1QBATOMIC.H(3)              libqb Programmer's Manual             QBATOMIC.H(3)
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NAME

6       qbatomic.h - Basic atomic integer and pointer operations.
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SYNOPSIS

10       #include <qb/qbatomic.h>
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DESCRIPTION

13       The  following  functions can be used to atomically access integers and
14       pointers. They are implemented as inline  assembler  function  on  most
15       platforms and use slower fall-backs otherwise. Using them can sometimes
16       save you from using a performance-expensive  pthread_mutex  to  protect
17       the integer or pointer.
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19       The    most    important    usage    is   reference   counting.   Using
20       qb_atomic_int_inc() and  qb_atomic_int_dec_and_test()  makes  reference
21       counting a very fast operation.
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23       You  must  not directly read integers or pointers concurrently accessed
24       by multiple threads, but use the  atomic  accessor  functions  instead.
25       That is, always use qb_atomic_int_get() and qb_atomic_pointer_get() for
26       read outs. They provide the necessary synchronization  mechanisms  like
27       memory barriers to access memory locations concurrently.
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29       If  you are using those functions for anything apart from simple refer‐
30       ence counting, you should really be aware of the implications of  doing
31       that.  There  are  literally thousands of ways to shoot yourself in the
32       foot. So if in doubt, use a pthread_mutex. If you don't know, what mem‐
33       ory  barriers  are,  do  not  use  anything but qb_atomic_int_inc() and
34       qb_atomic_int_dec_and_test().
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36       It is not safe to set an integer or pointer just by  assigning  to  it,
37       when  it  is  concurrently accessed by other threads with the following
38       functions.      Use       qb_atomic_int_compare_and_exchange()       or
39       qb_atomic_pointer_compare_and_exchange() respectively.
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SEE ALSO

42       qb_atomic_int_set(3), qb_atomic_int_compare_and_exchange(3),
43       qb_atomic_int_get(3), qb_atomic_int_add(3), qb_atomic_init(3),
44       qb_atomic_pointer_get(3), qb_atomic_int_exchange_and_add(3),
45       qb_atomic_pointer_compare_and_exchange(3), qb_atomic_pointer_set(3)
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48       Copyright (C) 2003 Sebastian Wilhelmi
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52LIBQB                             2021-03-03                     QBATOMIC.H(3)
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