/*

 * 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

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 */

// Implementation of StubQueue

//

// Standard wrap-around queue implementation; the queue dimensions

// are specified by the _queue_begin & _queue_end indices. The queue

// can be in two states (transparent to the outside):

//

// a) contiguous state: all queue entries in one block (or empty)

//

// Queue: |...|XXXXXXX|...............|

//        ^0  ^begin  ^end            ^size = limit

//            |_______|

//            one block

//

// b) non-contiguous state: queue entries in two blocks

//

// Queue: |XXX|.......|XXXXXXX|.......|

//        ^0  ^end    ^begin  ^limit  ^size

//        |___|       |_______|

//         1st block  2nd block

//

// In the non-contiguous state, the wrap-around point is

// indicated via the _buffer_limit index since the last

// queue entry may not fill up the queue completely in

// which case we need to know where the 2nd block's end

// is to do the proper wrap-around. When removing the

// last entry of the 2nd block, _buffer_limit is reset

// to _buffer_size.

//

// CAUTION: DO NOT MESS WITH THIS CODE IF YOU CANNOT PROVE

// ITS CORRECTNESS! THIS CODE IS MORE SUBTLE THAN IT LOOKS!

StubQueue::StubQueue(StubInterface* stub_interface, int buffer_size,

                     Mutex* lock, const char* name) : _mutex(lock) {

  intptr_t size = round_to(buffer_size, 2*BytesPerWord);

  BufferBlob* blob = BufferBlob::create(name, size);

  if( blob == NULL) {

    vm_exit_out_of_memory(size, err_msg("CodeCache: no room for %s", name));

  }

  _stub_interface  = stub_interface;

  _buffer_size     = blob->content_size();

  _buffer_limit    = blob->content_size();

  _stub_buffer     = blob->content_begin();

  _queue_begin     = 0;

  _queue_end       = 0;

  _number_of_stubs = 0;

  register_queue(this);

}

StubQueue::~StubQueue() {

  // Note: Currently StubQueues are never destroyed so nothing needs to be done here.

  //       If we want to implement the destructor, we need to release the BufferBlob

  //       allocated in the constructor (i.e., we need to keep it around or look it

  //       up via CodeCache::find_blob(...).

  Unimplemented();

}

Stub* StubQueue::stub_containing(address pc) const {

  if (contains(pc)) {

    for (Stub* s = first(); s != NULL; s = next(s)) {

      if (stub_contains(s, pc)) return s;

    }

  }

  return NULL;

}

Stub* StubQueue::request_committed(int code_size) {

  Stub* s = request(code_size);

  if (s != NULL) commit(code_size);

  return s;

}

Stub* StubQueue::request(int requested_code_size) {

  assert(requested_code_size > 0, "requested_code_size must be > 0");

  if (_mutex != NULL) _mutex->lock();

  Stub* s = current_stub();

  int requested_size = round_to(stub_code_size_to_size(requested_code_size), CodeEntryAlignment);

  if (requested_size <= available_space()) {

    if (is_contiguous()) {

      // Queue: |...|XXXXXXX|.............|

      //        ^0  ^begin  ^end          ^size = limit

      assert(_buffer_limit == _buffer_size, "buffer must be fully usable");

      if (_queue_end + requested_size <= _buffer_size) {

        // code fits in at the end => nothing to do

        stub_initialize(s, requested_size);

        return s;

      } else {

        // stub doesn't fit in at the queue end

        // => reduce buffer limit & wrap around

        assert(!is_empty(), "just checkin'");

        _buffer_limit = _queue_end;

        _queue_end = 0;

      }

    }

  }

  if (requested_size <= available_space()) {

    assert(!is_contiguous(), "just checkin'");

    assert(_buffer_limit <= _buffer_size, "queue invariant broken");

    // Queue: |XXX|.......|XXXXXXX|.......|

    //        ^0  ^end    ^begin  ^limit  ^size

    s = current_stub();

    stub_initialize(s, requested_size);

    return s;

  }

  // Not enough space left

  if (_mutex != NULL) _mutex->unlock();

  return NULL;

}

void StubQueue::commit(int committed_code_size) {

  assert(committed_code_size > 0, "committed_code_size must be > 0");

  int committed_size = round_to(stub_code_size_to_size(committed_code_size), CodeEntryAlignment);

  Stub* s = current_stub();

  assert(committed_size <= stub_size(s), "committed size must not exceed requested size");

  stub_initialize(s, committed_size);

  _queue_end += committed_size;

  _number_of_stubs++;

  if (_mutex != NULL) _mutex->unlock();

  debug_only(stub_verify(s);)

}

void StubQueue::remove_first() {

  if (number_of_stubs() == 0) return;

  Stub* s = first();

  debug_only(stub_verify(s);)

  stub_finalize(s);

  _queue_begin += stub_size(s);

  assert(_queue_begin <= _buffer_limit, "sanity check");

  if (_queue_begin == _queue_end) {

    // buffer empty

    // => reset queue indices

    _queue_begin  = 0;

    _queue_end    = 0;

    _buffer_limit = _buffer_size;

  } else if (_queue_begin == _buffer_limit) {

    // buffer limit reached

    // => reset buffer limit & wrap around

    _buffer_limit = _buffer_size;

    _queue_begin = 0;

  }

  _number_of_stubs--;

}

void StubQueue::remove_first(int n) {

  int i = MIN2(n, number_of_stubs());

  while (i-- > 0) remove_first();

}

void StubQueue::remove_all(){

  debug_only(verify();)

  remove_first(number_of_stubs());

  assert(number_of_stubs() == 0, "sanity check");

}

enum { StubQueueLimit = 10 };  // there are only a few in the world

static StubQueue* registered_stub_queues[StubQueueLimit];

void StubQueue::register_queue(StubQueue* sq) {

  for (int i = 0; i < StubQueueLimit; i++) {

    if (registered_stub_queues[i] == NULL) {

      registered_stub_queues[i] = sq;

      return;

    }

  }

  ShouldNotReachHere();

}

void StubQueue::queues_do(void f(StubQueue* sq)) {

  for (int i = 0; i < StubQueueLimit; i++) {

    if (registered_stub_queues[i] != NULL) {

      f(registered_stub_queues[i]);

    }

  }

}

void StubQueue::stubs_do(void f(Stub* s)) {

  debug_only(verify();)

  MutexLockerEx lock(_mutex);

  for (Stub* s = first(); s != NULL; s = next(s)) f(s);

}

void StubQueue::verify() {

  // verify only if initialized

  if (_stub_buffer == NULL) return;

  MutexLockerEx lock(_mutex);

  // verify index boundaries

  guarantee(0 <= _buffer_size, "buffer size must be positive");

  guarantee(0 <= _buffer_limit && _buffer_limit <= _buffer_size , "_buffer_limit out of bounds");

  guarantee(0 <= _queue_begin  && _queue_begin  <  _buffer_limit, "_queue_begin out of bounds");

  guarantee(0 <= _queue_end    && _queue_end    <= _buffer_limit, "_queue_end   out of bounds");

  // verify alignment

  guarantee(_buffer_size  % CodeEntryAlignment == 0, "_buffer_size  not aligned");

  guarantee(_buffer_limit % CodeEntryAlignment == 0, "_buffer_limit not aligned");

  guarantee(_queue_begin  % CodeEntryAlignment == 0, "_queue_begin  not aligned");

  guarantee(_queue_end    % CodeEntryAlignment == 0, "_queue_end    not aligned");

  // verify buffer limit/size relationship

  if (is_contiguous()) {

    guarantee(_buffer_limit == _buffer_size, "_buffer_limit must equal _buffer_size");

  }

  // verify contents

  int n = 0;

  for (Stub* s = first(); s != NULL; s = next(s)) {

    stub_verify(s);

    n++;

  }

  guarantee(n == number_of_stubs(), "number of stubs inconsistent");

  guarantee(_queue_begin != _queue_end || n == 0, "buffer indices must be the same");

}

void StubQueue::print() {

  MutexLockerEx lock(_mutex);

  for (Stub* s = first(); s != NULL; s = next(s)) {

    stub_print(s);

  }

}