Add some nullness annotations, re-jig some logic and reformat

libraries/common/src/main/java/androidx/media3/common/util/Util.java

@@ -212,7 +212,7 @@ public final class Util {
   private static final String ISM_HLS_FORMAT_EXTENSION = "format=m3u8-aapl";
   private static final String ISM_DASH_FORMAT_EXTENSION = "format=mpd-time-csf";
 
-  private static final int INFLATE_HEADER = 0x78;
+  private static final int ZLIB_INFLATE_HEADER = 0x78;
 
   // Replacement map of ISO language codes used for normalization.
   @Nullable private static HashMap<String, String> languageTagReplacementMap;
@@ -3105,25 +3105,23 @@ public final class Util {
   }
 
   /**
-   * Uncompresses the data in {@code input} if it starts with {@code INFLATE_HEADER}
+   * Uncompresses the data in {@code input} if it starts with the zlib marker {@code 0x78}.
-   * ({@code 0x78}).
    *
    * @param input Wraps the compressed input data.
    * @param output Wraps an output buffer to be used to store the uncompressed data. If {@code
    *     output.data} isn't big enough to hold the uncompressed data, a new array is created. If
    *     {@code true} is returned then the output's position will be set to 0 and its limit will be
    *     set to the length of the uncompressed data.
-   * @param inflater If not null, used to uncompressed the input. Otherwise a new {@link Inflater}
+   * @param inflater If not null, used to uncompress the input. Otherwise a new {@link Inflater} is
-   *     is created.
+   *     created.
    * @return Whether the input is uncompressed successfully.
    */
   @UnstableApi
   public static boolean maybeInflate(
       ParsableByteArray input, ParsableByteArray output, @Nullable Inflater inflater) {
-    if (input.bytesLeft() > 0 && input.peekUnsignedByte() == INFLATE_HEADER) {
+    return input.bytesLeft() > 0
-        return inflate(input, output, inflater);
+        && input.peekUnsignedByte() == ZLIB_INFLATE_HEADER
-    }
+        && inflate(input, output, inflater);
-    return false;
   }
 
   /**

libraries/extractor/src/main/java/androidx/media3/extractor/text/DefaultSubtitleParserFactory.java

@@ -22,11 +22,11 @@ import androidx.media3.common.MimeTypes;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.extractor.text.dvb.DvbParser;
 import androidx.media3.extractor.text.pgs.PgsParser;
-import androidx.media3.extractor.text.vobsub.VobsubParser;
 import androidx.media3.extractor.text.ssa.SsaParser;
 import androidx.media3.extractor.text.subrip.SubripParser;
 import androidx.media3.extractor.text.ttml.TtmlParser;
 import androidx.media3.extractor.text.tx3g.Tx3gParser;
+import androidx.media3.extractor.text.vobsub.VobsubParser;
 import androidx.media3.extractor.text.webvtt.Mp4WebvttParser;
 import androidx.media3.extractor.text.webvtt.WebvttParser;
 import java.util.Objects;

libraries/extractor/src/main/java/androidx/media3/extractor/text/vobsub/VobsubParser.java

@@ -1,8 +1,10 @@
 package androidx.media3.extractor.text.vobsub;
 
 import static java.lang.Math.min;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 import android.graphics.Bitmap;
+import android.graphics.Rect;
 import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
@@ -16,12 +18,10 @@ import androidx.media3.common.util.Util;
 import androidx.media3.extractor.text.CuesWithTiming;
 import androidx.media3.extractor.text.SubtitleParser;
 import com.google.common.collect.ImmutableList;
-import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.zip.Inflater;
-import android.graphics.Rect;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 // Much of this is taken from or very similar to PgsParser
 
@@ -36,19 +36,18 @@ public final class VobsubParser implements SubtitleParser {
   public static final @CueReplacementBehavior int CUE_REPLACEMENT_BEHAVIOR =
       Format.CUE_REPLACEMENT_BEHAVIOR_REPLACE;
 
-  private static final int DEFAULT_DURATION = 5000000;
+  private static final int DEFAULT_DURATION_US = 5_000_000;
 
-  private final ParsableByteArray buffer;
+  private final ParsableByteArray scratch;
-  private final ParsableByteArray inflatedBuffer;
+  private final ParsableByteArray inflatedScratch;
   private final CueBuilder cueBuilder;
   @Nullable private Inflater inflater;
 
   public VobsubParser(List<byte[]> initializationData) {
-
+    scratch = new ParsableByteArray();
-    buffer = new ParsableByteArray();
+    inflatedScratch = new ParsableByteArray();
-    inflatedBuffer = new ParsableByteArray();
     cueBuilder = new CueBuilder();
-    cueBuilder.parseIdx(new String(initializationData.get(0), StandardCharsets.UTF_8));
+    cueBuilder.parseIdx(new String(initializationData.get(0), UTF_8));
   }
 
   @Override
@@ -63,32 +62,33 @@ public final class VobsubParser implements SubtitleParser {
       int length,
       OutputOptions outputOptions,
       Consumer<CuesWithTiming> output) {
-
+    scratch.reset(data, offset + length);
-    buffer.reset(data, offset + length);
+    scratch.setPosition(offset);
-    buffer.setPosition(offset);
+    @Nullable Cue cue = parse();
-    if (inflater == null) {
-      inflater = new Inflater();
-    }
-    if (Util.maybeInflate(buffer, inflatedBuffer, inflater)) {
-      buffer.reset(inflatedBuffer.getData(), inflatedBuffer.limit());
-    }
-    cueBuilder.reset();
-    Cue cue = null;
-
-    int blen = buffer.bytesLeft();
-    if (blen >= 2) {
-      int len = buffer.readUnsignedShort();
-
-      if (len == blen) {
-        cueBuilder.parseSpu(buffer);
-        cue = cueBuilder.build(buffer);
-      }
-    }
     output.accept(
         new CuesWithTiming(
             cue != null ? ImmutableList.of(cue) : ImmutableList.of(),
             /* startTimeUs= */ C.TIME_UNSET,
-                 /* durationUs= */ DEFAULT_DURATION));
+            /* durationUs= */ DEFAULT_DURATION_US));
+  }
+
+  @Nullable
+  private Cue parse() {
+    if (inflater == null) {
+      inflater = new Inflater();
+    }
+    if (Util.maybeInflate(scratch, inflatedScratch, inflater)) {
+      scratch.reset(inflatedScratch.getData(), inflatedScratch.limit());
+    }
+    cueBuilder.reset();
+    Cue cue = null;
+
+    int bytesLeft = scratch.bytesLeft();
+    if (bytesLeft < 2 || scratch.readUnsignedShort() != bytesLeft) {
+      return null;
+    }
+    cueBuilder.parseSpu(scratch);
+    return cueBuilder.build(scratch);
   }
 
   private static final class CueBuilder {
@@ -99,16 +99,17 @@ public final class VobsubParser implements SubtitleParser {
     private static final int CMD_OFFSETS = 6;
     private static final int CMD_END = 255;
 
+    private final int[] colors;
+
     private boolean hasPlane;
     private boolean hasColors;
     private boolean hasDataOffsets;
-    private int[] palette;
+    private int @MonotonicNonNull [] palette;
     private int planeWidth;
     private int planeHeight;
-    private int[] colors;
+    private @Nullable Rect boundingBox;
-    private Rect boundingBox;
+    private int dataOffset0;
-    private int dataOffset0, dataOffset1;
+    private int dataOffset1;
-    private int dataSize;
 
     public CueBuilder() {
       colors = new int[4];
@@ -124,10 +125,8 @@ public final class VobsubParser implements SubtitleParser {
             palette[i] = parseColor(values[i].trim());
           }
         } else if (line.startsWith("size: ")) {
-
+          // We need this line to calculate the relative positions and size required when building
-          // NOTE: we need this line to calculate the relative positions
+          // the Cue below.
-          //       and size required by Cue.Builder() below.
-
           String[] sizes = Util.split(line.substring("size: ".length()).trim(), "x");
 
           if (sizes.length == 2) {
@@ -151,42 +150,38 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     public void parseSpu(ParsableByteArray buffer) {
-
+      if (palette == null || !hasPlane) {
         // Give up if we don't have the color palette or the video size.
-      // (See also the NOTE above)
+        return;
-
+      }
-      if (palette == null || !hasPlane) return;
+      buffer.skipBytes(buffer.readUnsignedShort());
-
-      int pos = buffer.getPosition();
-
-      dataSize = buffer.readUnsignedShort();
-      pos += dataSize;
-      buffer.setPosition(pos);
-
       int end = buffer.readUnsignedShort();
       parseControl(buffer, end);
     }
 
     private void parseControl(ParsableByteArray buffer, int end) {
-
       while (buffer.getPosition() < end && buffer.bytesLeft() > 0) {
         switch (buffer.readUnsignedByte()) {
           case CMD_COLORS:
-            if (!parseControlColors(buffer)) return;
+            if (!parseControlColors(buffer)) {
+              return;
+            }
             break;
-
           case CMD_ALPHA:
-            if (!parseControlAlpha(buffer)) return;
+            if (!parseControlAlpha(buffer)) {
+              return;
+            }
             break;
-
           case CMD_AREA:
-            if (!parseControlArea(buffer)) return;
+            if (!parseControlArea(buffer)) {
+              return;
+            }
             break;
-
           case CMD_OFFSETS:
-            if (!parseControlOffsets(buffer)) return;
+            if (!parseControlOffsets(buffer)) {
+              return;
+            }
             break;
-
           case CMD_END:
             return;
         }
@@ -194,7 +189,9 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     private boolean parseControlColors(ParsableByteArray buffer) {
-      if (buffer.bytesLeft() < 2) return false;
+      if (buffer.bytesLeft() < 2) {
+        return false;
+      }
 
       int byte0 = buffer.readUnsignedByte();
       int byte1 = buffer.readUnsignedByte();
@@ -209,7 +206,9 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     private boolean parseControlAlpha(ParsableByteArray buffer) {
-      if (buffer.bytesLeft() < 2) return false;
+      if (buffer.bytesLeft() < 2) {
+        return false;
+      }
 
       int byte0 = buffer.readUnsignedByte();
       int byte1 = buffer.readUnsignedByte();
@@ -223,7 +222,9 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     private boolean parseControlArea(ParsableByteArray buffer) {
-      if (buffer.bytesLeft() < 6) return false;
+      if (buffer.bytesLeft() < 6) {
+        return false;
+      }
 
       int byte0 = buffer.readUnsignedByte();
       int byte1 = buffer.readUnsignedByte();
@@ -245,7 +246,9 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     private boolean parseControlOffsets(ParsableByteArray buffer) {
-      if (buffer.bytesLeft() < 4) return false;
+      if (buffer.bytesLeft() < 4) {
+        return false;
+      }
 
       dataOffset0 = buffer.readUnsignedShort();
       dataOffset1 = buffer.readUnsignedShort();
@@ -255,8 +258,7 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     private int getColor(int index) {
-      if (index >= 0 && index < palette.length) return palette[index];
+      return index >= 0 && index < palette.length ? palette[index] : palette[0];
-      return palette[0];
     }
 
     private int setAlpha(int color, int alpha) {
@@ -283,7 +285,9 @@ public final class VobsubParser implements SubtitleParser {
       bitBuffer.reset(buffer);
       parseRleData(bitBuffer, 1, bitmapData);
 
-      Bitmap bitmap = Bitmap.createBitmap(bitmapData, boundingBox.width(), boundingBox.height(), Bitmap.Config.ARGB_8888);
+      Bitmap bitmap =
+          Bitmap.createBitmap(
+              bitmapData, boundingBox.width(), boundingBox.height(), Bitmap.Config.ARGB_8888);
 
       return new Cue.Builder()
           .setBitmap(bitmap)
@@ -297,9 +301,9 @@ public final class VobsubParser implements SubtitleParser {
     }
 
     /**
-     * Parse run-length encoded data into the {@code bitmapData} array. The
+     * Parse run-length encoded data into the {@code bitmapData} array. The subtitle bitmap is
-     * subtitle bitmap is encoded in two blocks of interlaced lines, {@code y}
+     * encoded in two blocks of interlaced lines, {@code y} gives the index of the starting line (0
-     * gives the index of the starting line (0 or 1).
+     * or 1).
      *
      * @param bitBuffer The RLE encoded data.
      * @param y Index of the first line.
@@ -316,7 +320,6 @@ public final class VobsubParser implements SubtitleParser {
         parseRun(bitBuffer, run);
 
         int length = min(run.length, width - x);
-
         if (length > 0) {
           Arrays.fill(bitmapData, outIndex, outIndex + length, run.color);
           outIndex += length;