This is a more complex semaphore wrapper that handles race conditions for initialization correctly...
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Public Types |
enum | { ACE_CREATE = IPC_CREAT,
ACE_OPEN = 0
} |
Public Member Functions |
| ACE_SV_Semaphore_Complex (void) |
| ACE_SV_Semaphore_Complex (key_t key, short create=ACE_SV_Semaphore_Complex::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS) |
| ACE_SV_Semaphore_Complex (const char *name, short create=ACE_SV_Semaphore_Complex::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS) |
| ~ACE_SV_Semaphore_Complex (void) |
int | open (const char *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS) |
int | open (key_t key, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS) |
int | close (void) |
int | acquire (u_short n=0, short flags=0) const |
| Acquire the semaphore.
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int | acquire_read (u_short n=0, short flags=0) const |
| Acquire a semaphore for reading.
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int | acquire_write (u_short n=0, short flags=0) const |
| Acquire a semaphore for writing.
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int | tryacquire (u_short n=0, short flags=0) const |
| Try to acquire the semaphore.
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int | tryacquire_read (u_short n=0, short flags=0) const |
| Try to acquire the semaphore for reading.
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int | tryacquire_write (u_short n=0, short flags=0) const |
| Try to acquire the semaphore for writing.
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int | release (u_short n=0, short flags=0) const |
| Release the semaphore.
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int | op (short val, u_short n=0, short flags=0) const |
int | op (sembuf op_vec[], u_short n) const |
| General ACE_SV_Semaphore operation on an array of SV_Semaphores.
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int | control (int cmd, semun arg, u_short n=0) const |
int | control (int cmd, int value=0, u_short n=0) const |
void | dump (void) const |
| Dump the state of an object.
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Public Attributes |
| ACE_ALLOC_HOOK_DECLARE |
| Declare the dynamic allocation hooks.
|
Static Private Attributes |
static const int | BIGCOUNT_ = 10000 |
static sembuf | op_lock_ [2] |
static sembuf | op_endcreate_ [2] |
static sembuf | op_open_ [1] |
static sembuf | op_close_ [3] |
static sembuf | op_unlock_ [1] |
This is a more complex semaphore wrapper that handles race conditions for initialization correctly...
This code is a port to C++, inspired by: W. Richard Stevens from his book: UNIX Network Programming (Prentice Hall, ISBN 0-13-949876-1 - 1990). We provide a simpler and easier to understand interface to the System V Semaphore system calls. We create and use a 2 + n-member set for the requested <ACE_SV_Semaphore_Complex>. The first member, [0], is a counter used to know when all processes have finished with the <ACE_SV_Semaphore_Complex>. The counter is initialized to a large number, decremented on every create or open and incremented on every close. This way we can use the "adjust" feature provided by System V so that any process that exit's without calling <close> is accounted for. It doesn't help us if the last process does this (as we have no way of getting control to remove the <ACE_SV_Semaphore_Complex>) but it will work if any process other than the last does an exit (intentional or unintentional). The second member, [1], of the semaphore is used as a lock variable to avoid any race conditions in the <create> and <close> functions. The members beyond [1] are actual semaphore values in the array of semaphores, which may be sized by the user in the constructor.