--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/persistentstorage/sql/SQLite364/mem6.c Fri Jan 22 11:06:30 2010 +0200
@@ -0,0 +1,498 @@
+/*
+** 2008 July 24
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** This file contains an alternative memory allocation system for SQLite.
+** This system is implemented as a wrapper around the system provided
+** by the operating system - vanilla malloc(), realloc() and free().
+**
+** This system differentiates between requests for "small" allocations
+** (by default those of 128 bytes or less) and "large" allocations (all
+** others). The 256 byte threshhold is configurable at runtime.
+**
+** All requests for large allocations are passed through to the
+** default system.
+**
+** Requests for small allocations are met by allocating space within
+** one or more larger "chunks" of memory obtained from the default
+** memory allocation system. Chunks of memory are usually 64KB or
+** larger. The algorithm used to manage space within each chunk is
+** the same as that used by mem5.c.
+**
+** This strategy is designed to prevent the default memory allocation
+** system (usually the system malloc) from suffering from heap
+** fragmentation. On some systems, heap fragmentation can cause a
+** significant real-time slowdown.
+**
+** $Id: mem6.c,v 1.10 2008/09/02 17:52:52 danielk1977 Exp $
+*/
+
+#ifdef SQLITE_ENABLE_MEMSYS6
+
+#include "sqliteInt.h"
+
+/*
+** Maximum size of any "small" allocation is ((1<<LOGMAX)*Mem6Chunk.nAtom).
+** Mem6Chunk.nAtom is always at least 8, so this is not a practical
+** limitation
+*/
+#define LOGMAX 30
+
+/*
+** Default value for the "small" allocation size threshold.
+*/
+#define SMALL_MALLOC_DEFAULT_THRESHOLD 256
+
+/*
+** Minimum size for a memory chunk.
+*/
+#define MIN_CHUNKSIZE (1<<16)
+
+#define LOG2_MINALLOC 4
+
+
+typedef struct Mem6Chunk Mem6Chunk;
+typedef struct Mem6Link Mem6Link;
+
+/*
+** A minimum allocation is an instance of the following structure.
+** Larger allocations are an array of these structures where the
+** size of the array is a power of 2.
+*/
+struct Mem6Link {
+ int next; /* Index of next free chunk */
+ int prev; /* Index of previous free chunk */
+};
+
+/*
+** Masks used for mem5.aCtrl[] elements.
+*/
+#define CTRL_LOGSIZE 0x1f /* Log2 Size of this block relative to POW2_MIN */
+#define CTRL_FREE 0x20 /* True if not checked out */
+
+struct Mem6Chunk {
+ Mem6Chunk *pNext;
+
+ /*
+ ** Lists of free blocks of various sizes.
+ */
+ int aiFreelist[LOGMAX+1];
+
+ int nCheckedOut; /* Number of currently outstanding allocations */
+
+ /*
+ ** Space for tracking which blocks are checked out and the size
+ ** of each block. One byte per block.
+ */
+ u8 *aCtrl;
+
+ /*
+ ** Memory available for allocation
+ */
+ int nAtom; /* Smallest possible allocation in bytes */
+ int nBlock; /* Number of nAtom sized blocks in zPool */
+ u8 *zPool; /* Pointer to memory chunk from which allocations are made */
+};
+
+#define MEM6LINK(idx) ((Mem6Link *)(&pChunk->zPool[(idx)*pChunk->nAtom]))
+
+static SQLITE_WSD struct Mem6Global {
+ int nMinAlloc; /* Minimum allowed allocation size */
+ int nThreshold; /* Allocs larger than this go to malloc() */
+ int nLogThreshold; /* log2 of (nThreshold/nMinAlloc) */
+ sqlite3_mutex *mutex;
+ Mem6Chunk *pChunk; /* Singly linked list of all memory chunks */
+} mem6 = { 48642791 };
+
+#define mem6 GLOBAL(struct Mem6Global, mem6)
+
+/*
+** Unlink the chunk at pChunk->aPool[i] from list it is currently
+** on. It should be found on pChunk->aiFreelist[iLogsize].
+*/
+static void memsys6Unlink(Mem6Chunk *pChunk, int i, int iLogsize){
+ int next, prev;
+ assert( i>=0 && i<pChunk->nBlock );
+ assert( iLogsize>=0 && iLogsize<=mem6.nLogThreshold );
+ assert( (pChunk->aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+ next = MEM6LINK(i)->next;
+ prev = MEM6LINK(i)->prev;
+ if( prev<0 ){
+ pChunk->aiFreelist[iLogsize] = next;
+ }else{
+ MEM6LINK(prev)->next = next;
+ }
+ if( next>=0 ){
+ MEM6LINK(next)->prev = prev;
+ }
+}
+
+/*
+** Link the chunk at mem5.aPool[i] so that is on the iLogsize
+** free list.
+*/
+static void memsys6Link(Mem6Chunk *pChunk, int i, int iLogsize){
+ int x;
+ assert( i>=0 && i<pChunk->nBlock );
+ assert( iLogsize>=0 && iLogsize<=mem6.nLogThreshold );
+ assert( (pChunk->aCtrl[i] & CTRL_LOGSIZE)==iLogsize );
+
+ x = MEM6LINK(i)->next = pChunk->aiFreelist[iLogsize];
+ MEM6LINK(i)->prev = -1;
+ if( x>=0 ){
+ assert( x<pChunk->nBlock );
+ MEM6LINK(x)->prev = i;
+ }
+ pChunk->aiFreelist[iLogsize] = i;
+}
+
+
+/*
+** Find the first entry on the freelist iLogsize. Unlink that
+** entry and return its index.
+*/
+static int memsys6UnlinkFirst(Mem6Chunk *pChunk, int iLogsize){
+ int i;
+ int iFirst;
+
+ assert( iLogsize>=0 && iLogsize<=mem6.nLogThreshold );
+ i = iFirst = pChunk->aiFreelist[iLogsize];
+ assert( iFirst>=0 );
+ memsys6Unlink(pChunk, iFirst, iLogsize);
+ return iFirst;
+}
+
+static int roundupLog2(int n){
+ static const char LogTable256[256] = {
+ 0, /* 1 */
+ 1, /* 2 */
+ 2, 2, /* 3..4 */
+ 3, 3, 3, 3, /* 5..8 */
+ 4, 4, 4, 4, 4, 4, 4, 4, /* 9..16 */
+ 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, /* 17..32 */
+ 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+ 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, /* 33..64 */
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+ 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, /* 65..128 */
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
+ 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, /* 129..256 */
+ };
+
+ assert(n<=(1<<16) && n>0);
+ if( n<=256 ) return LogTable256[n-1];
+ return LogTable256[(n>>8) - ((n&0xFF)?0:1)] + 8;
+}
+
+/*
+** Allocate and return a block of (pChunk->nAtom << iLogsize) bytes from chunk
+** pChunk. If the allocation request cannot be satisfied, return 0.
+*/
+static void *chunkMalloc(Mem6Chunk *pChunk, int iLogsize){
+ int i; /* Index of a mem5.aPool[] slot */
+ int iBin; /* Index into mem5.aiFreelist[] */
+
+ /* Make sure mem5.aiFreelist[iLogsize] contains at least one free
+ ** block. If not, then split a block of the next larger power of
+ ** two in order to create a new free block of size iLogsize.
+ */
+ for(iBin=iLogsize; pChunk->aiFreelist[iBin]<0 && iBin<=mem6.nLogThreshold; iBin++){}
+ if( iBin>mem6.nLogThreshold ) return 0;
+ i = memsys6UnlinkFirst(pChunk, iBin);
+ while( iBin>iLogsize ){
+ int newSize;
+ iBin--;
+ newSize = 1 << iBin;
+ pChunk->aCtrl[i+newSize] = CTRL_FREE | iBin;
+ memsys6Link(pChunk, i+newSize, iBin);
+ }
+ pChunk->aCtrl[i] = iLogsize;
+
+ /* Return a pointer to the allocated memory. */
+ pChunk->nCheckedOut++;
+ return (void*)&pChunk->zPool[i*pChunk->nAtom];
+}
+
+/*
+** Free the allocation pointed to by p, which is guaranteed to be non-zero
+** and a part of chunk object pChunk.
+*/
+static void chunkFree(Mem6Chunk *pChunk, void *pOld){
+ u32 size, iLogsize;
+ int iBlock;
+
+ /* Set iBlock to the index of the block pointed to by pOld in
+ ** the array of pChunk->nAtom byte blocks pointed to by pChunk->zPool.
+ */
+ iBlock = ((u8 *)pOld-pChunk->zPool)/pChunk->nAtom;
+
+ /* Check that the pointer pOld points to a valid, non-free block. */
+ assert( iBlock>=0 && iBlock<pChunk->nBlock );
+ assert( ((u8 *)pOld-pChunk->zPool)%pChunk->nAtom==0 );
+ assert( (pChunk->aCtrl[iBlock] & CTRL_FREE)==0 );
+
+ iLogsize = pChunk->aCtrl[iBlock] & CTRL_LOGSIZE;
+ size = 1<<iLogsize;
+ assert( iBlock+size-1<pChunk->nBlock );
+
+ pChunk->aCtrl[iBlock] |= CTRL_FREE;
+ pChunk->aCtrl[iBlock+size-1] |= CTRL_FREE;
+
+ pChunk->aCtrl[iBlock] = CTRL_FREE | iLogsize;
+ while( iLogsize<mem6.nLogThreshold ){
+ int iBuddy;
+ if( (iBlock>>iLogsize) & 1 ){
+ iBuddy = iBlock - size;
+ }else{
+ iBuddy = iBlock + size;
+ }
+ assert( iBuddy>=0 );
+ if( (iBuddy+(1<<iLogsize))>pChunk->nBlock ) break;
+ if( pChunk->aCtrl[iBuddy]!=(CTRL_FREE | iLogsize) ) break;
+ memsys6Unlink(pChunk, iBuddy, iLogsize);
+ iLogsize++;
+ if( iBuddy<iBlock ){
+ pChunk->aCtrl[iBuddy] = CTRL_FREE | iLogsize;
+ pChunk->aCtrl[iBlock] = 0;
+ iBlock = iBuddy;
+ }else{
+ pChunk->aCtrl[iBlock] = CTRL_FREE | iLogsize;
+ pChunk->aCtrl[iBuddy] = 0;
+ }
+ size *= 2;
+ }
+ pChunk->nCheckedOut--;
+ memsys6Link(pChunk, iBlock, iLogsize);
+}
+
+/*
+** Return the actual size of the block pointed to by p, which is guaranteed
+** to have been allocated from chunk pChunk.
+*/
+static int chunkSize(Mem6Chunk *pChunk, void *p){
+ int iSize = 0;
+ if( p ){
+ int i = ((u8 *)p-pChunk->zPool)/pChunk->nAtom;
+ assert( i>=0 && i<pChunk->nBlock );
+ iSize = pChunk->nAtom * (1 << (pChunk->aCtrl[i]&CTRL_LOGSIZE));
+ }
+ return iSize;
+}
+
+/*
+** Return true if there are currently no outstanding allocations.
+*/
+static int chunkIsEmpty(Mem6Chunk *pChunk){
+ return (pChunk->nCheckedOut==0);
+}
+
+/*
+** Initialize the buffer zChunk, which is nChunk bytes in size, as
+** an Mem6Chunk object. Return a copy of the zChunk pointer.
+*/
+static Mem6Chunk *chunkInit(u8 *zChunk, int nChunk, int nMinAlloc){
+ int ii;
+ int iOffset;
+ Mem6Chunk *pChunk = (Mem6Chunk *)zChunk;
+
+ assert( nChunk>sizeof(Mem6Chunk) );
+ assert( nMinAlloc>sizeof(Mem6Link) );
+
+ memset(pChunk, 0, sizeof(Mem6Chunk));
+ pChunk->nAtom = nMinAlloc;
+ pChunk->nBlock = ((nChunk-sizeof(Mem6Chunk)) / (pChunk->nAtom+sizeof(u8)));
+
+ pChunk->zPool = (u8 *)&pChunk[1];
+ pChunk->aCtrl = &pChunk->zPool[pChunk->nBlock*pChunk->nAtom];
+
+ for(ii=0; ii<=mem6.nLogThreshold; ii++){
+ pChunk->aiFreelist[ii] = -1;
+ }
+
+ iOffset = 0;
+ for(ii=mem6.nLogThreshold; ii>=0; ii--){
+ int nAlloc = (1<<ii);
+ while( (iOffset+nAlloc)<=pChunk->nBlock ){
+ pChunk->aCtrl[iOffset] = ii | CTRL_FREE;
+ memsys6Link(pChunk, iOffset, ii);
+ iOffset += nAlloc;
+ }
+ }
+
+ return pChunk;
+}
+
+
+static void mem6Enter(void){
+ sqlite3_mutex_enter(mem6.mutex);
+}
+
+static void mem6Leave(void){
+ sqlite3_mutex_leave(mem6.mutex);
+}
+
+/*
+** Based on the number and size of the currently allocated chunks, return
+** the size of the next chunk to allocate, in bytes.
+*/
+static int nextChunkSize(void){
+ int iTotal = MIN_CHUNKSIZE;
+ Mem6Chunk *p;
+ for(p=mem6.pChunk; p; p=p->pNext){
+ iTotal = iTotal*2;
+ }
+ return iTotal;
+}
+
+static void freeChunk(Mem6Chunk *pChunk){
+ Mem6Chunk **pp = &mem6.pChunk;
+ for( pp=&mem6.pChunk; *pp!=pChunk; pp = &(*pp)->pNext );
+ *pp = (*pp)->pNext;
+ free(pChunk);
+}
+
+static void *memsys6Malloc(int nByte){
+ Mem6Chunk *pChunk;
+ void *p = 0;
+ int nTotal = nByte+8;
+ int iOffset = 0;
+
+ if( nTotal>mem6.nThreshold ){
+ p = malloc(nTotal);
+ }else{
+ int iLogsize = 0;
+ if( nTotal>(1<<LOG2_MINALLOC) ){
+ iLogsize = roundupLog2(nTotal) - LOG2_MINALLOC;
+ }
+ mem6Enter();
+ for(pChunk=mem6.pChunk; pChunk; pChunk=pChunk->pNext){
+ p = chunkMalloc(pChunk, iLogsize);
+ if( p ){
+ break;
+ }
+ }
+ if( !p ){
+ int iSize = nextChunkSize();
+ p = malloc(iSize);
+ if( p ){
+ pChunk = chunkInit((u8 *)p, iSize, mem6.nMinAlloc);
+ pChunk->pNext = mem6.pChunk;
+ mem6.pChunk = pChunk;
+ p = chunkMalloc(pChunk, iLogsize);
+ assert(p);
+ }
+ }
+ iOffset = ((u8*)p - (u8*)pChunk);
+ mem6Leave();
+ }
+
+ if( !p ){
+ return 0;
+ }
+ ((u32 *)p)[0] = iOffset;
+ ((u32 *)p)[1] = nByte;
+ return &((u32 *)p)[2];
+}
+
+static int memsys6Size(void *pPrior){
+ if( pPrior==0 ) return 0;
+ return ((u32*)pPrior)[-1];
+}
+
+static void memsys6Free(void *pPrior){
+ int iSlot;
+ void *p = &((u32 *)pPrior)[-2];
+ iSlot = ((u32 *)p)[0];
+ if( iSlot ){
+ Mem6Chunk *pChunk;
+ mem6Enter();
+ pChunk = (Mem6Chunk *)(&((u8 *)p)[-1 * iSlot]);
+ chunkFree(pChunk, p);
+ if( chunkIsEmpty(pChunk) ){
+ freeChunk(pChunk);
+ }
+ mem6Leave();
+ }else{
+ free(p);
+ }
+}
+
+static void *memsys6Realloc(void *p, int nByte){
+ void *p2;
+
+ if( p && nByte<=memsys6Size(p) ){
+ p2 = p;
+ }else{
+ p2 = memsys6Malloc(nByte);
+ if( p && p2 ){
+ memcpy(p2, p, memsys6Size(p));
+ memsys6Free(p);
+ }
+ }
+
+ return p2;
+}
+
+static int memsys6Roundup(int n){
+ if( n>mem6.nThreshold ){
+ return n;
+ }else{
+ return (1<<roundupLog2(n));
+ }
+}
+
+static int memsys6Init(void *pCtx){
+ u8 bMemstat = sqlite3GlobalConfig.bMemstat;
+ mem6.nMinAlloc = (1 << LOG2_MINALLOC);
+ mem6.pChunk = 0;
+ mem6.nThreshold = sqlite3GlobalConfig.nSmall;
+ if( mem6.nThreshold<=0 ){
+ mem6.nThreshold = SMALL_MALLOC_DEFAULT_THRESHOLD;
+ }
+ mem6.nLogThreshold = roundupLog2(mem6.nThreshold) - LOG2_MINALLOC;
+ if( !bMemstat ){
+ mem6.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+ }
+ return SQLITE_OK;
+}
+
+static void memsys6Shutdown(void *pCtx){
+ memset(&mem6, 0, sizeof(mem6));
+}
+
+/*
+** This routine is the only routine in this file with external
+** linkage. It returns a pointer to a static sqlite3_mem_methods
+** struct populated with the memsys6 methods.
+*/
+const sqlite3_mem_methods *sqlite3MemGetMemsys6(void){
+ static const sqlite3_mem_methods memsys6Methods = {
+ memsys6Malloc,
+ memsys6Free,
+ memsys6Realloc,
+ memsys6Size,
+ memsys6Roundup,
+ memsys6Init,
+ memsys6Shutdown,
+ 0
+ };
+ return &memsys6Methods;
+}
+
+#endif