// Create a view on the given GCS object generation. If rl is non-nil, it must
// contain a lease for the contents of the object and will be used when
// possible instead of re-reading the object.
//
// If the object is larger than the given chunk size, we will only read
// and cache portions of it at a time.
func NewReadProxy(
o *gcs.Object,
rl lease.ReadLease,
chunkSize uint64,
leaser lease.FileLeaser,
bucket gcs.Bucket) (rp lease.ReadProxy) {
// Sanity check: the read lease's size should match the object's size if it
// is present.
if rl != nil && uint64(rl.Size()) != o.Size {
panic(fmt.Sprintf(
"Read lease size %d doesn't match object size %d",
rl.Size(),
o.Size))
}
// Special case: don't bring in the complication of a multi-read proxy if we
// have only one refresher.
refreshers := makeRefreshers(chunkSize, o, bucket)
if len(refreshers) == 1 {
rp = lease.NewReadProxy(leaser, refreshers[0], rl)
} else {
rp = lease.NewMultiReadProxy(leaser, refreshers, rl)
}
return
}
// Upgrade the supplied lease or panic.
func upgrade(rl lease.ReadLease) (rwl lease.ReadWriteLease) {
var err error
defer panicIf(&err)
// Attempt to upgrade.
rwl, err = rl.Upgrade()
return
}