gsmstack: add new unfinished GSM burst/channel demultiplex

This is some unfinished work on a new codebase for 'proper'
demultiplex of all the various physical and logical channel
types.

Basically this includes everything needed to get from the
differential-decoded bursts up to the MAC blocks that can
be passed up to layer 2.

1 files changed, 143 insertions, 0 deletions

diff --git a/gsmstack/channel.c b/gsmstack/channel.c
new file mode 100644
index 0000000..768ed65
--- /dev/null
+++ b/gsmstack/channel.c
@@ -0,0 +1,143 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "gsmstack.h"
+
+/* convert an 18byte 8-bit-per-byte burst to a 142byte 1bit-per-byte */
+static void bit_per_byte(unsigned char *dest, const unsigned char *src)
+{
+	int bit, byte;	
+
+	for (byte = 0; byte < BURST_BYTES; src++) {
+		for (bit = 0; bit < 8; bit++) {
+			if (src[byte] >> bit &= 0x01)
+				*dest++ = 0x01;
+			else
+				*dest++ = 0x00;
+		}
+	}
+}
+
+static int add_burst_to_lchan(struct gsm_logi_chan *lchan,
+			      struct gsm_burst *burst)
+{
+	int rc = 0;
+
+	/* copy burst to burst buffer */
+	memcpy(lchan->burst_buf[lchan->next_burst], burst, sizeof(*burst));
+	lchan->next_burst++;
+
+	switch (lchan->type) {
+	case GSM_LCHAN_TCH_F:
+		/* FIXME */
+		break;
+	case GSM_LCHAN_TCH_H:
+		/* FIXME */
+	default:
+		if (lchan->next_burst == 4) {
+			lchan->next_burst = 0;
+			/* FIXME: decode the four bursts into a MAC block */
+	
+			/* pass the resulting MAC block up the stack */
+			rc = gsm_lchan_macblock()
+		}
+	}
+
+	return rc;
+}
+
+static int gsm_rx_sdcch8(struct gsm_burst *burst)
+{
+	struct gsm_phys_chan *pchan = burst->gsm_pchan;
+	int rc = -EINVAL;
+
+	if (burst_type == GSM_BURST_DUMMY)
+		return;
+
+	if (burst->type != GSM_BURST_NORMAL) {
+		fprintf(stderr, "Burst type %u not allowed in SDCCH8\n",
+			burst->type);
+		/* FIXME: statistics */
+		return rc;
+	}
+
+	lchan = get_lchan(pchan, burst->fnr);
+	return add_burst_to_lchan(lchan, burst);
+}
+
+static int gsm_rx_tch(struct gsm_burst *burst)
+{
+	struct gsm_phys_chan *pchan = burst->gsm_pchan;
+	struct gsm_logi_chan *lchan;
+	int rc = -EINVAL;
+
+	if (burst->type != GSM_BURST_NORMAL)
+		return rc;
+
+	lchan = get_lchan(pchan, fnr);
+	return add_burst_to_lchan(lchan, burst);
+}
+
+/* input a new GSM Um burst on a CCCH */
+static int gsm_rx_ccch(struct gsm_burst *burst)
+{
+	struct gsm_phys_chan *pchan = burst->gsm_pchan;
+	struct gsm_logi_chan *lchan;
+	int rc = -EINVAL;
+
+	switch (burst->type) {
+	case GSM_BURST_FCCH:
+		/* FIXME */
+		/* obtain the frequency offset and report to caller */
+		break;
+	case GSM_BURST_SCH:
+		/* obtain the RFN from the SCH burst */
+		/* FIXME */
+		break;
+	case GSM_BURST_NORMAL:
+		/* determine logical channel and append burst */
+		lchan = get_lchan(pchan, burst->fnr);
+		rc = add_burst_to_lchan(lchan, burst);
+		break;
+	default:
+		break;
+	};
+	return rc;
+}
+
+/* input a new GSM Um interface burst into the stack */
+int gsm_rx_burst(struct gsm_burst *burst, int bits)
+{
+	struct gsm_phys_chan *pchan;
+	int rc = -EINVAL;
+
+	/* we assume the following fields have already been
+	 * filled-in by the caller:
+	 * phys_chan, rx_time, rx_frame_nr, decoded/decoded_bits */
+
+	pchan = burst->phys_chan;
+
+	if (!bits)
+		bit_per_byte(burst->decoded_bits, burst->decoded);
+
+	pchan->stats.rx_total++;
+	pchan->stats.rx_type[burst->type]++;
+
+	switch (pchan->config) {
+	case GSM_PCHAN_CCCH:
+		rc = gsm_rx_ccch(burst);
+		break;
+	case GSM_PCHAN_SDCCH8_SACCH8C:
+		rc = gsm_rx_sdcch8(burst);
+		break;
+	case GSM_PCHAN_TCH_F:
+		rc = 
+		break;
+	case GSM_PCHAN_UNKNOWN:
+	default:
+		fprintf(stderr, "unknown pchan config (ts=%u\n)\n",
+			pchan->timeslot);
+		return;
+		break;
+	}
+}