isdnhdlc.c File Reference

#include <string.h>
#include <osmocom/core/crc16.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/isdnhdlc.h>

Macros
#define	crc_ccitt_byte   osmo_crc16_ccitt_byte
#define	handle_fast_flag(h)
#define	handle_abort(h)

Enumerations
enum	{   HDLC_FAST_IDLE ,   HDLC_GET_FLAG_B0 ,   HDLC_GETFLAG_B1A6 ,   HDLC_GETFLAG_B7 ,   HDLC_GET_DATA ,   HDLC_FAST_FLAG }
enum	{   HDLC_SEND_DATA ,   HDLC_SEND_CRC1 ,   HDLC_SEND_FAST_FLAG ,   HDLC_SEND_FIRST_FLAG ,   HDLC_SEND_CRC2 ,   HDLC_SEND_CLOSING_FLAG ,   HDLC_SEND_IDLE1 ,   HDLC_SEND_FAST_IDLE ,   HDLC_SENDFLAG_B0 ,   HDLC_SENDFLAG_B1A6 ,   HDLC_SENDFLAG_B7 ,   STOPPED ,   HDLC_SENDFLAG_ONE }

Functions
void	osmo_isdnhdlc_rcv_init (struct osmo_isdnhdlc_vars *hdlc, uint32_t features)
void	osmo_isdnhdlc_out_init (struct osmo_isdnhdlc_vars *hdlc, uint32_t features)
static int	check_frame (struct osmo_isdnhdlc_vars *hdlc)
int	osmo_isdnhdlc_decode (struct osmo_isdnhdlc_vars *hdlc, const uint8_t *src, int slen, int *count, uint8_t *dst, int dsize)
	decodes HDLC frames from a transparent bit stream. More...
int	osmo_isdnhdlc_encode (struct osmo_isdnhdlc_vars *hdlc, const uint8_t *src, uint16_t slen, int *count, uint8_t *dst, int dsize)
	encodes HDLC frames to a transparent bit stream. More...

Macro Definition Documentation

crc_ccitt_byte

#define crc_ccitt_byte   osmo_crc16_ccitt_byte

handle_abort

#define handle_abort

(

h

)

Value:

        do {                                                    \
                h->shift_reg = fast_abort[h->ffbit_shift - 1];  \
                h->hdlc_bits1 = h->ffbit_shift - 2;             \
                if (h->hdlc_bits1 < 0)                          \
                        h->hdlc_bits1 = 0;                      \
                h->data_bits = h->ffbit_shift - 1;              \
                h->state = HDLC_GET_DATA;                       \
                h->data_received = 0;                           \
        } while (0)

handle_fast_flag

#define handle_fast_flag

(

h

)

Value:

        do {                                                            \
                if (h->cbin == fast_flag[h->bit_shift]) {               \
                        h->ffvalue = fast_flag_value[h->bit_shift];     \
                        h->state = HDLC_FAST_FLAG;                      \
                        h->ffbit_shift = h->bit_shift;                  \
                        h->bit_shift = 1;                               \
                } else {                                                \
                        h->state = HDLC_GET_DATA;                       \
                        h->data_received = 0;                           \
                }                                                       \
        } while (0)

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
HDLC_FAST_IDLE
HDLC_GET_FLAG_B0
HDLC_GETFLAG_B1A6
HDLC_GETFLAG_B7
HDLC_GET_DATA
HDLC_FAST_FLAG

anonymous enum

anonymous enum

Enumerator
HDLC_SEND_DATA
HDLC_SEND_CRC1
HDLC_SEND_FAST_FLAG
HDLC_SEND_FIRST_FLAG
HDLC_SEND_CRC2
HDLC_SEND_CLOSING_FLAG
HDLC_SEND_IDLE1
HDLC_SEND_FAST_IDLE
HDLC_SENDFLAG_B0
HDLC_SENDFLAG_B1A6
HDLC_SENDFLAG_B7
STOPPED
HDLC_SENDFLAG_ONE

Function Documentation

check_frame()

static int check_frame ( struct osmo_isdnhdlc_vars *  hdlc )

static

References osmo_isdnhdlc_vars::crc, osmo_isdnhdlc_vars::dstpos, OSMO_HDLC_CRC_ERROR, and OSMO_HDLC_FRAMING_ERROR.

Referenced by osmo_isdnhdlc_decode().

osmo_isdnhdlc_decode()

int osmo_isdnhdlc_decode	(	struct osmo_isdnhdlc_vars *	hdlc,
		const uint8_t *	src,
		int	slen,
		int *	count,
		uint8_t *	dst,
		int	dsize
	)

decodes HDLC frames from a transparent bit stream.

The source buffer is scanned for valid HDLC frames looking for flags (01111110) to indicate the start of a frame. If the start of the frame is found, the bit stuffing is removed (0 after 5 1's). When a new flag is found, the complete frame has been received and the CRC is checked. If a valid frame is found, the function returns the frame length excluding the CRC. If the beginning of a valid frame is found, the function returns the length. If a framing error is found (too many 1s and not a flag) the function returns -OSMO_HDLC_FRAMING_ERROR. If a CRC error is found the function returns -OSMO_HDLC_CRC_ERROR. If the frame length exceeds the destination buffer size, the function returns the length with the bit OSMO_HDLC_LENGTH_ERROR set.

Parameters

[in]	src	source buffer
[in]	slen	source buffer length
[out]	count	number of bytes removed (decoded) from the source buffer
[out]	dst	destination buffer
[in]	dsize	destination buffer size

Returns

number of decoded bytes in the destination buffer and status flag.

References osmo_isdnhdlc_vars::bit_shift, osmo_isdnhdlc_vars::cbin, check_frame(), osmo_isdnhdlc_vars::crc, crc_ccitt_byte, osmo_isdnhdlc_vars::data_bits, osmo_isdnhdlc_vars::data_received, osmo_isdnhdlc_vars::do_adapt56, osmo_isdnhdlc_vars::do_bitreverse, osmo_isdnhdlc_vars::dstpos, osmo_isdnhdlc_vars::ffbit_shift, osmo_isdnhdlc_vars::ffvalue, handle_abort, handle_fast_flag, osmo_isdnhdlc_vars::hdlc_bits1, HDLC_FAST_FLAG, HDLC_FAST_IDLE, HDLC_GET_DATA, HDLC_GET_FLAG_B0, HDLC_GETFLAG_B1A6, HDLC_GETFLAG_B7, OSMO_HDLC_FRAMING_ERROR, OSMO_HDLC_LENGTH_ERROR, osmo_revbytebits_8(), osmo_isdnhdlc_vars::shift_reg, osmo_isdnhdlc_vars::state, and STOPPED.

osmo_isdnhdlc_encode()

int osmo_isdnhdlc_encode	(	struct osmo_isdnhdlc_vars *	hdlc,
		const uint8_t *	src,
		uint16_t	slen,
		int *	count,
		uint8_t *	dst,
		int	dsize
	)

encodes HDLC frames to a transparent bit stream.

The bit stream starts with a beginning flag (01111110). After that each byte is added to the bit stream with bit stuffing added (0 after 5 1's). When the last byte has been removed from the source buffer, the CRC (2 bytes is added) and the frame terminates with the ending flag. For the dchannel, the idle character (all 1's) is also added at the end. If this function is called with empty source buffer (slen=0), flags or idle character will be generated.

Parameters

[in]	src	source buffer
[in]	slen	source buffer length
[out]	count	number of bytes removed (encoded) from source buffer
[out]	dst	destination buffer
[in]	dsize	destination buffer size

Returns

- number of encoded bytes in the destination buffer

References osmo_isdnhdlc_vars::bit_shift, osmo_isdnhdlc_vars::cbin, osmo_isdnhdlc_vars::crc, crc_ccitt_byte, osmo_isdnhdlc_vars::data_bits, osmo_isdnhdlc_vars::data_received, osmo_isdnhdlc_vars::dchannel, osmo_isdnhdlc_vars::do_adapt56, osmo_isdnhdlc_vars::do_bitreverse, osmo_isdnhdlc_vars::do_closing, osmo_isdnhdlc_vars::ffvalue, osmo_isdnhdlc_vars::hdlc_bits1, HDLC_SEND_CLOSING_FLAG, HDLC_SEND_CRC1, HDLC_SEND_CRC2, HDLC_SEND_DATA, HDLC_SEND_FAST_FLAG, HDLC_SEND_FAST_IDLE, HDLC_SEND_FIRST_FLAG, HDLC_SEND_IDLE1, HDLC_SENDFLAG_B0, HDLC_SENDFLAG_B1A6, HDLC_SENDFLAG_B7, HDLC_SENDFLAG_ONE, len(), osmo_revbytebits_8(), osmo_isdnhdlc_vars::shift_reg, osmo_isdnhdlc_vars::state, and STOPPED.

osmo_isdnhdlc_out_init()

void osmo_isdnhdlc_out_init	(	struct osmo_isdnhdlc_vars *	hdlc,
		uint32_t	features
	)

References osmo_isdnhdlc_vars::cbin, osmo_isdnhdlc_vars::data_bits, osmo_isdnhdlc_vars::dchannel, osmo_isdnhdlc_vars::do_adapt56, osmo_isdnhdlc_vars::do_bitreverse, osmo_isdnhdlc_vars::ffvalue, HDLC_SEND_FAST_FLAG, HDLC_SEND_FIRST_FLAG, HDLC_SENDFLAG_B0, OSMO_HDLC_F_56KBIT, OSMO_HDLC_F_BITREVERSE, OSMO_HDLC_F_DCHANNEL, and osmo_isdnhdlc_vars::state.

osmo_isdnhdlc_rcv_init()

void osmo_isdnhdlc_rcv_init	(	struct osmo_isdnhdlc_vars *	hdlc,
		uint32_t	features
	)

References osmo_isdnhdlc_vars::do_adapt56, osmo_isdnhdlc_vars::do_bitreverse, HDLC_GET_DATA, OSMO_HDLC_F_56KBIT, OSMO_HDLC_F_BITREVERSE, and osmo_isdnhdlc_vars::state.