Rewrite EGPRS Packet Uplink IA Rest Octets for SBA

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 partially based on reverted commit 529ce885450946d85d1920fb3d1a994c3efe5849.

Change-Id: I143b3dd02aa54b9ce206d9e780a5554f6d9fd118
Related: OS#3014

1 files changed, 58 insertions, 26 deletions

diff --git a/src/encoding.cpp b/src/encoding.cpp
index ba0e4744..4c8cdb06 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -85,6 +85,33 @@ static int write_tbf_start_time(bitvec *dest, uint32_t fn)
 	return rc;
 }
 
+/* 3GPP TS 44.018 §10.5.2.16:
+   < TFI_ASSIGNMENT : bit (5) >
+   < POLLING : bit >
+   0 -- The value '1' was allocated in an earlier version of the protocol and shall not be used.
+   < USF: bit (3) >
+   < USF_GRANULARITY : bit >
+   { 0 | 1 < P0 : bit (4) > < PR_MODE : bit (1) > }
+*/
+static int write_tfi_usf(bitvec *dest, const gprs_rlcmac_ul_tbf *tbf, uint8_t usf)
+{
+       int rc = bitvec_set_u64(dest, tbf->tfi(), 5, false); /* TFI_ASSIGNMENT */
+       CHECK(rc);
+
+       SET_0(dest); /* POLLING -- no action is required from MS */
+
+       SET_0(dest);
+
+       rc = bitvec_set_u64(dest, usf, 3, false); /* USF */
+       CHECK(rc);
+
+       SET_0(dest); /* USF_GRANULARITY -- the mobile station shall transmit one RLC/MAC block */
+
+       SET_0(dest); /* No P0 nor PR_MODE */
+
+       return 0;
+}
+
 /* { 0 | 1 < TIMING_ADVANCE_INDEX : bit (4) > } */
 static int write_ta_index(bitvec *dest, int8_t tai)
 {
@@ -278,38 +305,42 @@ static int write_ia_rest_egprs_uplink_mba(bitvec * dest, uint32_t fn, uint8_t al
 }
 
 static int write_ia_rest_egprs_uplink_sba(const gprs_rlcmac_ul_tbf *tbf, bitvec * dest, uint8_t usf,
-					  uint8_t alpha, uint8_t gamma, unsigned& wp)
+					  uint8_t alpha, uint8_t gamma)
 {
 	int rc = 0;
 
-	bitvec_write_field(dest, &wp, 1, 1);     /* single block allocation */
-	bitvec_write_field(dest, &wp, tbf->tfi(), 5); /* TFI assignment */
-	bitvec_write_field(dest, &wp, 0, 1);     /* polling bit */
-	bitvec_write_field(dest, &wp, 0, 1);     /* constant */
-	bitvec_write_field(dest, &wp, usf, 3);   /* USF bit */
-	bitvec_write_field(dest, &wp, 0, 1);     /* USF granularity */
-	bitvec_write_field(dest, &wp, 0, 1);     /* P0 */
+	SET_1(dest); /* Single Block Allocation */
 
-	/* MCS */
-	bitvec_write_field(dest, &wp, tbf->current_cs().to_num() - 1, 4);
+	rc = write_tfi_usf(dest, tbf, usf);
+	CHECK(rc);
 
-	/* TLLI channel block */
-	bitvec_write_field(dest, &wp, tbf->tlli(), 1);
-	bitvec_write_field(dest, &wp, 0, 1);   /* BEP period present */
-	bitvec_write_field(dest, &wp, 0, 1);   /* resegmentation */
-	write_ws(dest, &wp, tbf->window_size()); /* EGPRS window size */
+	/* 3GPP TS 44.060 §12.10d EGPRS Modulation and coding Scheme description: */
+	rc = bitvec_set_u64(dest, tbf->current_cs().to_num() - 1, 4, false); /* EGPRS CHANNEL_CODING_COMMAND */
+	CHECK(rc);
 
-	if (alpha) {
-		bitvec_write_field(dest, &wp, 0x1, 1);   /* ALPHA = yes */
-		bitvec_write_field(dest, &wp, alpha, 4); /* ALPHA */
-	} else {
-		bitvec_write_field(dest, &wp, 0x0, 1);   /* ALPHA = no */
-	}
+	/* TLLI_BLOCK_CHANNEL_CODING */
+	rc = bitvec_set_bit(dest, (bit_value)tbf->tlli());
+
+	/* No BEP_PERIOD2 */
+	SET_0(dest);
+
+	/* Retransmitted RLC data blocks shall not be re-segmented: (see 3GPP TS 44.060 §12.10e) */
+	SET_0(dest); /* RESEGMENT */
+
+	rc = bitvec_set_u64(dest, enc_ws(tbf->window_size()), 5, false); /* EGPRS Window Size */
+	CHECK(rc);
 
-	bitvec_write_field(dest, &wp, gamma, 5); /* GAMMA power contrl */
-	bitvec_write_field(dest, &wp, 0, 1); /* TIMING_ADVANCE_INDEX */
-	bitvec_write_field(dest, &wp, 0, 1); /* TBF_STARTING_TIME_FLAG */
-	bitvec_write_field(dest, &wp, 0, 1); /* NULL */
+	rc = write_alpha_gamma(dest, alpha, gamma);
+	CHECK(rc);
+
+	/* No TIMING_ADVANCE_INDEX */
+	SET_0(dest);
+
+	/* No TBF_STARTING_TIME */
+	SET_0(dest);
+
+	/* No Additions for Rel-7 */
+	SET_0(dest);
 
 	return rc;
 }
@@ -476,7 +507,8 @@ int Encoding::write_immediate_assignment(
 		bitvec_write_field(dest, &wp, 0, 1);    /* Access technology Request */
 
 		if (as_ul_tbf(tbf) != NULL) {
-			rc = write_ia_rest_egprs_uplink_sba(as_ul_tbf(tbf), dest, usf, alpha, gamma, wp);
+			dest->cur_bit = wp;
+			rc = write_ia_rest_egprs_uplink_sba(as_ul_tbf(tbf), dest, usf, alpha, gamma);
 		} else {
 			dest->cur_bit = wp;
 			rc = write_ia_rest_egprs_uplink_mba(dest, fn, alpha, gamma);