/*

 * Copyright 1997-2005 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

// A BytecodeStream is used for fast iteration over the bytecodes

// of a methodOop.

//

// Usage:

//

// BytecodeStream s(method);

// Bytecodes::Code c;

// while ((c = s.next()) >= 0) {

//   ...

// }

//

// A RawBytecodeStream is a simple version of BytecodeStream.

// It is used ONLY when we know the bytecodes haven't been rewritten

// yet, such as in the rewriter or the verifier. Currently only the

// verifier uses this class.

class RawBytecodeStream: StackObj {

 protected:

  // stream buffer

  methodHandle    _method;                       // read from method directly

  // reading position

  int             _bci;                          // bci if current bytecode

  int             _next_bci;                     // bci of next bytecode

  int             _end_bci;                      // bci after the current iteration interval

  // last bytecode read

  Bytecodes::Code _code;

  bool            _is_wide;

 public:

  // Construction

  RawBytecodeStream(methodHandle method) : _method(method) {

    set_interval(0, _method->code_size());

  }

  // Iteration control

  void set_interval(int beg_bci, int end_bci) {

    // iterate over the interval [beg_bci, end_bci)

    assert(0 <= beg_bci && beg_bci <= method()->code_size(), "illegal beg_bci");

    assert(0 <= end_bci && end_bci <= method()->code_size(), "illegal end_bci");

    // setup of iteration pointers

    _bci      = beg_bci;

    _next_bci = beg_bci;

    _end_bci  = end_bci;

  }

  void set_start   (int beg_bci) {

    set_interval(beg_bci, _method->code_size());

  }

  // Iteration

  // Use raw_next() rather than next() for faster method reference

  Bytecodes::Code raw_next() {

    Bytecodes::Code code;

    // set reading position

    _bci = _next_bci;

    assert(!is_last_bytecode(), "caller should check is_last_bytecode()");

    address bcp = RawBytecodeStream::bcp();

    code        = Bytecodes::code_or_bp_at(bcp);

    // set next bytecode position

    int l = Bytecodes::length_for(code);

    if (l > 0 && (_bci + l) <= _end_bci) {

      assert(code != Bytecodes::_wide && code != Bytecodes::_tableswitch

             && code != Bytecodes::_lookupswitch, "can't be special bytecode");

      _is_wide = false;

      _next_bci += l;

      _code = code;

      return code;

    } else if (code == Bytecodes::_wide && _bci + 1 >= _end_bci) {

      return Bytecodes::_illegal;

    } else {

      return raw_next_special(code);

    }

  }

  Bytecodes::Code raw_next_special(Bytecodes::Code code);

  // Stream attributes

  methodHandle    method() const                 { return _method; }

  int             bci() const                    { return _bci; }

  int             next_bci() const               { return _next_bci; }

  int             end_bci() const                { return _end_bci; }

  Bytecodes::Code code() const                   { return _code; }

  bool            is_wide() const                { return _is_wide; }

  bool            is_last_bytecode() const       { return _next_bci >= _end_bci; }

  address         bcp() const                    { return method()->code_base() + _bci; }

  address         next_bcp()                     { return method()->code_base() + _next_bci; }

  // State changes

  void            set_next_bci(int bci)          { assert(0 <= bci && bci <= method()->code_size(), "illegal bci"); _next_bci = bci; }

  // Bytecode-specific attributes

  int             dest() const                   { return bci() + (short)Bytes::get_Java_u2(bcp() + 1); }

  int             dest_w() const                 { return bci() + (int  )Bytes::get_Java_u4(bcp() + 1); }

  // Unsigned indices, widening

  int             get_index() const              { return (is_wide()) ? Bytes::get_Java_u2(bcp() + 2) : bcp()[1]; }

  int             get_index_big() const          { return (int)Bytes::get_Java_u2(bcp() + 1);  }

};

// In BytecodeStream, non-java bytecodes will be translated into the

// corresponding java bytecodes.

class BytecodeStream: public RawBytecodeStream {

 public:

  // Construction

  BytecodeStream(methodHandle method) : RawBytecodeStream(method) { }

  // Iteration

  Bytecodes::Code next() {

    Bytecodes::Code code;

    // set reading position

    _bci = _next_bci;

    if (is_last_bytecode()) {

      // indicate end of bytecode stream

      code = Bytecodes::_illegal;

    } else {

      // get bytecode

      address bcp = BytecodeStream::bcp();

      code        = Bytecodes::java_code_at(bcp);

      // set next bytecode position

      //

      // note that we cannot advance before having the

      // tty bytecode otherwise the stepping is wrong!

      // (carefull: length_for(...) must be used first!)

      int l = Bytecodes::length_for(code);

      if (l == 0) l = Bytecodes::length_at(bcp);

      _next_bci  += l;

      assert(_bci < _next_bci, "length must be > 0");

      // set attributes

      _is_wide      = false;

      // check for special (uncommon) cases

      if (code == Bytecodes::_wide) {

        code = (Bytecodes::Code)bcp[1];

        _is_wide = true;

      }

      assert(Bytecodes::is_java_code(code), "sanity check");

    }

    _code = code;

    return _code;

  }

  bool            is_active_breakpoint() const   { return Bytecodes::is_active_breakpoint_at(bcp()); }

};