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Oracle® Call Interface Programmer's Guide
12c Release 1 (12.1)

E17625-19
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Thread Management Functions

Table 17-5 lists the thread management functions that are described in this section.

Table 17-5 Thread Management Functions

Function Purpose

"OCIThreadClose()"

Close a thread handle

"OCIThreadCreate()"

Create a new thread

"OCIThreadHandleGet()"

Retrieve the OCIThreadHandle of the thread in which it is called

"OCIThreadHndDestroy()"

Destroy and deallocate the thread handle

"OCIThreadHndInit()"

Allocate and initialize the thread handle

"OCIThreadIdDestroy()"

Destroy and deallocate a thread ID

"OCIThreadIdGet()"

Retrieve the OCIThreadId of the thread in which it is called

"OCIThreadIdInit()"

Allocate and initialize the thread ID

"OCIThreadIdNull()"

Determine whether a given OCIThreadId is the NULL thread ID

"OCIThreadIdSame()"

Determine whether two OCIThreadIds represent the same thread

"OCIThreadIdSet()"

Set one OCIThreadId to another

"OCIThreadIdSetNull()"

Set the NULL thread ID to a given OCIThreadId

"OCIThreadInit()"

Initialize OCIThread context

"OCIThreadIsMulti()"

Tell the caller whether the application is running in a multithreaded environment or a single-threaded environment

"OCIThreadJoin()"

Allow the calling thread to join with another thread

"OCIThreadKeyDestroy()"

Destroy and deallocate the key pointed to by key

"OCIThreadKeyGet()"

Get the calling thread's current value for a key

"OCIThreadKeyInit()"

Create a key

"OCIThreadKeySet()"

Set the calling thread's value for a key

"OCIThreadMutexAcquire()"

Acquire a mutex for the thread in which it is called

"OCIThreadMutexDestroy()"

Destroy and deallocate a mutex

"OCIThreadMutexInit()"

Allocate and initialize a mutex

"OCIThreadMutexRelease()"

Release a mutex

"OCIThreadProcessInit()"

Perform OCIThread process initialization

"OCIThreadTerm()"

Release the OCIThread context


OCIThreadClose()

Purpose

Closes a thread handle.

Syntax

sword OCIThreadClose ( void             *hndl, 
                       OCIError         *err, 
                       OCIThreadHandle  *tHnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tHnd (IN/OUT)

The OCIThread thread handle to close.

Comments

The tHnd parameter should be initialized by OCIThreadHndInit(). Both the thread handle and the thread ID that was returned by the same call to OCIThreadCreate() are invalid after the call to OCIThreadClose().

Related Functions

OCIThreadCreate()

OCIThreadCreate()

Purpose

Creates a new thread.

Syntax

sword OCIThreadCreate ( void             *hndl, 
                        OCIError         *err, 
                        void (*start)    (void *),
                        void             *arg, 
                        OCIThreadId      *tid, 
                        OCIThreadHandle  *tHnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

start (IN)

The function in which the new thread should begin execution.

arg (IN)

The argument to give the function pointed to by start.

tid (IN/OUT)

If not NULL, gets the ID for the new thread.

tHnd (IN/OUT)

If not NULL, gets the handle for the new thread.

Comments

The new thread starts by executing a call to the function pointed to by start with the argument given by arg. When that function returns, the new thread terminates. The function should not return a value and should accept one parameter, a void. The call to OCIThreadCreate() must be matched by a call to OCIThreadClose() if and only if tHnd is non-NULL.

If tHnd is NULL, a thread ID placed in *tid is not valid in the calling thread because the timing of the spawned threads termination is unknown.

The tid parameter should be initialized by OCIThreadIdInit() and tHnd should be initialized by OCIThreadHndInit().

OCIThreadHandleGet()

Purpose

Retrieves the OCIThreadHandle of the thread in which it is called.

Syntax

sword OCIThreadHandleGet ( void             *hndl,
                           OCIError         *err,
                           OCIThreadHandle  *tHnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tHnd (IN/OUT)

If not NULL, the location to place the thread handle for the thread.

Comments

The tHnd parameter should be initialized by OCIThreadHndInit().

The thread handle tHnd retrieved by this function must be closed with OCIThreadClose() and destroyed by OCIThreadHndDestroy() after it is used.

OCIThreadHndDestroy()

Purpose

Destroys and deallocates the thread handle.

Syntax

sword OCIThreadHndDestroy ( void             *hndl, 
                            OCIError         *err, 
                            OCIThreadHandle  **thnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

thnd (IN/OUT)

The address of pointer to the thread handle to destroy.

Comments

The thnd parameter should be initialized by OCIThreadHndInit().

OCIThreadHndInit()

Purpose

Allocates and initializes the thread handle.

Syntax

sword OCIThreadHndInit ( void            *hndl, 
                         OCIError        *err,
                         OCIThreadHandle **thnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

thnd (OUT)

The address of the pointer to the thread handle to initialize.

OCIThreadIdDestroy()

Purpose

Destroys and deallocates a thread ID.

Syntax

sword OCIThreadIdDestroy (void         *hndl,
                          OCIError     *err,
                          OCIThreadId  **tid );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

tid (IN/OUT)

Pointer to the thread ID to destroy.

Comments

The tid parameter should be initialized by OCIThreadHndInit().

OCIThreadIdGet()

Purpose

Retrieves the OCIThreadId of the thread in which it is called.

Syntax

sword OCIThreadIdGet ( void         *hndl,
                       OCIError     *err, 
                       OCIThreadId  *tid );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tid (OUT)

This should point to the location in which to place the ID of the calling thread.

Comments

The tid parameter should be initialized by OCIThreadHndInit(). When OCIThread is used in a single-threaded environment, OCIThreadIdGet() always places the same value in the location pointed to by tid. The exact value itself is not important. The important thing is that it is different from the NULL thread ID and that it is always the same value.

OCIThreadIdInit()

Purpose

Allocate and initialize the thread ID tid.

Syntax

sword OCIThreadIdInit ( void         *hndl,
                        OCIError     *err, 
                        OCIThreadId  **tid );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

tid (OUT)

Pointer to the thread ID to initialize.

OCIThreadIdNull()

Purpose

Determines whether a given OCIThreadId is the NULL thread ID.

Syntax

sword OCIThreadIdNull ( void         *hndl, 
                        OCIError     *err, 
                        OCIThreadId  *tid, 
                        boolean      *result );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tid (IN)

Pointer to the OCIThreadId to check.

result (IN/OUT)

Pointer to the result.

Comments

If tid is the NULL thread ID, result is set to TRUE. Otherwise, result is set to FALSE. The tid parameter should be initialized by OCIThreadIdInit().

OCIThreadIdSame()

Purpose

Determines whether two OCIThreadIds represent the same thread.

Syntax

sword OCIThreadIdSame ( void          *hndl, 
                        OCIError      *err,
                        OCIThreadId   *tid1, 
                        OCIThreadId   *tid2, 
                        boolean       *result );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tid1 (IN)

Pointer to the first OCIThreadId.

tid2 (IN)

Pointer to the second OCIThreadId.

result (IN/OUT)

Pointer to the result.

Comments

If tid1 and tid2 represent the same thread, result is set to TRUE. Otherwise, result is set to FALSE. The result parameter is set to TRUE if both tid1 and tid2 are the NULL thread ID. The parameters tid1 and tid2 should be initialized by OCIThreadIdInit().

OCIThreadIdSet()

Purpose

Sets one OCIThreadId to another.

Syntax

sword OCIThreadIdSet ( void         *hndl,
                       OCIError     *err,
                       OCIThreadId  *tidDest, 
                       OCIThreadId  *tidSrc );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

tidDest (OUT)

This should point to the location of the OCIThreadId to set to.

tidSrc (IN)

This should point to the OCIThreadId to set from.

Comments

The tid parameter should be initialized by OCIThreadIdInit().

OCIThreadIdSetNull()

Purpose

Sets the NULL thread ID to a given OCIThreadId.

Syntax

sword OCIThreadIdSetNull ( void         *hndl,
                           OCIError     *err, 
                           OCIThreadId  *tid );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tid (OUT)

This should point to the OCIThreadId in which to put the NULL thread ID.

Comments

The tid parameter should be initialized by OCIThreadIdInit().

OCIThreadInit()

Purpose

Initializes the OCIThread context.

Syntax

sword OCIThreadInit ( void      *hndl,
                      OCIError  *err );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

Comments

It is illegal for OCIThread clients to try to examine the memory pointed to by the returned pointer. It is safe to make concurrent calls to OCIThreadInit(). Unlike OCIThreadProcessInit(), there is no need to have a first call that occurs before all the others.

The first time OCIThreadInit() is called, it initializes the OCIThread context. It also saves a pointer to the context in some system-dependent manner. Subsequent calls to OCIThreadInit() return the same context.

Each call to OCIThreadInit() must eventually be matched by a call to OCIThreadTerm().

Related Functions

OCIThreadTerm()

OCIThreadIsMulti()

Purpose

Tells the caller whether the application is running in a multithreaded environment or a single-threaded environment.

Syntax

boolean OCIThreadIsMulti ( );

Returns

TRUE if the environment is multithreaded.

FALSE if the environment is single-threaded.

OCIThreadJoin()

Purpose

Allows the calling thread to join with another thread.

Syntax

sword OCIThreadJoin ( void             *hndl,
                      OCIError         *err, 
                      OCIThreadHandle  *tHnd );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

tHnd (IN)

The OCIThreadHandle of the thread to join with.

Comments

This function blocks the caller until the specified thread terminates.

The tHnd parameter should be initialized by OCIThreadHndInit(). The result of multiple threads all trying to join with the same thread is undefined.

OCIThreadKeyDestroy()

Purpose

Destroys and deallocates the key pointed to by key.

Syntax

sword OCIThreadKeyDestroy ( void          *hndl,
                            OCIError      *err, 
                            OCIThreadKey  **key );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

key (IN/OUT)

The OCIThreadKey in which to destroy the key.

Comments

This is different from the destructor function callback passed to the key create routine. The function OCIThreadKeyDestroy() is used to terminate any resources that the OCIThread acquired when it created key. The OCIThreadKeyDestFunc callback of OCIThreadKeyInit() is a key value destructor; it does not operate on the key itself.

This must be called after the user has finished using the key. Not calling the OCIThreadKeyDestroy() function may result in memory leaks.

OCIThreadKeyGet()

Purpose

Gets the calling thread's current value for a key.

Syntax

sword OCIThreadKeyGet ( void          *hndl, 
                        OCIError      *err, 
                        OCIThreadKey  *key, 
                        void          **pValue );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

key (IN)

The key.

pValue (IN/OUT)

The location in which to place the thread-specific key value.

Comments

It is illegal to use this function on a key that has not been created using OCIThreadKeyInit().

If the calling thread has not yet assigned a value to the key, NULL is placed in the location pointed to by pValue.

OCIThreadKeyInit()

Purpose

Creates a key.

Syntax

sword OCIThreadKeyInit (void                  *hndl, 
                        OCIError              *err,
                        OCIThreadKey          **key,
                        OCIThreadKeyDestFunc  destFn );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

key (OUT)

The OCIThreadKey in which to create the new key.

destFn (IN)

The destructor for the key. NULL is permitted.

Comments

Each call to this routine allocates and generates a new key that is distinct from all other keys. After this function executes successfully, a pointer to an allocated and initialized key is returned. That key can be used with OCIThreadKeyGet() and OCIThreadKeySet(). The initial value of the key is NULL for all threads.

It is illegal for this function to be called more than once with the same value for the key parameter.

If the destFn parameter is not NULL, the routine pointed to by destFn is called whenever a thread that has a non-NULL value for the key terminates. The routine is called with one parameter. The parameter is the key's value for the thread at the time at which the thread terminated. If the key does not need a destructor function, pass NULL for destFn.

OCIThreadKeySet()

Purpose

Sets the calling thread's value for a key.

Syntax

sword OCIThreadKeySet ( void           *hndl,
                        OCIError       *err, 
                        OCIThreadKey   *key,
                        void           *value );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

key (IN/OUT)

The key.

value (IN)

The thread-specific value to set in the key.

Comments

It is illegal to use this function on a key that has not been created using OCIThreadKeyInit().

OCIThreadMutexAcquire()

Purpose

Acquires a mutex for the thread in which it is called.

Syntax

sword OCIThreadMutexAcquire ( void            *hndl,
                              OCIError        *err, 
                              OCIThreadMutex  *mutex );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error, it is recorded in err and this function returns OCI_ERROR. Diagnostic information can be obtained by calling OCIErrorGet().

mutex (IN/OUT)

The mutex to acquire.

Comments

If the mutex is held by another thread, the calling thread is blocked until it can acquire the mutex.

It is illegal to attempt to acquire an uninitialized mutex.

This function's behavior is undefined if it is used by a thread to acquire a mutex that is already held by that thread.

OCIThreadMutexDestroy()

Purpose

Destroys and deallocates a mutex.

Syntax

sword OCIThreadMutexDestroy ( void           *hndl, 
                              OCIError       *err, 
                              OCIThreadMutex **mutex );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

mutex (IN/OUT)

The mutex to destroy.

Comments

Each mutex must be destroyed after it is no longer needed.

It is not legal to destroy a mutex that is uninitialized or is currently held by a thread. The destruction of a mutex must not occur concurrently with any other operations on the mutex. A mutex must not be used after it has been destroyed.

OCIThreadMutexInit()

Purpose

Allocates and initializes a mutex.

Syntax

sword OCIThreadMutexInit ( void            *hndl,
                           OCIError        *err, 
                           OCIThreadMutex  **mutex );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

mutex (OUT)

The mutex to initialize.

Comments

All mutexes must be initialized before use.

Multiple threads must not initialize the same mutex simultaneously. Also, a mutex must not be reinitialized until it has been destroyed (see OCIThreadMutexDestroy()).

OCIThreadMutexRelease()

Purpose

Releases a mutex.

Syntax

sword OCIThreadMutexRelease ( void            *hndl,
                              OCIError        *err, 
                              OCIThreadMutex  *mutex );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

mutex (IN/OUT)

The mutex to release.

Comments

If there are any threads blocked on the mutex, one of them acquires it and becomes unblocked.

It is illegal to attempt to release an uninitialized mutex. It is also illegal for a thread to release a mutex that it does not hold.

OCIThreadProcessInit()

Purpose

Performs OCIThread process initialization.

Syntax

void OCIThreadProcessInit ( );

Comments

Whether this function must be called depends on how OCIThread is going to be used.

In a single-threaded application, calling this function is optional. If it is called at all, the first call to it must occur before calls to any other OCIThread functions. Subsequent calls can be made without restriction; they do not have any effect.

In a multithreaded application, this function must be called. The first call to it must occur strictly before any other OCIThread calls; that is, no other calls to OCIThread functions (including other calls to this one) can be concurrent with the first call.

Subsequent calls to this function can be made without restriction; they do not have any effect.

OCIThreadTerm()

Purpose

Releases the OCIThread context.

Syntax

sword OCIThreadTerm ( void      *hndl, 
                      OCIError  *err );

Parameters

hndl (IN/OUT)

The OCI environment or user session handle.

err (IN/OUT)

The OCI error handle. If there is an error and OCI_ERROR is returned, the error is recorded in err and diagnostic information can be obtained by calling OCIErrorGet().

Comments

This function should be called exactly once for each call made to OCIThreadInit().

It is safe to make concurrent calls to OCIThreadTerm(). OCIThreadTerm() does not do anything until it has been called as many times as OCIThreadInit() has been called. When that happens, OCIThreadTerm() terminates the OCIThread layer and frees the memory allocated for the context. Once this happens, the context should not be reused. It is necessary to obtain a new one by calling OCIThreadInit().

Related Functions

OCIThreadInit()