proxy.java

gcc的组建

      return data;
    }
  } // class ProxyData

  /**
   * Does all the work of building a class. By making this a nested class,
   * this code is not loaded in memory if the VM has a native
   * implementation instead.
   *
   * @author Eric Blake ([e-mail])
   */
  private static final class ClassFactory
  {
    /** Constants for assisting the compilation */
    private static final byte FIELD = 1;
    private static final byte METHOD = 2;
    private static final byte INTERFACE = 3;
    private static final String CTOR_SIG
      = "(Ljava/lang/reflect/InvocationHandler;)V";
    private static final String INVOKE_SIG = "(Ljava/lang/Object;"
      + "Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;";

    /** Bytecodes for insertion in the class definition byte[] */
    private static final char ACONST_NULL = 1;
    private static final char ICONST_0 = 3;
    private static final char BIPUSH = 16;
    private static final char SIPUSH = 17;
    private static final char ILOAD = 21;
    private static final char ILOAD_0 = 26;
    private static final char ALOAD_0 = 42;
    private static final char ALOAD_1 = 43;
    private static final char AALOAD = 50;
    private static final char AASTORE = 83;
    private static final char DUP = 89;
    private static final char DUP_X1 = 90;
    private static final char SWAP = 95;
    private static final char IRETURN = 172;
    private static final char LRETURN = 173;
    private static final char FRETURN = 174;
    private static final char DRETURN = 175;
    private static final char ARETURN = 176;
    private static final char RETURN = 177;
    private static final char GETSTATIC = 178;
    private static final char GETFIELD = 180;
    private static final char INVOKEVIRTUAL = 182;
    private static final char INVOKESPECIAL = 183;
    private static final char INVOKEINTERFACE = 185;
    private static final char NEW = 187;
    private static final char ANEWARRAY = 189;
    private static final char ATHROW = 191;
    private static final char CHECKCAST = 192;

    // Implementation note: we use StringBuffers to hold the byte data, since
    // they automatically grow.  However, we only use the low 8 bits of
    // every char in the array, so we are using twice the necessary memory
    // for the ease StringBuffer provides.

    /** The constant pool. */
    private final StringBuffer pool = new StringBuffer();
    /** The rest of the class data. */
    private final StringBuffer stream = new StringBuffer();

    /** Map of strings to byte sequences, to minimize size of pool. */
    private final Map poolEntries = new HashMap();

    /** The VM name of this proxy class. */
    private final String qualName;

    /**
     * The Method objects the proxy class refers to when calling the
     * invocation handler.
     */
    private final Method[] methods;

    /**
     * Initializes the buffers with the bytecode contents for a proxy class.
     *
     * @param data the remainder of the class data
     * @throws IllegalArgumentException if anything else goes wrong this
     *         late in the game; as far as I can tell, this will only happen
     *         if the constant pool overflows, which is possible even when
     *         the user doesn't exceed the 65535 interface limit
     */
    ClassFactory(ProxyData data)
    {
      methods = data.methods;

      // magic = 0xcafebabe
      // minor_version = 0
      // major_version = 46
      // constant_pool_count: place-holder for now
      pool.append("\u00ca\u00fe\u00ba\u00be\0\0\0\56\0\0");
      // constant_pool[], filled in as we go

      // access_flags
      putU2(Modifier.SUPER | Modifier.FINAL | Modifier.PUBLIC);
      // this_class
      qualName = (data.pack + "$Proxy" + data.id);
      putU2(classInfo(TypeSignature.getEncodingOfClass(qualName, false)));
      // super_class
      putU2(classInfo("java/lang/reflect/Proxy"));

      // interfaces_count
      putU2(data.interfaces.length);
      // interfaces[]
      for (int i = 0; i < data.interfaces.length; i++)
        putU2(classInfo(data.interfaces[i]));

      // Recall that Proxy classes serialize specially, so we do not need
      // to worry about a <clinit> method for this field.  Instead, we
      // just assign it by reflection after the class is successfully loaded.
      // fields_count - private static Method[] m;
      putU2(1);
      // fields[]
      // m.access_flags
      putU2(Modifier.PRIVATE | Modifier.STATIC);
      // m.name_index
      putU2(utf8Info("m"));
      // m.descriptor_index
      putU2(utf8Info("[Ljava/lang/reflect/Method;"));
      // m.attributes_count
      putU2(0);
      // m.attributes[]

      // methods_count - # handler methods, plus <init>
      putU2(methods.length + 1);
      // methods[]
      // <init>.access_flags
      putU2(Modifier.PUBLIC);
      // <init>.name_index
      putU2(utf8Info("<init>"));
      // <init>.descriptor_index
      putU2(utf8Info(CTOR_SIG));
      // <init>.attributes_count - only Code is needed
      putU2(1);
      // <init>.Code.attribute_name_index
      putU2(utf8Info("Code"));
      // <init>.Code.attribute_length = 18
      // <init>.Code.info:
      //   $Proxynn(InvocationHandler h) { super(h); }
      // <init>.Code.max_stack = 2
      // <init>.Code.max_locals = 2
      // <init>.Code.code_length = 6
      // <init>.Code.code[]
      stream.append("\0\0\0\22\0\2\0\2\0\0\0\6" + ALOAD_0 + ALOAD_1
                    + INVOKESPECIAL);
      putU2(refInfo(METHOD, "java/lang/reflect/Proxy", "<init>", CTOR_SIG));
      // <init>.Code.exception_table_length = 0
      // <init>.Code.exception_table[]
      // <init>.Code.attributes_count = 0
      // <init>.Code.attributes[]
      stream.append(RETURN + "\0\0\0\0");

      for (int i = methods.length - 1; i >= 0; i--)
        emitMethod(i, data.exceptions[i]);

      // attributes_count
      putU2(0);
      // attributes[] - empty; omit SourceFile attribute
      // XXX should we mark this with a Synthetic attribute?
    }

    /**
     * Produce the bytecode for a single method.
     *
     * @param i the index of the method we are building
     * @param e the exceptions possible for the method
     */
    private void emitMethod(int i, Class[] e)
    {
      // First, we precalculate the method length and other information.

      Method m = methods[i];
      Class[] paramtypes = m.getParameterTypes();
      int wrap_overhead = 0; // max words taken by wrapped primitive
      int param_count = 1; // 1 for this
      int code_length = 16; // aload_0, getfield, aload_0, getstatic, const,
      // aaload, const/aconst_null, invokeinterface
      if (i > 5)
        {
          if (i > Byte.MAX_VALUE)
            code_length += 2; // sipush
          else
            code_length++; // bipush
        }
      if (paramtypes.length > 0)
        {
          code_length += 3; // anewarray
          if (paramtypes.length > Byte.MAX_VALUE)
            code_length += 2; // sipush
          else if (paramtypes.length > 5)
            code_length++; // bipush
          for (int j = 0; j < paramtypes.length; j++)
            {
              code_length += 4; // dup, const, load, store
              Class type = paramtypes[j];
              if (j > 5)
                {
                  if (j > Byte.MAX_VALUE)
                    code_length += 2; // sipush
                  else
                    code_length++; // bipush
                }
              if (param_count >= 4)
                code_length++; // 2-byte load
              param_count++;
              if (type.isPrimitive())
                {
                  code_length += 7; // new, dup, invokespecial
                  if (type == long.class || type == double.class)
                    {
                      wrap_overhead = 3;
                      param_count++;
                    }
                  else if (wrap_overhead < 2)
                    wrap_overhead = 2;
                }
            }
        }
      int end_pc = code_length;
      Class ret_type = m.getReturnType();
      if (ret_type == void.class)
        code_length++; // return
      else if (ret_type.isPrimitive())
        code_length += 7; // cast, invokevirtual, return
      else
        code_length += 4; // cast, return
      int exception_count = 0;
      boolean throws_throwable = false;
      for (int j = 0; j < e.length; j++)
        if (e[j] == Throwable.class)
          {
            throws_throwable = true;
            break;
          }
      if (! throws_throwable)
        {
          exception_count = e.length + 3; // Throwable, Error, RuntimeException
          code_length += 9; // new, dup_x1, swap, invokespecial, athrow
        }
      int handler_pc = code_length - 1;
      StringBuffer signature = new StringBuffer("(");
      for (int j = 0; j < paramtypes.length; j++)
        signature.append(TypeSignature.getEncodingOfClass(paramtypes[j]));
      signature.append(")").append(TypeSignature.getEncodingOfClass(ret_type));

      // Now we have enough information to emit the method.

      // handler.access_flags
      putU2(Modifier.PUBLIC | Modifier.FINAL);
      // handler.name_index
      putU2(utf8Info(m.getName()));
      // handler.descriptor_index
      putU2(utf8Info(signature.toString()));
      // handler.attributes_count - Code is necessary, Exceptions possible
      putU2(e.length > 0 ? 2 : 1);

      // handler.Code.info:
      //   type name(args) {
      //     try {
      //       return (type) h.invoke(this, methods[i], new Object[] {args});
      //     } catch (<declared Exceptions> e) {
      //       throw e;
      //     } catch (Throwable t) {
      //       throw new UndeclaredThrowableException(t);
      //     }
      //   }
      // Special cases:
      //  if arg_n is primitive, wrap it
      //  if method throws Throwable, try-catch is not needed
      //  if method returns void, return statement not needed
      //  if method returns primitive, unwrap it
      //  save space by sharing code for all the declared handlers

      // handler.Code.attribute_name_index
      putU2(utf8Info("Code"));
      // handler.Code.attribute_length
      putU4(12 + code_length + 8 * exception_count);
      // handler.Code.max_stack
      putU2(param_count == 1 ? 4 : 7 + wrap_overhead);
      // handler.Code.max_locals
      putU2(param_count);
      // handler.Code.code_length
      putU4(code_length);
      // handler.Code.code[]
      putU1(ALOAD_0);
      putU1(GETFIELD);
      putU2(refInfo(FIELD, "java/lang/reflect/Proxy", "h",
                    "Ljava/lang/reflect/InvocationHandler;"));
      putU1(ALOAD_0);
      putU1(GETSTATIC);
      putU2(refInfo(FIELD, TypeSignature.getEncodingOfClass(qualName, false),
                    "m", "[Ljava/lang/reflect/Method;"));
      putConst(i);
      putU1(AALOAD);
      if (paramtypes.length > 0)
        {
          putConst(paramtypes.length);
          putU1(ANEWARRAY);
          putU2(classInfo("java/lang/Object"));
          param_count = 1;
          for (int j = 0; j < paramtypes.length; j++, param_count++)
            {
              putU1(DUP);
              putConst(j);
              if (paramtypes[j].isPrimitive())
                {
                  putU1(NEW);
                  putU2(classInfo(wrapper(paramtypes[j])));
                  putU1(DUP);
                }
              putLoad(param_count, paramtypes[j]);
              if (paramtypes[j].isPrimitive())
                {
                  putU1(INVOKESPECIAL);
                  putU2(refInfo(METHOD, wrapper(paramtypes[j]), "<init>",
                                '(' + (TypeSignature
                                       .getEncodingOfClass(paramtypes[j])
                                       + ")V")));
                  if (paramtypes[j] == long.class
                      || paramtypes[j] == double.class)
                    param_count++;
                }
              putU1(AASTORE);
            }
        }
      else
        putU1(ACONST_NULL);
      putU1(INVOKEINTERFACE);
      putU2(refInfo(INTERFACE, "java/lang/reflect/InvocationHandler",
                    "invoke", INVOKE_SIG));
      putU1(4); // InvocationHandler, this, Method, Object[]
      putU1(0);
      if (ret_type == void.class)
        putU1(RETURN);
      else if (ret_type.isPrimitive())
        {
          putU1(CHECKCAST);
          putU2(classInfo(wrapper(ret_type)));
          putU1(INVOKEVIRTUAL);
          putU2(refInfo(METHOD, wrapper(ret_type),
                        ret_type.getName() + "Value",
                        "()" + TypeSignature.getEncodingOfClass(ret_type)));
          if (ret_type == long.class)
            putU1(LRETURN);
          else if (ret_type == float.class)
            putU1(FRETURN);
          else if (ret_type == double.class)
            putU1(DRETURN);
          else
            putU1(IRETURN);
        }
      else
        {
          putU1(CHECKCAST);
          putU2(classInfo(ret_type));
          putU1(ARETURN);
        }
      if (! throws_throwable)
        {
          putU1(NEW);
          putU2(classInfo("java/lang/reflect/UndeclaredThrowableException"));
          putU1(DUP_X1);
          putU1(SWAP);
          putU1(INVOKESPECIAL);
          putU2(refInfo(METHOD,
                        "java/lang/reflect/UndeclaredThrowableException",
                        "<init>", "(Ljava/lang/Throwable;)V"));
          putU1(ATHROW);
        }

      // handler.Code.exception_table_length
      putU2(exception_count);
      // handler.Code.exception_table[]
      if (! throws_throwable)
        {