add iniital HDLC soft decoder for playing with RBS2308 via DAHDI

README

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+Some experimental tools to play with Ericsson RBS

hdlc/Makefile

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+LDFLAGS=-losmocore
+
+hdlcsync: hdlcsync.o
+	$(CC) $(LDFLAGS) -o $@ $^
+
+clean:
+	@rm -f hdlcsync hdlcsync.o

hdlc/hdlcsync.c

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+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <osmocore/utils.h>
+#include <osmocore/bits.h>
+
+enum hdlc_proc_state {
+	STATE_INIT,
+	STATE_FLAG_WAIT_ZERO,
+	STATE_PAYLOAD,
+};
+	
+struct hdlc_proc {
+	ubit_t history[8];
+	ubit_t next_outbyte[8];
+	enum hdlc_proc_state state;
+	uint8_t num_bits;
+};
+
+const ubit_t five_ones[] = { 1,1,1,1,1 };
+
+static int append_bit(struct hdlc_proc *hdlc, uint8_t bit, int ignore)
+{
+	memmove(hdlc->history+1, hdlc->history, sizeof(hdlc->history)-1);
+	hdlc->history[0] = bit;
+	if (ignore)
+		return -1;
+
+	memmove(hdlc->next_outbyte+1, hdlc->next_outbyte, sizeof(hdlc->next_outbyte)-1);
+	hdlc->next_outbyte[0] = bit;
+	hdlc->num_bits++;
+
+	if (hdlc->num_bits == 8) {
+		pbit_t out;
+		/* generate one output byte */
+		osmo_ubit2pbit_ext(&out, 0, hdlc->next_outbyte, 0, 8, 0);
+		hdlc->num_bits = 0;
+		return out;
+	}
+
+	return -1;
+}
+
+static int process_hdlc_bit(struct hdlc_proc *hdlc, uint8_t bit)
+{
+	int ignore = 0;
+	int out;
+
+	printf("bit=%u, history_in = %s, ", bit, ubit_dump(hdlc->history, sizeof(hdlc->history)));
+
+	switch (hdlc->state) {
+	case STATE_FLAG_WAIT_ZERO:
+		if (bit == 0) {
+			printf("F ");
+			hdlc->state = STATE_PAYLOAD;
+		} else {
+			hdlc->state = STATE_INIT;
+		}
+		ignore = 1;
+		hdlc->num_bits = 0;
+		break;
+	default:
+		if (!memcmp(five_ones, hdlc->history, sizeof(five_ones))) {
+			if (bit == 1) {
+				//printf("F ");
+				hdlc->state = STATE_FLAG_WAIT_ZERO;
+				ignore = 1;
+			} else {
+				/* discard bit */
+				ignore = 1;
+			}
+		}
+		break;
+	}
+	out = append_bit(hdlc, bit, ignore);
+	printf("history_out = %s", ubit_dump(hdlc->history, sizeof(hdlc->history)));
+	if (out > 0)
+		printf(", out 0x%02x\n", out);
+	else
+		printf("\n");
+
+	return out;
+}
+
+static int process_raw_hdlc(struct hdlc_proc *hdlc, uint8_t *data, unsigned int len)
+{
+	unsigned int i;
+	int out;
+
+	for (i = 0; i < len; i ++) {
+		out = process_hdlc_bit(hdlc, data[i]);
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int fd, rc, bitlen;
+	uint8_t buf[512];
+	ubit_t bitbuf[512*8];
+	struct hdlc_proc hdlc;
+
+	memset(&hdlc, 0, sizeof(hdlc));
+
+	if (argc < 2) {
+		fprintf(stderr, "You have to specify the input file\n");
+		exit(2);
+	}
+
+	printf("opening '%s'\n", argv[1]);
+
+	fd = open(argv[1], O_RDONLY);
+	if (fd < 0) {
+		perror("opening infile");
+		exit(2);
+	}
+
+	rc = read(fd, buf, sizeof(buf));
+	if (rc <= 0)
+		exit(1);
+
+	bitlen = osmo_pbit2ubit_ext(bitbuf, 0, buf, 0, rc*8, 0);
+	printf("%s\n", ubit_dump(bitbuf, bitlen));
+	process_raw_hdlc(&hdlc, bitbuf, bitlen);
+
+	exit(0);
+}