Rewrite Packet Downlink Assignment

Use bitvec_set_*() directly without external write pointer tracking to
simplify the code. This is part of IA Rest Octets (3GPP TS 44.018
§10.5.2.16) which is the last part of the message so it should not
interfere with the rest of encoding functions.

The tests are adjusted accordingly.

Change-Id: I52ec9b07413daabba8cd5f1fba5c7b3af6a33389
Related: OS#1526

1 files changed, 73 insertions, 48 deletions

diff --git a/src/encoding.cpp b/src/encoding.cpp
index 7b711b81..279bbfe8 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -44,6 +44,21 @@ extern "C" {
 #define set_H(bv) set_x(bv, H)
 
 /* { 0 | 1 < TIMING_ADVANCE_INDEX : bit (4) > } */
+static inline int write_ta_index(bitvec *dest, int8_t tai)
+{
+	int rc;
+
+	if (tai < 0) /* No TIMING_ADVANCE_INDEX: */
+		set_0(dest);
+
+	/* TIMING_ADVANCE_INDEX: */
+	set_1(dest);
+	rc = bitvec_set_u64(dest, tai, 4, false);
+	check(rc);
+
+	return 0;
+}
+
 static inline bool write_tai(bitvec *dest, unsigned& wp, int8_t tai)
 {
 	if (tai < 0) { /* No TIMING_ADVANCE_INDEX: */
@@ -159,52 +174,58 @@ static inline int write_tfi_usf(bitvec *dest, const gprs_rlcmac_ul_tbf *tbf, uin
 	return 0;
 }
 
-static int write_ia_rest_downlink(
-	gprs_rlcmac_dl_tbf *tbf,
-	bitvec * dest, unsigned& wp,
-	uint8_t polling, bool ta_valid, uint32_t fn,
-	uint8_t alpha, uint8_t gamma, int8_t ta_idx)
+/* 3GPP TS 44.018 §10.5.2.16 IA Rest Octets ::= Packet Downlink Assignment */
+static inline int write_ia_rest_downlink(const gprs_rlcmac_dl_tbf *tbf, bitvec *dest,
+					 bool polling, bool ta_valid, uint32_t fn,
+					 uint8_t alpha, uint8_t gamma, int8_t ta_idx)
 {
-	if (!tbf) {
-		LOGP(DRLCMACDL, LOGL_ERROR,
-			"Cannot encode DL IMMEDIATE ASSIGNMENT without TBF\n");
-		return -EINVAL;
-	}
-	// GSM 04.08 10.5.2.16 IA Rest Octets
-	bitvec_write_field(dest, &wp, 3, 2);   // "HH"
-	bitvec_write_field(dest, &wp, 1, 2);   // "01" Packet Downlink Assignment
-	bitvec_write_field(dest, &wp,tbf->tlli(),32); // TLLI
-	bitvec_write_field(dest, &wp,0x1,1);   // switch TFI   : on
-	bitvec_write_field(dest, &wp,tbf->tfi(),5);   // TFI
-	bitvec_write_field(dest, &wp,0x0,1);   // RLC acknowledged mode
-	if (alpha) {
-		bitvec_write_field(dest, &wp,0x1,1);   // ALPHA = present
-		bitvec_write_field(dest, &wp,alpha,4);   // ALPHA
-	} else {
-		bitvec_write_field(dest, &wp,0x0,1);   // ALPHA = not present
-	}
-	bitvec_write_field(dest, &wp,gamma,5);   // GAMMA power control parameter
-	bitvec_write_field(dest, &wp,polling,1);   // Polling Bit
-	bitvec_write_field(dest, &wp, ta_valid, 1); // N. B: NOT related to TAI!
-	write_tai(dest, wp, ta_idx);
+	int rc;
+
+	set_H(dest); set_H(dest);
+	set_0(dest); set_1(dest); /* 00 Packet Downlink Assignment */
+
+	rc = bitvec_set_u64(dest, tbf->tlli(), 32, false); /* TLLI */
+	check(rc);
+
+	set_1(dest);
+	rc = bitvec_set_u64(dest, tbf->tfi(), 5, false);   /* TFI_ASSIGNMENT */
+	check(rc);
+
+	/* RLC acknowledged mode */
+	set_0(dest); /* RLC_MODE */
+
+	rc = write_alpha_gamma(dest, alpha, gamma);        /* ALPHA and GAMMA */
+	check(rc);
+
+	rc = bitvec_set_bit(dest, (bit_value)polling); /* POLLING */
+	check(rc);
+
+	/* N. B: NOT related to TAI! */
+	rc = bitvec_set_bit(dest, (bit_value)ta_valid); /* TA_VALID */
+	check(rc);
+
+	rc = write_ta_index(dest, ta_idx);
+	check(rc);
+
 	if (polling) {
-		bitvec_write_field(dest, &wp,0x1,1);   // TBF Starting TIME present
-		bitvec_write_field(dest, &wp,(fn / (26 * 51)) % 32,5); // T1'
-		bitvec_write_field(dest, &wp,fn % 51,6);               // T3
-		bitvec_write_field(dest, &wp,fn % 26,5);               // T2
-	} else {
-		bitvec_write_field(dest, &wp,0x0,1);   // TBF Starting TIME present
-	}
-	bitvec_write_field(dest, &wp,0x0,1);   // P0 not present
-	//		bitvec_write_field(dest, &wp,0x1,1);   // P0 not present
-	//		bitvec_write_field(dest, &wp,,0xb,4);
+		set_1(dest);
+		rc = write_tbf_start_time(dest, fn);	/* TBF_STARTING_TIME */
+		check(rc);
+	} else
+		set_0(dest);	                     /* No TBF_STARTING_TIME */
+
+	set_0(dest); /* No P0 nor PR_MODE */
+
 	if (tbf->is_egprs_enabled()) {
-		/* see GMS 44.018, 10.5.2.16 */
-		bitvec_write_field(dest, &wp, 1, 1);  // "H"
-		write_ws(dest, &wp, tbf->window_size()); // EGPRS Window Size
-		bitvec_write_field(dest, &wp, 0x0, 2);    // LINK_QUALITY_MEASUREMENT_MODE
-		bitvec_write_field(dest, &wp, 0, 1);      // BEP_PERIOD2 not present
-	}
+		set_H(dest);
+		rc = bitvec_set_u64(dest, enc_ws(tbf->window_size()), 5, false); /* EGPRS Window Size */
+		check(rc);
+
+		/* The mobile station shall not report measurements: (see 3GPP TS 44.060 Table 11.2.7.1) */
+		set_0(dest); set_0(dest); /* LINK_QUALITY_MEASUREMENT_MODE */
+		set_1(dest);              /* No BEP_PERIOD2 */
+	} else
+		set_L(dest);              /* No Additions for Rel-6 */
 
 	return 0;
 }
@@ -460,11 +481,15 @@ int Encoding::write_immediate_assignment(
 
 	plen = wp / 8;
 
-	if (downlink)
-		rc = write_ia_rest_downlink(as_dl_tbf(tbf), dest, wp,
-					    polling, gsm48_ta_is_valid(ta), fn,
-			alpha, gamma, ta_idx);
-	else if (((burst_type == GSM_L1_BURST_TYPE_ACCESS_1) ||
+	if (downlink) {
+		if (!as_dl_tbf(tbf)) {
+			LOGP(DRLCMACDL, LOGL_ERROR, "Cannot encode DL IMMEDIATE ASSIGNMENT without TBF\n");
+			return -EINVAL;
+		}
+		dest->cur_bit = wp;
+		rc = write_ia_rest_downlink(as_dl_tbf(tbf), dest, polling, gsm48_ta_is_valid(ta), fn,
+					    alpha, gamma, ta_idx);
+	} else if (((burst_type == GSM_L1_BURST_TYPE_ACCESS_1) ||
 		  (burst_type == GSM_L1_BURST_TYPE_ACCESS_2))) {
 		dest->cur_bit = wp;
 		rc = write_ia_rest_egprs_uplink(as_ul_tbf(tbf), dest, usf, fn, alpha, gamma, ta_idx, burst_type, ra);