WIP: bitmap decoding

Ticket: OW#????
Sponsored-by: On-Waves ehf

src/bts.cpp

@@ -1008,6 +1008,30 @@ void gprs_rlcmac_pdch::rcv_control_egprs_dl_ack_nack(EGPRS_PD_AckNack_t *ack_nac
 		return;
 	}
 #endif
+	int num_blocks;
+	uint8_t bits_data[RLC_EGPRS_MAX_WS/8];
+	char show_bits[RLC_EGPRS_MAX_WS + 1];
+
+	bitvec bits;
+	int bsn_begin, bsn_end;
+
+	bits.data = bits_data;
+	bits.data_len = sizeof(bits_data);
+	bits.cur_bit = 0;
+
+	num_blocks = Decoding::decode_egprs_acknack_bits(
+		&ack_nack->EGPRS_AckNack.Desc, &bits,
+		&bsn_begin, &bsn_end, &tbf->m_window);
+
+	for (int i = 0; i < num_blocks; i++) {
+		show_bits[i] = bitvec_get_bit_pos(&bits, i) ? 'R' : 'I';
+	}
+	show_bits[num_blocks] = 0;
+
+	LOGP(DRLCMAC, LOGL_DEBUG,
+		"EGPRS DL ACK bitmap: BSN %d to %d - 1 (%d blocks): %s\n",
+		bsn_begin, bsn_end, num_blocks, show_bits);
+
 	if (ack_nack->EGPRS_AckNack.Desc.URBB_LENGTH == 0 &&
 		!ack_nack->EGPRS_AckNack.Desc.Exist_CRBB)
 	{

src/decoding.cpp

@@ -493,3 +493,51 @@ const uint8_t *Decoding::rlc_get_data_aligned(
 	Decoding::rlc_copy_to_aligned_buffer(rlc, data_block_idx, src, buffer);
 	return buffer;
 }
+
+int Decoding::decode_egprs_acknack_bits(const EGPRS_AckNack_Desc_t *desc,
+	bitvec *bits, int *bsn_begin, int *bsn_end, gprs_rlc_dl_window *window)
+{
+	int urbb_len = desc->URBB_LENGTH;
+	int crbb_len = 0;
+	int num_blocks;
+	struct bitvec urbb;
+
+	if (desc->Exist_CRBB)
+		crbb_len = desc->CRBB_LENGTH;
+
+	num_blocks = urbb_len + crbb_len;
+
+	if (num_blocks == 0) {
+		*bsn_begin = desc->STARTING_SEQUENCE_NUMBER;
+		*bsn_end = window->mod_sns(*bsn_begin - 1);
+
+		return num_blocks;
+	}
+
+
+	/* first bit refers to V(Q) and thus is always zero (and not
+	 * transmitted) */
+	bitvec_set_bit(bits, ZERO);
+	num_blocks += 1;
+
+	*bsn_begin = window->mod_sns(desc->STARTING_SEQUENCE_NUMBER - 1);
+	*bsn_end   = window->mod_sns(*bsn_begin + num_blocks);
+
+	if (crbb_len > 0) {
+		/*
+		decode_t4_rle(bits, desc->CRBB, desc->CRBB_LENGTH, desc->CRBB_STARTING_COLOR_CODE);
+		*/
+	}
+
+	urbb.cur_bit = 0;
+	urbb.data = (uint8_t *)desc->URBB;
+	urbb.data_len = sizeof(desc->URBB);
+
+	for (int i = urbb_len; i > 0; i--) {
+		/* Set bit at the appropriate position (see 3GPP TS 04.60 12.3.1) */
+		int is_ack = bitvec_get_bit_pos(&urbb, i-1);
+		bitvec_set_bit(bits, is_ack ? ONE : ZERO);
+	}
+
+	return num_blocks;
+}

src/decoding.h

@@ -24,6 +24,8 @@
 
 #include <stdint.h>
 
+struct bitvec;
+
 class Decoding {
 public:
 	struct RlcData {
@@ -51,4 +53,8 @@ public:
 		const struct gprs_rlc_data_info *rlc,
 		unsigned int data_block_idx,
 		const uint8_t *src, uint8_t *buffer);
+	static int decode_egprs_acknack_bits(
+		const EGPRS_AckNack_Desc_t *desc,
+		struct bitvec *bits, int *bsn_begin, int *bsn_end,
+		struct gprs_rlc_dl_window *window);
 };