Import gsm48_construct_ra() from openbsc

2 files changed, 26 insertions, 0 deletions

diff --git a/include/osmocore/gsm48.h b/include/osmocore/gsm48.h
index a509a096..be9fbbd1 100644
--- a/include/osmocore/gsm48.h
+++ b/include/osmocore/gsm48.h
@@ -29,5 +29,6 @@ int gsm48_mi_to_string(char *string, const int str_len,
 
 /* Parse Routeing Area Identifier */
 void gsm48_parse_ra(struct gprs_ra_id *raid, const uint8_t *buf);
+int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid);
 
 #endif
diff --git a/src/gsm48.c b/src/gsm48.c
index 7e510664..d957aef6 100644
--- a/src/gsm48.c
+++ b/src/gsm48.c
@@ -326,3 +326,28 @@ void gsm48_parse_ra(struct gprs_ra_id *raid, const uint8_t *buf)
 	raid->lac = ntohs(*(uint16_t *)(buf + 3));
 	raid->rac = buf[5];
 }
+
+int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid)
+{
+	uint16_t mcc = raid->mcc;
+	uint16_t mnc = raid->mnc;
+
+	buf[0] = ((mcc / 100) % 10) | (((mcc / 10) % 10) << 4);
+	buf[1] = (mcc % 10);
+
+	/* I wonder who came up with the stupidity of encoding the MNC
+	 * differently depending on how many digits its decimal number has! */
+	if (mnc < 100) {
+		buf[1] |= 0xf0;
+		buf[2] = ((mnc / 10) % 10) | ((mnc % 10) << 4);
+	} else {
+		buf[1] |= (mnc % 10) << 4;
+		buf[2] = ((mnc / 100) % 10) | (((mcc / 10) % 10) << 4);
+	}
+
+	*(uint16_t *)(buf+3) = htons(raid->lac);
+
+	buf[5] = raid->rac;
+
+	return 6;
+}