interval.h File Reference

Compute the interpretation interval for LSB and W-LSB encoding. More...

#include <rohc/rohc.h>
#include <stdlib.h>
#include <stdint.h>

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Data Structures
struct	rohc_interval8
	An interval of 8-bit values. More...
struct	rohc_interval16
	An interval of 16-bit values. More...
struct	rohc_interval32
	An interval of 32-bit values. More...

Macros
#define	ROHC_WLSB_WIDTH_MAX   64U
#define	ROHC_LSB_SHIFT_TCP_TS_1B   ROHC_LSB_SHIFT_SN
#define	ROHC_LSB_SHIFT_TCP_TS_2B   ROHC_LSB_SHIFT_SN
#define	ROHC_LSB_SHIFT_TCP_ACK_SCALED   ROHC_LSB_SHIFT_TCP_TTL

Enumerations
enum	rohc_lsb_shift_t {   ROHC_LSB_SHIFT_SN = -1, ROHC_LSB_SHIFT_IP_ID = 0, ROHC_LSB_SHIFT_TCP_TTL = 3, ROHC_LSB_SHIFT_TCP_SN = 4,   ROHC_LSB_SHIFT_TCP_SEQ_SCALED = 7, ROHC_LSB_SHIFT_RTP_TS = 100, ROHC_LSB_SHIFT_RTP_SN = 101, ROHC_LSB_SHIFT_ESP_SN = 102,   ROHC_LSB_SHIFT_VAR = 103, ROHC_LSB_SHIFT_TCP_WINDOW = 16383, ROHC_LSB_SHIFT_TCP_TS_3B = 0x00040000, ROHC_LSB_SHIFT_TCP_TS_4B = 0x04000000 }
	the different values of the shift parameter of the LSB algorithm More...

Functions
static int32_t	rohc_interval_compute_p (const size_t k, const rohc_lsb_shift_t p)
	Compute the shift parameter p for the f function. More...
struct rohc_interval32	rohc_f_32bits (const uint32_t v_ref, const size_t k, const rohc_lsb_shift_t p)
	The f function as defined in LSB encoding for 32-bit fields. More...
int32_t	rohc_interval_get_rfc5225_msn_p (const size_t k, rohc_reordering_offset_t reorder_ratio)
	Get shift parameter p from number of bytes k and reorder ratio. More...
int32_t	rohc_interval_get_rfc5225_id_id_p (const size_t k)
	Get shift parameter p from number of bytes k for ip_id_lsb. More...

Detailed Description

Compute the interpretation interval for LSB and W-LSB encoding.

Author

Didier Barvaux didie.nosp@m.r.ba.nosp@m.rvaux.nosp@m.@tou.nosp@m.louse.nosp@m..viv.nosp@m.eris..nosp@m.com

Macro Definition Documentation

ROHC_LSB_SHIFT_TCP_ACK_SCALED

#define ROHC_LSB_SHIFT_TCP_ACK_SCALED   ROHC_LSB_SHIFT_TCP_TTL

ROHC_LSB_SHIFT_TCP_TS_1B

#define ROHC_LSB_SHIFT_TCP_TS_1B   ROHC_LSB_SHIFT_SN

real value for TCP TS

ROHC_LSB_SHIFT_TCP_TS_2B

#define ROHC_LSB_SHIFT_TCP_TS_2B   ROHC_LSB_SHIFT_SN

real value for TCP TS

ROHC_WLSB_WIDTH_MAX

#define ROHC_WLSB_WIDTH_MAX   64U

The maximum width of the W-LSB window (implementation specific)

Enumeration Type Documentation

rohc_lsb_shift_t

enum rohc_lsb_shift_t

the different values of the shift parameter of the LSB algorithm

The shift parameter is also named 'p' in some RFCs.

Some values are the real values to use directly. Some others are code that means that the real value to use shall be computed from the number of least significant bits that are transmitted.

Enumerator
ROHC_LSB_SHIFT_SN	real value for non-RTP SN
ROHC_LSB_SHIFT_IP_ID	real value for IP-ID
ROHC_LSB_SHIFT_TCP_TTL	real value for TCP TTL/HL
ROHC_LSB_SHIFT_TCP_SN	real value for TCP MSN
ROHC_LSB_SHIFT_TCP_SEQ_SCALED	real value for TCP seq/ack scaled
ROHC_LSB_SHIFT_RTP_TS	need to compute real value for RTP TS
ROHC_LSB_SHIFT_RTP_SN	need to compute real value for RTP SN
ROHC_LSB_SHIFT_ESP_SN	need to compute real value for ESP SN
ROHC_LSB_SHIFT_VAR	real value is variable
ROHC_LSB_SHIFT_TCP_WINDOW	real value for TCP window
ROHC_LSB_SHIFT_TCP_TS_3B	real value for TCP TS
ROHC_LSB_SHIFT_TCP_TS_4B	real value for TCP TS

Function Documentation

rohc_f_32bits()

struct rohc_interval32 rohc_f_32bits	(	const uint32_t	v_ref,
		const size_t	k,
		const rohc_lsb_shift_t	p
	)

The f function as defined in LSB encoding for 32-bit fields.

Find out the interval [v_ref - p, v_ref + (2^k - 1) - p] for a given k. See 4.5.1 in the RFC 3095 for details.

As stated RFC, the values to be encoded have a finite range and the interpretation interval can straddle the wraparound boundary. So, the min value may be greater than the max value!

Parameters

v_ref	The reference value
k	The number of least significant bits of the value that are transmitted
p	The shift parameter (may be negative)

Returns

The computed interval

rohc_interval_compute_p()

static int32_t rohc_interval_compute_p ( const size_t  k, const rohc_lsb_shift_t  p  )

inlinestatic

Compute the shift parameter p for the f function.

Parameters

k	The number of least significant bits of the value that are transmitted
p	The shift parameter (may be negative)

Returns

The computed shift parameter p

rohc_interval_get_rfc5225_id_id_p()

int32_t rohc_interval_get_rfc5225_id_id_p

(

const size_t

k

)

Get shift parameter p from number of bytes k for ip_id_lsb.

Parameters

k	The number of least significant bits of the value that are transmitted

Returns

The shift parameter p

rohc_interval_get_rfc5225_msn_p()

int32_t rohc_interval_get_rfc5225_msn_p	(	const size_t	k,
		rohc_reordering_offset_t	reorder_ratio
	)

Get shift parameter p from number of bytes k and reorder ratio.

Parameters

k	The number of least significant bits of the value that are transmitted
reorder_ratio	The reordering ratio

Returns

The shift parameter p