--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libcoding/ucs2_decode.c	Thu Jun 13 02:29:29 2024 +0000
@@ -0,0 +1,62 @@
+/*
+ * This library module implements the conversion of UCS2-encoded data
+ * (typically received in SMS) into ASCII, ISO 8859-1 or UTF-8,
+ * maintaining parallelism with the corresponding function for decoding
+ * GSM7-encoded data.
+ */
+
+#include <sys/types.h>
+#include <stdio.h>
+
+ucs2_to_ascii_or_ext(inbuf, inlen, outbuf, outlenp, ascii_ext, newline_ok)
+	u_char *inbuf, *outbuf;
+	unsigned inlen, *outlenp;
+{
+	u_char *inp, *endp, *outp;
+	unsigned uni;
+
+	inp = inbuf;
+	endp = inbuf + (inlen & ~1);
+	outp = outbuf;
+	while (inp < endp) {
+		if ((endp - inp) >= 4 && (inp[0] & 0xFC) == 0xD8 &&
+		    (inp[2] & 0xFC) == 0xDC) {
+			uni = ((inp[0] & 3) << 18) | (inp[1] << 10) |
+			      ((inp[2] & 3) << 8) | inp[3];
+			inp += 4;
+			uni += 0x10000;
+			if (ascii_ext == 2)
+				outp += emit_utf8_char(uni, outp);
+			else {
+				sprintf(outp, "\\U%06X", uni);
+				outp += 8;
+			}
+			continue;
+		}
+		uni = (inp[0] << 8) | inp[1];
+		inp += 2;
+		if (uni == '\\') {
+			*outp++ = '\\';
+			*outp++ = '\\';
+		} else if (uni == '\r') {
+			*outp++ = '\\';
+			*outp++ = 'r';
+		} else if (uni == '\n') {
+			if (newline_ok)
+				*outp++ = '\n';
+			else {
+				*outp++ = '\\';
+				*outp++ = 'n';
+			}
+		} else if (!is_decoded_char_ok(uni, ascii_ext)) {
+			sprintf(outp, "\\u%04X", uni);
+			outp += 6;
+		} else if (ascii_ext == 2)
+			outp += emit_utf8_char(uni, outp);
+		else
+			*outp++ = uni;
+	}
+	*outp = '\0';
+	if (outlenp)
+		*outlenp = outp - outbuf;
+}