L4Re – L4 Runtime Environment
counting_cap_alloc
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1 // vim:set ft=cpp: -*- Mode: C++ -*-
6 /*
7  * (c) 2008-2010 Alexander Warg <warg@os.inf.tu-dresden.de>
8  * economic rights: Technische Universität Dresden (Germany)
9  *
10  * This file is part of TUD:OS and distributed under the terms of the
11  * GNU General Public License 2.
12  * Please see the COPYING-GPL-2 file for details.
13  *
14  * As a special exception, you may use this file as part of a free software
15  * library without restriction. Specifically, if other files instantiate
16  * templates or use macros or inline functions from this file, or you compile
17  * this file and link it with other files to produce an executable, this
18  * file does not by itself cause the resulting executable to be covered by
19  * the GNU General Public License. This exception does not however
20  * invalidate any other reasons why the executable file might be covered by
21  * the GNU General Public License.
22  */
23 
24 #pragma once
25 
26 #include <l4/sys/task>
27 #include <l4/sys/assert.h>
28 #include <l4/re/consts>
29 
30 namespace L4Re { namespace Util {
31 
35 template< typename COUNTER = unsigned char >
36 struct Counter
37 {
38  typedef COUNTER Type;
39  Type _cnt;
40 
41  static Type nil() { return 0; }
42 
43  void free() { _cnt = 0; }
44  bool is_free() const { return _cnt == 0; }
45  void inc() { ++_cnt; }
46  Type dec() { return --_cnt; }
47  void alloc() { _cnt = 1; }
48 };
49 
74 template <typename COUNTERTYPE = L4Re::Util::Counter<unsigned char> >
76 {
77 private:
78  void operator = (Counting_cap_alloc const &) { }
79  typedef COUNTERTYPE Counter;
80 
81  COUNTERTYPE *_items;
82  long _free_hint;
83  long _bias;
84  long _capacity;
85 
86 
87 public:
88 
89  template <unsigned COUNT>
90  struct Counter_storage
91  {
92  COUNTERTYPE _buf[COUNT];
93  typedef COUNTERTYPE Buf_type[COUNT];
94  enum { Size = COUNT };
95  };
96 
97 protected:
98 
105  : _items(0), _free_hint(0), _bias(0), _capacity(0)
106  {}
107 
121  void setup(void *m, long capacity, long bias) noexcept
122  {
123  _items = (Counter*)m;
124  _capacity = capacity;
125  _bias = bias;
126  }
127 
128 public:
135  L4::Cap<void> alloc() noexcept
136  {
137  for (long i = _free_hint; i < _capacity; ++i)
138  {
139  if (_items[i].is_free())
140  {
141  _items[i].alloc();
142  _free_hint = i + 1;
143 
144  return L4::Cap<void>((i + _bias) << L4_CAP_SHIFT);
145  }
146  }
147 
148  return L4::Cap<void>::Invalid;
149  }
150 
152  template <typename T>
153  L4::Cap<T> alloc() noexcept
154  {
155  return L4::cap_cast<T>(alloc());
156  }
157 
158 
168  void take(L4::Cap<void> cap) noexcept
169  {
170  long c = cap.cap() >> L4_CAP_SHIFT;
171  if (c < _bias)
172  return;
173 
174  c -= _bias;
175  if (c >= _capacity)
176  return;
177 
178  _items[c].inc();
179  }
180 
181 
196  unsigned unmap_flags = L4_FP_ALL_SPACES) noexcept
197  {
198  long c = cap.cap() >> L4_CAP_SHIFT;
199  if (c < _bias)
200  return false;
201 
202  c -= _bias;
203 
204  if (c >= _capacity)
205  return false;
206 
207  l4_assert(!_items[c].is_free());
208 
209  if (l4_is_valid_cap(task))
210  l4_task_unmap(task, cap.fpage(), unmap_flags);
211 
212  if (c < _free_hint)
213  _free_hint = c;
214 
215  _items[c].free();
216 
217  return true;
218  }
219 
239  unsigned unmap_flags = L4_FP_ALL_SPACES) noexcept
240  {
241  long c = cap.cap() >> L4_CAP_SHIFT;
242  if (c < _bias)
243  return false;
244 
245  c -= _bias;
246 
247  if (c >= _capacity)
248  return false;
249 
250  l4_assert(!_items[c].is_free());
251 
252  if (_items[c].dec() == Counter::nil())
253  {
254  if (task != L4_INVALID_CAP)
255  l4_task_unmap(task, cap.fpage(), unmap_flags);
256 
257  if (c < _free_hint)
258  _free_hint = c;
259 
260  return true;
261  }
262  return false;
263  }
264 
265 
269  long last() noexcept
270  {
271  return _capacity + _bias - 1;
272  }
273 };
274 
275 }}
276 
Internal reference-counting cap allocator.
void take(L4::Cap< void > cap) noexcept
Increase the reference counter for the capability.
L4::Cap< void > alloc() noexcept
Allocate a new capability slot.
bool free(L4::Cap< void > cap, l4_cap_idx_t task=L4_INVALID_CAP, unsigned unmap_flags=L4_FP_ALL_SPACES) noexcept
Free the capability.
L4::Cap< T > alloc() noexcept
Allocate a new capability slot.
void setup(void *m, long capacity, long bias) noexcept
Set up the backing memory for the allocator and the area of managed capability slots.
Counting_cap_alloc() noexcept
Create a new, empty allocator.
long last() noexcept
Return highest capability id managed by this allocator.
bool release(L4::Cap< void > cap, l4_cap_idx_t task=L4_INVALID_CAP, unsigned unmap_flags=L4_FP_ALL_SPACES) noexcept
Decrease the reference counter for a capability.
C++ interface for capabilities.
Definition: capability.h:219
unsigned long l4_cap_idx_t
L4 Capability selector Type.
Definition: types.h:342
unsigned l4_is_valid_cap(l4_cap_idx_t c) L4_NOTHROW
Test if a capability selector is a valid selector.
Definition: types.h:396
@ L4_CAP_SHIFT
Capability index shift.
Definition: consts.h:131
@ L4_INVALID_CAP
Invalid capability selector.
Definition: consts.h:141
l4_msgtag_t l4_task_unmap(l4_cap_idx_t task, l4_fpage_t fpage, l4_umword_t map_mask) L4_NOTHROW
Revoke rights from the task.
Definition: task.h:346
@ L4_FP_ALL_SPACES
Flag to tell the unmap operation to unmap all child mappings including the mapping in the invoked tas...
Definition: consts.h:165
L4Re C++ Interfaces.
Definition: cmd_control:15
IOModifier const dec
Modifies the stream to print numbers as decimal values.
Constants.
Counter for Counting_cap_alloc with variable data width.
Low-level assert implementation.
#define l4_assert(expr)
Low-level assert.
Definition: assert.h:43
Common task related definitions.