--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nspr/lib/ds/plarena.c	Mon Jul 28 10:47:06 2014 +0200
@@ -0,0 +1,442 @@
+/* -*- 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"
+
+static PLArena *arena_freelist;
+
+#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)
+
+static PRLock    *arenaLock;
+static PRCallOnceType once;
+static const PRCallOnceType pristineCallOnce;
+
+/*
+** InitializeArenas() -- Initialize arena operations.
+**
+** InitializeArenas() is called exactly once and only once from 
+** LockArena(). This function creates the arena protection 
+** lock: arenaLock.
+**
+** Note: If the arenaLock cannot be created, InitializeArenas()
+** fails quietly, returning only PR_FAILURE. This percolates up
+** to the application using the Arena API. He gets no arena
+** from PL_ArenaAllocate(). It's up to him to fail gracefully
+** or recover.
+**
+*/
+static PRStatus InitializeArenas( void )
+{
+    PR_ASSERT( arenaLock == NULL );
+    arenaLock = PR_NewLock();
+    if ( arenaLock == NULL )
+        return PR_FAILURE;
+    else
+        return PR_SUCCESS;
+} /* end ArenaInitialize() */
+
+static PRStatus LockArena( void )
+{
+    PRStatus rc = PR_CallOnce( &once, InitializeArenas );
+
+    if ( PR_FAILURE != rc )
+        PR_Lock( arenaLock );
+    return(rc);
+} /* end LockArena() */
+
+static void UnlockArena( void )
+{
+    PR_Unlock( arenaLock );
+    return;
+} /* end UnlockArena() */
+
+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;
+    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.
+**
+** If there is not enough space in the arena pool->current, try
+** to claim an arena, on a first fit basis, from the global
+** freelist (arena_freelist).
+** 
+** If no arena in arena_freelist is suitable, 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 */
+
+    PR_ASSERT((nb & pool->mask) == 0);
+    
+    nb = (PRUword)PL_ARENA_ALIGN(pool, nb); /* force alignment */
+
+    /* 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 arena_freelist */
+    {
+        PLArena *p; /* previous pointer, for unlinking from freelist */
+
+        /* lock the arena_freelist. Make access to the freelist MT-Safe */
+        if ( PR_FAILURE == LockArena())
+            return(0);
+
+        for ( a = arena_freelist, p = NULL; a != NULL ; p = a, a = a->next ) {
+            if ( nb <= a->limit - a->base )  {
+                if ( p == NULL )
+                    arena_freelist = a->next;
+                else
+                    p->next = a->next;
+                UnlockArena();
+                a->avail = a->base;
+                rp = (char *)a->avail;
+                a->avail += nb;
+                /* 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;
+                return(rp);
+            }
+        }
+        UnlockArena();
+    }
+
+    /* 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;
+            /* 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;
+
+    PL_ARENA_ALLOCATE(newp, pool, size + incr);
+    if (newp)
+        memcpy(newp, p, size);
+    return newp;
+}
+
+static void ClearArenaList(PLArena *a, PRInt32 pattern)
+{
+
+    for (; 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);
+    }
+}
+
+PR_IMPLEMENT(void) PL_ClearArenaPool(PLArenaPool *pool, PRInt32 pattern)
+{
+    ClearArenaList(pool->first.next, pattern);
+}
+
+/*
+ * 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, PRBool reallyFree)
+{
+    PLArena **ap, *a;
+
+    ap = &head->next;
+    a = *ap;
+    if (!a)
+        return;
+
+#ifdef DEBUG
+    ClearArenaList(a, PL_FREE_PATTERN);
+#endif
+
+    if (reallyFree) {
+        do {
+            *ap = a->next;
+            PL_CLEAR_ARENA(a);
+            PL_COUNT_ARENA(pool,--);
+            PR_DELETE(a);
+        } while ((a = *ap) != 0);
+    } else {
+        /* Insert the whole arena chain at the front of the freelist. */
+        do {
+            PL_MAKE_MEM_NOACCESS((void*)(*ap)->base,
+                                 (*ap)->limit - (*ap)->base);
+            ap = &(*ap)->next;
+        } while (*ap);
+        LockArena();
+        *ap = arena_freelist;
+        arena_freelist = a;
+        head->next = 0;
+        UnlockArena();
+    }
+
+    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, PR_FALSE);
+            return;
+        }
+    }
+}
+
+PR_IMPLEMENT(void) PL_FreeArenaPool(PLArenaPool *pool)
+{
+    FreeArenaList(pool, &pool->first, PR_FALSE);
+    COUNT(pool, ndeallocs);
+}
+
+PR_IMPLEMENT(void) PL_FinishArenaPool(PLArenaPool *pool)
+{
+    FreeArenaList(pool, &pool->first, PR_TRUE);
+#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)
+{
+    PLArena *a, *next;
+
+    for (a = arena_freelist; a; a = next) {
+        next = a->next;
+        PR_DELETE(a);
+    }
+    arena_freelist = NULL;
+
+    if (arenaLock) {
+        PR_DestroyLock(arenaLock);
+        arenaLock = NULL;
+    }
+    once = pristineCallOnce;
+}
+
+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 */