From ef753e60d269623cd564ba1951e5f52dc1ba439d Mon Sep 17 00:00:00 2001
From: "Paul \"TBBle\" Hampson" <Paul.Hampson@Pobox.com>
Date: Sun, 13 Dec 2020 01:36:51 +1100
Subject: [PATCH] Implement winio.GetFileStandardInfo

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>
---
 fileinfo.go      |  19 +++++++
 fileinfo_test.go | 134 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 153 insertions(+)
 create mode 100644 fileinfo_test.go

diff --git a/fileinfo.go b/fileinfo.go
index 980dfbc..3ab6bff 100644
--- a/fileinfo.go
+++ b/fileinfo.go
@@ -36,6 +36,25 @@ func SetFileBasicInfo(f *os.File, bi *FileBasicInfo) error {
 	return nil
 }
 
+// FileStandardInfo contains extended information for the file.
+// FILE_STANDARD_INFO in WinBase.h
+// https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_standard_info
+type FileStandardInfo struct {
+	AllocationSize, EndOfFile int64
+	NumberOfLinks             uint32
+	DeletePending, Directory  bool
+}
+
+// GetFileStandardInfo retrieves ended information for the file.
+func GetFileStandardInfo(f *os.File) (*FileStandardInfo, error) {
+	si := &FileStandardInfo{}
+	if err := windows.GetFileInformationByHandleEx(windows.Handle(f.Fd()), windows.FileStandardInfo, (*byte)(unsafe.Pointer(si)), uint32(unsafe.Sizeof(*si))); err != nil {
+		return nil, &os.PathError{Op: "GetFileInformationByHandleEx", Path: f.Name(), Err: err}
+	}
+	runtime.KeepAlive(f)
+	return si, nil
+}
+
 // FileIDInfo contains the volume serial number and file ID for a file. This pair should be
 // unique on a system.
 type FileIDInfo struct {
diff --git a/fileinfo_test.go b/fileinfo_test.go
new file mode 100644
index 0000000..e79700b
--- /dev/null
+++ b/fileinfo_test.go
@@ -0,0 +1,134 @@
+package winio
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+// Checks if current matches expected. Note that AllocationSize is filesystem-specific,
+// so we check that the current.AllocationSize is >= expected.AllocationSize.
+// https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/5afa7f66-619c-48f3-955f-68c4ece704ae
+func checkFileStandardInfo(t *testing.T, current, expected *FileStandardInfo) {
+	if current.AllocationSize < expected.AllocationSize {
+		t.Fatalf("FileStandardInfo unexpectedly had AllocationSize %d, expecting >=%d", current.AllocationSize, expected.AllocationSize)
+	}
+
+	if current.EndOfFile != expected.EndOfFile {
+		t.Fatalf("FileStandardInfo unexpectedly had EndOfFile %d, expecting %d", current.EndOfFile, expected.EndOfFile)
+	}
+
+	if current.NumberOfLinks != expected.NumberOfLinks {
+		t.Fatalf("FileStandardInfo unexpectedly had NumberOfLinks %d, expecting %d", current.NumberOfLinks, expected.NumberOfLinks)
+	}
+
+	if current.DeletePending != expected.DeletePending {
+		if current.DeletePending {
+			t.Fatalf("FileStandardInfo unexpectedly DeletePending")
+		} else {
+			t.Fatalf("FileStandardInfo unexpectedly not DeletePending")
+		}
+	}
+
+	if current.Directory != expected.Directory {
+		if current.Directory {
+			t.Fatalf("FileStandardInfo unexpectedly Directory")
+		} else {
+			t.Fatalf("FileStandardInfo unexpectedly not Directory")
+		}
+	}
+}
+
+func TestGetFileStandardInfo_File(t *testing.T) {
+	f, err := ioutil.TempFile("", "tst")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	defer os.Remove(f.Name())
+
+	expectedFileInfo := &FileStandardInfo{
+		AllocationSize: 0,
+		EndOfFile:      0,
+		NumberOfLinks:  1,
+		DeletePending:  false,
+		Directory:      false,
+	}
+
+	info, err := GetFileStandardInfo(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkFileStandardInfo(t, info, expectedFileInfo)
+
+	bytesWritten, err := f.Write([]byte("0123456789"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedFileInfo.EndOfFile = int64(bytesWritten)
+	expectedFileInfo.AllocationSize = int64(bytesWritten)
+
+	info, err = GetFileStandardInfo(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkFileStandardInfo(t, info, expectedFileInfo)
+
+	linkName := f.Name() + ".link"
+
+	if err = os.Link(f.Name(), linkName); err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(linkName)
+
+	expectedFileInfo.NumberOfLinks = 2
+
+	info, err = GetFileStandardInfo(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkFileStandardInfo(t, info, expectedFileInfo)
+
+	os.Remove(linkName)
+
+	expectedFileInfo.NumberOfLinks = 1
+
+	info, err = GetFileStandardInfo(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkFileStandardInfo(t, info, expectedFileInfo)
+}
+
+func TestGetFileStandardInfo_Directory(t *testing.T) {
+	tempDir, err := ioutil.TempDir("", "tst")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// os.Open returns the Search Handle, not the Directory Handle
+	// See https://github.com/golang/go/issues/13738
+	f, err := OpenForBackup(tempDir, windows.GENERIC_READ, 0, windows.OPEN_EXISTING)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	expectedFileInfo := &FileStandardInfo{
+		AllocationSize: 0,
+		EndOfFile:      0,
+		NumberOfLinks:  1,
+		DeletePending:  false,
+		Directory:      true,
+	}
+
+	info, err := GetFileStandardInfo(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	checkFileStandardInfo(t, info, expectedFileInfo)
+}