/*

 ** 2007 October 14

 **

 ** 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 the C functions that implement a memory

 ** allocation subsystem for use by SQLite. 

 **

 ** This version of the memory allocation subsystem omits all

 ** use of malloc(). The SQLite user supplies a block of memory

 ** before calling sqlite3_initialize() from which allocations

 ** are made and returned by the xMalloc() and xRealloc() 

 ** implementations. Once sqlite3_initialize() has been called,

 ** the amount of memory available to SQLite is fixed and cannot

 ** be changed.

 **

 ** This version of the memory allocation subsystem is included

 ** in the build only if SQLITE_ENABLE_MEMSYS5 is defined.

 **

 ** $Id: mem5.c,v 1.14 2008/09/02 17:52:52 danielk1977 Exp $

 */

 #include "sqliteInt.h"

 /*

 ** This version of the memory allocator is used only when 

 ** SQLITE_POW2_MEMORY_SIZE is defined.

 */

 #ifdef SQLITE_ENABLE_MEMSYS5

 /*

 ** Log2 of the minimum size of an allocation.  For example, if

 ** 4 then all allocations will be rounded up to at least 16 bytes.

 ** If 5 then all allocations will be rounded up to at least 32 bytes.

 */

 #ifndef SQLITE_POW2_LOGMIN

 # define SQLITE_POW2_LOGMIN 6

 #endif

 /*

 ** Log2 of the maximum size of an allocation.

 */

 #ifndef SQLITE_POW2_LOGMAX

 # define SQLITE_POW2_LOGMAX 20

 #endif

 #define POW2_MAX (((unsigned int)1)<<SQLITE_POW2_LOGMAX)

 /*

 ** Number of distinct allocation sizes.

 */

 #define NSIZE (SQLITE_POW2_LOGMAX - SQLITE_POW2_LOGMIN + 1)

 /*

 ** 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.

 */

 typedef struct Mem5Link Mem5Link;

 struct Mem5Link {

   int next;       /* Index of next free chunk */

   int prev;       /* Index of previous free chunk */

 };

 /*

 ** Maximum size of any allocation is ((1<<LOGMAX)*mem5.nAtom). Since

 ** mem5.nAtom is always at least 8, this is not really a practical

 ** limitation.

 */

 #define LOGMAX 30

 /*

 ** 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 */

 /*

 ** All of the static variables used by this module are collected

 ** into a single structure named "mem5".  This is to keep the

 ** static variables organized and to reduce namespace pollution

 ** when this module is combined with other in the amalgamation.

 */

 static SQLITE_WSD struct Mem5Global {

   /*

   ** Memory available for allocation

   */

   int nAtom;       /* Smallest possible allocation in bytes */

   int nBlock;      /* Number of nAtom sized blocks in zPool */

   u8 *zPool;

   /*

   ** Mutex to control access to the memory allocation subsystem.

   */

   sqlite3_mutex *mutex;

   /*

   ** Performance statistics

   */

   u64 nAlloc;         /* Total number of calls to malloc */

   u64 totalAlloc;     /* Total of all malloc calls - includes internal frag */

   u64 totalExcess;    /* Total internal fragmentation */

   u32 currentOut;     /* Current checkout, including internal fragmentation */

   u32 currentCount;   /* Current number of distinct checkouts */

   u32 maxOut;         /* Maximum instantaneous currentOut */

   u32 maxCount;       /* Maximum instantaneous currentCount */

   u32 maxRequest;     /* Largest allocation (exclusive of internal frag) */

   /*

   ** Lists of free blocks of various sizes.

   */

   int aiFreelist[LOGMAX+1];

   /*

   ** Space for tracking which blocks are checked out and the size

   ** of each block.  One byte per block.

   */

   u8 *aCtrl;

 } mem5 = { 19804167 };

 #define mem5 GLOBAL(struct Mem5Global, mem5)

 #define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.nAtom]))

 /*

 ** Unlink the chunk at mem5.aPool[i] from list it is currently

 ** on.  It should be found on mem5.aiFreelist[iLogsize].

 */

 static void memsys5Unlink(int i, int iLogsize){

   int next, prev;

   assert( i>=0 && i<mem5.nBlock );

   assert( iLogsize>=0 && iLogsize<=LOGMAX );

   assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );

   next = MEM5LINK(i)->next;

   prev = MEM5LINK(i)->prev;

   if( prev<0 ){

     mem5.aiFreelist[iLogsize] = next;

   }else{

     MEM5LINK(prev)->next = next;

   }

   if( next>=0 ){

     MEM5LINK(next)->prev = prev;

   }

 }

 /*

 ** Link the chunk at mem5.aPool[i] so that is on the iLogsize

 ** free list.

 */

 static void memsys5Link(int i, int iLogsize){

   int x;

   assert( sqlite3_mutex_held(mem5.mutex) );

   assert( i>=0 && i<mem5.nBlock );

   assert( iLogsize>=0 && iLogsize<=LOGMAX );

   assert( (mem5.aCtrl[i] & CTRL_LOGSIZE)==iLogsize );

   x = MEM5LINK(i)->next = mem5.aiFreelist[iLogsize];

   MEM5LINK(i)->prev = -1;

   if( x>=0 ){

     assert( x<mem5.nBlock );

     MEM5LINK(x)->prev = i;

   }

   mem5.aiFreelist[iLogsize] = i;

 }

 /*

 ** If the STATIC_MEM mutex is not already held, obtain it now. The mutex

 ** will already be held (obtained by code in malloc.c) if

 ** sqlite3GlobalConfig.bMemStat is true.

 */

 static void memsys5Enter(void){

   if( sqlite3GlobalConfig.bMemstat==0 && mem5.mutex==0 ){

     mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);

   }

   sqlite3_mutex_enter(mem5.mutex);

 }

 static void memsys5Leave(void){

   sqlite3_mutex_leave(mem5.mutex);

 }

 /*

 ** Return the size of an outstanding allocation, in bytes.  The

 ** size returned omits the 8-byte header overhead.  This only

 ** works for chunks that are currently checked out.

 */

 static int memsys5Size(void *p){

   int iSize = 0;

   if( p ){

     int i = ((u8 *)p-mem5.zPool)/mem5.nAtom;

     assert( i>=0 && i<mem5.nBlock );

     iSize = mem5.nAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));

   }

   return iSize;

 }

 /*

 ** Find the first entry on the freelist iLogsize.  Unlink that

 ** entry and return its index. 

 */

 static int memsys5UnlinkFirst(int iLogsize){

   int i;

   int iFirst;

   assert( iLogsize>=0 && iLogsize<=LOGMAX );

   i = iFirst = mem5.aiFreelist[iLogsize];

   assert( iFirst>=0 );

   while( i>0 ){

     if( i<iFirst ) iFirst = i;

     i = MEM5LINK(i)->next;

   }

   memsys5Unlink(iFirst, iLogsize);

   return iFirst;

 }

 /*

 ** Return a block of memory of at least nBytes in size.

 ** Return NULL if unable.

 */

 static void *memsys5MallocUnsafe(int nByte){

   int i;           /* Index of a mem5.aPool[] slot */

   int iBin;        /* Index into mem5.aiFreelist[] */

   int iFullSz;     /* Size of allocation rounded up to power of 2 */

   int iLogsize;    /* Log2 of iFullSz/POW2_MIN */

   /* Keep track of the maximum allocation request.  Even unfulfilled

   ** requests are counted */

   if( nByte>mem5.maxRequest ){

     mem5.maxRequest = nByte;

   }

   /* Round nByte up to the next valid power of two */

   if( nByte>POW2_MAX ) return 0;

   for(iFullSz=mem5.nAtom, iLogsize=0; iFullSz<nByte; iFullSz *= 2, iLogsize++){}

   /* 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; mem5.aiFreelist[iBin]<0 && iBin<=LOGMAX; iBin++){}

   if( iBin>LOGMAX ) return 0;

   i = memsys5UnlinkFirst(iBin);

   while( iBin>iLogsize ){

     int newSize;

     iBin--;

     newSize = 1 << iBin;

     mem5.aCtrl[i+newSize] = CTRL_FREE | iBin;

     memsys5Link(i+newSize, iBin);

   }

   mem5.aCtrl[i] = iLogsize;

   /* Update allocator performance statistics. */

   mem5.nAlloc++;

   mem5.totalAlloc += iFullSz;

   mem5.totalExcess += iFullSz - nByte;

   mem5.currentCount++;

   mem5.currentOut += iFullSz;

   if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;

   if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;

   /* Return a pointer to the allocated memory. */

   return (void*)&mem5.zPool[i*mem5.nAtom];

 }

 /*

 ** Free an outstanding memory allocation.

 */

 static void memsys5FreeUnsafe(void *pOld){

   u32 size, iLogsize;

   int iBlock;             

   /* Set iBlock to the index of the block pointed to by pOld in 

   ** the array of mem5.nAtom byte blocks pointed to by mem5.zPool.

   */

   iBlock = ((u8 *)pOld-mem5.zPool)/mem5.nAtom;

   /* Check that the pointer pOld points to a valid, non-free block. */

   assert( iBlock>=0 && iBlock<mem5.nBlock );

   assert( ((u8 *)pOld-mem5.zPool)%mem5.nAtom==0 );

   assert( (mem5.aCtrl[iBlock] & CTRL_FREE)==0 );

   iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;

   size = 1<<iLogsize;

   assert( iBlock+size-1<mem5.nBlock );

   mem5.aCtrl[iBlock] |= CTRL_FREE;

   mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;

   assert( mem5.currentCount>0 );

   assert( mem5.currentOut>=0 );

   mem5.currentCount--;

   mem5.currentOut -= size*mem5.nAtom;

   assert( mem5.currentOut>0 || mem5.currentCount==0 );

   assert( mem5.currentCount>0 || mem5.currentOut==0 );

   mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;

   while( iLogsize<LOGMAX ){

     int iBuddy;

     if( (iBlock>>iLogsize) & 1 ){

       iBuddy = iBlock - size;

     }else{

       iBuddy = iBlock + size;

     }

     assert( iBuddy>=0 );

     if( (iBuddy+(1<<iLogsize))>mem5.nBlock ) break;

     if( mem5.aCtrl[iBuddy]!=(CTRL_FREE | iLogsize) ) break;

     memsys5Unlink(iBuddy, iLogsize);

     iLogsize++;

     if( iBuddy<iBlock ){

       mem5.aCtrl[iBuddy] = CTRL_FREE | iLogsize;

       mem5.aCtrl[iBlock] = 0;

       iBlock = iBuddy;

     }else{

       mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;

       mem5.aCtrl[iBuddy] = 0;

     }

     size *= 2;

   }

   memsys5Link(iBlock, iLogsize);

 }

 /*

 ** Allocate nBytes of memory

 */

 static void *memsys5Malloc(int nBytes){

   sqlite3_int64 *p = 0;

   if( nBytes>0 ){

     memsys5Enter();

     p = memsys5MallocUnsafe(nBytes);

     memsys5Leave();

   }

   return (void*)p; 

 }

 /*

 ** Free memory.

 */

 static void memsys5Free(void *pPrior){

   if( pPrior==0 ){

 assert(0);

     return;

   }

   memsys5Enter();

   memsys5FreeUnsafe(pPrior);

   memsys5Leave();  

 }

 /*

 ** Change the size of an existing memory allocation

 */

 static void *memsys5Realloc(void *pPrior, int nBytes){

   int nOld;

   void *p;

   if( pPrior==0 ){

     return memsys5Malloc(nBytes);

   }

   if( nBytes<=0 ){

     memsys5Free(pPrior);

     return 0;

   }

   nOld = memsys5Size(pPrior);

   if( nBytes<=nOld ){

     return pPrior;

   }

   memsys5Enter();

   p = memsys5MallocUnsafe(nBytes);

   if( p ){

     memcpy(p, pPrior, nOld);

     memsys5FreeUnsafe(pPrior);

   }

   memsys5Leave();

   return p;

 }

 /*

 ** Round up a request size to the next valid allocation size.

 */

 static int memsys5Roundup(int n){

   int iFullSz;

   for(iFullSz=mem5.nAtom; iFullSz<n; iFullSz *= 2);

   return iFullSz;

 }

 static int memsys5Log(int iValue){

   int iLog;

   for(iLog=0; (1<<iLog)<iValue; iLog++);

   return iLog;

 }

 /*

 ** Initialize this module.

 */

 static int memsys5Init(void *NotUsed){

   int ii;

   int nByte = sqlite3GlobalConfig.nHeap;

   u8 *zByte = (u8 *)sqlite3GlobalConfig.pHeap;

   int nMinLog;                 /* Log of minimum allocation size in bytes*/

   int iOffset;

   if( !zByte ){

     return SQLITE_ERROR;

   }

   nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);

   mem5.nAtom = (1<<nMinLog);

   while( sizeof(Mem5Link)>mem5.nAtom ){

     mem5.nAtom = mem5.nAtom << 1;

   }

   mem5.nBlock = (nByte / (mem5.nAtom+sizeof(u8)));

   mem5.zPool = zByte;

   mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.nAtom];

   for(ii=0; ii<=LOGMAX; ii++){

     mem5.aiFreelist[ii] = -1;

   }

   iOffset = 0;

   for(ii=LOGMAX; ii>=0; ii--){

     int nAlloc = (1<<ii);

     if( (iOffset+nAlloc)<=mem5.nBlock ){

       mem5.aCtrl[iOffset] = ii | CTRL_FREE;

       memsys5Link(iOffset, ii);

       iOffset += nAlloc;

     }

     assert((iOffset+nAlloc)>mem5.nBlock);

   }

   return SQLITE_OK;

 }

 /*

 ** Deinitialize this module.

 */

 static void memsys5Shutdown(void *NotUsed){

   return;

 }

 /*

 ** Open the file indicated and write a log of all unfreed memory 

 ** allocations into that log.

 */

 void sqlite3Memsys5Dump(const char *zFilename){

 #ifdef SQLITE_DEBUG

   FILE *out;

   int i, j, n;

   int nMinLog;

   if( zFilename==0 || zFilename[0]==0 ){

     out = stdout;

   }else{

     out = fopen(zFilename, "w");

     if( out==0 ){

       fprintf(stderr, "** Unable to output memory debug output log: %s **\n",

                       zFilename);

       return;

     }

   }

   memsys5Enter();

   nMinLog = memsys5Log(mem5.nAtom);

   for(i=0; i<=LOGMAX && i+nMinLog<32; i++){

     for(n=0, j=mem5.aiFreelist[i]; j>=0; j = MEM5LINK(j)->next, n++){}

     fprintf(out, "freelist items of size %d: %d\n", mem5.nAtom << i, n);

   }

   fprintf(out, "mem5.nAlloc       = %llu\n", mem5.nAlloc);

   fprintf(out, "mem5.totalAlloc   = %llu\n", mem5.totalAlloc);

   fprintf(out, "mem5.totalExcess  = %llu\n", mem5.totalExcess);

   fprintf(out, "mem5.currentOut   = %u\n", mem5.currentOut);

   fprintf(out, "mem5.currentCount = %u\n", mem5.currentCount);

   fprintf(out, "mem5.maxOut       = %u\n", mem5.maxOut);

   fprintf(out, "mem5.maxCount     = %u\n", mem5.maxCount);

   fprintf(out, "mem5.maxRequest   = %u\n", mem5.maxRequest);

   memsys5Leave();

   if( out==stdout ){

     fflush(stdout);

   }else{

     fclose(out);

   }

 #endif

 }

 /*

 ** 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 memsys5 methods.

 */

 const sqlite3_mem_methods *sqlite3MemGetMemsys5(void){

   static const sqlite3_mem_methods memsys5Methods = {

      memsys5Malloc,

      memsys5Free,

      memsys5Realloc,

      memsys5Size,

      memsys5Roundup,

      memsys5Init,

      memsys5Shutdown,

      0

   };

   return &memsys5Methods;

 }

 #endif /* SQLITE_ENABLE_MEMSYS5 */