FrameOptions.java

package org.pitest.bytecode;

import org.objectweb.asm.ClassWriter;

public class FrameOptions {

  private static final int JAVA_7 = 51;

  /**
   * Java 7 and above require frame info for class version above 7. The ASM
   * compute frame options does not support the JSR opcode used by some pre 7
   * compilers when generating java 5 bytecode.
   *
   * We dodge this issue by only computing frames for classes with a version
   * above 6.
   *
   * @param bs
   *          a class
   * @return appropriate flags
   */
  public static int pickFlags(byte[] bs) {
    if (needsFrames(bs)) {
      return ClassWriter.COMPUTE_FRAMES;
    }
    return ClassWriter.COMPUTE_MAXS;
  }

  public static boolean needsFrames(byte[] bs) {
    short majorVersion = (short) (((bs[6] & 0xFF) << 8) | (bs[7] & 0xFF));
    return majorVersion >= JAVA_7;
  }

}