Inline character unescaping. This saves ~10% on the READER_LONG benchmark.

gson/src/main/java/com/google/gson/stream/JsonReader.java

@@ -1145,9 +1145,23 @@ public class JsonReader implements Closeable {
       if (pos + 4 > limit && !fillBuffer(4)) {
         throw syntaxError("Unterminated escape sequence");
       }
-      String hex = stringPool.get(buffer, pos, 4);
+      // Equivalent to Integer.parseInt(stringPool.get(buffer, pos, 4), 16);
+      char result = 0;
+      for (int i = pos, end = i + 4; i < end; i++) {
+        char c = buffer[i];
+        result <<= 4;
+        if (c >= '0' && c <= '9') {
+          result += (c - '0');
+        } else if (c >= 'a' && c <= 'f') {
+          result += (c - 'a' + 10);
+        } else if (c >= 'A' && c <= 'F') {
+          result += (c - 'A' + 10);
+        } else {
+          throw new NumberFormatException("\\u" + stringPool.get(buffer, pos, 4));
+        }
+      }
       pos += 4;
-      return (char) Integer.parseInt(hex, 16);
+      return result;
 
     case 't':
       return '\t';

gson/src/test/java/com/google/gson/stream/JsonReaderTest.java

@@ -161,6 +161,28 @@ public final class JsonReaderTest extends TestCase {
     assertEquals(JsonToken.END_DOCUMENT, reader.peek());
   }
 
+  public void testUnescapingInvalidCharacters() throws IOException {
+    String json = "[\"\\u000g\"]";
+    JsonReader reader = new JsonReader(new StringReader(json));
+    reader.beginArray();
+    try {
+      reader.nextString();
+      fail();
+    } catch (NumberFormatException expected) {
+    }
+  }
+
+  public void testUnescapingTruncatedCharacters() throws IOException {
+    String json = "[\"\\u000";
+    JsonReader reader = new JsonReader(new StringReader(json));
+    reader.beginArray();
+    try {
+      reader.nextString();
+      fail();
+    } catch (IOException expected) {
+    }
+  }
+
   public void testIntegersWithFractionalPartSpecified() throws IOException {
     JsonReader reader = new JsonReader(new StringReader("[1.0,1.0,1.0]"));
     reader.beginArray();