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Diffstat (limited to 'nsprpub/pr/src/threads/prtpd.c')
| -rw-r--r-- | nsprpub/pr/src/threads/prtpd.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/nsprpub/pr/src/threads/prtpd.c b/nsprpub/pr/src/threads/prtpd.c new file mode 100644 index 0000000000..e6385cf700 --- /dev/null +++ b/nsprpub/pr/src/threads/prtpd.c @@ -0,0 +1,252 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* +** Thread Private Data +** +** There is an aribitrary limit on the number of keys that will be allocated +** by the runtime. It's largish, so it is intended to be a sanity check, not +** an impediment. +** +** There is a counter, initialized to zero and incremented every time a +** client asks for a new key, that holds the high water mark for keys. All +** threads logically have the same high water mark and are permitted to +** ask for TPD up to that key value. +** +** The vector to hold the TPD are allocated when PR_SetThreadPrivate() is +** called. The size of the vector will be some value greater than or equal +** to the current high water mark. Each thread has its own TPD length and +** vector. +** +** Threads that get private data for keys they have not set (or perhaps +** don't even exist for that thread) get a NULL return. If the key is +** beyond the high water mark, an error will be returned. +*/ + +/* +** As of this time, BeOS has its own TPD implementation. Integrating +** this standard one is a TODO for anyone with a bit of spare time on +** their hand. For now, we just #ifdef out this whole file and use +** the routines in pr/src/btthreads/ +*/ + + +#include "primpl.h" + +#include <string.h> + +#if defined(WIN95) +/* +** Some local variables report warnings on Win95 because the code paths +** using them are conditioned on HAVE_CUSTOME_USER_THREADS. +** The pragma suppresses the warning. +** +*/ +#pragma warning(disable : 4101) +#endif + +#define _PR_TPD_LIMIT 128 /* arbitary limit on the TPD slots */ +static PRInt32 _pr_tpd_length = 0; /* current length of destructor vector */ +static PRInt32 _pr_tpd_highwater = 0; /* next TPD key to be assigned */ +static PRThreadPrivateDTOR *_pr_tpd_destructors = NULL; +/* the destructors are associated with + the keys, therefore asserting that + the TPD key depicts the data's 'type' */ + +/* +** Initialize the thread private data manipulation +*/ +void _PR_InitTPD(void) +{ + _pr_tpd_destructors = (PRThreadPrivateDTOR*) + PR_CALLOC(_PR_TPD_LIMIT * sizeof(PRThreadPrivateDTOR*)); + PR_ASSERT(NULL != _pr_tpd_destructors); + _pr_tpd_length = _PR_TPD_LIMIT; +} + +/* +** Clean up the thread private data manipulation +*/ +void _PR_CleanupTPD(void) +{ +} /* _PR_CleanupTPD */ + +/* +** This routine returns a new index for per-thread-private data table. +** The index is visible to all threads within a process. This index can +** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines +** to save and retrieve data associated with the index for a thread. +** +** The index independently maintains specific values for each binding thread. +** A thread can only get access to its own thread-specific-data. +** +** Upon a new index return the value associated with the index for all threads +** is NULL, and upon thread creation the value associated with all indices for +** that thread is NULL. +** +** "dtor" is the destructor function to invoke when the private +** data is set or destroyed +** +** Returns PR_FAILURE if the total number of indices will exceed the maximun +** allowed. +*/ + +PR_IMPLEMENT(PRStatus) PR_NewThreadPrivateIndex( + PRUintn *newIndex, PRThreadPrivateDTOR dtor) +{ + PRStatus rv; + PRInt32 index; + + if (!_pr_initialized) { + _PR_ImplicitInitialization(); + } + + PR_ASSERT(NULL != newIndex); + PR_ASSERT(NULL != _pr_tpd_destructors); + + index = PR_ATOMIC_INCREMENT(&_pr_tpd_highwater) - 1; /* allocate index */ + if (_PR_TPD_LIMIT <= index) + { + PR_SetError(PR_TPD_RANGE_ERROR, 0); + rv = PR_FAILURE; /* that's just wrong */ + } + else + { + _pr_tpd_destructors[index] = dtor; /* record destructor @index */ + *newIndex = (PRUintn)index; /* copy into client's location */ + rv = PR_SUCCESS; /* that's okay */ + } + + return rv; +} + +/* +** Define some per-thread-private data. +** "index" is an index into the per-thread private data table +** "priv" is the per-thread-private data +** +** If the per-thread private data table has a previously registered +** destructor function and a non-NULL per-thread-private data value, +** the destructor function is invoked. +** +** This can return PR_FAILURE if index is invalid (ie., beyond the limit +** on the TPD slots) or memory is insufficient to allocate an expanded +** vector. +*/ + +PR_IMPLEMENT(PRStatus) PR_SetThreadPrivate(PRUintn index, void *priv) +{ + PRThread *self = PR_GetCurrentThread(); + + /* + ** To improve performance, we don't check if the index has been + ** allocated. + */ + if (index >= _PR_TPD_LIMIT) + { + PR_SetError(PR_TPD_RANGE_ERROR, 0); + return PR_FAILURE; + } + + PR_ASSERT(((NULL == self->privateData) && (0 == self->tpdLength)) + || ((NULL != self->privateData) && (0 != self->tpdLength))); + + /* + ** If this thread does not have a sufficient vector for the index + ** being set, go ahead and extend this vector now. + */ + if ((NULL == self->privateData) || (self->tpdLength <= index)) + { + void *extension = PR_CALLOC(_pr_tpd_length * sizeof(void*)); + if (NULL == extension) + { + PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0); + return PR_FAILURE; + } + if (self->privateData) { + (void)memcpy( + extension, self->privateData, + self->tpdLength * sizeof(void*)); + PR_DELETE(self->privateData); + } + self->tpdLength = _pr_tpd_length; + self->privateData = (void**)extension; + } + /* + ** There wasn't much chance of having to call the destructor + ** unless the slot already existed. + */ + else if (self->privateData[index] && _pr_tpd_destructors[index]) + { + void *data = self->privateData[index]; + self->privateData[index] = NULL; + (*_pr_tpd_destructors[index])(data); + } + + PR_ASSERT(index < self->tpdLength); + self->privateData[index] = priv; + + return PR_SUCCESS; +} + +/* +** Recover the per-thread-private data for the current thread. "index" is +** the index into the per-thread private data table. +** +** The returned value may be NULL which is indistinguishable from an error +** condition. +** +*/ + +PR_IMPLEMENT(void*) PR_GetThreadPrivate(PRUintn index) +{ + PRThread *self = PR_GetCurrentThread(); + void *tpd = ((NULL == self->privateData) || (index >= self->tpdLength)) ? + NULL : self->privateData[index]; + + return tpd; +} + +/* +** Destroy the thread's private data, if any exists. This is called at +** thread termination time only. There should be no threading issues +** since this is being called by the thread itself. +*/ +void _PR_DestroyThreadPrivate(PRThread* self) +{ +#define _PR_TPD_DESTRUCTOR_ITERATIONS 4 + + if (NULL != self->privateData) /* we have some */ + { + PRBool clean; + PRUint32 index; + PRInt32 passes = _PR_TPD_DESTRUCTOR_ITERATIONS; + PR_ASSERT(0 != self->tpdLength); + do + { + clean = PR_TRUE; + for (index = 0; index < self->tpdLength; ++index) + { + void *priv = self->privateData[index]; /* extract */ + if (NULL != priv) /* we have data at this index */ + { + if (NULL != _pr_tpd_destructors[index]) + { + self->privateData[index] = NULL; /* precondition */ + (*_pr_tpd_destructors[index])(priv); /* destroy */ + clean = PR_FALSE; /* unknown side effects */ + } + } + } + } while ((--passes > 0) && !clean); /* limit # of passes */ + /* + ** We give up after a fixed number of passes. Any non-NULL + ** thread-private data value with a registered destructor + ** function is not destroyed. + */ + memset(self->privateData, 0, self->tpdLength * sizeof(void*)); + } +} /* _PR_DestroyThreadPrivate */ + |