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add libosmo-sdp: fmtp_amr_match()

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Change-Id: I0fb77c022c4fb195ba45631dda9cbd2215c02510
This commit is contained in:
Neels Hofmeyr
2024-02-25 03:59:15 +01:00
parent c74c3d02c8
commit ef5f1d3d7b
2 changed files with 44 additions and 0 deletions
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1
include/osmocom/sdp/fmtp.h
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@@ -31,3 +31,4 @@ bool osmo_sdp_fmtp_get_val(char *val, size_t val_size, const char *fmtp, const c
int64_t osmo_sdp_fmtp_get_int(const char *fmtp, const char *option_name, int64_t default_value);
bool osmo_sdp_fmtp_amr_is_octet_aligned(const char *fmtp);
bool osmo_sdp_fmtp_amr_match(const char *a, const char *b);

43
src/libosmo-sdp/fmtp.c
View File

@@ -148,3 +148,46 @@ static void strip_whitespace(char *str)
break;
}
}
/* Return true when the two AMR type fmtp strings can be considered equivalent.
* - Omission of octet-align is equivalent to having octet-align=0 present (0 is the default).
* - Omission of 'mode-set' means, match any and all codec modes. So if either a or b have no 'mode-set', it's a match.
* If both have 'mode-set' present, they must be identical to match. Do not sort the mode-set string, but strip
* whitespace.
* - TODO all other parameters are currently completely ignored.
*/
bool osmo_sdp_fmtp_amr_match(const char *a, const char *b)
{
char a_modeset[32] = {};
char b_modeset[32] = {};
bool a_ok;
bool b_ok;
if (!a)
a = "";
if (!b)
b = "";
/* octet-align=1. Omission means octet-align=0 */
if (osmo_sdp_fmtp_amr_is_octet_aligned(a) != osmo_sdp_fmtp_amr_is_octet_aligned(b))
return false;
/* mode-set=0,1,2,3,4,5,6,7 */
a_ok = osmo_sdp_fmtp_get_val(a_modeset, sizeof(a_modeset), a, "mode-set");
b_ok = osmo_sdp_fmtp_get_val(b_modeset, sizeof(b_modeset), b, "mode-set");
if (a_ok && b_ok) {
/* Strip whitespace: We don't know what remote SDP peers may throw at us. There could be whitespace
* around the separators like 'mode-set=2,3 ; octet-align=1', which may show up here as whitespace in
* the value string as "2,3 ", which would mismatch "2,3". */
strip_whitespace(a_modeset);
strip_whitespace(b_modeset);
if (strcmp(a_modeset, b_modeset))
return false;
}
/* TODO: treat other AMR traits, see RFC4867 8.1. Maybe generically match all values that are present?
* So far we have no need for other values than octet-align and mode-set. */
/* No mismatch found, it's a match */
return true;
}