Add support for variable substition in HLS

Issue:#4422

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=209958623

RELEASENOTES.md

@@ -70,6 +70,8 @@
   * Allow configuration of the Loader retry delay
     ([#3370](https://github.com/google/ExoPlayer/issues/3370)).
 * HLS:
+  * Add support for variable substitution
+    ([#4422](https://github.com/google/ExoPlayer/issues/4422)).
   * Add support for PlayReady.
   * Add support for alternative EXT-X-KEY tags.
   * Set the bitrate on primary track sample formats

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsMasterPlaylist.java

@@ -21,6 +21,7 @@ import com.google.android.exoplayer2.util.MimeTypes;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 
 /** Represents an HLS master playlist. */
 public final class HlsMasterPlaylist extends HlsPlaylist {
@@ -35,7 +36,8 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
           /* subtitles= */ Collections.emptyList(),
           /* muxedAudioFormat= */ null,
           /* muxedCaptionFormats= */ Collections.emptyList(),
-          /* hasIndependentSegments= */ false);
+          /* hasIndependentSegments= */ false,
+          /* variableDefinitions= */ Collections.emptyMap());
 
   public static final int GROUP_INDEX_VARIANT = 0;
   public static final int GROUP_INDEX_AUDIO = 1;
@@ -110,6 +112,8 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
    * captions information.
    */
   public final List<Format> muxedCaptionFormats;
+  /** Contains variable definitions, as defined by the #EXT-X-DEFINE tag. */
+  public final Map<String, String> variableDefinitions;
 
   /**
    * @param baseUri See {@link #baseUri}.
@@ -120,6 +124,7 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
    * @param muxedAudioFormat See {@link #muxedAudioFormat}.
    * @param muxedCaptionFormats See {@link #muxedCaptionFormats}.
    * @param hasIndependentSegments See {@link #hasIndependentSegments}.
+   * @param variableDefinitions See {@link #variableDefinitions}.
    */
   public HlsMasterPlaylist(
       String baseUri,
@@ -129,7 +134,8 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
       List<HlsUrl> subtitles,
       Format muxedAudioFormat,
       List<Format> muxedCaptionFormats,
-      boolean hasIndependentSegments) {
+      boolean hasIndependentSegments,
+      Map<String, String> variableDefinitions) {
     super(baseUri, tags, hasIndependentSegments);
     this.variants = Collections.unmodifiableList(variants);
     this.audios = Collections.unmodifiableList(audios);
@@ -137,6 +143,7 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
     this.muxedAudioFormat = muxedAudioFormat;
     this.muxedCaptionFormats = muxedCaptionFormats != null
         ? Collections.unmodifiableList(muxedCaptionFormats) : null;
+    this.variableDefinitions = Collections.unmodifiableMap(variableDefinitions);
   }
 
   @Override
@@ -149,7 +156,8 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
         copyRenditionsList(subtitles, GROUP_INDEX_SUBTITLE, streamKeys),
         muxedAudioFormat,
         muxedCaptionFormats,
-        hasIndependentSegments);
+        hasIndependentSegments,
+        variableDefinitions);
   }
 
   /**
@@ -169,7 +177,8 @@ public final class HlsMasterPlaylist extends HlsPlaylist {
         emptyList,
         /* muxedAudioFormat= */ null,
         /* muxedCaptionFormats= */ null,
-        /* hasIndependentSegments= */ false);
+        /* hasIndependentSegments= */ false,
+        /* variableDefinitions= */ Collections.emptyMap());
   }
 
   private static List<HlsUrl> copyRenditionsList(

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/HlsMasterPlaylistParserTest.java

@@ -117,6 +117,15 @@ public class HlsMasterPlaylistParserTest {
           + "#EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS=\"mp4a.40.2 , avc1.66.30 \"\n"
           + "http://example.com/spaces_in_codecs.m3u8\n";
 
+  private static final String PLAYLIST_WITH_VARIABLE_SUBSTITUTION =
+      " #EXTM3U \n"
+          + "\n"
+          + "#EXT-X-DEFINE:NAME=\"codecs\",VALUE=\"mp4a.40.5\"\n"
+          + "#EXT-X-DEFINE:NAME=\"tricky\",VALUE=\"This/{$nested}/reference/shouldnt/work\"\n"
+          + "#EXT-X-DEFINE:NAME=\"nested\",VALUE=\"This should not be inserted\"\n"
+          + "#EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS=\"{$codecs}\"\n"
+          + "http://example.com/{$tricky}\n";
+
   @Test
   public void testParseMasterPlaylist() throws IOException {
     HlsMasterPlaylist masterPlaylist = parseMasterPlaylist(PLAYLIST_URI, PLAYLIST_SIMPLE);
@@ -218,6 +227,15 @@ public class HlsMasterPlaylistParserTest {
     assertThat(playlistWithoutIndependentSegments.hasIndependentSegments).isFalse();
   }
 
+  @Test
+  public void testVariableSubstitution() throws IOException {
+    HlsMasterPlaylist playlistWithSubstitutions =
+        parseMasterPlaylist(PLAYLIST_URI, PLAYLIST_WITH_VARIABLE_SUBSTITUTION);
+    HlsMasterPlaylist.HlsUrl variant = playlistWithSubstitutions.variants.get(0);
+    assertThat(variant.format.codecs).isEqualTo("mp4a.40.5");
+    assertThat(variant.url).isEqualTo("http://example.com/This/{$nested}/reference/shouldnt/work");
+  }
+
   private static HlsMasterPlaylist parseMasterPlaylist(String uri, String playlistString)
       throws IOException {
     Uri playlistUri = Uri.parse(uri);

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/HlsMediaPlaylistParserTest.java

@@ -25,6 +25,7 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -397,9 +398,71 @@ public class HlsMediaPlaylistParserTest {
             /* subtitles= */ Collections.emptyList(),
             /* muxedAudioFormat= */ null,
             /* muxedCaptionFormats= */ null,
-            /* hasIndependentSegments= */ true);
+            /* hasIndependentSegments= */ true,
+            /* variableDefinitions */ Collections.emptyMap());
     HlsMediaPlaylist playlistWithInheritance =
         (HlsMediaPlaylist) new HlsPlaylistParser(masterPlaylist).parse(playlistUri, inputStream);
     assertThat(playlistWithInheritance.hasIndependentSegments).isTrue();
   }
+
+  @Test
+  public void testVariableSubstitution() throws IOException {
+    Uri playlistUri = Uri.parse("https://example.com/substitution.m3u8");
+    String playlistString =
+        "#EXTM3U\n"
+            + "#EXT-X-VERSION:8\n"
+            + "#EXT-X-DEFINE:NAME=\"underscore_1\",VALUE=\"{\"\n"
+            + "#EXT-X-DEFINE:NAME=\"dash-1\",VALUE=\"replaced_value.ts\"\n"
+            + "#EXT-X-TARGETDURATION:5\n"
+            + "#EXT-X-MEDIA-SEQUENCE:10\n"
+            + "#EXTINF:5.005,\n"
+            + "segment1.ts\n"
+            + "#EXT-X-MAP:URI=\"{$dash-1}\""
+            + "#EXTINF:5.005,\n"
+            + "segment{$underscore_1}$name_1}\n";
+    InputStream inputStream = new ByteArrayInputStream(Util.getUtf8Bytes(playlistString));
+    HlsMediaPlaylist playlist =
+        (HlsMediaPlaylist) new HlsPlaylistParser().parse(playlistUri, inputStream);
+    Segment segment = playlist.segments.get(1);
+    assertThat(segment.initializationSegment.url).isEqualTo("replaced_value.ts");
+    assertThat(segment.url).isEqualTo("segment{$name_1}");
+  }
+
+  @Test
+  public void testInheritedVariableSubstitution() throws IOException {
+    Uri playlistUri = Uri.parse("https://example.com/test3.m3u8");
+    String playlistString =
+        "#EXTM3U\n"
+            + "#EXT-X-VERSION:8\n"
+            + "#EXT-X-TARGETDURATION:5\n"
+            + "#EXT-X-MEDIA-SEQUENCE:10\n"
+            + "#EXT-X-DEFINE:IMPORT=\"imported_base\"\n"
+            + "#EXTINF:5.005,\n"
+            + "{$imported_base}1.ts\n"
+            + "#EXTINF:5.005,\n"
+            + "{$imported_base}2.ts\n"
+            + "#EXTINF:5.005,\n"
+            + "{$imported_base}3.ts\n"
+            + "#EXTINF:5.005,\n"
+            + "{$imported_base}4.ts\n";
+    InputStream inputStream = new ByteArrayInputStream(Util.getUtf8Bytes(playlistString));
+    HashMap<String, String> variableDefinitions = new HashMap<>();
+    variableDefinitions.put("imported_base", "long_path");
+    HlsMasterPlaylist masterPlaylist =
+        new HlsMasterPlaylist(
+            /* baseUri= */ "",
+            /* tags= */ Collections.emptyList(),
+            /* variants= */ Collections.emptyList(),
+            /* audios= */ Collections.emptyList(),
+            /* subtitles= */ Collections.emptyList(),
+            /* muxedAudioFormat= */ null,
+            /* muxedCaptionFormats= */ Collections.emptyList(),
+            /* hasIndependentSegments= */ false,
+            variableDefinitions);
+    HlsMediaPlaylist playlist =
+        (HlsMediaPlaylist) new HlsPlaylistParser(masterPlaylist).parse(playlistUri, inputStream);
+    for (int i = 1; i <= 4; i++) {
+      assertThat(playlist.segments.get(i - 1).url).isEqualTo("long_path" + i + ".ts");
+    }
+  }
 }