uinput: don't read next line of evemu recording until peek

When EvemuParser "accepts" a line of an evemu recording (i.e. it's found
the line type it was expecting and is ready to process it), it calls
CommentAwareReader#advance() before processing the current line.
advance() was reading the next line of the file, ready for peeking,
even though the current line hadn't been processed yet.

When playing from standard input, this meant that a line wouldn't be
executed until the next one was written, requiring a no-op line to be
added to the end of event recordings. To fix this, only load the next
line when peekLine() is called after the advance().

Test: $ atest --host UinputTestsRavenwood
Test: $ atest InputTests:com.android.test.input.UinputRecordingIntegrationTests
Bug: 367419268
Flag: TEST_ONLY
Change-Id: I69c2cb651cd871ea0ceea9702c66b76abb37285a

1 files changed, 22 insertions, 11 deletions

diff --git a/cmds/uinput/src/com/android/commands/uinput/EvemuParser.java b/cmds/uinput/src/com/android/commands/uinput/EvemuParser.java
index da991624e685..d3e62d5351f0 100644
--- a/cmds/uinput/src/com/android/commands/uinput/EvemuParser.java
+++ b/cmds/uinput/src/com/android/commands/uinput/EvemuParser.java
@@ -48,12 +48,17 @@ public class EvemuParser implements EventParser {
 
     private static class CommentAwareReader {
         private final LineNumberReader mReader;
-        private String mPreviousLine;
-        private String mNextLine;
+        /** The previous line of the file, or {@code null} if we're at the start of the file. */
+        private @Nullable String mPreviousLine;
+        /**
+         * The next line of the file to be returned from {@link #peekLine()}, or {@code null} if we
+         * haven't peeked since the last {@link #advance()} or are at the end of the file.
+         */
+        private @Nullable String mNextLine;
+        private boolean mAtEndOfFile = false;
 
-        CommentAwareReader(LineNumberReader in) throws IOException {
+        CommentAwareReader(LineNumberReader in) {
             mReader = in;
-            mNextLine = findNextLine();
         }
 
         private @Nullable String findNextLine() throws IOException {
@@ -61,7 +66,7 @@ public class EvemuParser implements EventParser {
             while (line != null && line.length() == 0) {
                 String unstrippedLine = mReader.readLine();
                 if (unstrippedLine == null) {
-                    // End of file.
+                    mAtEndOfFile = true;
                     return null;
                 }
                 line = stripComments(unstrippedLine);
@@ -85,22 +90,28 @@ public class EvemuParser implements EventParser {
          * {@code null} if the end of the file is reached. However, it does not advance to the
          * next line of the file.
          */
-        public @Nullable String peekLine() {
+        public @Nullable String peekLine() throws IOException {
+            if (mNextLine == null && !mAtEndOfFile) {
+                mNextLine = findNextLine();
+            }
             return mNextLine;
         }
 
         /** Moves to the next line of the file. */
-        public void advance() throws IOException {
+        public void advance() {
             mPreviousLine = mNextLine;
-            mNextLine = findNextLine();
+            mNextLine = null;
         }
 
         public boolean isAtEndOfFile() {
-            return mNextLine == null;
+            return mAtEndOfFile;
         }
 
-        /** Returns the previous line, for error messages. */
-        public String getPreviousLine() {
+        /**
+         * Returns the previous line, for error messages. Will be {@code null} if we're at the start
+         * of the file.
+         */
+        public @Nullable String getPreviousLine() {
             return mPreviousLine;
         }