Add disk package

Implements

   - Stat returns total and free disk space supported across platforms
   - Type returns type of the filesystem underneath

pkg/disk/stat_windows.go

@@ -0,0 +1,69 @@
+// +build windows
+
+/*
+ * Minio Cloud Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package disk
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// Stat returns total and free bytes available in a directory, e.g. `C:\`.
+// It returns free space available to the user (including quota limitations)
+//
+// https://msdn.microsoft.com/en-us/library/windows/desktop/aa364937(v=vs.85).aspx
+func Stat(path string) (total, free int64, err error) {
+	kernel32, err := syscall.LoadLibrary("Kernel32.dll")
+	if err != nil {
+		return 0, 0, err
+	}
+	defer syscall.FreeLibrary(kernel32)
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa364937(v=vs.85).aspx
+	// Retrieves information about the amount of space that is available on a disk volume,
+	// which is the total amount of space, the total amount of free space, and the total
+	// amount of free space available to the user that is associated with the calling thread.
+	GetDiskFreeSpaceEx, err := syscall.GetProcAddress(syscall.Handle(kernel32), "GetDiskFreeSpaceExW")
+	if err != nil {
+		return 0, 0, err
+	}
+	lpFreeBytesAvailable := int64(0)
+	lpTotalNumberOfBytes := int64(0)
+	lpTotalNumberOfFreeBytes := int64(0)
+
+	// Extract values safely
+	// BOOL WINAPI GetDiskFreeSpaceEx(
+	// _In_opt_  LPCTSTR         lpDirectoryName,
+	// _Out_opt_ PULARGE_INTEGER lpFreeBytesAvailable,
+	// _Out_opt_ PULARGE_INTEGER lpTotalNumberOfBytes,
+	// _Out_opt_ PULARGE_INTEGER lpTotalNumberOfFreeBytes
+	// );
+	r1, _, e1 := syscall.Syscall6(uintptr(GetDiskFreeSpaceEx), 4,
+		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(path))),
+		uintptr(unsafe.Pointer(&lpFreeBytesAvailable)),
+		uintptr(unsafe.Pointer(&lpTotalNumberOfBytes)),
+		uintptr(unsafe.Pointer(&lpTotalNumberOfFreeBytes)), 0, 0)
+	if e1 != 0 {
+		return 0, 0, error(e1)
+	}
+	if r1 == 0 {
+		return 0, 0, syscall.EINVAL
+	}
+	total = int64(lpTotalNumberOfBytes)
+	free = int64(lpFreeBytesAvailable)
+	return total, free, nil
+}