API:Data.DBXPlatform.TDBXSemaphore.Create
Delphi
constructor Create(Count: Integer);
C++
__fastcall TDBXSemaphore(int Count);
Properties
| Type | Visibility | Source | Unit | Parent |
|---|---|---|---|---|
| constructor | public | Data.DBXPlatform.pas Data.DBXPlatform.hpp |
Data.DBXPlatform | TDBXSemaphore |
Description
Instantiates a TSemaphore object.
Data.DBXPlatform.TDBXSemaphore.Create inherits from System.SyncObjs.TSemaphore.Create. All content below this line refers to System.SyncObjs.TSemaphore.Create.
Instantiates a TSemaphore object.
Call Create to create a TSemaphore object.
The first version of the constructor creates an unnamed binary semaphore with an initial counter value of one. Also, the semaphore is created with the default security descriptor. This means that the child processes of the current process cannot inherit the handle to this semaphore. This is basically equivalent to creating an unnamed TMutex object. Set the UseCOMWait parameter to ensure that when a thread is blocked and waiting for the object, any STA (single-threaded apartment) COM calls can still be made back into this thread.
The second version of the constructor allows opening an existing semaphore, identified by its name. The parameters have the following meaning:
|
Parameter |
Meaning |
|
DesiredAccess |
The type of access to the semaphore. The constructor fails if the requested type of access is not permitted. It can be any combination of the following constants: SEMAPHORE_ALL_ACCESS, SEMAPHORE_MODIFY_STATE, SYNCHRONIZE, _DELETE, READ_CONTROL, WRITE_DAC, WRITE_OWNER. |
|
InheritHandle |
Set this paremeter for the child processes to inherit the handle. |
|
Name |
The name of the semaphore to open. Names are case-sensitive. |
|
UseCOMWait |
Set this parameter in order to ensure that when a thread is blocked and waiting for the object, any STA COM calls can still be made back into this thread. |
The third version of the constructor creates a named semaphore with several attributes, given through the following list of parameters:
|
Parameter |
Meaning |
|
SemaphoreAttributes |
The security attributes of the semaphore. SemaphoreAttributes is of a pointer type to a _SECURITY_ATTRIBUTES record, with the following fields: nLength, lpSecurityDescriptor, InheritHandle. The nLength field should always be equal to the size, in bytes, of the _SECURITY_ATTRIBUTES record. lpSecurityDescriptor is a pointer to the security descriptor of the semaphore. Finally, InheritHandle is True if the handle to the semaphore is to be inherited by child processes. |
|
AInitialCount |
The initial value of the semaphore counter variable, giving the initial number of free units of the shared resource. |
|
AMaximumCount |
The maximum value of the semaphore counter variable, giving the number of available units of the shared resource. |
|
Name |
The name of the semaphore. Names are case-sensitive. |
|
UseCOMWait |
Set this parameter in order to ensure that when a thread is blocked and waiting for the object, any STA COM calls can still be made back into this thread. |