msvcrt: Add support for fflush to clear an input buffer.

dlls/msvcrt/file.c

@@ -792,6 +792,13 @@ int CDECL MSVCRT_fflush(MSVCRT_FILE* file)
         MSVCRT__unlock_file(file);
 
         return res;
+    } else if(file->_flag & MSVCRT__IOREAD) {
+        MSVCRT__lock_file(file);
+        file->_cnt = 0;
+        file->_ptr = file->_base;
+        MSVCRT__unlock_file(file);
+
+        return 0;
     }
     return 0;
 }

dlls/msvcrt/tests/file.c

@@ -619,7 +619,7 @@ static void test_fflush( void )
   ok(ret == 0, "expected 0, got %d\n", ret);
   memset(buf2, '?', sizeof(buf2));
   fread(buf2, 1, sizeof(buf2), tempfh);
-  todo_wine ok(memcmp(buf1, buf2, sizeof(buf1)) == 0, "Got unexpected data (%c)\n", buf2[0]);
+  ok(memcmp(buf1, buf2, sizeof(buf1)) == 0, "Got unexpected data (%c)\n", buf2[0]);
 
   /* fflush(NULL) doesn't clear input buffer. */
   _lseek(_fileno(tempfh), 0, SEEK_SET);