ROHC compression/decompression library: sdvl.h File Reference

ROHC compression/decompression library

Self-Describing Variable-Length (SDVL) encoding. More...

#include "dllexport.h"
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>

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Enumerations
enum	rohc_sdvl_max_bits_t { ROHC_SDVL_MAX_BITS_IN_1_BYTE = 7U, ROHC_SDVL_MAX_BITS_IN_2_BYTES = 14U, ROHC_SDVL_MAX_BITS_IN_3_BYTES = 21U, ROHC_SDVL_MAX_BITS_IN_4_BYTES = 29U }
Functions
bool ROHC_EXPORT	sdvl_can_value_be_encoded (uint32_t value)
	Can the given value be encoded with SDVL?
bool ROHC_EXPORT	sdvl_can_length_be_encoded (size_t bits_nr)
	Is the given length (in bits) compatible with SDVL?
size_t ROHC_EXPORT	sdvl_get_min_len (const size_t nr_min_required, const size_t nr_encoded)
	Find out how many SDVL bits are needed to represent a value.
size_t ROHC_EXPORT	c_bytesSdvl (uint32_t value, size_t length)
	Find out how many bytes are needed to represent the value using Self-Describing Variable-Length (SDVL) encoding.
int ROHC_EXPORT	c_encodeSdvl (unsigned char *dest, uint32_t value, size_t length)
	Encode a value using Self-Describing Variable-Length (SDVL) encoding.
int ROHC_EXPORT	d_sdvalue_size (const unsigned char *data)
	Find out a size of the Self-Describing Variable-Length (SDVL) value.
size_t ROHC_EXPORT	sdvl_decode (const unsigned char data, const size_t length, uint32_t const value, size_t *const bits_nr)
	Decode a Self-Describing Variable-Length (SDVL) value.

Detailed Description

Self-Describing Variable-Length (SDVL) encoding.

Author:: Didier Barvaux <didier.barvaux@toulouse.viveris.com>; The hackers from ROHC for Linux

Enumeration Type Documentation

enum rohc_sdvl_max_bits_t

The maximum numbers of bits that can be SDVL-encoded in 1, 2, 3 and 4 bytes

Enumerator:

ROHC_SDVL_MAX_BITS_IN_1_BYTE	Maximum number of bits in 1 SDVL-encoded byte
ROHC_SDVL_MAX_BITS_IN_2_BYTES	Maximum number of bits in 2 SDVL-encoded byte
ROHC_SDVL_MAX_BITS_IN_3_BYTES	Maximum number of bits in 3 SDVL-encoded byte
ROHC_SDVL_MAX_BITS_IN_4_BYTES	Maximum number of bits in 4 SDVL-encoded byte

Function Documentation

size_t ROHC_EXPORT c_bytesSdvl	(	uint32_t	value,
		size_t	length
	)

Find out how many bytes are needed to represent the value using Self-Describing Variable-Length (SDVL) encoding.

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

value	The value to encode
length	The length of the value to encode (0 to let the SDVL encoding find the length itself)

Returns:: The size needed to represent the SDVL-encoded value

References rohc_debugf, ROHC_SDVL_MAX_BITS_IN_1_BYTE, ROHC_SDVL_MAX_BITS_IN_2_BYTES, ROHC_SDVL_MAX_BITS_IN_3_BYTES, ROHC_SDVL_MAX_BITS_IN_4_BYTES, ROHC_SDVL_MAX_VALUE_IN_1_BYTE, ROHC_SDVL_MAX_VALUE_IN_2_BYTES, ROHC_SDVL_MAX_VALUE_IN_3_BYTES, and ROHC_SDVL_MAX_VALUE_IN_4_BYTES.

Referenced by c_encodeSdvl(), code_cid_values(), code_EXT3_packet(), f_append_cid(), rtp_code_dynamic_rtp_part(), and rtp_header_flags_and_fields().

int ROHC_EXPORT c_encodeSdvl	(	unsigned char *	dest,
		uint32_t	value,
		size_t	length
	)

Encode a value using Self-Describing Variable-Length (SDVL) encoding.

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

dest	The destination to write the SDVL-encoded to
value	The value to encode
length	The length of the value to encode (0 to let the SDVL encoding find the length itself)

Returns:: 1 if SDVL encoding is successful, 0 in case of failure (failure may be due to a value greater than 2^29)

References c_bytesSdvl(), and rohc_debugf.

Referenced by code_cid_values(), code_EXT3_packet(), f_append_cid(), rtp_code_dynamic_rtp_part(), and rtp_header_flags_and_fields().

int ROHC_EXPORT d_sdvalue_size ( const unsigned char * data )

Find out a size of the Self-Describing Variable-Length (SDVL) value.

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

data	The SDVL data to analyze

Returns:: The size of the SDVL value (possible values are 1-4)

References GET_BIT_5_7, GET_BIT_6_7, GET_BIT_7, and rohc_debugf.

bool ROHC_EXPORT sdvl_can_length_be_encoded ( size_t bits_nr )

Is the given length (in bits) compatible with SDVL?

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

bits_nr The length (in bits) of the value to encode

Returns:: Whether the value can be encoded with SDVL or not

References ROHC_SDVL_MAX_BITS_IN_4_BYTES.

bool ROHC_EXPORT sdvl_can_value_be_encoded ( uint32_t value )

Can the given value be encoded with SDVL?

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

value The value to encode

Returns:: Whether the value can be encoded with SDVL or not

References ROHC_SDVL_MAX_VALUE_IN_4_BYTES.

Referenced by c_add_ts().

size_t ROHC_EXPORT sdvl_decode	(	const unsigned char *	data,
		const size_t	length,
		uint32_t *const	value,
		size_t *const	bits_nr
	)

Decode a Self-Describing Variable-Length (SDVL) value.

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

data	The SDVL data to decode
length	The maximum data length available (in bytes)
value	OUT: The decoded value
bits_nr	OUT: The number of useful bits

Returns:: The number of bytes used by the SDVL field

References GET_BIT_0_4, GET_BIT_0_5, GET_BIT_0_6, GET_BIT_0_7, GET_BIT_5_7, GET_BIT_6_7, GET_BIT_7, rohc_debugf, ROHC_SDVL_MAX_BITS_IN_1_BYTE, ROHC_SDVL_MAX_BITS_IN_2_BYTES, ROHC_SDVL_MAX_BITS_IN_3_BYTES, and ROHC_SDVL_MAX_BITS_IN_4_BYTES.

Referenced by c_deliver_feedback().

size_t ROHC_EXPORT sdvl_get_min_len	(	const size_t	nr_min_required,
		const size_t	nr_encoded
	)

Find out how many SDVL bits are needed to represent a value.

The number of bits already encoded in another field may be specified.

See 4.5.6 in the RFC 3095 for details about SDVL encoding.

Parameters:

nr_min_required	The minimum required number of bits to encode
nr_encoded	The number of bits already encoded in another field

Returns:: The number of bits needed to encode the value

References ROHC_SDVL_MAX_BITS_IN_1_BYTE, ROHC_SDVL_MAX_BITS_IN_2_BYTES, ROHC_SDVL_MAX_BITS_IN_3_BYTES, and ROHC_SDVL_MAX_BITS_IN_4_BYTES.

Referenced by code_UOR2_ID_bytes(), code_UOR2_RTP_bytes(), and code_UOR2_TS_bytes().