/*

 * 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

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 */

#include "asm/codeBuffer.hpp"

#include "memory/allocation.hpp"

// The classes in this file provide a simple framework for the

// management of little pieces of machine code - or stubs -

// created on the fly and frequently discarded. In this frame-

// work stubs are stored in a queue.

// Stub serves as abstract base class. A concrete stub

// implementation is a subclass of Stub, implementing

// all (non-virtual!) functions required sketched out

// in the Stub class.

//

// A concrete stub layout may look like this (both data

// and code sections could be empty as well):

//

//                ________

// stub       -->|        | <--+

//               |  data  |    |

//               |________|    |

// code_begin -->|        |    |

//               |        |    |

//               |  code  |    | size

//               |        |    |

//               |________|    |

// code_end   -->|        |    |

//               |  data  |    |

//               |________|    |

//                          <--+

class Stub {

 public:

  // Initialization/finalization

  void    initialize(int size,

                     CodeStrings& strings)       { ShouldNotCallThis(); }                // called to initialize/specify the stub's size

  void    finalize()                             { ShouldNotCallThis(); }                // called before the stub is deallocated

  // General info/converters

  int     size() const                           { ShouldNotCallThis(); return 0; }      // must return the size provided by initialize

  static  int code_size_to_size(int code_size)   { ShouldNotCallThis(); return 0; }      // computes the size given the code size

  // Code info

  address code_begin() const                     { ShouldNotCallThis(); return NULL; }   // points to the first byte of    the code

  address code_end() const                       { ShouldNotCallThis(); return NULL; }   // points to the first byte after the code

  // Debugging

  void    verify()                               { ShouldNotCallThis(); }                // verifies the Stub

  void    print()                                { ShouldNotCallThis(); }                // prints some information about the stub

};

// A stub interface defines the interface between a stub queue

// and the stubs it queues. In order to avoid a vtable and

// (and thus the extra word) in each stub, a concrete stub

// interface object is created and associated with a stub

// buffer which in turn uses the stub interface to interact

// with its stubs.

//

// StubInterface serves as an abstract base class. A concrete

// stub interface implementation is a subclass of StubInterface,

// forwarding its virtual function calls to non-virtual calls

// of the concrete stub (see also macro below). There's exactly

// one stub interface instance required per stub queue.

class StubInterface: public CHeapObj<mtCode> {

 public:

  // Initialization/finalization

  virtual void    initialize(Stub* self, int size,

                             CodeStrings& strings)         = 0; // called after creation (called twice if allocated via (request, commit))

  virtual void    finalize(Stub* self)                     = 0; // called before deallocation

  // General info/converters

  virtual int     size(Stub* self) const                   = 0; // the total size of the stub in bytes (must be a multiple of CodeEntryAlignment)

  virtual int     code_size_to_size(int code_size) const   = 0; // computes the total stub size in bytes given the code size in bytes

  // Code info

  virtual address code_begin(Stub* self) const             = 0; // points to the first code byte

  virtual address code_end(Stub* self) const               = 0; // points to the first byte after the code

  // Debugging

  virtual void    verify(Stub* self)                       = 0; // verifies the stub

  virtual void    print(Stub* self)                        = 0; // prints information about the stub

};

// DEF_STUB_INTERFACE is used to create a concrete stub interface

// class, forwarding stub interface calls to the corresponding

// stub calls.

#define DEF_STUB_INTERFACE(stub)                           \

  class stub##Interface: public StubInterface {            \

   private:                                                \

    static stub*    cast(Stub* self)                       { return (stub*)self; }                 \

                                                           \

   public:                                                 \

    /* Initialization/finalization */                      \

    virtual void    initialize(Stub* self, int size,       \

                               CodeStrings& strings)       { cast(self)->initialize(size, strings); } \

    virtual void    finalize(Stub* self)                   { cast(self)->finalize(); }             \

                                                           \

    /* General info */                                     \

    virtual int     size(Stub* self) const                 { return cast(self)->size(); }          \

    virtual int     code_size_to_size(int code_size) const { return stub::code_size_to_size(code_size); } \

                                                           \

    /* Code info */                                        \

    virtual address code_begin(Stub* self) const           { return cast(self)->code_begin(); }    \

    virtual address code_end(Stub* self) const             { return cast(self)->code_end(); }      \

                                                           \

    /* Debugging */                                        \

    virtual void    verify(Stub* self)                     { cast(self)->verify(); }               \

    virtual void    print(Stub* self)                      { cast(self)->print(); }                \

  };

// A StubQueue maintains a queue of stubs.

// Note: All sizes (spaces) are given in bytes.

class StubQueue: public CHeapObj<mtCode> {

  friend class VMStructs;

 private:

  StubInterface* _stub_interface;                // the interface prototype

  address        _stub_buffer;                   // where all stubs are stored

  int            _buffer_size;                   // the buffer size in bytes

  int            _buffer_limit;                  // the (byte) index of the actual buffer limit (_buffer_limit <= _buffer_size)

  int            _queue_begin;                   // the (byte) index of the first queue entry (word-aligned)

  int            _queue_end;                     // the (byte) index of the first entry after the queue (word-aligned)

  int            _number_of_stubs;               // the number of buffered stubs

  Mutex* const   _mutex;                         // the lock used for a (request, commit) transaction

  void  check_index(int i) const                 { assert(0 <= i && i < _buffer_limit && i % CodeEntryAlignment == 0, "illegal index"); }

  bool  is_contiguous() const                    { return _queue_begin <= _queue_end; }

  int   index_of(Stub* s) const                  { int i = (address)s - _stub_buffer; check_index(i); return i; }

  Stub* stub_at(int i) const                     { check_index(i); return (Stub*)(_stub_buffer + i); }

  Stub* current_stub() const                     { return stub_at(_queue_end); }

  // Stub functionality accessed via interface

  void  stub_initialize(Stub* s, int size,

                        CodeStrings& strings)    { assert(size % CodeEntryAlignment == 0, "size not aligned"); _stub_interface->initialize(s, size, strings); }

  void  stub_finalize(Stub* s)                   { _stub_interface->finalize(s); }

  int   stub_size(Stub* s) const                 { return _stub_interface->size(s); }

  bool  stub_contains(Stub* s, address pc) const { return _stub_interface->code_begin(s) <= pc && pc < _stub_interface->code_end(s); }

  int   stub_code_size_to_size(int code_size) const { return _stub_interface->code_size_to_size(code_size); }

  void  stub_verify(Stub* s)                     { _stub_interface->verify(s); }

  void  stub_print(Stub* s)                      { _stub_interface->print(s); }

 public:

  StubQueue(StubInterface* stub_interface, int buffer_size, Mutex* lock,

            const char* name);

  ~StubQueue();

  // General queue info

  bool  is_empty() const                         { return _queue_begin == _queue_end; }

  int   total_space() const                      { return _buffer_size - 1; }

  int   available_space() const                  { int d = _queue_begin - _queue_end - 1; return d < 0 ? d + _buffer_size : d; }

  int   used_space() const                       { return total_space() - available_space(); }

  int   number_of_stubs() const                  { return _number_of_stubs; }

  bool  contains(address pc) const               { return _stub_buffer <= pc && pc < _stub_buffer + _buffer_limit; }

  Stub* stub_containing(address pc) const;

  address code_start() const                     { return _stub_buffer; }

  address code_end() const                       { return _stub_buffer + _buffer_limit; }

  // Stub allocation (atomic transactions)

  Stub* request_committed(int code_size);        // request a stub that provides exactly code_size space for code

  Stub* request(int requested_code_size);        // request a stub with a (maximum) code space - locks the queue

  void  commit (int committed_code_size,

                CodeStrings& strings);           // commit the previously requested stub - unlocks the queue

  // Stub deallocation

  void  remove_first();                          // remove the first stub in the queue

  void  remove_first(int n);                     // remove the first n stubs in the queue

  void  remove_all();                            // remove all stubs in the queue

  void deallocate_unused_tail();                 // deallocate the unused tail of the underlying CodeBlob

                                                 // only used from TemplateInterpreter::initialize()

  // Iteration

  Stub* first() const                            { return number_of_stubs() > 0 ? stub_at(_queue_begin) : NULL; }

  Stub* next(Stub* s) const                      { int i = index_of(s) + stub_size(s);

                                                   // Only wrap around in the non-contiguous case (see stubss.cpp)

                                                   if (i == _buffer_limit && _queue_end < _buffer_limit) i = 0;

                                                   return (i == _queue_end) ? NULL : stub_at(i);

                                                 }

  // Debugging/printing

  void  verify();                                // verifies the stub queue

  void  print();                                 // prints information about the stub queue

};