shared_source/c_tcl_base_7_5_w_mods/tclasync.c

/* $Header$ */
/* 
 * tclAsync.c --
 *
 *      This file provides low-level support needed to invoke signal
 *      handlers in a safe way.  The code here doesn't actually handle
 *      signals, though.  This code is based on proposals made by
 *      Mark Diekhans and Don Libes.
 *
 * Copyright (c) 1993 The Regents of the University of California.
 * Copyright (c) 1994 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclasync.c,v 1.1.1.1 2001/06/13 04:33:03 dtashley Exp $
 */

#include "tclInt.h"
#include "tclPort.h"

/*
 * One of the following structures exists for each asynchronous
 * handler:
 */

typedef struct AsyncHandler {
    int ready;                          /* Non-zero means this handler should
                                         * be invoked in the next call to
                                         * Tcl_AsyncInvoke. */
    struct AsyncHandler *nextPtr;       /* Next in list of all handlers for
                                         * the process. */
    Tcl_AsyncProc *proc;                /* Procedure to call when handler
                                         * is invoked. */
    ClientData clientData;              /* Value to pass to handler when it
                                         * is invoked. */
} AsyncHandler;

/*
 * The variables below maintain a list of all existing handlers.
 */

static AsyncHandler *firstHandler;      /* First handler defined for process,
                                         * or NULL if none. */
static AsyncHandler *lastHandler;       /* Last handler or NULL. */

TCL_DECLARE_MUTEX(asyncMutex)           /* Process-wide async handler lock */

/*
 * The variable below is set to 1 whenever a handler becomes ready and
 * it is cleared to zero whenever Tcl_AsyncInvoke is called.  It can be
 * checked elsewhere in the application by calling Tcl_AsyncReady to see
 * if Tcl_AsyncInvoke should be invoked.
 */

static int asyncReady = 0;

/*
 * The variable below indicates whether Tcl_AsyncInvoke is currently
 * working.  If so then we won't set asyncReady again until
 * Tcl_AsyncInvoke returns.
 */

static int asyncActive = 0;

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AsyncCreate --
 *
 *      This procedure creates the data structures for an asynchronous
 *      handler, so that no memory has to be allocated when the handler
 *      is activated.
 *
 * Results:
 *      The return value is a token for the handler, which can be used
 *      to activate it later on.
 *
 * Side effects:
 *      Information about the handler is recorded.
 *
 *----------------------------------------------------------------------
 */

Tcl_AsyncHandler
Tcl_AsyncCreate(proc, clientData)
    Tcl_AsyncProc *proc;                /* Procedure to call when handler
                                         * is invoked. */
    ClientData clientData;              /* Argument to pass to handler. */
{
    AsyncHandler *asyncPtr;

    asyncPtr = (AsyncHandler *) ckalloc(sizeof(AsyncHandler));
    asyncPtr->ready = 0;
    asyncPtr->nextPtr = NULL;
    asyncPtr->proc = proc;
    asyncPtr->clientData = clientData;
    Tcl_MutexLock(&asyncMutex);
    if (firstHandler == NULL) {
        firstHandler = asyncPtr;
    } else {
        lastHandler->nextPtr = asyncPtr;
    }
    lastHandler = asyncPtr;
    Tcl_MutexUnlock(&asyncMutex);
    return (Tcl_AsyncHandler) asyncPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AsyncMark --
 *
 *      This procedure is called to request that an asynchronous handler
 *      be invoked as soon as possible.  It's typically called from
 *      an interrupt handler, where it isn't safe to do anything that
 *      depends on or modifies application state.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The handler gets marked for invocation later.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AsyncMark(async)
    Tcl_AsyncHandler async;             /* Token for handler. */
{
    Tcl_MutexLock(&asyncMutex);
    ((AsyncHandler *) async)->ready = 1;
    if (!asyncActive) {
        asyncReady = 1;
        TclpAsyncMark(async);
    }
    Tcl_MutexUnlock(&asyncMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AsyncInvoke --
 *
 *      This procedure is called at a "safe" time at background level
 *      to invoke any active asynchronous handlers.
 *
 * Results:
 *      The return value is a normal Tcl result, which is intended to
 *      replace the code argument as the current completion code for
 *      interp.
 *
 * Side effects:
 *      Depends on the handlers that are active.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_AsyncInvoke(interp, code)
    Tcl_Interp *interp;                 /* If invoked from Tcl_Eval just after
                                         * completing a command, points to
                                         * interpreter.  Otherwise it is
                                         * NULL. */
    int code;                           /* If interp is non-NULL, this gives
                                         * completion code from command that
                                         * just completed. */
{
    AsyncHandler *asyncPtr;
    Tcl_MutexLock(&asyncMutex);

    if (asyncReady == 0) {
        Tcl_MutexUnlock(&asyncMutex);
        return code;
    }
    asyncReady = 0;
    asyncActive = 1;
    if (interp == NULL) {
        code = 0;
    }

    /*
     * Make one or more passes over the list of handlers, invoking
     * at most one handler in each pass.  After invoking a handler,
     * go back to the start of the list again so that (a) if a new
     * higher-priority handler gets marked while executing a lower
     * priority handler, we execute the higher-priority handler
     * next, and (b) if a handler gets deleted during the execution
     * of a handler, then the list structure may change so it isn't
     * safe to continue down the list anyway.
     */

    while (1) {
        for (asyncPtr = firstHandler; asyncPtr != NULL;
                asyncPtr = asyncPtr->nextPtr) {
            if (asyncPtr->ready) {
                break;
            }
        }
        if (asyncPtr == NULL) {
            break;
        }
        asyncPtr->ready = 0;
        Tcl_MutexUnlock(&asyncMutex);
        code = (*asyncPtr->proc)(asyncPtr->clientData, interp, code);
        Tcl_MutexLock(&asyncMutex);
    }
    asyncActive = 0;
    Tcl_MutexUnlock(&asyncMutex);
    return code;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AsyncDelete --
 *
 *      Frees up all the state for an asynchronous handler.  The handler
 *      should never be used again.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The state associated with the handler is deleted.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AsyncDelete(async)
    Tcl_AsyncHandler async;             /* Token for handler to delete. */
{
    AsyncHandler *asyncPtr = (AsyncHandler *) async;
    AsyncHandler *prevPtr;

    Tcl_MutexLock(&asyncMutex);
    if (firstHandler == asyncPtr) {
        firstHandler = asyncPtr->nextPtr;
        if (firstHandler == NULL) {
            lastHandler = NULL;
        }
    } else {
        prevPtr = firstHandler;
        while (prevPtr->nextPtr != asyncPtr) {
            prevPtr = prevPtr->nextPtr;
        }
        prevPtr->nextPtr = asyncPtr->nextPtr;
        if (lastHandler == asyncPtr) {
            lastHandler = prevPtr;
        }
    }
    Tcl_MutexUnlock(&asyncMutex);
    ckfree((char *) asyncPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AsyncReady --
 *
 *      This procedure can be used to tell whether Tcl_AsyncInvoke
 *      needs to be called.  This procedure is the external interface
 *      for checking the internal asyncReady variable.
 *
 * Results:
 *      The return value is 1 whenever a handler is ready and is 0
 *      when no handlers are ready.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_AsyncReady()
{
    return asyncReady;
}

/* End of tclasync.c */
1	/* $Header$ */
2	/*
3	* tclAsync.c --
4	*
5	* This file provides low-level support needed to invoke signal
6	* handlers in a safe way. The code here doesn't actually handle
7	* signals, though. This code is based on proposals made by
8	* Mark Diekhans and Don Libes.
9	*
10	* Copyright (c) 1993 The Regents of the University of California.
11	* Copyright (c) 1994 Sun Microsystems, Inc.
12	*
13	* See the file "license.terms" for information on usage and redistribution
14	* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
15	*
16	* RCS: @(#) $Id: tclasync.c,v 1.1.1.1 2001/06/13 04:33:03 dtashley Exp $
17	*/
18
19	#include "tclInt.h"
20	#include "tclPort.h"
21
22	/*
23	* One of the following structures exists for each asynchronous
24	* handler:
25	*/
26
27	typedef struct AsyncHandler {
28	int ready; /* Non-zero means this handler should
29	* be invoked in the next call to
30	* Tcl_AsyncInvoke. */
31	struct AsyncHandler nextPtr; / Next in list of all handlers for
32	* the process. */
33	Tcl_AsyncProc proc; / Procedure to call when handler
34	* is invoked. */
35	ClientData clientData; /* Value to pass to handler when it
36	* is invoked. */
37	} AsyncHandler;
38
39	/*
40	* The variables below maintain a list of all existing handlers.
41	*/
42
43	static AsyncHandler firstHandler; / First handler defined for process,
44	* or NULL if none. */
45	static AsyncHandler lastHandler; / Last handler or NULL. */
46
47	TCL_DECLARE_MUTEX(asyncMutex) /* Process-wide async handler lock */
48
49	/*
50	* The variable below is set to 1 whenever a handler becomes ready and
51	* it is cleared to zero whenever Tcl_AsyncInvoke is called. It can be
52	* checked elsewhere in the application by calling Tcl_AsyncReady to see
53	* if Tcl_AsyncInvoke should be invoked.
54	*/
55
56	static int asyncReady = 0;
57
58	/*
59	* The variable below indicates whether Tcl_AsyncInvoke is currently
60	* working. If so then we won't set asyncReady again until
61	* Tcl_AsyncInvoke returns.
62	*/
63
64	static int asyncActive = 0;
65
66	/*
67	*----------------------------------------------------------------------
68	*
69	* Tcl_AsyncCreate --
70	*
71	* This procedure creates the data structures for an asynchronous
72	* handler, so that no memory has to be allocated when the handler
73	* is activated.
74	*
75	* Results:
76	* The return value is a token for the handler, which can be used
77	* to activate it later on.
78	*
79	* Side effects:
80	* Information about the handler is recorded.
81	*
82	*----------------------------------------------------------------------
83	*/
84
85	Tcl_AsyncHandler
86	Tcl_AsyncCreate(proc, clientData)
87	Tcl_AsyncProc proc; / Procedure to call when handler
88	* is invoked. */
89	ClientData clientData; /* Argument to pass to handler. */
90	{
91	AsyncHandler *asyncPtr;
92
93	asyncPtr = (AsyncHandler *) ckalloc(sizeof(AsyncHandler));
94	asyncPtr->ready = 0;
95	asyncPtr->nextPtr = NULL;
96	asyncPtr->proc = proc;
97	asyncPtr->clientData = clientData;
98	Tcl_MutexLock(&asyncMutex);
99	if (firstHandler == NULL) {
100	firstHandler = asyncPtr;
101	} else {
102	lastHandler->nextPtr = asyncPtr;
103	}
104	lastHandler = asyncPtr;
105	Tcl_MutexUnlock(&asyncMutex);
106	return (Tcl_AsyncHandler) asyncPtr;
107	}
108
109	/*
110	*----------------------------------------------------------------------
111	*
112	* Tcl_AsyncMark --
113	*
114	* This procedure is called to request that an asynchronous handler
115	* be invoked as soon as possible. It's typically called from
116	* an interrupt handler, where it isn't safe to do anything that
117	* depends on or modifies application state.
118	*
119	* Results:
120	* None.
121	*
122	* Side effects:
123	* The handler gets marked for invocation later.
124	*
125	*----------------------------------------------------------------------
126	*/
127
128	void
129	Tcl_AsyncMark(async)
130	Tcl_AsyncHandler async; /* Token for handler. */
131	{
132	Tcl_MutexLock(&asyncMutex);
133	((AsyncHandler *) async)->ready = 1;
134	if (!asyncActive) {
135	asyncReady = 1;
136	TclpAsyncMark(async);
137	}
138	Tcl_MutexUnlock(&asyncMutex);
139	}
140
141	/*
142	*----------------------------------------------------------------------
143	*
144	* Tcl_AsyncInvoke --
145	*
146	* This procedure is called at a "safe" time at background level
147	* to invoke any active asynchronous handlers.
148	*
149	* Results:
150	* The return value is a normal Tcl result, which is intended to
151	* replace the code argument as the current completion code for
152	* interp.
153	*
154	* Side effects:
155	* Depends on the handlers that are active.
156	*
157	*----------------------------------------------------------------------
158	*/
159
160	int
161	Tcl_AsyncInvoke(interp, code)
162	Tcl_Interp interp; / If invoked from Tcl_Eval just after
163	* completing a command, points to
164	* interpreter. Otherwise it is
165	* NULL. */
166	int code; /* If interp is non-NULL, this gives
167	* completion code from command that
168	* just completed. */
169	{
170	AsyncHandler *asyncPtr;
171	Tcl_MutexLock(&asyncMutex);
172
173	if (asyncReady == 0) {
174	Tcl_MutexUnlock(&asyncMutex);
175	return code;
176	}
177	asyncReady = 0;
178	asyncActive = 1;
179	if (interp == NULL) {
180	code = 0;
181	}
182
183	/*
184	* Make one or more passes over the list of handlers, invoking
185	* at most one handler in each pass. After invoking a handler,
186	* go back to the start of the list again so that (a) if a new
187	* higher-priority handler gets marked while executing a lower
188	* priority handler, we execute the higher-priority handler
189	* next, and (b) if a handler gets deleted during the execution
190	* of a handler, then the list structure may change so it isn't
191	* safe to continue down the list anyway.
192	*/
193
194	while (1) {
195	for (asyncPtr = firstHandler; asyncPtr != NULL;
196	asyncPtr = asyncPtr->nextPtr) {
197	if (asyncPtr->ready) {
198	break;
199	}
200	}
201	if (asyncPtr == NULL) {
202	break;
203	}
204	asyncPtr->ready = 0;
205	Tcl_MutexUnlock(&asyncMutex);
206	code = (*asyncPtr->proc)(asyncPtr->clientData, interp, code);
207	Tcl_MutexLock(&asyncMutex);
208	}
209	asyncActive = 0;
210	Tcl_MutexUnlock(&asyncMutex);
211	return code;
212	}
213
214	/*
215	*----------------------------------------------------------------------
216	*
217	* Tcl_AsyncDelete --
218	*
219	* Frees up all the state for an asynchronous handler. The handler
220	* should never be used again.
221	*
222	* Results:
223	* None.
224	*
225	* Side effects:
226	* The state associated with the handler is deleted.
227	*
228	*----------------------------------------------------------------------
229	*/
230
231	void
232	Tcl_AsyncDelete(async)
233	Tcl_AsyncHandler async; /* Token for handler to delete. */
234	{
235	AsyncHandler asyncPtr = (AsyncHandler ) async;
236	AsyncHandler *prevPtr;
237
238	Tcl_MutexLock(&asyncMutex);
239	if (firstHandler == asyncPtr) {
240	firstHandler = asyncPtr->nextPtr;
241	if (firstHandler == NULL) {
242	lastHandler = NULL;
243	}
244	} else {
245	prevPtr = firstHandler;
246	while (prevPtr->nextPtr != asyncPtr) {
247	prevPtr = prevPtr->nextPtr;
248	}
249	prevPtr->nextPtr = asyncPtr->nextPtr;
250	if (lastHandler == asyncPtr) {
251	lastHandler = prevPtr;
252	}
253	}
254	Tcl_MutexUnlock(&asyncMutex);
255	ckfree((char *) asyncPtr);
256	}
257
258	/*
259	*----------------------------------------------------------------------
260	*
261	* Tcl_AsyncReady --
262	*
263	* This procedure can be used to tell whether Tcl_AsyncInvoke
264	* needs to be called. This procedure is the external interface
265	* for checking the internal asyncReady variable.
266	*
267	* Results:
268	* The return value is 1 whenever a handler is ready and is 0
269	* when no handlers are ready.
270	*
271	* Side effects:
272	* None.
273	*
274	*----------------------------------------------------------------------
275	*/
276
277	int
278	Tcl_AsyncReady()
279	{
280	return asyncReady;
281	}
282
283	/* End of tclasync.c */