1 : /**********************************************************************
2 : * $Id: cpl_atomic_ops.h 16035 2009-01-01 23:11:24Z tamas $
3 : *
4 : * Name: cpl_atomic_ops.h
5 : * Project: CPL - Common Portability Library
6 : * Purpose: Atomic operation functions.
7 : * Author: Even Rouault, <even dot rouault at mines dash paris dot org>
8 : *
9 : **********************************************************************
10 : * Copyright (c) 2009, Even Rouault, <even dot rouault at mines dash paris dot org>
11 : *
12 : * Permission is hereby granted, free of charge, to any person obtaining a
13 : * copy of this software and associated documentation files (the "Software"),
14 : * to deal in the Software without restriction, including without limitation
15 : * the rights to use, copy, modify, merge, publish, distribute, sublicense,
16 : * and/or sell copies of the Software, and to permit persons to whom the
17 : * Software is furnished to do so, subject to the following conditions:
18 : *
19 : * The above copyright notice and this permission notice shall be included
20 : * in all copies or substantial portions of the Software.
21 : *
22 : * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
23 : * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
24 : * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
25 : * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
26 : * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
27 : * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
28 : * DEALINGS IN THE SOFTWARE.
29 : ****************************************************************************/
30 :
31 : #ifndef _CPL_ATOMIC_OPS_INCLUDED
32 : #define _CPL_ATOMIC_OPS_INCLUDED
33 :
34 : #include "cpl_port.h"
35 :
36 : CPL_C_START
37 :
38 : /** Add a value to a pointed integer in a thread and SMP-safe way
39 : * and return the resulting value of the operation.
40 : *
41 : * This function, which in most cases is implemented by a few
42 : * efficient machine instructions, guarantees that the value pointed
43 : * by ptr will be incremented in a thread and SMP-safe way.
44 : * The variables for this function must be aligned on a 32-bit boundary.
45 : *
46 : * Depending on the platforms, this function can also act as a
47 : * memory barrier, but this should not be assumed.
48 : *
49 : * Current platforms/architectures where an efficient implementation
50 : * exists are MacOSX, MS Windows, i386/x86_64 with GCC and platforms
51 : * supported by GCC 4.1 or higher. For other platforms supporting
52 : * the pthread library, and when GDAL is configured with thread-support,
53 : * the atomicity will be done with a mutex, but with
54 : * reduced efficiently. For the remaining platforms, a simple addition
55 : * with no locking will be done...
56 : *
57 : * @param ptr a pointer to an integer to increment
58 : * @param increment the amount to add to the pointed integer
59 : * @return the pointed value AFTER the result of the addition
60 : */
61 : int CPL_DLL CPLAtomicAdd(volatile int* ptr, int increment);
62 :
63 : /** Increment of 1 the pointed integer in a thread and SMP-safe way
64 : * and return the resulting value of the operation.
65 : *
66 : * @see CPLAtomicAdd for the details and guarantees of this atomic
67 : * operation
68 : *
69 : * @param ptr a pointer to an integer to increment
70 : * @return the pointed value AFTER the opeation: *ptr + 1
71 : */
72 94710 : CPL_INLINE int CPLAtomicInc(volatile int* ptr)
73 : {
74 94710 : return CPLAtomicAdd(ptr, 1);
75 : }
76 :
77 : /** Decrement of 1 the pointed integer in a thread and SMP-safe way
78 : * and return the resulting value of the operation.
79 : *
80 : * @see CPLAtomicAdd for the details and guarantees of this atomic
81 : * operation
82 : *
83 : * @param ptr a pointer to an integer to decrement
84 : * @return the pointed value AFTER the opeation: *ptr - 1
85 : */
86 95984 : CPL_INLINE int CPLAtomicDec(volatile int* ptr)
87 : {
88 95984 : return CPLAtomicAdd(ptr, -1);
89 : }
90 :
91 : CPL_C_END
92 :
93 : #endif /* _CPL_ATOMIC_OPS_INCLUDED */
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