/**
 * force the current thread to yield the processor
 */
APR_DECLARE(void) apr_thread_yield(void);

/**
 * Initialize the control variable for apr_thread_once.  If this isn't
 * called, apr_initialize won't work.
 * @param control The control variable to initialize
 * @param p The pool to allocate data from.
 */
APR_DECLARE(apr_status_t) apr_thread_once_init(apr_thread_once_t **control,
                                               apr_pool_t *p);

/**
 * Run the specified function one time, regardless of how many threads
 * call it.
 * @param control The control variable.  The same variable should
 *                be passed in each time the function is tried to be
 *                called.  This is how the underlying functions determine
 *                if the function has ever been called before.
 * @param func The function to call.
 */
APR_DECLARE(apr_status_t) apr_thread_once(apr_thread_once_t *control,
                                          void (*func)(void));

/**
 * detach a thread
 * @param thd The thread to detach 
 */
APR_DECLARE(apr_status_t) apr_thread_detach(apr_thread_t *thd);

/**
 * Return the pool associated with the current thread.
 * @param data The user data associated with the thread.
 * @param key The key to associate with the data
 * @param thread The currently open thread.
 */
APR_DECLARE(apr_status_t) apr_thread_data_get(void **data, const char *key,
                                             apr_thread_t *thread);

/**
 * Return the pool associated with the current thread.
 * @param data The user data to associate with the thread.
 * @param key The key to use for associating the data with the thread
 * @param cleanup The cleanup routine to use when the thread is destroyed.
 * @param thread The currently open thread.
 */
APR_DECLARE(apr_status_t) apr_thread_data_set(void *data, const char *key,
                                             apr_status_t (*cleanup) (void *),
                                             apr_thread_t *thread);

/**
 * Create and initialize a new thread private address space
 * @param key The thread private handle.
 * @param dest The destructor to use when freeing the private memory.
 * @param cont The pool to use
 */
APR_DECLARE(apr_status_t) apr_threadkey_private_create(apr_threadkey_t **key, 
                                                    void (*dest)(void *),
                                                    apr_pool_t *cont);

/**
 * Get a pointer to the thread private memory
 * @param new_mem The data stored in private memory 
 * @param key The handle for the desired thread private memory 
 */
APR_DECLARE(apr_status_t) apr_threadkey_private_get(void **new_mem, 
                                                 apr_threadkey_t *key);

/**
 * Set the data to be stored in thread private memory
 * @param priv The data to be stored in private memory 
 * @param key The handle for the desired thread private memory 
 */
APR_DECLARE(apr_status_t) apr_threadkey_private_set(void *priv, 
                                                 apr_threadkey_t *key);

/**
 * Free the thread private memory
 * @param key The handle for the desired thread private memory 
 */
APR_DECLARE(apr_status_t) apr_threadkey_private_delete(apr_threadkey_t *key);

/**
 * Return the pool associated with the current threadkey.
 * @param data The user data associated with the threadkey.
 * @param key The key associated with the data
 * @param threadkey The currently open threadkey.
 */
APR_DECLARE(apr_status_t) apr_threadkey_data_get(void **data, const char *key,
                                                apr_threadkey_t *threadkey);

/**
 * Return the pool associated with the current threadkey.
 * @param data The data to set.
 * @param key The key to associate with the data.
 * @param cleanup The cleanup routine to use when the file is destroyed.
 * @param threadkey The currently open threadkey.
 */
APR_DECLARE(apr_status_t) apr_threadkey_data_set(void *data, const char *key,
                                                apr_status_t (*cleanup) (void *),
                                                apr_threadkey_t *threadkey);

#endif

/**
 * Create and initialize a new procattr variable
 * @param new_attr The newly created procattr. 
 * @param cont The pool to use
 */
APR_DECLARE(apr_status_t) apr_procattr_create(apr_procattr_t **new_attr,
                                                  apr_pool_t *cont);

/**
 * Determine if any of stdin, stdout, or stderr should be linked to pipes 
 * when starting a child process.
 * @param attr The procattr we care about. 
 * @param in Should stdin be a pipe back to the parent?
 * @param out Should stdout be a pipe back to the parent?
 * @param err Should stderr be a pipe back to the parent?
 */
APR_DECLARE(apr_status_t) apr_procattr_io_set(apr_procattr_t *attr, 
                                             apr_int32_t in, apr_int32_t out,
                                             apr_int32_t err);

/**
 * Set the child_in and/or parent_in values to existing apr_file_t values.
 * @param attr The procattr we care about. 
 * @param child_in apr_file_t value to use as child_in. Must be a valid file.
 * @param parent_in apr_file_t value to use as parent_in. Must be a valid file.
 * @remark  This is NOT a required initializer function. This is
 *          useful if you have already opened a pipe (or multiple files)
 *          that you wish to use, perhaps persistently across multiple
 *          process invocations - such as a log file. You can save some 
 *          extra function calls by not creating your own pipe since this
 *          creates one in the process space for you.
 */
APR_DECLARE(apr_status_t) apr_procattr_child_in_set(struct apr_procattr_t *attr,
                                                  apr_file_t *child_in,
                                                  apr_file_t *parent_in);

/**
 * Set the child_out and parent_out values to existing apr_file_t values.
 * @param attr The procattr we care about. 
 * @param child_out apr_file_t value to use as child_out. Must be a valid file.
 * @param parent_out apr_file_t value to use as parent_out. Must be a valid file.
 * @remark This is NOT a required initializer function. This is
 *         useful if you have already opened a pipe (or multiple files)
 *         that you wish to use, perhaps persistently across multiple
 *         process invocations - such as a log file. 
 */
APR_DECLARE(apr_status_t) apr_procattr_child_out_set(struct apr_procattr_t *attr,
                                                   apr_file_t *child_out,
                                                   apr_file_t *parent_out);

/**
 * Set the child_err and parent_err values to existing apr_file_t values.
 * @param attr The procattr we care about. 
 * @param child_err apr_file_t value to use as child_err. Must be a valid file.
 * @param parent_err apr_file_t value to use as parent_err. Must be a valid file.
 * @remark This is NOT a required initializer function. This is
 *         useful if you have already opened a pipe (or multiple files)
 *         that you wish to use, perhaps persistently across multiple
 *         process invocations - such as a log file. 
 */
APR_DECLARE(apr_status_t) apr_procattr_child_err_set(struct apr_procattr_t *attr,
                                                   apr_file_t *child_err,
                                                   apr_file_t *parent_err);

/**
 * Set which directory the child process should start executing in.
 * @param attr The procattr we care about. 
 * @param dir Which dir to start in.  By default, this is the same dir as
 *            the parent currently resides in, when the createprocess call
 *            is made. 
 */
APR_DECLARE(apr_status_t) apr_procattr_dir_set(apr_procattr_t *attr, 
                                              const char *dir);

/**
 * Set what type of command the child process will call.
 * @param attr The procattr we care about. 
 * @param cmd The type of command.  One of:
 * <PRE>
 *            APR_SHELLCMD     --  Anything that the shell can handle
 *            APR_PROGRAM      --  Executable program   (default) 
 *            APR_PROGRAM_ENV  --  Executable program, copy environment
 *            APR_PROGRAM_PATH --  Executable program on PATH, copy env
 * </PRE>
 */
APR_DECLARE(apr_status_t) apr_procattr_cmdtype_set(apr_procattr_t *attr,
                                                  apr_cmdtype_e cmd);

/**
 * Determine if the child should start in detached state.
 * @param attr The procattr we care about. 
 * @param detach Should the child start in detached state?  Default is no. 
 */
APR_DECLARE(apr_status_t) apr_procattr_detach_set(apr_procattr_t *attr, 
                                                 apr_int32_t detach);

#if APR_HAVE_STRUCT_RLIMIT
/**
 * Set the Resource Utilization limits when starting a new process.
 * @param attr The procattr we care about. 
 * @param what Which limit to set, one of:
 * <PRE>
 *                 APR_LIMIT_CPU
 *                 APR_LIMIT_MEM
 *                 APR_LIMIT_NPROC
 *                 APR_LIMIT_NOFILE
 * </PRE>
 * @param limit Value to set the limit to.
 */
APR_DECLARE(apr_status_t) apr_procattr_limit_set(apr_procattr_t *attr, 
                                                apr_int32_t what,
                                                struct rlimit *limit);
#endif

/**
 * Specify an error function to be called in the child process if APR
 * encounters an error in the child prior to running the specified program.
 * @param attr The procattr describing the child process to be created.
 * @param errfn The function to call in the child process.
 * @remark At the present time, it will only be called from apr_proc_create()
 *         on platforms where fork() is used.  It will never be called on other
 *         platforms, on those platforms apr_proc_create() will return the error
 *         in the parent process rather than invoke the callback in the now-forked
 *         child process.
 */
APR_DECLARE(apr_status_t) apr_procattr_child_errfn_set(apr_procattr_t *attr,
                                                       apr_child_errfn_t *errfn);

/**
 * Specify that apr_proc_create() should do whatever it can to report
 * failures to the caller of apr_proc_create(), rather than find out in
 * the child.
 * @param attr The procattr describing the child process to be created.
 * @param chk Flag to indicate whether or not extra work should be done
 *            to try to report failures to the caller.
 * @remark This flag only affects apr_proc_create() on platforms where
 *         fork() is used.  This leads to extra overhead in the calling
 *         process, but that may help the application handle such
 *         errors more gracefully.
 */
APR_DECLARE(apr_status_t) apr_procattr_error_check_set(apr_procattr_t *attr,
                                                       apr_int32_t chk);

/**
 * Determine if the child should start in its own address space or using the 
 * current one from its parent
 * @param attr The procattr we care about. 
 * @param addrspace Should the child start in its own address space?  Default
 *                  is no on NetWare and yes on other platforms.
 */
APR_DECLARE(apr_status_t) apr_procattr_addrspace_set(apr_procattr_t *attr,
                                                       apr_int32_t addrspace);