swarm/api: support mounting manifests via FUSE (#3690)

vendor/bazil.org/fuse/fuseutil/fuseutil.go

@@ -0,0 +1,20 @@
+package fuseutil // import "bazil.org/fuse/fuseutil"
+
+import (
+	"bazil.org/fuse"
+)
+
+// HandleRead handles a read request assuming that data is the entire file content.
+// It adjusts the amount returned in resp according to req.Offset and req.Size.
+func HandleRead(req *fuse.ReadRequest, resp *fuse.ReadResponse, data []byte) {
+	if req.Offset >= int64(len(data)) {
+		data = nil
+	} else {
+		data = data[req.Offset:]
+	}
+	if len(data) > req.Size {
+		data = data[:req.Size]
+	}
+	n := copy(resp.Data[:req.Size], data)
+	resp.Data = resp.Data[:n]
+}