Merge branch '317816-fix-class-reader-with-empty-file' into 'master'

Resolve "ClassReader constructor goes into infinite loop on zero length input streams"

Closes #317816

See merge request asm/asm!140

asm-test/src/main/java/org/objectweb/asm/test/AsmTest.java

@@ -85,6 +85,10 @@ import java.util.stream.Stream;
  */
 public abstract class AsmTest {
 
+  /** The size of the temporary byte array used to read class input streams chunk by chunk. */
+  private static final int INPUT_STREAM_DATA_CHUNK_SIZE = 4096;
+
+  /** The name of JDK9 module classes. */
   private static final String MODULE_INFO = "module-info";
 
   /**
@@ -436,7 +440,7 @@ public abstract class AsmTest {
     try (InputStream inputStream = ClassLoader.getSystemResourceAsStream(resourceName)) {
       assertNotNull(inputStream, "Class not found " + name);
       ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-      byte[] data = new byte[inputStream.available()];
+      byte[] data = new byte[INPUT_STREAM_DATA_CHUNK_SIZE];
       int bytesRead;
       while ((bytesRead = inputStream.read(data, 0, data.length)) != -1) {
         outputStream.write(data, 0, bytesRead);

asm/src/main/java/org/objectweb/asm/ClassReader.java

@@ -87,6 +87,9 @@ public class ClassReader {
    */
   static final int EXPAND_ASM_INSNS = 256;
 
+  /** The size of the temporary byte array used to read class input streams chunk by chunk. */
+  private static final int INPUT_STREAM_DATA_CHUNK_SIZE = 4096;
+
   /**
    * A byte array containing the JVMS ClassFile structure to be parsed. <i>The content of this array
    * must not be modified. This field is intended for {@link Attribute} sub classes, and is normally
@@ -262,7 +265,7 @@ public class ClassReader {
     }
     try {
       ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-      byte[] data = new byte[inputStream.available()];
+      byte[] data = new byte[INPUT_STREAM_DATA_CHUNK_SIZE];
       int bytesRead;
       while ((bytesRead = inputStream.read(data, 0, data.length)) != -1) {
         outputStream.write(data, 0, bytesRead);

asm/src/test/java/org/objectweb/asm/ClassReaderTest.java

@@ -31,11 +31,13 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.objectweb.asm.test.Assertions.assertThat;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.time.Duration;
 import java.util.concurrent.atomic.AtomicBoolean;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -185,6 +187,27 @@ public class ClassReaderTest extends AsmTest implements Opcodes {
     assertNotNull(classReader.getInterfaces());
   }
 
+  /** Tests {@link ClassReader(java.io.InputStream)} with an empty stream. */
+  @Test
+  public void testStreamConstructorWithEmptyStream() throws IOException {
+    InputStream inputStream =
+        new InputStream() {
+
+          @Override
+          public int available() throws IOException {
+            return 0;
+          }
+
+          @Override
+          public int read() throws IOException {
+            return -1;
+          }
+        };
+    assertTimeoutPreemptively(
+        Duration.ofMillis(100),
+        () -> assertThrows(RuntimeException.class, () -> new ClassReader(inputStream)));
+  }
+
   /** Tests the ClassReader accept method with a default visitor. */
   @ParameterizedTest
   @MethodSource(ALL_CLASSES_AND_ALL_APIS)