Threads, heap args, and directory enumeration

This chapter covers passing a structure to a worker thread with CreateThread, and enumerating files with FindFirstFileA / FindNextFileA / FindClose.

Passing a parameter to CreateThread

Allocate a struct (e.g. ARGS) on the heap, fill fields such as a search pattern, pass the pointer as lpParameter, then wait and clean up:

typedef struct _ARGS {
    CHAR fileName[MAX_PATH];
} ARGS, *PARGS;

PARGS pArgs = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(ARGS));
if (!pArgs)
    return GetLastError();

memcpy(pArgs->fileName, "C:\\Users\\*", strlen("C:\\Users\\*") + 1);

HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)DirSearch, pArgs, 0, NULL);
if (!hThread) {
    HeapFree(GetProcessHeap(), 0, pArgs);
    return GetLastError();
}

WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
HeapFree(GetProcessHeap(), 0, pArgs);

Warning

Casting DirSearch to LPTHREAD_START_ROUTINE only works if DirSearch uses the correct return type and calling convention (DWORD WINAPI ThreadProc(LPVOID)). Mismatches cause stack corruption.

Thread procedure: FindFirstFile loop

Inside DirSearch (or your name):

• If lpParam is non-NULL, read ((PARGS)lpParam)->fileName (or use a default pattern).
• FindFirstFileA → check INVALID_HANDLE_VALUE → GetLastError on failure.
• do … while (FindNextFileA(...)).
• FileTimeToSystemTime for display.
• Combine nFileSizeHigh / nFileSizeLow with LARGE_INTEGER for 64-bit size.
• Skip . and ..; branch on FILE_ATTRIBUTE_DIRECTORY.
• FindClose before return.

Note

Pick a directory you are allowed to scan. C:\* or C:\Users\* are teaching examples only.

Implement

1. Define ARGS (or use the template’s typedef), implement DirSearch in its own .c file if your rubric splits modules.
2. CreateThread from main, wait, free heap.
3. Build, run, commit, and push.