File change notifications on Windows

DirectoryWatch.cpp

#include <windows.h>
#include <stdio.h>

struct DirectoryWatch
{
	char filePath[1024];
	char changeBuffer[65536];
	HANDLE directoryHandle;
	FILE_NOTIFY_INFORMATION* nextChange;
};

DirectoryWatch createDirectoryWatch(const char* directoryPath)
{
	DirectoryWatch watch = {0};
	watch.directoryHandle = CreateFile(directoryPath, FILE_LIST_DIRECTORY, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, 0, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0);
	return watch;
}

bool waitForDirectoryChanges(DirectoryWatch* watch)
{
	if (!watch->nextChange)
	{
		DWORD bytesWritten;
		if (!ReadDirectoryChangesW(watch->directoryHandle, watch->changeBuffer, sizeof(watch->changeBuffer), true, FILE_NOTIFY_CHANGE_FILE_NAME | FILE_NOTIFY_CHANGE_LAST_WRITE | FILE_NOTIFY_CHANGE_ATTRIBUTES | FILE_NOTIFY_CHANGE_SIZE | FILE_NOTIFY_CHANGE_SECURITY | FILE_NOTIFY_CHANGE_CREATION | FILE_NOTIFY_CHANGE_DIR_NAME, &bytesWritten, 0, 0)) {
			return false;
		}
		Sleep(100); // Wait a bit for writes to finish
		watch->nextChange = (FILE_NOTIFY_INFORMATION*)&watch->changeBuffer;
	}

	int utf8Size = WideCharToMultiByte(CP_UTF8, 0, watch->nextChange->FileName, watch->nextChange->FileNameLength/2, watch->filePath, sizeof(watch->filePath)-1, 0, 0);
	watch->filePath[utf8Size] = '\0';

	if (watch->nextChange->NextEntryOffset) watch->nextChange = (FILE_NOTIFY_INFORMATION*)(((char*)watch->nextChange) + watch->nextChange->NextEntryOffset);
	else watch->nextChange = 0;

	return true;
}

// Usage example

void main()
{
	// You would probably run this in a separate thread and send messages to your
	// window, or queue asset reloads in your game.
	DirectoryWatch watch = createDirectoryWatch(".");
	while (waitForDirectoryChanges(&watch)) {
		puts(watch.filePath);
	}
}