Implement ITU-T I.460 multiplex / demultiplex
This implements a multiplexer and de-multiplexer for the ITU-T I.460
standard. The latter covers the transmission of sub-slots of 32/16/8k
inside 64k timeslots.
Change-Id: Id522f06e73b77332b437b7a27e4966872da70eda
diff --git a/include/Makefile.am b/include/Makefile.am
index 572c880..456b8ef 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -103,6 +103,7 @@
osmocom/gsm/gsm_utils.h \
osmocom/gsm/gsup.h \
osmocom/gsm/gsup_sms.h \
+ osmocom/gsm/i460_mux.h \
osmocom/gsm/ipa.h \
osmocom/gsm/lapd_core.h \
osmocom/gsm/lapdm.h \
diff --git a/include/osmocom/gsm/i460_mux.h b/include/osmocom/gsm/i460_mux.h
new file mode 100644
index 0000000..2e33b37
--- /dev/null
+++ b/include/osmocom/gsm/i460_mux.h
@@ -0,0 +1,104 @@
+/*! \file i460_mux.h
+ * ITU-T I.460 sub-channel multiplexer + demultiplexer */
+/*
+ * (C) 2020 by Harald Welte <laforge@gnumonks.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#pragma once
+#include <stdint.h>
+#include <osmocom/core/bits.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/msgb.h>
+
+/* I.460 sub-slot rate */
+enum osmo_i460_rate {
+ OSMO_I460_RATE_NONE, /* disabled */
+ OSMO_I460_RATE_64k,
+ OSMO_I460_RATE_32k,
+ OSMO_I460_RATE_16k,
+ OSMO_I460_RATE_8k,
+};
+
+typedef void (*out_cb_bits_t)(void *user_data, const ubit_t *bits, unsigned int num_bits);
+typedef void (*out_cb_bytes_t)(void *user_data, const uint8_t *bytes, unsigned int num_bytes);
+
+struct osmo_i460_subchan_demux {
+ /*! bit-buffer for output bits */
+ uint8_t *out_bitbuf;
+ /*! size of out_bitbuf in bytes */
+ unsigned int out_bitbuf_size;
+ /*! offset of next bit to be written in out_bitbuf */
+ unsigned int out_idx;
+ /*! callback to be called once we have received out_bitbuf_size bits */
+ out_cb_bits_t out_cb_bits;
+ out_cb_bytes_t out_cb_bytes;
+ void *user_data;
+};
+
+struct osmo_i460_subchan_mux {
+ /*! list of to-be-transmitted message buffers */
+ struct llist_head tx_queue;
+};
+
+struct osmo_i460_subchan {
+ enum osmo_i460_rate rate; /* 8/16/32/64k */
+ uint8_t bit_offset; /* bit offset inside each byte of the B-channel */
+ struct osmo_i460_subchan_demux demux;
+ struct osmo_i460_subchan_mux mux;
+};
+
+struct osmo_i460_timeslot {
+ struct osmo_i460_subchan schan[8];
+};
+
+/*! description of a sub-channel; passed by caller */
+struct osmo_i460_schan_desc {
+ enum osmo_i460_rate rate;
+ uint8_t bit_offset;
+ struct {
+ /* size (in bits) of the internal buffer; determines granularity */
+ size_t num_bits;
+ /*! call-back function called whenever we received num_bits */
+ out_cb_bits_t out_cb_bits;
+ /*! out_cb_bytes call-back function called whenever we received num_bits.
+ * The user is usually expected to provide either out_cb_bits or out_cb_bytes. If only
+ * out_cb_bits is provided, output data will always be provided as unpacked bits; if only
+ * out_cb_bytes is provided, output data will always be provided as packet bits (bytes). If
+ * both are provided, it is up to the I.460 multiplex to decide if it calls either of the two,
+ * depending on what can be provided without extra conversion. */
+ out_cb_bytes_t out_cb_bytes;
+ /* opaque user data pointer to pass to out_cb */
+ void *user_data;
+ } demux;
+};
+
+void osmo_i460_demux_in(struct osmo_i460_timeslot *ts, const uint8_t *data, size_t data_len);
+
+void osmo_i460_mux_enqueue(struct osmo_i460_subchan *schan, struct msgb *msg);
+int osmo_i460_mux_out(struct osmo_i460_timeslot *ts, uint8_t *out, size_t out_len);
+
+void osmo_i460_ts_init(struct osmo_i460_timeslot *ts);
+
+struct osmo_i460_subchan *
+osmo_i460_subchan_add(void *ctx, struct osmo_i460_timeslot *ts, const struct osmo_i460_schan_desc *chd);
+
+void osmo_i460_subchan_del(struct osmo_i460_subchan *schan);
+
+/*! @} */