--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libcoding/grokdcs.c	Thu Jun 13 02:29:29 2024 +0000
@@ -0,0 +1,46 @@
+/*
+ * This library module implements the function that distills the complex
+ * set of possible SMS DCS octet values to just one of 4 possibilities:
+ * 7-bit text (7), 8-bit data octets (8), UCS-2 text (16) or compressed
+ * data (9).
+ *
+ * The decoding is based on the 3GPP TS 23.038 V11.0.0 spec;
+ * reserved encodings are treated as 7-bit text as the spec instructs.
+ */
+
+sms_dcs_classify(dcs)
+{
+	if (!(dcs & 0x80)) {
+		if (dcs & 0x20)
+			return(9);
+		switch (dcs & 0xC) {
+		case 0:
+			return(7);
+		case 4:
+			return(8);
+		case 8:
+			return(16);
+		default:
+			/* reserved, treating as 7-bit per the spec */
+			return(7);
+		}
+	}
+	switch (dcs & 0xF0) {
+	case 0x80:
+	case 0x90:
+	case 0xA0:
+	case 0xB0:
+		/* reserved, treating as 7-bit per the spec */
+		return(7);
+	case 0xC0:
+	case 0xD0:
+		return(7);
+	case 0xE0:
+		return(16);
+	case 0xF0:
+		if (dcs & 4)
+			return(8);
+		else
+			return(7);
+	}
+}