| /* A E1 sub-channel (de)multiplexer with TRAU frame sync */ |
| |
| /* (C) 2009 by Harald Welte <laforge@gnumonks.org> |
| * All Rights Reserved |
| * |
| * SPDX-License-Identifier: AGPL-3.0+ |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU Affero General Public License as published by |
| * the Free Software Foundation; either version 3 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 Affero General Public License for more details. |
| * |
| * You should have received a copy of the GNU Affero General Public License |
| * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| * |
| */ |
| |
| #include "internal.h" |
| |
| #include <unistd.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <errno.h> |
| |
| #include <osmocom/abis/subchan_demux.h> |
| #include <osmocom/abis/trau_frame.h> |
| #include <osmocom/core/talloc.h> |
| |
| /*! \addtogroup subchan_demux |
| * @{ |
| * |
| * \file subchan_demux.c |
| */ |
| |
| void *tall_tqe_ctx; |
| |
| static inline void append_bit(struct demux_subch *sch, uint8_t bit) |
| { |
| sch->out_bitbuf[sch->out_idx++] = bit; |
| } |
| |
| #define SYNC_HDR_BITS 16 |
| |
| /* check if we have just completed the 16 bit zero + 1 bit one sync |
| * header, in accordance with GSM TS 08.60 Chapter 4.8.1 */ |
| static int sync_hdr_complete(struct demux_subch *sch, uint8_t bit) |
| { |
| if (bit == 0) |
| sch->consecutive_zeros++; |
| else { |
| if (sch->consecutive_zeros >= SYNC_HDR_BITS) { |
| sch->consecutive_zeros = 0; |
| return 1; |
| } |
| sch->consecutive_zeros = 0; |
| } |
| |
| return 0; |
| } |
| |
| /* resynchronize to current location */ |
| static void resync_to_here(struct demux_subch *sch) |
| { |
| memset(sch->out_bitbuf, 0, SYNC_HDR_BITS); |
| sch->out_bitbuf[SYNC_HDR_BITS] = 1; |
| |
| /* set index in a way that we can continue receiving bits after |
| * the end of the SYNC header */ |
| sch->out_idx = SYNC_HDR_BITS + 1; |
| sch->in_sync = 1; |
| } |
| |
| /*! \brief initialize subchannel demuxer structure |
| * \param[in,out] dmx subchannel demuxer |
| */ |
| int subch_demux_init(struct subch_demux *dmx) |
| { |
| int i; |
| |
| dmx->chan_activ = 0; |
| for (i = 0; i < NR_SUBCH; i++) { |
| struct demux_subch *sch = &dmx->subch[i]; |
| sch->out_idx = 0; |
| memset(sch->out_bitbuf, 0xff, sizeof(sch->out_bitbuf)); |
| } |
| return 0; |
| } |
| |
| /*! \brief Input some data from the 64k full-slot into subchannel demux |
| * \param[in] dmx subchannel demuxer |
| * \param[in] data pointer to buffer containing input data |
| * \param[in] len length of \a data in bytes |
| * \returns 0 in case of success, <0 otherwise. |
| * |
| * Input some arbitrary (modulo 4) number of bytes of a 64k E1 channel, |
| * split it into the 16k subchannels */ |
| int subch_demux_in(struct subch_demux *dmx, uint8_t *data, int len) |
| { |
| int i, c; |
| |
| for (i = 0; i < len; i++) { |
| uint8_t inbyte = data[i]; |
| |
| for (c = 0; c < NR_SUBCH; c++) { |
| struct demux_subch *sch = &dmx->subch[c]; |
| uint8_t inbits; |
| uint8_t bit; |
| |
| /* ignore inactive subchannels */ |
| if (!(dmx->chan_activ & (1 << c))) |
| continue; |
| |
| inbits = inbyte >> (c << 1); |
| |
| /* two bits for each subchannel */ |
| if (inbits & 0x01) |
| bit = 1; |
| else |
| bit = 0; |
| append_bit(sch, bit); |
| |
| if (sync_hdr_complete(sch, bit)) |
| resync_to_here(sch); |
| |
| if (inbits & 0x02) |
| bit = 1; |
| else |
| bit = 0; |
| append_bit(sch, bit); |
| |
| if (sync_hdr_complete(sch, bit)) |
| resync_to_here(sch); |
| |
| /* FIXME: verify the first bit in octet 2, 4, 6, ... |
| * according to TS 08.60 4.8.1 */ |
| |
| /* once we have reached TRAU_FRAME_BITS, call |
| * the TRAU frame handler callback function */ |
| if (sch->out_idx >= TRAU_FRAME_BITS) { |
| if (sch->in_sync) { |
| dmx->out_cb(dmx, c, sch->out_bitbuf, |
| sch->out_idx, dmx->data); |
| sch->in_sync = 0; |
| } |
| sch->out_idx = 0; |
| } |
| } |
| } |
| return i; |
| } |
| |
| /*! \brief activate a given sub-channel |
| * \param[in] dmx subchannel demuxer |
| * \param[in] subch sub-channel number |
| * \returns 0 in case of success, <0 otherwise |
| * |
| * Activating a sub-channel will casuse the \ref subch_demux::out_cb |
| * callback to be called for any incoming data from the full slot |
| */ |
| int subch_demux_activate(struct subch_demux *dmx, int subch) |
| { |
| if (subch >= NR_SUBCH) |
| return -EINVAL; |
| |
| dmx->chan_activ |= (1 << subch); |
| return 0; |
| } |
| |
| /*! \brief deactivate a given sub-channel |
| * \param[in] dmx subchannel demuxer |
| * \param[in] subch sub-channel number |
| * \returns 0 in case of success, <0 otherwise |
| * |
| * Deactivating a sub-channel will casuse the \ref subch_demux::out_cb |
| * callback no longer to be called. |
| */ |
| int subch_demux_deactivate(struct subch_demux *dmx, int subch) |
| { |
| if (subch >= NR_SUBCH) |
| return -EINVAL; |
| |
| dmx->chan_activ &= ~(1 << subch); |
| return 0; |
| } |
| |
| /* MULTIPLEXER */ |
| |
| static int alloc_add_idle_frame(struct subch_mux *mx, int sch_nr) |
| { |
| /* allocate and initialize with idle pattern */ |
| return subchan_mux_enqueue(mx, sch_nr, trau_idle_frame(), |
| TRAU_FRAME_BITS); |
| } |
| |
| /* return the requested number of bits from the specified subchannel */ |
| static int get_subch_bits(struct subch_mux *mx, int subch, |
| uint8_t *bits, int num_requested) |
| { |
| struct mux_subch *sch = &mx->subch[subch]; |
| int num_bits = 0; |
| |
| while (num_bits < num_requested) { |
| struct subch_txq_entry *txe; |
| int num_bits_left; |
| int num_bits_thistime; |
| |
| /* make sure we have a valid entry at top of tx queue. |
| * if not, add an idle frame */ |
| if (llist_empty(&sch->tx_queue)) |
| alloc_add_idle_frame(mx, subch); |
| |
| if (llist_empty(&sch->tx_queue)) |
| return -EIO; |
| |
| txe = llist_entry(sch->tx_queue.next, struct subch_txq_entry, list); |
| num_bits_left = txe->bit_len - txe->next_bit; |
| |
| if (num_bits_left < num_requested) |
| num_bits_thistime = num_bits_left; |
| else |
| num_bits_thistime = num_requested; |
| |
| /* pull the bits from the txe */ |
| memcpy(bits + num_bits, txe->bits + txe->next_bit, num_bits_thistime); |
| txe->next_bit += num_bits_thistime; |
| |
| /* free the tx_queue entry if it is fully consumed */ |
| if (txe->next_bit >= txe->bit_len) { |
| llist_del(&txe->list); |
| talloc_free(txe); |
| } |
| |
| /* increment global number of bits dequeued */ |
| num_bits += num_bits_thistime; |
| } |
| |
| return num_requested; |
| } |
| |
| /* compact an array of 8 single-bit bytes into one byte of 8 bits */ |
| static uint8_t compact_bits(const uint8_t *bits) |
| { |
| uint8_t ret = 0; |
| int i; |
| |
| for (i = 0; i < 8; i++) |
| ret |= (bits[i] ? 1 : 0) << i; |
| |
| return ret; |
| } |
| |
| /* obtain a single output byte from the subchannel muxer */ |
| static int mux_output_byte(struct subch_mux *mx, uint8_t *byte) |
| { |
| uint8_t bits[8]; |
| int rc; |
| |
| /* combine two bits of every subchan */ |
| rc = get_subch_bits(mx, 0, &bits[0], 2); |
| rc = get_subch_bits(mx, 1, &bits[2], 2); |
| rc = get_subch_bits(mx, 2, &bits[4], 2); |
| rc = get_subch_bits(mx, 3, &bits[6], 2); |
| |
| *byte = compact_bits(bits); |
| |
| return rc; |
| } |
| |
| /*! \brief Request the output of some muxed bytes from the subchan muxer |
| * \param[in] mx subchannel muxer |
| * \param[out] data caller-allocated buffer for data |
| * \param[in] len number of bytes to be filled into \a data |
| * \returns actual number of bytes filled into \a data |
| */ |
| int subchan_mux_out(struct subch_mux *mx, uint8_t *data, int len) |
| { |
| int i; |
| |
| for (i = 0; i < len; i++) { |
| int rc; |
| rc = mux_output_byte(mx, &data[i]); |
| if (rc < 0) |
| break; |
| } |
| return i; |
| } |
| |
| /* evict the 'num_evict' number of oldest entries in the queue */ |
| static void tx_queue_evict(struct mux_subch *sch, int num_evict) |
| { |
| struct subch_txq_entry *tqe; |
| int i; |
| |
| for (i = 0; i < num_evict; i++) { |
| if (llist_empty(&sch->tx_queue)) |
| return; |
| |
| tqe = llist_entry(sch->tx_queue.next, struct subch_txq_entry, list); |
| llist_del(&tqe->list); |
| talloc_free(tqe); |
| } |
| } |
| |
| /*! \brief enqueue some data into the tx_queue of a given subchannel |
| * \param[in] mx subchannel muxer instance |
| * \param[in] s_nr subchannel number |
| * \param[in] data pointer to buffer with data |
| * \param[in] len length of \a data |
| * \returns 0 in case of success, <0 in case of error |
| */ |
| int subchan_mux_enqueue(struct subch_mux *mx, int s_nr, const uint8_t *data, |
| int len) |
| { |
| struct mux_subch *sch = &mx->subch[s_nr]; |
| unsigned int list_len = llist_count(&sch->tx_queue); |
| struct subch_txq_entry *tqe = talloc_zero_size(tall_tqe_ctx, |
| sizeof(*tqe) + len); |
| if (!tqe) |
| return -ENOMEM; |
| |
| tqe->bit_len = len; |
| memcpy(tqe->bits, data, len); |
| |
| if (list_len > 2) |
| tx_queue_evict(sch, list_len-2); |
| |
| llist_add_tail(&tqe->list, &sch->tx_queue); |
| |
| return 0; |
| } |
| |
| /*! \brief initialize one subchannel muxer instance |
| * \param[in,out] mx subchannel muxer instance, caller-allocated |
| * \returns 0 in success, < 0 in case of error |
| */ |
| int subchan_mux_init(struct subch_mux *mx) |
| { |
| int i; |
| |
| memset(mx, 0, sizeof(*mx)); |
| for (i = 0; i < NR_SUBCH; i++) { |
| struct mux_subch *sch = &mx->subch[i]; |
| INIT_LLIST_HEAD(&sch->tx_queue); |
| } |
| |
| return 0; |
| } |
| |
| /* }@ */ |