static_cast<DWORD>(*data.data()) };
				case WMT_TYPE_QWORD:
					return Attribute{ static_cast<QWORD>(*data.data()) };
				case WMT_TYPE_STRING:
					return Attribute{ std::wstring(reinterpret_cast<wchar_t*>(data.data()), dataLen)};
				case WMT_TYPE_BINARY:
					return Attribute{ data };
				case WMT_TYPE_BOOL:
					return Attribute{ static_cast<BOOL>(*data.data()) };
				case WMT_TYPE_GUID:
					return Attribute{ static_cast<DWORD>(*data.data()) };
				}
				throw std::runtime_error{ "unknown attribute type" };
			}()
		};
		fileMetadata.emplace_back(metaName, attribute);
	}

	return fileMetadata;
}

Metadata getFileAttributes(path fileName)
{
	WIN32_FILE_ATTRIBUTE_DATA buffer{};
	if (!GetFileAttributesExW(fileName.wstring().c_str(), GetFileExInfoStandard, &buffer))
	{
		throw std::runtime_error{ "error in GetFileAttributesExW" };
	}
	return {};
}

int main(int argc, char* args[])
{
	if (argc < 2)
	{
		writeHelp();
		return 0;
	}
	path path{ args[1] };
	if (!std::filesystem::exists(path))
	{
		writeHelp(L"the file path given doesnt exist");
	}
	const auto metadata{ getFileMetadata(path)};
}