rtp: helpers to parse a=fmtp lines

modules/access/rtp/Makefile.am

@@ -28,6 +28,8 @@ librtp_plugin_la_LIBADD += libvlc_srtp.la $(GCRYPT_LIBS)
 librtp_plugin_la_DEPENDENCIES += libvlc_srtp.la
 endif
 
+noinst_HEADERS += access/rtp/fmtp.h
+
 # RTP payload parser plugins
 rtpparsedir = $(accessdir)/rtp
 rtpparse_LTLIBRARIES = \

modules/access/rtp/fmtp.h

@@ -0,0 +1,106 @@
+/**
+ * @file fmtp.h
+ * @brief SDP format parameters (fmtp) helpers
+ */
+/*****************************************************************************
+ * Copyright © 2022 Rémi Denis-Courmont
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1
+ * of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ ****************************************************************************/
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+static inline
+const char *vlc_sdp_fmtp_get_str(const struct vlc_sdp_pt *desc,
+                                 const char *name, size_t *restrict lenp)
+{
+    const char *p = desc->parameters;
+    size_t namelen = strlen(name);
+
+    while (p != NULL) {
+        p += strspn(p, " ");
+
+        if (strncmp(p, name, namelen) == 0 && p[namelen] == '=') {
+            p += namelen + 1;
+            *lenp = strcspn(p, ";");
+            return p;
+        }
+
+        p = strchr(p, ';');
+        if (p != NULL)
+            p++;
+    }
+
+    return NULL;
+}
+
+static
+int vlc_sdp_fmtp_get_ull(const struct vlc_sdp_pt *desc, const char *name,
+                         unsigned long long *restrict res)
+{
+    size_t len;
+    const char *n = vlc_sdp_fmtp_get_str(desc, name, &len);
+    if (n == NULL)
+        return -ENOENT;
+    if (len == 0)
+        return -EINVAL;
+
+    char *end;
+    unsigned long long ull = strtoull(n, &end, 10);
+    if (end != n + len)
+        return -EINVAL;
+
+    *res = ull;
+    return 0;
+}
+
+static inline
+int vlc_sdp_fmtp_get_u16(const struct vlc_sdp_pt *desc, const char *name,
+                         uint16_t *restrict res)
+{
+    unsigned long long ull;
+    int err = vlc_sdp_fmtp_get_ull(desc, name, &ull);
+    if (err == 0) {
+        if (ull >> 16)
+            return -ERANGE;
+
+        *res = ull;
+    }
+    return err;
+}
+
+static inline
+int vlc_sdp_fmtp_get_u8(const struct vlc_sdp_pt *desc, const char *name,
+                        uint8_t *restrict res)
+{
+    unsigned long long ull;
+    int err = vlc_sdp_fmtp_get_ull(desc, name, &ull);
+    if (err == 0) {
+        if (ull >> 8)
+            return -ERANGE;
+
+        *res = ull;
+    }
+    return err;
+}
+
+#define vlc_sdp_fmtp_get(desc, name, vp) \
+    _Generic (*(vp), \
+        uint16_t: vlc_sdp_fmtp_get_u16(desc, name, (uint16_t *)(vp)), \
+        uint8_t:  vlc_sdp_fmtp_get_u8(desc, name, (uint8_t *)(vp)))
+