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.

That's updated version of commit with the same topic reverted earlier.

Change-Id: Ie180733d2584ebb16fb80b84526d0dbc70e3d441
Related: OS#3014

1 files changed, 112 insertions, 33 deletions

diff --git a/src/encoding.cpp b/src/encoding.cpp
index 2648b027..e7e13ac1 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -35,7 +35,72 @@ extern "C" {
 #include <errno.h>
 #include <string.h>
 
+#define CHECK(rc) { if (rc < 0) return rc; }
+#define SET_X(bv, x) { if (bitvec_set_bit(bv, x) < 0) return -EOWNERDEAD; }
+#define SET_0(bv) SET_X(bv, ZERO)
+#define SET_1(bv) SET_X(bv, ONE)
+#define SET_L(bv) SET_X(bv, L)
+#define SET_H(bv) SET_X(bv, H)
+
+/* 3GPP TS 44.018 § 10.5.2.16:
+   { 0 | 1 < ALPHA : bit (4) > }
+   < GAMMA : bit (5) >
+*/
+static int write_alpha_gamma(bitvec *dest, uint8_t alpha, uint8_t gamma)
+{
+	int rc;
+
+	if (alpha) {
+		SET_1(dest);
+		rc = bitvec_set_u64(dest, alpha, 4, false);
+		CHECK(rc);
+	} else
+		SET_0(dest);
+
+	rc = bitvec_set_u64(dest, gamma, 5, false);
+	CHECK(rc);
+
+	return 0;
+}
+
+/* TBF_STARTING_TIME -- same as 3GPP TS 44.018 §10.5.2.38 Starting Time without tag: */
+static int write_tbf_start_time(bitvec *dest, uint32_t fn)
+{
+	int rc;
+
+	/* Set values according to 3GPP TS 44.018 Table 10.5.2.38.1 */
+
+	/* T1' */
+	rc = bitvec_set_u64(dest, (fn / (26 * 51)) % 32, 5, false);
+	CHECK(rc);
+
+	/* T3  */
+	rc = bitvec_set_u64(dest, fn % 51, 6, false);
+	CHECK(rc);
+
+	/* T2  */
+	rc = bitvec_set_u64(dest, fn % 26, 5, false);
+	CHECK(rc);
+
+	return rc;
+}
+
 /* { 0 | 1 < TIMING_ADVANCE_INDEX : bit (4) > } */
+static 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: */
@@ -88,43 +153,55 @@ static inline void write_ta_ie(bitvec *dest, unsigned& wp,
 }
 
 static 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, unsigned& wp)
+				  uint32_t fn, uint8_t alpha, uint8_t gamma, int8_t ta_idx)
 {
 	int rc = 0;
 
-	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);
+	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);
+	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);
+		CHECK(rc);
+       } else
+		SET_0(dest);
+
+	SET_0(dest); /* No P0 nor PR_MODE */
+
 	if (tbf->is_egprs_enabled()) {
-		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 rc;
 }
@@ -393,8 +470,10 @@ int Encoding::write_immediate_assignment(
 			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, wp);
+					    ta_idx);
 	} else if (((burst_type == GSM_L1_BURST_TYPE_ACCESS_1) || (burst_type == GSM_L1_BURST_TYPE_ACCESS_2))) {
 		bitvec_write_field(dest, &wp, 1, 2);    /* LH */
 		bitvec_write_field(dest, &wp, 0, 2);    /* 0 EGPRS Uplink Assignment */