l5

Author: stream-rahul

_posts/2024-01-30-lesson5.md

@@ -0,0 +1,118 @@
+---
+layout: default
+title: "Lesson 5: Free Space "
+date: 2024-01-30
+categories: rust
+permalink: /lesson5/
+---
+
+## Rust
+
+```rust
+
+
+
+
+
+
+
+
+```
+
+## C++ Implementation
+
+```cpp
+// C++ implementation will be added here
+
+#include <windows.h>
+#include <tchar.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void ReportError(LPCTSTR msg, DWORD exitCode, BOOL exitProgram);
+void ReportSpace(LPCTSTR Message);
+
+int _tmain(int argc, LPTSTR argv[]) {
+    HANDLE hFile;
+    LARGE_INTEGER FileLen, FileLenH;
+    BYTE Buffer[256];
+    OVERLAPPED ov = {0};
+    DWORD nWrite;
+
+    while (1) {
+        FileLen.QuadPart = 0;
+        _tprintf(_T("Enter file length in bytes (0 to quit): "));
+        _tscanf_s(_T("%I64d"), &FileLen.QuadPart);
+        
+        if (FileLen.QuadPart == 0)
+            break;
+        
+        _tprintf(_T("\nRequested file size: %,20I64d bytes\n"), FileLen.QuadPart);
+        FileLenH.QuadPart = FileLen.QuadPart / 2;
+
+        ReportSpace(_T("Before file creation"));
+
+        hFile = CreateFile(_T("TempTestFile"), GENERIC_READ | GENERIC_WRITE, 0, NULL,
+                           CREATE_NEW, FILE_ATTRIBUTE_NORMAL, NULL);
+        if (hFile == INVALID_HANDLE_VALUE)
+            ReportError(_T("Cannot create TempTestFile"), 2, TRUE);
+        ReportSpace(_T("After file creation"));
+
+        if (!SetFilePointerEx(hFile, FileLen, NULL, FILE_BEGIN))
+            ReportError(_T("Cannot set file pointer"), 3, TRUE);
+
+        if (!SetEndOfFile(hFile))
+            ReportError(_T("Cannot set end of file"), 4, TRUE);
+        ReportSpace(_T("After setting file length"));
+
+        ov.Offset = FileLenH.LowPart;
+        ov.OffsetHigh = FileLenH.HighPart;
+
+        if (!WriteFile(hFile, Buffer, sizeof(Buffer), &nWrite, &ov))
+            ReportError(_T("Cannot write to middle of file"), 5, TRUE);
+        ReportSpace(_T("After writing to middle"));
+
+        CloseHandle(hFile);
+        DeleteFile(_T("TempTestFile"));
+        _tprintf(_T("\n----------------------------------------\n"));
+    }
+    
+    _tprintf(_T("\nEnd of FreeSpace demonstration\n"));
+    return 0;
+}
+
+void ReportError(LPCTSTR msg, DWORD exitCode, BOOL exitProgram) {
+    LPVOID lpMsgBuf;
+    DWORD dw = GetLastError();
+
+    FormatMessage(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+        NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+        (LPTSTR)&lpMsgBuf, 0, NULL);
+
+    _tprintf(_T("\nERROR [%d]: %s\n"), dw, (LPCTSTR)lpMsgBuf);
+    LocalFree(lpMsgBuf);
+
+    if (exitProgram) {
+        ExitProcess(exitCode);
+    }
+}
+
+void ReportSpace(LPCTSTR Message) {
+    ULARGE_INTEGER FreeBytes, TotalBytes, NumFreeBytes;
+    const double GB = 1024.0 * 1024.0 * 1024.0;
+
+    if (!GetDiskFreeSpaceEx(NULL, &FreeBytes, &TotalBytes, &NumFreeBytes))
+        ReportError(_T("Cannot get free space"), 1, TRUE);
+
+    _tprintf(_T("\n%25s status:\n"), Message);
+    _tprintf(_T("  Total disk space:   %12.2f GB\n"), (double)TotalBytes.QuadPart / GB);
+    _tprintf(_T("  Actual free space:  %12.2f GB\n"), (double)NumFreeBytes.QuadPart / GB);
+    _tprintf(_T("  Available to user:  %12.2f GB\n"), (double)FreeBytes.QuadPart / GB);
+}
+```
+
+### Exercise
+
+Let us implement this for small disks and observe, in C++23 or C++20. 
+