tbf/rlc: Move the parsing of RBB to Decoding, move window marking out

Move the parsing of the bitbmap out of the TBF code into Decoding.
Move the updating of the V_B into the V_B class. Add some comments
about handling the mod_sns, mod_sns_half parameters by using template
code.

src/decoding.cpp

@@ -83,3 +83,17 @@ uint8_t Decoding::get_ms_class_by_capability(MS_Radio_Access_capability_t *cap)
 	return 0;
 }
 
+/**
+ * show_rbb needs to be an array with 65 elements
+ */
+void Decoding::extract_rbb(const uint8_t *rbb, char *show_rbb)
+{
+	for (int i = 63; i >= 0; i--) {
+		uint8_t bit;
+
+		bit = (rbb[i >> 3]  >>  (7 - (i&7)))   & 1;
+		show_rbb[i] = bit ? '1' : 'o';
+	}
+
+	show_rbb[64] = '\0';
+}

src/decoding.h

@@ -28,4 +28,6 @@ public:
 	static int tlli_from_ul_data(const uint8_t *data, uint8_t len,
 					uint32_t *tlli);
 	static uint8_t get_ms_class_by_capability(MS_Radio_Access_capability_t *cap);
+
+	static void extract_rbb(const uint8_t *rbb, char *extracted_rbb);
 };

src/rlc.cpp

@@ -17,6 +17,8 @@
  */
 
 #include "tbf.h"
+#include "bts.h"
+#include "gprs_debug.h"
 
 extern "C" {
 #include <osmocom/core/utils.h>
@@ -68,3 +70,30 @@ int gprs_rlc_v_b::mark_for_resend(const uint16_t v_a, const uint16_t v_s,
 
 	return resend;
 }
+
+void gprs_rlc_v_b::update(BTS *bts, char *show_rbb, uint8_t ssn,
+			const uint16_t v_a,
+			const uint16_t mod_sns, const uint16_t mod_sns_half,
+			uint16_t *lost, uint16_t *received)
+{
+	uint16_t bsn;
+	int i;
+
+	/* SSN - 1 is in range V(A)..V(S)-1 */
+	for (i = 63, bsn = (ssn - 1) & mod_sns;
+	     i >= 0 && bsn != ((v_a - 1) & mod_sns);
+	     i--, bsn = (bsn - 1) & mod_sns) {
+
+		if (show_rbb[i] == '1') {
+			LOGP(DRLCMACDL, LOGL_DEBUG, "- got ack for BSN=%d\n", bsn);
+			if (!is_acked(bsn & mod_sns_half))
+				*received += 1;
+			mark_acked(bsn & mod_sns_half);
+		} else {
+			LOGP(DRLCMACDL, LOGL_DEBUG, "- got NACK for BSN=%d\n", bsn);
+			mark_nacked(bsn & mod_sns_half);
+			bts->rlc_nacked();
+			*lost += 1;
+		}
+	}
+}

src/rlc.h

@@ -25,6 +25,7 @@
 #define RLC_MAX_WS  64 /* max window size */
 #define RLC_MAX_LEN 54 /* CS-4 including spare bits */
 
+class BTS;
 
 struct gprs_rlc_data {
 	uint8_t *prepare(size_t block_data_length);
@@ -43,11 +44,18 @@ struct gprs_rlc {
 	gprs_rlc_data blocks[RLC_MAX_SNS/2];
 };
 
+/**
+ * TODO: for GPRS/EDGE maybe make sns a template parameter
+ * so we create specialized versions...
+ */
 struct gprs_rlc_v_b {
 	int resend_needed(const uint16_t acked, const uint16_t sent,
 			const uint16_t mod_sns, const uint16_t mod_sns_half);
 	int mark_for_resend(const uint16_t acked, const uint16_t sent,
 			const uint16_t mod_sns, const uint16_t mod_sns_half);
+	void update(BTS *bts, char *show_rbb, uint8_t ssn, const uint16_t v_a,
+			const uint16_t mod_sns, const uint16_t mod_sns_half,
+			uint16_t *lost, uint16_t *received);
 
 	/* Check for an individual frame */
 	bool is_unacked(int index) const;

src/tbf.cpp

@@ -1363,12 +1363,11 @@ struct msgb *gprs_rlcmac_tbf::create_ul_ack(uint32_t fn)
 
 int gprs_rlcmac_tbf::snd_dl_ack(uint8_t final, uint8_t ssn, uint8_t *rbb)
 {
-	char show_rbb[65], show_v_b[RLC_MAX_SNS + 1];
+	char show_v_b[RLC_MAX_SNS + 1];
 	uint16_t mod_sns = m_sns - 1;
 	uint16_t mod_sns_half = (m_sns >> 1) - 1;
 	int i; /* must be signed */
 	int16_t dist; /* must be signed */
-	uint8_t bit;
 	uint16_t bsn;
 	struct msgb *msg;
 	uint16_t lost = 0, received = 0;
@@ -1376,12 +1375,9 @@ int gprs_rlcmac_tbf::snd_dl_ack(uint8_t final, uint8_t ssn, uint8_t *rbb)
 	LOGP(DRLCMACDL, LOGL_DEBUG, "%s downlink acknowledge\n", tbf_name(this));
 
 	if (!final) {
+		char show_rbb[65];
+		Decoding::extract_rbb(rbb, show_rbb);
 		/* show received array in debug (bit 64..1) */
-		for (i = 63; i >= 0; i--) {
-			bit = (rbb[i >> 3]  >>  (7 - (i&7)))   & 1;
-			show_rbb[i] = (bit) ? '1' : 'o';
-		}
-		show_rbb[64] = '\0';
 		LOGP(DRLCMACDL, LOGL_DEBUG, "- ack:  (BSN=%d)\"%s\""
 			"(BSN=%d)  1=ACK o=NACK\n", (ssn - 64) & mod_sns,
 			show_rbb, (ssn - 1) & mod_sns);
@@ -1400,25 +1396,11 @@ int gprs_rlcmac_tbf::snd_dl_ack(uint8_t final, uint8_t ssn, uint8_t *rbb)
 				"V(A)..V(S) range %s Free TBF!\n", tbf_name(this));
 			return 1; /* indicate to free TBF */
 		}
-		/* SSN - 1 is in range V(A)..V(S)-1 */
-		for (i = 63, bsn = (ssn - 1) & mod_sns;
-		     i >= 0 && bsn != ((dir.dl.v_a - 1) & mod_sns);
-		     i--, bsn = (bsn - 1) & mod_sns) {
-			bit = (rbb[i >> 3]  >>  (7 - (i&7)))   & 1;
-			if (bit) {
-				LOGP(DRLCMACDL, LOGL_DEBUG, "- got "
-					"ack for BSN=%d\n", bsn);
-				if (!dir.dl.v_b.is_acked(bsn & mod_sns_half))
-					received++;
-				dir.dl.v_b.mark_acked(bsn & mod_sns_half);
-			} else {
-				LOGP(DRLCMACDL, LOGL_DEBUG, "- got "
-					"NACK for BSN=%d\n", bsn);
-				dir.dl.v_b.mark_nacked(bsn & mod_sns_half);
-				bts->rlc_nacked();
-				lost++;
-			}
-		}
+
+		dir.dl.v_b.update(bts, show_rbb, ssn, dir.dl.v_a,
+				mod_sns, mod_sns_half,
+				&lost, &received);
+
 		/* report lost and received packets */
 		gprs_rlcmac_received_lost(this, received, lost);