Data commit

Task/Truncate-a-file/C/truncate-a-file-1.c

@@ -0,0 +1,81 @@
+#include <windows.h>
+#include <stdio.h>
+#include <wchar.h>
+
+/* Print "message: last Win32 error" to stderr. */
+void
+oops(const wchar_t *message)
+{
+	wchar_t *buf;
+	DWORD error;
+
+	buf = NULL;
+	error = GetLastError();
+	FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+	    FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+	    NULL, error, 0, (wchar_t *)&buf, 0, NULL);
+
+	if (buf) {
+		fwprintf(stderr, L"%ls: %ls", message, buf);
+		LocalFree(buf);
+	} else {
+		/* FormatMessageW failed. */
+		fwprintf(stderr, L"%ls: unknown error 0x%x\n",
+		    message, error);
+	}
+}
+
+int
+dotruncate(wchar_t *fn, LARGE_INTEGER fp)
+{
+	HANDLE fh;
+
+	fh = CreateFileW(fn, GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
+	if (fh == INVALID_HANDLE_VALUE) {
+		oops(fn);
+		return 1;
+	}
+
+	if (SetFilePointerEx(fh, fp, NULL, FILE_BEGIN) == 0 ||
+	    SetEndOfFile(fh) == 0) {
+		oops(fn);
+		CloseHandle(fh);
+		return 1;
+	}
+
+	CloseHandle(fh);
+	return 0;
+}
+
+/*
+ * Truncate or extend a file to the given length.
+ */
+int
+main()
+{
+	LARGE_INTEGER fp;
+	int argc;
+	wchar_t **argv, *fn, junk[2];
+
+	/* MinGW never provides wmain(argc, argv). */
+	argv = CommandLineToArgvW(GetCommandLineW(), &argc);
+	if (argv == NULL) {
+		oops(L"CommandLineToArgvW");
+		return 1;
+	}
+
+	if (argc != 3) {
+		fwprintf(stderr, L"usage: %ls filename length\n", argv[0]);
+		return 1;
+	}
+
+	fn = argv[1];
+
+	/* fp = argv[2] converted to a LARGE_INTEGER. */
+	if (swscanf(argv[2], L"%lld%1ls", &fp.QuadPart, &junk) != 1) {
+		fwprintf(stderr, L"%ls: not a number\n", argv[2]);
+		return 1;
+	}
+
+	return dotruncate(fn, fp);
+}

Task/Truncate-a-file/C/truncate-a-file-2.c

@@ -0,0 +1,7 @@
+#include <unistd.h>
+#include <sys/types.h>
+
+...
+truncate(filename, length);
+ftruncate(fd, length);
+...