7121: Replace Get(loc,true) with CompareAndTouch(). Add Compare method to Volume...

[arvados.git] / services / keepstore / volume.go

diff --git a/services/keepstore/volume.go b/services/keepstore/volume.go
index 64fea34bfe1c32ad9b6b6b33a74c82f8b9f0252f..d3616d0812d4081bf3cdd49be3082759661c4ec4 100644 (file)
--- a/services/keepstore/volume.go
+++ b/services/keepstore/volume.go
@@ -15,7 +15,12 @@ type Volume interface {
        // put the returned slice back into the buffer pool when it's
        // finished with it.
        Get(loc string) ([]byte, error)
-       Put(loc string, block []byte) error
+       // Confirm Get() would return buf. If so, return nil. If not,
+       // return CollisionError or DiskHashError (depending on
+       // whether the data on disk matches the expected hash), or
+       // whatever error was encountered opening/reading the file.
+       Compare(loc string, data []byte) error
+       Put(loc string, data []byte) error
        Touch(loc string) error
        Mtime(loc string) (time.Time, error)
        IndexTo(prefix string, writer io.Writer) error