rrdbinary: Decode CDEF RPN tokens crammed in to Unival parameters

1 files changed, 29 insertions, 0 deletions

diff --git a/rrdformat/rrdbinary/cdef.go b/rrdformat/rrdbinary/cdef.go
new file mode 100644
index 0000000..5fbea4c
--- /dev/null
+++ b/rrdformat/rrdbinary/cdef.go
@@ -0,0 +1,29 @@
+package rrdbinary
+
+// RPNToken is one of the things that can be stored in a Unival; used
+// by DST_CDEF.
+type RPNToken struct {
+	Op  uint8 // rpn operator type
+	Val int32 // used by OP_NUMBER (0), OP_VARIABLE (1), and OP_PREV_OTHER (36)
+}
+
+// AsRPNTokens returns 1 or 2 RPNTokens (depending on the
+// Architecture.ShortSize).
+func (u Unival) AsRPNTokens() []RPNToken {
+	var ret []RPNToken
+	data := u.data
+	for len(data) > 0 {
+		rpnpData := data[:u.arch.ShortAlign+u.arch.ShortWidth]
+		var rpnp RPNToken
+		rpnp.Op = rpnpData[0]
+		switch u.arch.ShortWidth {
+		case 2:
+			rpnp.Val = int32(int16(u.arch.ByteOrder.Uint16(rpnpData[u.arch.ShortAlign:])))
+		case 4:
+			rpnp.Val = int32(u.arch.ByteOrder.Uint32(rpnpData[u.arch.ShortAlign:]))
+		}
+		ret = append(ret, rpnp)
+		data = data[len(rpnpData):]
+	}
+	return ret
+}