Break out parsing of FMTP lines so that others can use it

Intended use is to convert between different representations of "codec".

Bug: webrtc:42226302
Change-Id: If6d985ad17c2ff6018c77c7858e602b9eefa9297
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/350562
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42319}

pc/webrtc_sdp.cc

@@ -3699,6 +3699,27 @@ bool ParseFmtpParam(absl::string_view line,
   return true;
 }
 
+bool ParseFmtpParameterSet(absl::string_view line_params,
+                           webrtc::CodecParameterMap& codec_params,
+                           SdpParseError* error) {
+  // Parse out format specific parameters.
+  for (absl::string_view param :
+       rtc::split(line_params, kSdpDelimiterSemicolonChar)) {
+    std::string name;
+    std::string value;
+    if (!ParseFmtpParam(absl::StripAsciiWhitespace(param), &name, &value,
+                        error)) {
+      return false;
+    }
+    if (codec_params.find(name) != codec_params.end()) {
+      RTC_LOG(LS_INFO) << "Overwriting duplicate fmtp parameter with key \""
+                       << name << "\".";
+    }
+    codec_params[name] = value;
+  }
+  return true;
+}
+
 bool ParseFmtpAttributes(absl::string_view line,
                          const cricket::MediaType media_type,
                          MediaContentDescription* media_desc,
@@ -3736,19 +3757,8 @@ bool ParseFmtpAttributes(absl::string_view line,
 
   // Parse out format specific parameters.
   webrtc::CodecParameterMap codec_params;
-  for (absl::string_view param :
+  if (!ParseFmtpParameterSet(line_params, codec_params, error)) {
-       rtc::split(line_params, kSdpDelimiterSemicolonChar)) {
+    return false;
-    std::string name;
-    std::string value;
-    if (!ParseFmtpParam(absl::StripAsciiWhitespace(param), &name, &value,
-                        error)) {
-      return false;
-    }
-    if (codec_params.find(name) != codec_params.end()) {
-      RTC_LOG(LS_INFO) << "Overwriting duplicate fmtp parameter with key \""
-                       << name << "\".";
-    }
-    codec_params[name] = value;
   }
 
   if (media_type == cricket::MEDIA_TYPE_AUDIO ||

pc/webrtc_sdp.h

@@ -112,6 +112,11 @@ RTC_EXPORT bool ParseCandidate(absl::string_view message,
 bool WriteFmtpParameters(const webrtc::CodecParameterMap& parameters,
                          rtc::StringBuilder* os);
 
+// Parses a string into an FMTP parameter set, in key-value format.
+bool ParseFmtpParameterSet(absl::string_view line_params,
+                           webrtc::CodecParameterMap& codec_params,
+                           SdpParseError* error);
+
 }  // namespace webrtc
 
 #endif  // PC_WEBRTC_SDP_H_

pc/webrtc_sdp_unittest.cc

@@ -5123,3 +5123,24 @@ TEST_F(WebRtcSdpTest, BackfillsDefaultFmtpValues) {
   EXPECT_TRUE(codecs[3].GetParam("tx-mode", &value));
   EXPECT_EQ(value, "SRST");
 }
+
+TEST_F(WebRtcSdpTest, ParsesKeyValueFmtpParameterSet) {
+  std::string params = "key1=value1;key2=value2";
+  webrtc::CodecParameterMap codec_params;
+  SdpParseError error;
+
+  ASSERT_TRUE(webrtc::ParseFmtpParameterSet(params, codec_params, &error));
+  EXPECT_EQ(2U, codec_params.size());
+  EXPECT_EQ(codec_params["key1"], "value1");
+  EXPECT_EQ(codec_params["key2"], "value2");
+}
+
+TEST_F(WebRtcSdpTest, ParsesNonKeyValueFmtpParameterSet) {
+  std::string params = "not-in-key-value-format";
+  webrtc::CodecParameterMap codec_params;
+  SdpParseError error;
+
+  ASSERT_TRUE(webrtc::ParseFmtpParameterSet(params, codec_params, &error));
+  EXPECT_EQ(1U, codec_params.size());
+  EXPECT_EQ(codec_params[""], "not-in-key-value-format");
+}