/* -*- 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/. */

/*

 * Lifetime-based fast allocation, inspired by much prior art, including

 * "Fast Allocation and Deallocation of Memory Based on Object Lifetimes"

 * David R. Hanson, Software -- Practice and Experience, Vol. 20(1).

 */

#include <stdlib.h>

#include <string.h>

#include "plarena.h"

#include "prmem.h"

#include "prbit.h"

#include "prlog.h"

#include "prlock.h"

#include "prinit.h"

#ifdef PL_ARENAMETER

static PLArenaStats* arena_stats_list;

#  define COUNT(pool, what) (pool)->stats.what++

#else

#  define COUNT(pool, what) /* nothing */

#endif

#define PL_ARENA_DEFAULT_ALIGN sizeof(double)

PR_IMPLEMENT(void)

PL_InitArenaPool(PLArenaPool* pool, const char* name, PRUint32 size,

                 PRUint32 align) {

  /*

   * Look-up table of PR_BITMASK(PR_CeilingLog2(align)) values for

   * align = 1 to 32.

   */

  static const PRUint8 pmasks[33] = {

      0, /*  not used */

      0,  1,  3,  3,  7,  7,  7,  7,

      15, 15, 15, 15, 15, 15, 15, 15, /*  1 ... 16 */

      31, 31, 31, 31, 31, 31, 31, 31,

      31, 31, 31, 31, 31, 31, 31, 31 /* 17 ... 32 */

  };

  if (align == 0) {

    align = PL_ARENA_DEFAULT_ALIGN;

  }

  if (align < sizeof(pmasks) / sizeof(pmasks[0])) {

    pool->mask = pmasks[align];

  } else {

    pool->mask = PR_BITMASK(PR_CeilingLog2(align));

  }

  pool->first.next = NULL;

  /* Set all three addresses in pool->first to the same dummy value.

   * These addresses are only compared with each other, but never

   * dereferenced. */

  pool->first.base = pool->first.avail = pool->first.limit =

      (PRUword)PL_ARENA_ALIGN(pool, &pool->first + 1);

  pool->current = &pool->first;

  /*

   * Compute the net size so that each arena's gross size is |size|.

   * sizeof(PLArena) + pool->mask is the header and alignment slop

   * that PL_ArenaAllocate adds to the net size.

   */

  if (size > sizeof(PLArena) + pool->mask) {

    pool->arenasize = size - (sizeof(PLArena) + pool->mask);

  } else {

    pool->arenasize = size;

  }

#ifdef PL_ARENAMETER

  memset(&pool->stats, 0, sizeof pool->stats);

  pool->stats.name = strdup(name);

  pool->stats.next = arena_stats_list;

  arena_stats_list = &pool->stats;

#endif

}

/*

** PL_ArenaAllocate() -- allocate space from an arena pool

**

** Description: PL_ArenaAllocate() allocates space from an arena

** pool.

**

** First, try to satisfy the request from arenas starting at

** pool->current. Then try to allocate a new arena from the heap.

**

** Returns: pointer to allocated space or NULL

**

** Notes: The original implementation had some difficult to

** solve bugs; the code was difficult to read. Sometimes it's

** just easier to rewrite it. I did that. larryh.

**

** See also: bugzilla: 45343.

**

*/

PR_IMPLEMENT(void*) PL_ArenaAllocate(PLArenaPool* pool, PRUint32 nb) {

  PLArena* a;

  char* rp; /* returned pointer */

  PRUint32 nbOld;

  PR_ASSERT((nb & pool->mask) == 0);

  nbOld = nb;

  nb = (PRUword)PL_ARENA_ALIGN(pool, nb); /* force alignment */

  if (nb < nbOld) {

    return NULL;

  }

  /* attempt to allocate from arenas at pool->current */

  {

    a = pool->current;

    do {

      if (nb <= a->limit - a->avail) {

        pool->current = a;

        rp = (char*)a->avail;

        a->avail += nb;

        return rp;

      }

    } while (NULL != (a = a->next));

  }

  /* attempt to allocate from the heap */

  {

    PRUint32 sz = PR_MAX(pool->arenasize, nb);

    if (PR_UINT32_MAX - sz < sizeof *a + pool->mask) {

      a = NULL;

    } else {

      sz += sizeof *a + pool->mask; /* header and alignment slop */

      a = (PLArena*)PR_MALLOC(sz);

    }

    if (NULL != a) {

      a->limit = (PRUword)a + sz;

      a->base = a->avail = (PRUword)PL_ARENA_ALIGN(pool, a + 1);

      PL_MAKE_MEM_NOACCESS((void*)a->avail, a->limit - a->avail);

      rp = (char*)a->avail;

      a->avail += nb;

      PR_ASSERT(a->avail <= a->limit);

      /* the newly allocated arena is linked after pool->current

       *  and becomes pool->current */

      a->next = pool->current->next;

      pool->current->next = a;

      pool->current = a;

      if (NULL == pool->first.next) {

        pool->first.next = a;

      }

      PL_COUNT_ARENA(pool, ++);

      COUNT(pool, nmallocs);

      return (rp);

    }

  }

  /* we got to here, and there's no memory to allocate */

  return (NULL);

} /* --- end PL_ArenaAllocate() --- */

PR_IMPLEMENT(void*)

PL_ArenaGrow(PLArenaPool* pool, void* p, PRUint32 size, PRUint32 incr) {

  void* newp;

  if (PR_UINT32_MAX - size < incr) {

    return NULL;

  }

  PL_ARENA_ALLOCATE(newp, pool, size + incr);

  if (newp) {

    memcpy(newp, p, size);

  }

  return newp;

}

PR_IMPLEMENT(void) PL_ClearArenaPool(PLArenaPool* pool, PRInt32 pattern) {

  PLArena* a;

  for (a = pool->first.next; a; a = a->next) {

    PR_ASSERT(a->base <= a->avail && a->avail <= a->limit);

    a->avail = a->base;

    PL_CLEAR_UNUSED_PATTERN(a, pattern);

    PL_MAKE_MEM_NOACCESS((void*)a->avail, a->limit - a->avail);

  }

}

/*

 * Free tail arenas linked after head, which may not be the true list head.

 * Reset pool->current to point to head in case it pointed at a tail arena.

 */

static void FreeArenaList(PLArenaPool* pool, PLArena* head) {

  PLArena* a = head->next;

  if (!a) {

    return;

  }

  head->next = NULL;

  do {

    PLArena* tmp = a;

    a = a->next;

    PL_CLEAR_ARENA(tmp);

    PL_COUNT_ARENA(pool, --);

    PR_DELETE(tmp);

  } while (a);

  pool->current = head;

}

PR_IMPLEMENT(void) PL_ArenaRelease(PLArenaPool* pool, char* mark) {

  PLArena* a;

  for (a = &pool->first; a; a = a->next) {

    if (PR_UPTRDIFF(mark, a->base) <= PR_UPTRDIFF(a->avail, a->base)) {

      a->avail = (PRUword)PL_ARENA_ALIGN(pool, mark);

      FreeArenaList(pool, a);

      return;

    }

  }

}

PR_IMPLEMENT(void) PL_FreeArenaPool(PLArenaPool* pool) {

  FreeArenaList(pool, &pool->first);

  COUNT(pool, ndeallocs);

}

PR_IMPLEMENT(void) PL_FinishArenaPool(PLArenaPool* pool) {

  FreeArenaList(pool, &pool->first);

#ifdef PL_ARENAMETER

  {

    PLArenaStats *stats, **statsp;

    if (pool->stats.name) {

      PR_DELETE(pool->stats.name);

    }

    for (statsp = &arena_stats_list; (stats = *statsp) != 0;

         statsp = &stats->next) {

      if (stats == &pool->stats) {

        *statsp = stats->next;

        return;

      }

    }

  }

#endif

}

PR_IMPLEMENT(void) PL_CompactArenaPool(PLArenaPool* ap) {}

PR_IMPLEMENT(void) PL_ArenaFinish(void) {}

PR_IMPLEMENT(size_t)

PL_SizeOfArenaPoolExcludingPool(const PLArenaPool* pool,

                                PLMallocSizeFn mallocSizeOf) {

  /*

   * The first PLArena is within |pool|, so don't measure it.  Subsequent

   * PLArenas are separate and must be measured.

   */

  size_t size = 0;

  const PLArena* arena = pool->first.next;

  while (arena) {

    size += mallocSizeOf(arena);

    arena = arena->next;

  }

  return size;

}

#ifdef PL_ARENAMETER

PR_IMPLEMENT(void) PL_ArenaCountAllocation(PLArenaPool* pool, PRUint32 nb) {

  pool->stats.nallocs++;

  pool->stats.nbytes += nb;

  if (nb > pool->stats.maxalloc) {

    pool->stats.maxalloc = nb;

  }

  pool->stats.variance += nb * nb;

}

PR_IMPLEMENT(void)

PL_ArenaCountInplaceGrowth(PLArenaPool* pool, PRUint32 size, PRUint32 incr) {

  pool->stats.ninplace++;

}

PR_IMPLEMENT(void)

PL_ArenaCountGrowth(PLArenaPool* pool, PRUint32 size, PRUint32 incr) {

  pool->stats.ngrows++;

  pool->stats.nbytes += incr;

  pool->stats.variance -= size * size;

  size += incr;

  if (size > pool->stats.maxalloc) {

    pool->stats.maxalloc = size;

  }

  pool->stats.variance += size * size;

}

PR_IMPLEMENT(void) PL_ArenaCountRelease(PLArenaPool* pool, char* mark) {

  pool->stats.nreleases++;

}

PR_IMPLEMENT(void) PL_ArenaCountRetract(PLArenaPool* pool, char* mark) {

  pool->stats.nfastrels++;

}

#  include <math.h>

#  include <stdio.h>

PR_IMPLEMENT(void) PL_DumpArenaStats(FILE* fp) {

  PLArenaStats* stats;

  double mean, variance;

  for (stats = arena_stats_list; stats; stats = stats->next) {

    if (stats->nallocs != 0) {

      mean = (double)stats->nbytes / stats->nallocs;

      variance = fabs(stats->variance / stats->nallocs - mean * mean);

    } else {

      mean = variance = 0;

    }

    fprintf(fp, "\n%s allocation statistics:\n", stats->name);

    fprintf(fp, "              number of arenas: %u\n", stats->narenas);

    fprintf(fp, "         number of allocations: %u\n", stats->nallocs);

    fprintf(fp, " number of free arena reclaims: %u\n", stats->nreclaims);

    fprintf(fp, "        number of malloc calls: %u\n", stats->nmallocs);

    fprintf(fp, "       number of deallocations: %u\n", stats->ndeallocs);

    fprintf(fp, "  number of allocation growths: %u\n", stats->ngrows);

    fprintf(fp, "    number of in-place growths: %u\n", stats->ninplace);

    fprintf(fp, "number of released allocations: %u\n", stats->nreleases);

    fprintf(fp, "       number of fast releases: %u\n", stats->nfastrels);

    fprintf(fp, "         total bytes allocated: %u\n", stats->nbytes);

    fprintf(fp, "          mean allocation size: %g\n", mean);

    fprintf(fp, "            standard deviation: %g\n", sqrt(variance));

    fprintf(fp, "       maximum allocation size: %u\n", stats->maxalloc);

  }

}

#endif /* PL_ARENAMETER */