/* 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 */