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/gecko_api/include/prthread.h

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  1/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
  2/* ***** BEGIN LICENSE BLOCK *****
  3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  4 *
  5 * The contents of this file are subject to the Mozilla Public License Version
  6 * 1.1 (the "License"); you may not use this file except in compliance with
  7 * the License. You may obtain a copy of the License at
  8 * http://www.mozilla.org/MPL/
  9 *
 10 * Software distributed under the License is distributed on an "AS IS" basis,
 11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 12 * for the specific language governing rights and limitations under the
 13 * License.
 14 *
 15 * The Original Code is the Netscape Portable Runtime (NSPR).
 16 *
 17 * The Initial Developer of the Original Code is
 18 * Netscape Communications Corporation.
 19 * Portions created by the Initial Developer are Copyright (C) 1998-2000
 20 * the Initial Developer. All Rights Reserved.
 21 *
 22 * Contributor(s):
 23 *
 24 * Alternatively, the contents of this file may be used under the terms of
 25 * either the GNU General Public License Version 2 or later (the "GPL"), or
 26 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 27 * in which case the provisions of the GPL or the LGPL are applicable instead
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 33 * the provisions above, a recipient may use your version of this file under
 34 * the terms of any one of the MPL, the GPL or the LGPL.
 35 *
 36 * ***** END LICENSE BLOCK ***** */
 37
 38#ifndef prthread_h___
 39#define prthread_h___
 40
 41/*
 42** API for NSPR threads. On some architectures (MAC and WIN16
 43** notably) pre-emptibility is not guaranteed. Hard priority scheduling
 44** is not guaranteed, so programming using priority based synchronization
 45** is a no-no.
 46**
 47** NSPR threads are scheduled based loosely on their client set priority.
 48** In general, a thread of a higher priority has a statistically better
 49** chance of running relative to threads of lower priority. However,
 50** NSPR uses multiple strategies to provide execution vehicles for thread
 51** abstraction of various host platforms. As it turns out, there is little
 52** NSPR can do to affect the scheduling attributes of "GLOBAL" threads.
 53** However, a semblance of GLOBAL threads is used to implement "LOCAL"
 54** threads. An arbitrary number of such LOCAL threads can be assigned to
 55** a single GLOBAL thread.
 56**
 57** For scheduling, NSPR will attempt to run the highest priority LOCAL
 58** thread associated with a given GLOBAL thread. It is further assumed
 59** that the host OS will apply some form of "fair" scheduling on the
 60** GLOBAL threads.
 61**
 62** Threads have a "system flag" which when set indicates the thread
 63** doesn't count for determining when the process should exit (the
 64** process exits when the last user thread exits).
 65**
 66** Threads also have a "scope flag" which controls whether the threads
 67** are scheduled in the local scope or scheduled by the OS globally. This 
 68** indicates whether a thread is permanently bound to a native OS thread. 
 69** An unbound thread competes for scheduling resources in the same process.
 70**
 71** Another flag is "state flag" which control whether the thread is joinable.
 72** It allows other threads to wait for the created thread to reach completion.
 73**
 74** Threads can have "per-thread-data" attached to them. Each thread has a
 75** per-thread error number and error string which are updated when NSPR
 76** operations fail.
 77*/
 78#include "prtypes.h"
 79#include "prinrval.h"
 80
 81PR_BEGIN_EXTERN_C
 82
 83typedef struct PRThread PRThread;
 84typedef struct PRThreadStack PRThreadStack;
 85
 86typedef enum PRThreadType {
 87    PR_USER_THREAD,
 88    PR_SYSTEM_THREAD
 89} PRThreadType;
 90
 91typedef enum PRThreadScope {
 92    PR_LOCAL_THREAD,
 93    PR_GLOBAL_THREAD,
 94    PR_GLOBAL_BOUND_THREAD
 95} PRThreadScope;
 96
 97typedef enum PRThreadState {
 98    PR_JOINABLE_THREAD,
 99    PR_UNJOINABLE_THREAD
100} PRThreadState;
101
102typedef enum PRThreadPriority
103{
104    PR_PRIORITY_FIRST = 0,      /* just a placeholder */
105    PR_PRIORITY_LOW = 0,        /* the lowest possible priority */
106    PR_PRIORITY_NORMAL = 1,     /* most common expected priority */
107    PR_PRIORITY_HIGH = 2,       /* slightly more aggressive scheduling */
108    PR_PRIORITY_URGENT = 3,     /* it does little good to have more than one */
109    PR_PRIORITY_LAST = 3        /* this is just a placeholder */
110} PRThreadPriority;
111
112/*
113** Create a new thread:
114**     "type" is the type of thread to create
115**     "start(arg)" will be invoked as the threads "main"
116**     "priority" will be created thread's priority
117**     "scope" will specify whether the thread is local or global
118**     "state" will specify whether the thread is joinable or not
119**     "stackSize" the size of the stack, in bytes. The value can be zero
120**        and then a machine specific stack size will be chosen.
121**
122** This can return NULL if some kind of error occurs, such as if memory is
123** tight.
124**
125** If you want the thread to start up waiting for the creator to do
126** something, enter a lock before creating the thread and then have the
127** threads start routine enter and exit the same lock. When you are ready
128** for the thread to run, exit the lock.
129**
130** If you want to detect the completion of the created thread, the thread
131** should be created joinable.  Then, use PR_JoinThread to synchrnoize the
132** termination of another thread.
133**
134** When the start function returns the thread exits. If it is the last
135** PR_USER_THREAD to exit then the process exits.
136*/
137NSPR_API(PRThread*) PR_CreateThread(PRThreadType type,
138                     void (PR_CALLBACK *start)(void *arg),
139                     void *arg,
140                     PRThreadPriority priority,
141                     PRThreadScope scope,
142                     PRThreadState state,
143                     PRUint32 stackSize);
144
145/*
146** Wait for thread termination:
147**     "thread" is the target thread 
148**
149** This can return PR_FAILURE if no joinable thread could be found 
150** corresponding to the specified target thread.
151**
152** The calling thread is blocked until the target thread completes.
153** Several threads cannot wait for the same thread to complete; one thread
154** will operate successfully and others will terminate with an error PR_FAILURE.
155** The calling thread will not be blocked if the target thread has already
156** terminated.
157*/
158NSPR_API(PRStatus) PR_JoinThread(PRThread *thread);
159
160/*
161** Return the current thread object for the currently running code.
162** Never returns NULL.
163*/
164NSPR_API(PRThread*) PR_GetCurrentThread(void);
165#ifndef NO_NSPR_10_SUPPORT
166#define PR_CurrentThread() PR_GetCurrentThread() /* for nspr1.0 compat. */
167#endif /* NO_NSPR_10_SUPPORT */
168
169/*
170** Get the priority of "thread".
171*/
172NSPR_API(PRThreadPriority) PR_GetThreadPriority(const PRThread *thread);
173
174/*
175** Change the priority of the "thread" to "priority".
176*/
177NSPR_API(void) PR_SetThreadPriority(PRThread *thread, PRThreadPriority priority);
178
179/*
180** This routine returns a new index for per-thread-private data table. 
181** The index is visible to all threads within a process. This index can 
182** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines 
183** to save and retrieve data associated with the index for a thread.
184**
185** Each index is associationed with a destructor function ('dtor'). The function
186** may be specified as NULL when the index is created. If it is not NULL, the
187** function will be called when:
188**      - the thread exits and the private data for the associated index
189**        is not NULL,
190**      - new thread private data is set and the current private data is
191**        not NULL.
192**
193** The index independently maintains specific values for each binding thread. 
194** A thread can only get access to its own thread-specific-data.
195**
196** Upon a new index return the value associated with the index for all threads
197** is NULL, and upon thread creation the value associated with all indices for 
198** that thread is NULL. 
199**
200** Returns PR_FAILURE if the total number of indices will exceed the maximun 
201** allowed.
202*/
203typedef void (PR_CALLBACK *PRThreadPrivateDTOR)(void *priv);
204
205NSPR_API(PRStatus) PR_NewThreadPrivateIndex(
206    PRUintn *newIndex, PRThreadPrivateDTOR destructor);
207
208/*
209** Define some per-thread-private data.
210**     "tpdIndex" is an index into the per-thread private data table
211**     "priv" is the per-thread-private data 
212**
213** If the per-thread private data table has a previously registered
214** destructor function and a non-NULL per-thread-private data value,
215** the destructor function is invoked.
216**
217** This can return PR_FAILURE if the index is invalid.
218*/
219NSPR_API(PRStatus) PR_SetThreadPrivate(PRUintn tpdIndex, void *priv);
220
221/*
222** Recover the per-thread-private data for the current thread. "tpdIndex" is
223** the index into the per-thread private data table. 
224**
225** The returned value may be NULL which is indistinguishable from an error 
226** condition.
227**
228** A thread can only get access to its own thread-specific-data.
229*/
230NSPR_API(void*) PR_GetThreadPrivate(PRUintn tpdIndex);
231
232/*
233** This routine sets the interrupt request for a target thread. The interrupt
234** request remains in the thread's state until it is delivered exactly once
235** or explicitly canceled.
236**
237** A thread that has been interrupted will fail all NSPR blocking operations
238** that return a PRStatus (I/O, waiting on a condition, etc).
239**
240** PR_Interrupt may itself fail if the target thread is invalid.
241*/
242NSPR_API(PRStatus) PR_Interrupt(PRThread *thread);
243
244/*
245** Clear the interrupt request for the calling thread. If no such request
246** is pending, this operation is a noop.
247*/
248NSPR_API(void) PR_ClearInterrupt(void);
249
250/*
251** Block the interrupt for the calling thread.
252*/
253NSPR_API(void) PR_BlockInterrupt(void);
254
255/*
256** Unblock the interrupt for the calling thread.
257*/
258NSPR_API(void) PR_UnblockInterrupt(void);
259
260/*
261** Make the current thread sleep until "ticks" time amount of time
262** has expired. If "ticks" is PR_INTERVAL_NO_WAIT then the call is
263** equivalent to calling PR_Yield. Calling PR_Sleep with an argument
264** equivalent to PR_INTERVAL_NO_TIMEOUT is an error and will result
265** in a PR_FAILURE error return.
266*/
267NSPR_API(PRStatus) PR_Sleep(PRIntervalTime ticks);
268
269/*
270** Get the scoping of this thread.
271*/
272NSPR_API(PRThreadScope) PR_GetThreadScope(const PRThread *thread);
273
274/*
275** Get the type of this thread.
276*/
277NSPR_API(PRThreadType) PR_GetThreadType(const PRThread *thread);
278
279/*
280** Get the join state of this thread.
281*/
282NSPR_API(PRThreadState) PR_GetThreadState(const PRThread *thread);
283
284PR_END_EXTERN_C
285
286#endif /* prthread_h___ */