codec/h264/h264dec/helpers.go: added helpers.go file and binToSlice func for converting binary string to a []byte

codec/h264/h264dec/helpers.go

@@ -0,0 +1,41 @@
+/*
+DESCRIPTION
+  helpers.go provides general helper utilities.
+
+AUTHORS
+  Saxon Nelson-Milton <saxon@ausocean.org>, The Australian Ocean Laboratory (AusOcean)
+*/
+package h264dec
+
+import "errors"
+
+// binToSlice is a helper function to convert a string of binary into a
+// corresponding byte slice, e.g. "0100 0001 1000 1100" => {0x41,0x8c}.
+// Spaces in the string are ignored.
+func binToSlice(s string) ([]byte, error) {
+	var (
+		a     byte = 0x80
+		cur   byte
+		bytes []byte
+	)
+
+	for _, c := range s {
+		switch c {
+		case ' ':
+			continue
+		case '1':
+			cur |= a
+		case '0':
+		default:
+			return nil, errors.New("invalid binary string")
+		}
+
+		a >>= 1
+		if a == 0 {
+			bytes = append(bytes, cur)
+			cur = 0
+			a = 0x80
+		}
+	}
+	return bytes, nil
+}