The functions in this section parse and populate the SDP session structure, clone an existing session, and convert an existing session to a string representation.
The sdp_parse() function parses the SDP description in the sdp_info parameter and populates the sdp_session_t structure. The len parameter specifies the length of the character buffer sdp_info. The function allocates the memory required for the sdp_session_t structure. To free that memory, call the sdp_free_session() function.
The value of the flags parameter must be set to zero. When the flags parameter has a nonzero value, the sdp_parse() function fails with a return value of EINVAL and sets the value of *session to NULL.
The p_error parameter takes on the values of any fields that have parsing errors. This parameter cannot have a value of NULL. Possible values for the p_error parameter are in the following list:
SDP_VERSION_ERROR 0x00000001 SDP_ORIGIN_ERROR 0x00000002 SDP_NAME_ERROR 0x00000004 SDP_INFO_ERROR 0x00000008 SDP_URI_ERROR 0x00000010 SDP_EMAIL_ERROR 0x00000020 SDP_PHONE_ERROR 0x00000040 SDP_CONNECTION_ERROR 0x00000080 SDP_BANDWIDTH_ERROR 0x00000100 SDP_TIME_ERROR 0x00000200 SDP_REPEAT_TIME_ERROR 0x00000400 SDP_ZONE_ERROR 0x00000800 SDP_KEY_ERROR 0x00001000 SDP_ATTRIBUTE_ERROR 0x00002000 SDP_MEDIA_ERROR 0x00004000 SDP_FIELDS_ORDER_ERROR 0x00008000 SDP_MISSING_FIELDS 0x00010000
When the SDP structure violates RFC 4566 by having fields out of order, the sdp_parse() function sets the value of the p_error parameter to SDP_FIELDS_ORDER_ERROR. When the SDP structure violates RFC 4566 by lacking mandatory fields, the sdp_parse() function sets the value of the p_error parameter to SDP_MISSING_FIELDS.
The sdp_parse() function continues to parse after processing a field with a parsing error, but the field with the parsing error will not be present in the resulting sdp_session_t structure.
Return Values: The sdp_parse() function returns 0 when the function completes successfully. When the session arguments are invalid, the sdp_parse()function returns EINVAL. When memory allocation fails while the sdp_parse() function is parsing sdp_info, the function returns ENOMEM. The value of errno does not change in the event of an error.
Example 2-5 Example: Parsing an SDP Session StructureIn this example, the SDP session structure is as follows:
v=0\r\n o=jdoe 23423423 234234234 IN IP4 192.168.1.1\r\n s=SDP seminar\r\n i=A seminar on the session description protocol\r\n [email protected] c=IN IP4 192.168.90.1\r\n t=2873397496 2873404696\r\n
After calling the sdp_parse_t() function, the resulting sdp_session_t structure is as follows:
session {
sdp_session_version = 1
s_version = 0
s_origin {
o_username = "jdoe"
o_id = 23423423ULL
o_version = 234234234ULL
o_nettype = "IN"
o_addrtype = "IP4"
o_address = "192.168.1.1"
}
s_name = "SDP seminar"
s_info = "A seminar on the session description protocol"
s_uri = (nil)
s_email {
value = "[email protected]"
next = (nil)
}
s_phone = (nil)
s_conn {
c_nettype = "IN"
c_addrtype = "IP4"
c_address = "192.168.90.1"
c_addrcount = 0
c_ttl = 0
c_next = (nil)
}
s_bw = (nil)
s_time {
t_start = 2873397496ULL
t_stop = 2873404696ULL
t_repeat = (nil)
t_next = (nil)
}
s_zone = (nil)
s_key = (nil)
s_attr = (nil)
s_media = (nil)
}
The sdp_clone_session() function creates a new SDP session structure that is identical to the SDP session structure that is identified in the session parameter. The sdp_clone_session() function returns the cloned session structure upon successful completion. The sdp_clone_session() function returns NULL on failure.
The sdp_session_to_str() function returns the string representation of the SDP session structure that is specified by the session parameter. The sdp_session_to_str() function appends a carriage return/line feed to the end of each SDP field before appending the field to the string.
Return Values: The sdp_session_to_str() function returns the string representation of the SDP session structure upon completing successfully. The sdp_session_to_str() function returns NULL in all other cases. The sdp_session_to_str() function returns an error pointer to EINVAL when the input is null. The sdp_session_to_str() function returns an error pointer to ENOMEM when a memory allocation failure occurs. The value of errno does not change in the event of an error.