/*

 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.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.

// Here is the common base class for both RawBytecodeStream and BytecodeStream:

class BaseBytecodeStream: 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 _raw_code;

  bool            _is_wide;

  bool            _is_raw;                       // false in 'cooked' BytecodeStream

  // Construction

  BaseBytecodeStream(methodHandle method) : _method(method) {

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

    _is_raw = false;

  }

 public:

  // 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());

  }

  bool is_raw() const { return _is_raw; }

  // 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 raw_code() const               { return _raw_code; }

  bool            is_wide() const                { return _is_wide; }

  int             instruction_size() const       { return (_next_bci - _bci); }

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

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

  Bytecode*       bytecode() const               { return Bytecode_at(bcp()); }

  // 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() + bytecode()->get_offset_s2(raw_code()); }

  int             dest_w() const                 { return bci() + bytecode()->get_offset_s4(raw_code()); }

  // One-byte indices.

  int             get_index_u1() const           { assert_raw_index_size(1); return *(jubyte*)(bcp()+1); }

 protected:

  void assert_raw_index_size(int size) const NOT_DEBUG_RETURN;

  void assert_raw_stream(bool want_raw) const NOT_DEBUG_RETURN;

};

class RawBytecodeStream: public BaseBytecodeStream {

 public:

  // Construction

  RawBytecodeStream(methodHandle method) : BaseBytecodeStream(method) {

    _is_raw = true;

  }

 public:

  // 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 = this->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;

      _raw_code = code;

      return code;

    } else {

      return raw_next_special(code);

    }

  }

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

  // Unsigned indices, widening, with no swapping of bytes

  int             get_index() const          { return (is_wide()) ? get_index_u2_raw(bcp() + 2) : get_index_u1(); }

  // Get an unsigned 2-byte index, with no swapping of bytes.

  int             get_index_u2() const       { assert(!is_wide(), ""); return get_index_u2_raw(bcp() + 1);  }

 private:

  int get_index_u2_raw(address p) const {

    assert_raw_index_size(2); assert_raw_stream(true);

    return Bytes::get_Java_u2(p);

  }

};

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

// corresponding java bytecodes.

class BytecodeStream: public BaseBytecodeStream {

  Bytecodes::Code _code;

 public:

  // Construction

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

  // Iteration

  Bytecodes::Code next() {

    Bytecodes::Code raw_code, code;

    // set reading position

    _bci = _next_bci;

    if (is_last_bytecode()) {

      // indicate end of bytecode stream

      raw_code = code = Bytecodes::_illegal;

    } else {

      // get bytecode

      address bcp = this->bcp();

      raw_code = Bytecodes::code_at(bcp);

      code = Bytecodes::java_code(raw_code);

      // 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) {

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

        code = raw_code;  // wide BCs are always Java-normal

        _is_wide = true;

      }

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

    }

    _raw_code = raw_code;

    _code = code;

    return _code;

  }

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

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

  // Unsigned indices, widening

  int             get_index() const              { return is_wide() ? bytecode()->get_index_u2(raw_code(), true) : get_index_u1(); }

  // Get an unsigned 2-byte index, swapping the bytes if necessary.

  int             get_index_u2() const           { assert_raw_stream(false);

                                                   return bytecode()->get_index_u2(raw_code(), false); }

  // Get an unsigned 2-byte index in native order.

  int             get_index_u2_cpcache() const   { assert_raw_stream(false);

                                                   return bytecode()->get_index_u2_cpcache(raw_code()); }

  int             get_index_u4() const           { assert_raw_stream(false);

                                                   return bytecode()->get_index_u4(raw_code()); }

  bool            has_index_u4() const           { return bytecode()->has_index_u4(raw_code()); }

};