filestore: be more specific when there is a problem reading the backing file.

License: MIT
Signed-off-by: Kevin Atkinson <k@kevina.org>

filestore/fsrefstore.go

@@ -27,8 +27,18 @@ type FileManager struct {
 	root string
 }
 
+type CorruptReferenceCode int
+
+const (
+	OtherErr    CorruptReferenceCode = 0
+	FileError   CorruptReferenceCode = 1
+	FileMissing CorruptReferenceCode = 2
+	FileChanged CorruptReferenceCode = 3
+)
+
 type CorruptReferenceError struct {
-	Err error
+	Code CorruptReferenceCode
+	Err  error
 }
 
 func (c CorruptReferenceError) Error() string {
@@ -127,20 +137,24 @@ func (f *FileManager) readDataObj(c *cid.Cid, d *pb.DataObj) ([]byte, error) {
 	abspath := filepath.Join(f.root, p)
 
 	fi, err := os.Open(abspath)
-	if err != nil {
-		return nil, &CorruptReferenceError{err}
+	if os.IsNotExist(err) {
+		return nil, &CorruptReferenceError{FileMissing, err}
+	} else if err != nil {
+		return nil, &CorruptReferenceError{FileError, err}
 	}
 	defer fi.Close()
 
 	_, err = fi.Seek(int64(d.GetOffset()), os.SEEK_SET)
 	if err != nil {
-		return nil, &CorruptReferenceError{err}
+		return nil, &CorruptReferenceError{FileError, err}
 	}
 
 	outbuf := make([]byte, d.GetSize_())
 	_, err = io.ReadFull(fi, outbuf)
-	if err != nil {
-		return nil, &CorruptReferenceError{err}
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
+		return nil, &CorruptReferenceError{FileChanged, err}
+	} else if err != nil {
+		return nil, &CorruptReferenceError{FileError, err}
 	}
 
 	outcid, err := c.Prefix().Sum(outbuf)
@@ -149,7 +163,8 @@ func (f *FileManager) readDataObj(c *cid.Cid, d *pb.DataObj) ([]byte, error) {
 	}
 
 	if !c.Equals(outcid) {
-		return nil, &CorruptReferenceError{fmt.Errorf("data in file did not match. %s offset %d", d.GetFilePath(), d.GetOffset())}
+		return nil, &CorruptReferenceError{FileChanged,
+			fmt.Errorf("data in file did not match. %s offset %d", d.GetFilePath(), d.GetOffset())}
 	}
 
 	return outbuf, nil

filestore/util.go

@@ -16,12 +16,12 @@ import (
 type Status int32
 
 const (
-	StatusOk        Status = 0
-	StatusFileError Status = 10 // Backing File Error
-	//StatusFileNotFound Status = 11 // Backing File Not Found
-	//StatusFileChanged  Status = 12 // Contents of the file changed
-	StatusOtherError  Status = 20 // Internal Error, likely corrupt entry
-	StatusKeyNotFound Status = 30
+	StatusOk           Status = 0
+	StatusFileError    Status = 10 // Backing File Error
+	StatusFileNotFound Status = 11 // Backing File Not Found
+	StatusFileChanged  Status = 12 // Contents of the file changed
+	StatusOtherError   Status = 20 // Internal Error, likely corrupt entry
+	StatusKeyNotFound  Status = 30
 )
 
 func (s Status) String() string {
@@ -30,6 +30,10 @@ func (s Status) String() string {
 		return "ok"
 	case StatusFileError:
 		return "error"
+	case StatusFileNotFound:
+		return "no-file"
+	case StatusFileChanged:
+		return "changed"
 	case StatusOtherError:
 		return "ERROR"
 	case StatusKeyNotFound:
@@ -139,8 +143,17 @@ func mkListRes(c *cid.Cid, d *pb.DataObj, err error) *ListRes {
 	if err != nil {
 		if err == ds.ErrNotFound || err == blockstore.ErrNotFound {
 			status = StatusKeyNotFound
-		} else if _, ok := err.(*CorruptReferenceError); ok {
-			status = StatusFileError
+		} else if err, ok := err.(*CorruptReferenceError); ok {
+			switch err.Code {
+			case FileError:
+				status = StatusFileError
+			case FileMissing:
+				status = StatusFileNotFound
+			case FileChanged:
+				status = StatusFileChanged
+			default:
+				status = StatusOtherError
+			}
 		} else {
 			status = StatusOtherError
 		}