sl@0: /*
sl@0: ** 2007 October 14
sl@0: **
sl@0: ** The author disclaims copyright to this source code.  In place of
sl@0: ** a legal notice, here is a blessing:
sl@0: **
sl@0: **    May you do good and not evil.
sl@0: **    May you find forgiveness for yourself and forgive others.
sl@0: **    May you share freely, never taking more than you give.
sl@0: **
sl@0: *************************************************************************
sl@0: ** This file contains the C functions that implement a memory
sl@0: ** allocation subsystem for use by SQLite. 
sl@0: **
sl@0: ** This version of the memory allocation subsystem omits all
sl@0: ** use of malloc(). The SQLite user supplies a block of memory
sl@0: ** before calling sqlite3_initialize() from which allocations
sl@0: ** are made and returned by the xMalloc() and xRealloc() 
sl@0: ** implementations. Once sqlite3_initialize() has been called,
sl@0: ** the amount of memory available to SQLite is fixed and cannot
sl@0: ** be changed.
sl@0: **
sl@0: ** This version of the memory allocation subsystem is included
sl@0: ** in the build only if SQLITE_ENABLE_MEMSYS3 is defined.
sl@0: **
sl@0: ** $Id: mem3.c,v 1.20 2008/07/18 18:56:17 drh Exp $
sl@0: */
sl@0: #include "sqliteInt.h"
sl@0: 
sl@0: /*
sl@0: ** This version of the memory allocator is only built into the library
sl@0: ** SQLITE_ENABLE_MEMSYS3 is defined. Defining this symbol does not
sl@0: ** mean that the library will use a memory-pool by default, just that
sl@0: ** it is available. The mempool allocator is activated by calling
sl@0: ** sqlite3_config().
sl@0: */
sl@0: #ifdef SQLITE_ENABLE_MEMSYS3
sl@0: 
sl@0: /*
sl@0: ** Maximum size (in Mem3Blocks) of a "small" chunk.
sl@0: */
sl@0: #define MX_SMALL 10
sl@0: 
sl@0: 
sl@0: /*
sl@0: ** Number of freelist hash slots
sl@0: */
sl@0: #define N_HASH  61
sl@0: 
sl@0: /*
sl@0: ** A memory allocation (also called a "chunk") consists of two or 
sl@0: ** more blocks where each block is 8 bytes.  The first 8 bytes are 
sl@0: ** a header that is not returned to the user.
sl@0: **
sl@0: ** A chunk is two or more blocks that is either checked out or
sl@0: ** free.  The first block has format u.hdr.  u.hdr.size4x is 4 times the
sl@0: ** size of the allocation in blocks if the allocation is free.
sl@0: ** The u.hdr.size4x&1 bit is true if the chunk is checked out and
sl@0: ** false if the chunk is on the freelist.  The u.hdr.size4x&2 bit
sl@0: ** is true if the previous chunk is checked out and false if the
sl@0: ** previous chunk is free.  The u.hdr.prevSize field is the size of
sl@0: ** the previous chunk in blocks if the previous chunk is on the
sl@0: ** freelist. If the previous chunk is checked out, then
sl@0: ** u.hdr.prevSize can be part of the data for that chunk and should
sl@0: ** not be read or written.
sl@0: **
sl@0: ** We often identify a chunk by its index in mem3.aPool[].  When
sl@0: ** this is done, the chunk index refers to the second block of
sl@0: ** the chunk.  In this way, the first chunk has an index of 1.
sl@0: ** A chunk index of 0 means "no such chunk" and is the equivalent
sl@0: ** of a NULL pointer.
sl@0: **
sl@0: ** The second block of free chunks is of the form u.list.  The
sl@0: ** two fields form a double-linked list of chunks of related sizes.
sl@0: ** Pointers to the head of the list are stored in mem3.aiSmall[] 
sl@0: ** for smaller chunks and mem3.aiHash[] for larger chunks.
sl@0: **
sl@0: ** The second block of a chunk is user data if the chunk is checked 
sl@0: ** out.  If a chunk is checked out, the user data may extend into
sl@0: ** the u.hdr.prevSize value of the following chunk.
sl@0: */
sl@0: typedef struct Mem3Block Mem3Block;
sl@0: struct Mem3Block {
sl@0:   union {
sl@0:     struct {
sl@0:       u32 prevSize;   /* Size of previous chunk in Mem3Block elements */
sl@0:       u32 size4x;     /* 4x the size of current chunk in Mem3Block elements */
sl@0:     } hdr;
sl@0:     struct {
sl@0:       u32 next;       /* Index in mem3.aPool[] of next free chunk */
sl@0:       u32 prev;       /* Index in mem3.aPool[] of previous free chunk */
sl@0:     } list;
sl@0:   } u;
sl@0: };
sl@0: 
sl@0: /*
sl@0: ** All of the static variables used by this module are collected
sl@0: ** into a single structure named "mem3".  This is to keep the
sl@0: ** static variables organized and to reduce namespace pollution
sl@0: ** when this module is combined with other in the amalgamation.
sl@0: */
sl@0: static struct {
sl@0:   /*
sl@0:   ** True if we are evaluating an out-of-memory callback.
sl@0:   */
sl@0:   int alarmBusy;
sl@0:   
sl@0:   /*
sl@0:   ** Mutex to control access to the memory allocation subsystem.
sl@0:   */
sl@0:   sqlite3_mutex *mutex;
sl@0:   
sl@0:   /*
sl@0:   ** The minimum amount of free space that we have seen.
sl@0:   */
sl@0:   u32 mnMaster;
sl@0: 
sl@0:   /*
sl@0:   ** iMaster is the index of the master chunk.  Most new allocations
sl@0:   ** occur off of this chunk.  szMaster is the size (in Mem3Blocks)
sl@0:   ** of the current master.  iMaster is 0 if there is not master chunk.
sl@0:   ** The master chunk is not in either the aiHash[] or aiSmall[].
sl@0:   */
sl@0:   u32 iMaster;
sl@0:   u32 szMaster;
sl@0: 
sl@0:   /*
sl@0:   ** Array of lists of free blocks according to the block size 
sl@0:   ** for smaller chunks, or a hash on the block size for larger
sl@0:   ** chunks.
sl@0:   */
sl@0:   u32 aiSmall[MX_SMALL-1];   /* For sizes 2 through MX_SMALL, inclusive */
sl@0:   u32 aiHash[N_HASH];        /* For sizes MX_SMALL+1 and larger */
sl@0: 
sl@0:   /*
sl@0:   ** Memory available for allocation. nPool is the size of the array
sl@0:   ** (in Mem3Blocks) pointed to by aPool less 2.
sl@0:   */
sl@0:   u32 nPool;
sl@0:   Mem3Block *aPool;
sl@0: } mem3;
sl@0: 
sl@0: /*
sl@0: ** Unlink the chunk at mem3.aPool[i] from list it is currently
sl@0: ** on.  *pRoot is the list that i is a member of.
sl@0: */
sl@0: static void memsys3UnlinkFromList(u32 i, u32 *pRoot){
sl@0:   u32 next = mem3.aPool[i].u.list.next;
sl@0:   u32 prev = mem3.aPool[i].u.list.prev;
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   if( prev==0 ){
sl@0:     *pRoot = next;
sl@0:   }else{
sl@0:     mem3.aPool[prev].u.list.next = next;
sl@0:   }
sl@0:   if( next ){
sl@0:     mem3.aPool[next].u.list.prev = prev;
sl@0:   }
sl@0:   mem3.aPool[i].u.list.next = 0;
sl@0:   mem3.aPool[i].u.list.prev = 0;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Unlink the chunk at index i from 
sl@0: ** whatever list is currently a member of.
sl@0: */
sl@0: static void memsys3Unlink(u32 i){
sl@0:   u32 size, hash;
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
sl@0:   assert( i>=1 );
sl@0:   size = mem3.aPool[i-1].u.hdr.size4x/4;
sl@0:   assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
sl@0:   assert( size>=2 );
sl@0:   if( size <= MX_SMALL ){
sl@0:     memsys3UnlinkFromList(i, &mem3.aiSmall[size-2]);
sl@0:   }else{
sl@0:     hash = size % N_HASH;
sl@0:     memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Link the chunk at mem3.aPool[i] so that is on the list rooted
sl@0: ** at *pRoot.
sl@0: */
sl@0: static void memsys3LinkIntoList(u32 i, u32 *pRoot){
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   mem3.aPool[i].u.list.next = *pRoot;
sl@0:   mem3.aPool[i].u.list.prev = 0;
sl@0:   if( *pRoot ){
sl@0:     mem3.aPool[*pRoot].u.list.prev = i;
sl@0:   }
sl@0:   *pRoot = i;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Link the chunk at index i into either the appropriate
sl@0: ** small chunk list, or into the large chunk hash table.
sl@0: */
sl@0: static void memsys3Link(u32 i){
sl@0:   u32 size, hash;
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( i>=1 );
sl@0:   assert( (mem3.aPool[i-1].u.hdr.size4x & 1)==0 );
sl@0:   size = mem3.aPool[i-1].u.hdr.size4x/4;
sl@0:   assert( size==mem3.aPool[i+size-1].u.hdr.prevSize );
sl@0:   assert( size>=2 );
sl@0:   if( size <= MX_SMALL ){
sl@0:     memsys3LinkIntoList(i, &mem3.aiSmall[size-2]);
sl@0:   }else{
sl@0:     hash = size % N_HASH;
sl@0:     memsys3LinkIntoList(i, &mem3.aiHash[hash]);
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
sl@0: ** will already be held (obtained by code in malloc.c) if
sl@0: ** sqlite3Config.bMemStat is true.
sl@0: */
sl@0: static void memsys3Enter(void){
sl@0:   if( sqlite3Config.bMemstat==0 && mem3.mutex==0 ){
sl@0:     mem3.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
sl@0:   }
sl@0:   sqlite3_mutex_enter(mem3.mutex);
sl@0: }
sl@0: static void memsys3Leave(void){
sl@0:   sqlite3_mutex_leave(mem3.mutex);
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Called when we are unable to satisfy an allocation of nBytes.
sl@0: */
sl@0: static void memsys3OutOfMemory(int nByte){
sl@0:   if( !mem3.alarmBusy ){
sl@0:     mem3.alarmBusy = 1;
sl@0:     assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:     sqlite3_mutex_leave(mem3.mutex);
sl@0:     sqlite3_release_memory(nByte);
sl@0:     sqlite3_mutex_enter(mem3.mutex);
sl@0:     mem3.alarmBusy = 0;
sl@0:   }
sl@0: }
sl@0: 
sl@0: 
sl@0: /*
sl@0: ** Chunk i is a free chunk that has been unlinked.  Adjust its 
sl@0: ** size parameters for check-out and return a pointer to the 
sl@0: ** user portion of the chunk.
sl@0: */
sl@0: static void *memsys3Checkout(u32 i, int nBlock){
sl@0:   u32 x;
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( i>=1 );
sl@0:   assert( mem3.aPool[i-1].u.hdr.size4x/4==nBlock );
sl@0:   assert( mem3.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
sl@0:   x = mem3.aPool[i-1].u.hdr.size4x;
sl@0:   mem3.aPool[i-1].u.hdr.size4x = nBlock*4 | 1 | (x&2);
sl@0:   mem3.aPool[i+nBlock-1].u.hdr.prevSize = nBlock;
sl@0:   mem3.aPool[i+nBlock-1].u.hdr.size4x |= 2;
sl@0:   return &mem3.aPool[i];
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Carve a piece off of the end of the mem3.iMaster free chunk.
sl@0: ** Return a pointer to the new allocation.  Or, if the master chunk
sl@0: ** is not large enough, return 0.
sl@0: */
sl@0: static void *memsys3FromMaster(int nBlock){
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( mem3.szMaster>=nBlock );
sl@0:   if( nBlock>=mem3.szMaster-1 ){
sl@0:     /* Use the entire master */
sl@0:     void *p = memsys3Checkout(mem3.iMaster, mem3.szMaster);
sl@0:     mem3.iMaster = 0;
sl@0:     mem3.szMaster = 0;
sl@0:     mem3.mnMaster = 0;
sl@0:     return p;
sl@0:   }else{
sl@0:     /* Split the master block.  Return the tail. */
sl@0:     u32 newi, x;
sl@0:     newi = mem3.iMaster + mem3.szMaster - nBlock;
sl@0:     assert( newi > mem3.iMaster+1 );
sl@0:     mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = nBlock;
sl@0:     mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x |= 2;
sl@0:     mem3.aPool[newi-1].u.hdr.size4x = nBlock*4 + 1;
sl@0:     mem3.szMaster -= nBlock;
sl@0:     mem3.aPool[newi-1].u.hdr.prevSize = mem3.szMaster;
sl@0:     x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
sl@0:     mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
sl@0:     if( mem3.szMaster < mem3.mnMaster ){
sl@0:       mem3.mnMaster = mem3.szMaster;
sl@0:     }
sl@0:     return (void*)&mem3.aPool[newi];
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** *pRoot is the head of a list of free chunks of the same size
sl@0: ** or same size hash.  In other words, *pRoot is an entry in either
sl@0: ** mem3.aiSmall[] or mem3.aiHash[].  
sl@0: **
sl@0: ** This routine examines all entries on the given list and tries
sl@0: ** to coalesce each entries with adjacent free chunks.  
sl@0: **
sl@0: ** If it sees a chunk that is larger than mem3.iMaster, it replaces 
sl@0: ** the current mem3.iMaster with the new larger chunk.  In order for
sl@0: ** this mem3.iMaster replacement to work, the master chunk must be
sl@0: ** linked into the hash tables.  That is not the normal state of
sl@0: ** affairs, of course.  The calling routine must link the master
sl@0: ** chunk before invoking this routine, then must unlink the (possibly
sl@0: ** changed) master chunk once this routine has finished.
sl@0: */
sl@0: static void memsys3Merge(u32 *pRoot){
sl@0:   u32 iNext, prev, size, i, x;
sl@0: 
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   for(i=*pRoot; i>0; i=iNext){
sl@0:     iNext = mem3.aPool[i].u.list.next;
sl@0:     size = mem3.aPool[i-1].u.hdr.size4x;
sl@0:     assert( (size&1)==0 );
sl@0:     if( (size&2)==0 ){
sl@0:       memsys3UnlinkFromList(i, pRoot);
sl@0:       assert( i > mem3.aPool[i-1].u.hdr.prevSize );
sl@0:       prev = i - mem3.aPool[i-1].u.hdr.prevSize;
sl@0:       if( prev==iNext ){
sl@0:         iNext = mem3.aPool[prev].u.list.next;
sl@0:       }
sl@0:       memsys3Unlink(prev);
sl@0:       size = i + size/4 - prev;
sl@0:       x = mem3.aPool[prev-1].u.hdr.size4x & 2;
sl@0:       mem3.aPool[prev-1].u.hdr.size4x = size*4 | x;
sl@0:       mem3.aPool[prev+size-1].u.hdr.prevSize = size;
sl@0:       memsys3Link(prev);
sl@0:       i = prev;
sl@0:     }else{
sl@0:       size /= 4;
sl@0:     }
sl@0:     if( size>mem3.szMaster ){
sl@0:       mem3.iMaster = i;
sl@0:       mem3.szMaster = size;
sl@0:     }
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Return a block of memory of at least nBytes in size.
sl@0: ** Return NULL if unable.
sl@0: **
sl@0: ** This function assumes that the necessary mutexes, if any, are
sl@0: ** already held by the caller. Hence "Unsafe".
sl@0: */
sl@0: static void *memsys3MallocUnsafe(int nByte){
sl@0:   u32 i;
sl@0:   int nBlock;
sl@0:   int toFree;
sl@0: 
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( sizeof(Mem3Block)==8 );
sl@0:   if( nByte<=12 ){
sl@0:     nBlock = 2;
sl@0:   }else{
sl@0:     nBlock = (nByte + 11)/8;
sl@0:   }
sl@0:   assert( nBlock>=2 );
sl@0: 
sl@0:   /* STEP 1:
sl@0:   ** Look for an entry of the correct size in either the small
sl@0:   ** chunk table or in the large chunk hash table.  This is
sl@0:   ** successful most of the time (about 9 times out of 10).
sl@0:   */
sl@0:   if( nBlock <= MX_SMALL ){
sl@0:     i = mem3.aiSmall[nBlock-2];
sl@0:     if( i>0 ){
sl@0:       memsys3UnlinkFromList(i, &mem3.aiSmall[nBlock-2]);
sl@0:       return memsys3Checkout(i, nBlock);
sl@0:     }
sl@0:   }else{
sl@0:     int hash = nBlock % N_HASH;
sl@0:     for(i=mem3.aiHash[hash]; i>0; i=mem3.aPool[i].u.list.next){
sl@0:       if( mem3.aPool[i-1].u.hdr.size4x/4==nBlock ){
sl@0:         memsys3UnlinkFromList(i, &mem3.aiHash[hash]);
sl@0:         return memsys3Checkout(i, nBlock);
sl@0:       }
sl@0:     }
sl@0:   }
sl@0: 
sl@0:   /* STEP 2:
sl@0:   ** Try to satisfy the allocation by carving a piece off of the end
sl@0:   ** of the master chunk.  This step usually works if step 1 fails.
sl@0:   */
sl@0:   if( mem3.szMaster>=nBlock ){
sl@0:     return memsys3FromMaster(nBlock);
sl@0:   }
sl@0: 
sl@0: 
sl@0:   /* STEP 3:  
sl@0:   ** Loop through the entire memory pool.  Coalesce adjacent free
sl@0:   ** chunks.  Recompute the master chunk as the largest free chunk.
sl@0:   ** Then try again to satisfy the allocation by carving a piece off
sl@0:   ** of the end of the master chunk.  This step happens very
sl@0:   ** rarely (we hope!)
sl@0:   */
sl@0:   for(toFree=nBlock*16; toFree<(mem3.nPool*16); toFree *= 2){
sl@0:     memsys3OutOfMemory(toFree);
sl@0:     if( mem3.iMaster ){
sl@0:       memsys3Link(mem3.iMaster);
sl@0:       mem3.iMaster = 0;
sl@0:       mem3.szMaster = 0;
sl@0:     }
sl@0:     for(i=0; i<N_HASH; i++){
sl@0:       memsys3Merge(&mem3.aiHash[i]);
sl@0:     }
sl@0:     for(i=0; i<MX_SMALL-1; i++){
sl@0:       memsys3Merge(&mem3.aiSmall[i]);
sl@0:     }
sl@0:     if( mem3.szMaster ){
sl@0:       memsys3Unlink(mem3.iMaster);
sl@0:       if( mem3.szMaster>=nBlock ){
sl@0:         return memsys3FromMaster(nBlock);
sl@0:       }
sl@0:     }
sl@0:   }
sl@0: 
sl@0:   /* If none of the above worked, then we fail. */
sl@0:   return 0;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Free an outstanding memory allocation.
sl@0: **
sl@0: ** This function assumes that the necessary mutexes, if any, are
sl@0: ** already held by the caller. Hence "Unsafe".
sl@0: */
sl@0: void memsys3FreeUnsafe(void *pOld){
sl@0:   Mem3Block *p = (Mem3Block*)pOld;
sl@0:   int i;
sl@0:   u32 size, x;
sl@0:   assert( sqlite3_mutex_held(mem3.mutex) );
sl@0:   assert( p>mem3.aPool && p<&mem3.aPool[mem3.nPool] );
sl@0:   i = p - mem3.aPool;
sl@0:   assert( (mem3.aPool[i-1].u.hdr.size4x&1)==1 );
sl@0:   size = mem3.aPool[i-1].u.hdr.size4x/4;
sl@0:   assert( i+size<=mem3.nPool+1 );
sl@0:   mem3.aPool[i-1].u.hdr.size4x &= ~1;
sl@0:   mem3.aPool[i+size-1].u.hdr.prevSize = size;
sl@0:   mem3.aPool[i+size-1].u.hdr.size4x &= ~2;
sl@0:   memsys3Link(i);
sl@0: 
sl@0:   /* Try to expand the master using the newly freed chunk */
sl@0:   if( mem3.iMaster ){
sl@0:     while( (mem3.aPool[mem3.iMaster-1].u.hdr.size4x&2)==0 ){
sl@0:       size = mem3.aPool[mem3.iMaster-1].u.hdr.prevSize;
sl@0:       mem3.iMaster -= size;
sl@0:       mem3.szMaster += size;
sl@0:       memsys3Unlink(mem3.iMaster);
sl@0:       x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
sl@0:       mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
sl@0:       mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
sl@0:     }
sl@0:     x = mem3.aPool[mem3.iMaster-1].u.hdr.size4x & 2;
sl@0:     while( (mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x&1)==0 ){
sl@0:       memsys3Unlink(mem3.iMaster+mem3.szMaster);
sl@0:       mem3.szMaster += mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.size4x/4;
sl@0:       mem3.aPool[mem3.iMaster-1].u.hdr.size4x = mem3.szMaster*4 | x;
sl@0:       mem3.aPool[mem3.iMaster+mem3.szMaster-1].u.hdr.prevSize = mem3.szMaster;
sl@0:     }
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Return the size of an outstanding allocation, in bytes.  The
sl@0: ** size returned omits the 8-byte header overhead.  This only
sl@0: ** works for chunks that are currently checked out.
sl@0: */
sl@0: static int memsys3Size(void *p){
sl@0:   Mem3Block *pBlock;
sl@0:   if( p==0 ) return 0;
sl@0:   pBlock = (Mem3Block*)p;
sl@0:   assert( (pBlock[-1].u.hdr.size4x&1)!=0 );
sl@0:   return (pBlock[-1].u.hdr.size4x&~3)*2 - 4;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Round up a request size to the next valid allocation size.
sl@0: */
sl@0: static int memsys3Roundup(int n){
sl@0:   if( n<=12 ){
sl@0:     return 12;
sl@0:   }else{
sl@0:     return ((n+11)&~7) - 4;
sl@0:   }
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Allocate nBytes of memory.
sl@0: */
sl@0: static void *memsys3Malloc(int nBytes){
sl@0:   sqlite3_int64 *p;
sl@0:   assert( nBytes>0 );          /* malloc.c filters out 0 byte requests */
sl@0:   memsys3Enter();
sl@0:   p = memsys3MallocUnsafe(nBytes);
sl@0:   memsys3Leave();
sl@0:   return (void*)p; 
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Free memory.
sl@0: */
sl@0: void memsys3Free(void *pPrior){
sl@0:   assert( pPrior );
sl@0:   memsys3Enter();
sl@0:   memsys3FreeUnsafe(pPrior);
sl@0:   memsys3Leave();
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Change the size of an existing memory allocation
sl@0: */
sl@0: void *memsys3Realloc(void *pPrior, int nBytes){
sl@0:   int nOld;
sl@0:   void *p;
sl@0:   if( pPrior==0 ){
sl@0:     return sqlite3_malloc(nBytes);
sl@0:   }
sl@0:   if( nBytes<=0 ){
sl@0:     sqlite3_free(pPrior);
sl@0:     return 0;
sl@0:   }
sl@0:   nOld = memsys3Size(pPrior);
sl@0:   if( nBytes<=nOld && nBytes>=nOld-128 ){
sl@0:     return pPrior;
sl@0:   }
sl@0:   memsys3Enter();
sl@0:   p = memsys3MallocUnsafe(nBytes);
sl@0:   if( p ){
sl@0:     if( nOld<nBytes ){
sl@0:       memcpy(p, pPrior, nOld);
sl@0:     }else{
sl@0:       memcpy(p, pPrior, nBytes);
sl@0:     }
sl@0:     memsys3FreeUnsafe(pPrior);
sl@0:   }
sl@0:   memsys3Leave();
sl@0:   return p;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Initialize this module.
sl@0: */
sl@0: static int memsys3Init(void *NotUsed){
sl@0:   if( !sqlite3Config.pHeap ){
sl@0:     return SQLITE_ERROR;
sl@0:   }
sl@0: 
sl@0:   /* Store a pointer to the memory block in global structure mem3. */
sl@0:   assert( sizeof(Mem3Block)==8 );
sl@0:   mem3.aPool = (Mem3Block *)sqlite3Config.pHeap;
sl@0:   mem3.nPool = (sqlite3Config.nHeap / sizeof(Mem3Block)) - 2;
sl@0: 
sl@0:   /* Initialize the master block. */
sl@0:   mem3.szMaster = mem3.nPool;
sl@0:   mem3.mnMaster = mem3.szMaster;
sl@0:   mem3.iMaster = 1;
sl@0:   mem3.aPool[0].u.hdr.size4x = (mem3.szMaster<<2) + 2;
sl@0:   mem3.aPool[mem3.nPool].u.hdr.prevSize = mem3.nPool;
sl@0:   mem3.aPool[mem3.nPool].u.hdr.size4x = 1;
sl@0: 
sl@0:   return SQLITE_OK;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Deinitialize this module.
sl@0: */
sl@0: static void memsys3Shutdown(void *NotUsed){
sl@0:   return;
sl@0: }
sl@0: 
sl@0: 
sl@0: 
sl@0: /*
sl@0: ** Open the file indicated and write a log of all unfreed memory 
sl@0: ** allocations into that log.
sl@0: */
sl@0: #ifdef SQLITE_DEBUG
sl@0: void sqlite3Memsys3Dump(const char *zFilename){
sl@0:   FILE *out;
sl@0:   int i, j;
sl@0:   u32 size;
sl@0:   if( zFilename==0 || zFilename[0]==0 ){
sl@0:     out = stdout;
sl@0:   }else{
sl@0:     out = fopen(zFilename, "w");
sl@0:     if( out==0 ){
sl@0:       fprintf(stderr, "** Unable to output memory debug output log: %s **\n",
sl@0:                       zFilename);
sl@0:       return;
sl@0:     }
sl@0:   }
sl@0:   memsys3Enter();
sl@0:   fprintf(out, "CHUNKS:\n");
sl@0:   for(i=1; i<=mem3.nPool; i+=size/4){
sl@0:     size = mem3.aPool[i-1].u.hdr.size4x;
sl@0:     if( size/4<=1 ){
sl@0:       fprintf(out, "%p size error\n", &mem3.aPool[i]);
sl@0:       assert( 0 );
sl@0:       break;
sl@0:     }
sl@0:     if( (size&1)==0 && mem3.aPool[i+size/4-1].u.hdr.prevSize!=size/4 ){
sl@0:       fprintf(out, "%p tail size does not match\n", &mem3.aPool[i]);
sl@0:       assert( 0 );
sl@0:       break;
sl@0:     }
sl@0:     if( ((mem3.aPool[i+size/4-1].u.hdr.size4x&2)>>1)!=(size&1) ){
sl@0:       fprintf(out, "%p tail checkout bit is incorrect\n", &mem3.aPool[i]);
sl@0:       assert( 0 );
sl@0:       break;
sl@0:     }
sl@0:     if( size&1 ){
sl@0:       fprintf(out, "%p %6d bytes checked out\n", &mem3.aPool[i], (size/4)*8-8);
sl@0:     }else{
sl@0:       fprintf(out, "%p %6d bytes free%s\n", &mem3.aPool[i], (size/4)*8-8,
sl@0:                   i==mem3.iMaster ? " **master**" : "");
sl@0:     }
sl@0:   }
sl@0:   for(i=0; i<MX_SMALL-1; i++){
sl@0:     if( mem3.aiSmall[i]==0 ) continue;
sl@0:     fprintf(out, "small(%2d):", i);
sl@0:     for(j = mem3.aiSmall[i]; j>0; j=mem3.aPool[j].u.list.next){
sl@0:       fprintf(out, " %p(%d)", &mem3.aPool[j],
sl@0:               (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
sl@0:     }
sl@0:     fprintf(out, "\n"); 
sl@0:   }
sl@0:   for(i=0; i<N_HASH; i++){
sl@0:     if( mem3.aiHash[i]==0 ) continue;
sl@0:     fprintf(out, "hash(%2d):", i);
sl@0:     for(j = mem3.aiHash[i]; j>0; j=mem3.aPool[j].u.list.next){
sl@0:       fprintf(out, " %p(%d)", &mem3.aPool[j],
sl@0:               (mem3.aPool[j-1].u.hdr.size4x/4)*8-8);
sl@0:     }
sl@0:     fprintf(out, "\n"); 
sl@0:   }
sl@0:   fprintf(out, "master=%d\n", mem3.iMaster);
sl@0:   fprintf(out, "nowUsed=%d\n", mem3.nPool*8 - mem3.szMaster*8);
sl@0:   fprintf(out, "mxUsed=%d\n", mem3.nPool*8 - mem3.mnMaster*8);
sl@0:   sqlite3_mutex_leave(mem3.mutex);
sl@0:   if( out==stdout ){
sl@0:     fflush(stdout);
sl@0:   }else{
sl@0:     fclose(out);
sl@0:   }
sl@0: }
sl@0: #endif
sl@0: 
sl@0: /*
sl@0: ** This routine is the only routine in this file with external 
sl@0: ** linkage.
sl@0: **
sl@0: ** Populate the low-level memory allocation function pointers in
sl@0: ** sqlite3Config.m with pointers to the routines in this file. The
sl@0: ** arguments specify the block of memory to manage.
sl@0: **
sl@0: ** This routine is only called by sqlite3_config(), and therefore
sl@0: ** is not required to be threadsafe (it is not).
sl@0: */
sl@0: const sqlite3_mem_methods *sqlite3MemGetMemsys3(void){
sl@0:   static const sqlite3_mem_methods mempoolMethods = {
sl@0:      memsys3Malloc,
sl@0:      memsys3Free,
sl@0:      memsys3Realloc,
sl@0:      memsys3Size,
sl@0:      memsys3Roundup,
sl@0:      memsys3Init,
sl@0:      memsys3Shutdown,
sl@0:      0
sl@0:   };
sl@0:   return &mempoolMethods;
sl@0: }
sl@0: 
sl@0: #endif /* SQLITE_ENABLE_MEMSYS3 */