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+/*
+** 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 application gives SQLite 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.
+**
+** This memory allocator uses the following algorithm:
+**
+** 1. All memory allocation sizes are rounded up to a power of 2.
+**
+** 2. If two adjacent free blocks are the halves of a larger block,
+** then the two blocks are coalesced into the single larger block.
+**
+** 3. New memory is allocated from the first available free block.
+**
+** This algorithm is described in: J. M. Robson. "Bounds for Some Functions
+** Concerning Dynamic Storage Allocation". Journal of the Association for
+** Computing Machinery, Volume 21, Number 8, July 1974, pages 491-499.
+**
+** Let n be the size of the largest allocation divided by the minimum
+** allocation size (after rounding all sizes up to a power of 2.) Let M
+** be the maximum amount of memory ever outstanding at one time. Let
+** N be the total amount of memory available for allocation. Robson
+** proved that this memory allocator will never breakdown due to
+** fragmentation as long as the following constraint holds:
+**
+** N >= M*(1 + log2(n)/2) - n + 1
+**
+** The sqlite3_status() logic tracks the maximum values of n and M so
+** that an application can, at any time, verify this constraint.
+*/
+#include "sqliteInt.h"
+
+/*
+** This version of the memory allocator is used only when
+** SQLITE_ENABLE_MEMSYS5 is defined.
+*/
+#ifdef SQLITE_ENABLE_MEMSYS5
+
+/*
+** 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.
+**
+** The size of this object must be a power of two. That fact is
+** verified in memsys5Init().
+*/
+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.szAtom). Since
+** mem5.szAtom is always at least 8 and 32-bit integers are used,
+** it is not actually possible to reach this limit.
+*/
+#define LOGMAX 30
+
+/*
+** Masks used for mem5.aCtrl[] elements.
+*/
+#define CTRL_LOGSIZE 0x1f /* Log2 Size of this block */
+#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 szAtom; /* Smallest possible allocation in bytes */
+ int nBlock; /* Number of szAtom sized blocks in zPool */
+ u8 *zPool; /* Memory available to be allocated */
+
+ /*
+ ** Mutex to control access to the memory allocation subsystem.
+ */
+ sqlite3_mutex *mutex;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+ /*
+ ** 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) */
+#endif
+
+ /*
+ ** Lists of free blocks. aiFreelist[0] is a list of free blocks of
+ ** size mem5.szAtom. aiFreelist[1] holds blocks of size szAtom*2.
+ ** aiFreelist[2] holds free blocks of size szAtom*4. And so forth.
+ */
+ 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;
+
+/*
+** Access the static variable through a macro for SQLITE_OMIT_WSD.
+*/
+#define mem5 GLOBAL(struct Mem5Global, mem5)
+
+/*
+** Assuming mem5.zPool is divided up into an array of Mem5Link
+** structures, return a pointer to the idx-th such link.
+*/
+#define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.szAtom]))
+
+/*
+** 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;
+}
+
+/*
+** Obtain or release the mutex needed to access global data structures.
+*/
+static void memsys5Enter(void){
+ sqlite3_mutex_enter(mem5.mutex);
+}
+static void memsys5Leave(void){
+ sqlite3_mutex_leave(mem5.mutex);
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes.
+** This only works for chunks that are currently checked out.
+*/
+static int memsys5Size(void *p){
+ int iSize, i;
+ assert( p!=0 );
+ i = (int)(((u8 *)p-mem5.zPool)/mem5.szAtom);
+ assert( i>=0 && i<mem5.nBlock );
+ iSize = mem5.szAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));
+ return iSize;
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable. Return NULL if nBytes==0.
+**
+** The caller guarantees that nByte is positive.
+**
+** The caller has obtained a mutex prior to invoking this
+** routine so there is never any chance that two or more
+** threads can be in this routine at the same time.
+*/
+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 */
+
+ /* nByte must be a positive */
+ assert( nByte>0 );
+
+ /* No more than 1GiB per allocation */
+ if( nByte > 0x40000000 ) return 0;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+ /* Keep track of the maximum allocation request. Even unfulfilled
+ ** requests are counted */
+ if( (u32)nByte>mem5.maxRequest ){
+ mem5.maxRequest = nByte;
+ }
+#endif
+
+
+ /* Round nByte up to the next valid power of two */
+ for(iFullSz=mem5.szAtom,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; iBin<=LOGMAX && mem5.aiFreelist[iBin]<0; iBin++){}
+ if( iBin>LOGMAX ){
+ testcase( sqlite3GlobalConfig.xLog!=0 );
+ sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes", nByte);
+ return 0;
+ }
+ i = mem5.aiFreelist[iBin];
+ memsys5Unlink(i, 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;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+ /* 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;
+#endif
+
+#ifdef SQLITE_DEBUG
+ /* Make sure the allocated memory does not assume that it is set to zero
+ ** or retains a value from a previous allocation */
+ memset(&mem5.zPool[i*mem5.szAtom], 0xAA, iFullSz);
+#endif
+
+ /* Return a pointer to the allocated memory. */
+ return (void*)&mem5.zPool[i*mem5.szAtom];
+}
+
+/*
+** 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.szAtom byte blocks pointed to by mem5.zPool.
+ */
+ iBlock = (int)(((u8 *)pOld-mem5.zPool)/mem5.szAtom);
+
+ /* Check that the pointer pOld points to a valid, non-free block. */
+ assert( iBlock>=0 && iBlock<mem5.nBlock );
+ assert( ((u8 *)pOld-mem5.zPool)%mem5.szAtom==0 );
+ assert( (mem5.aCtrl[iBlock] & CTRL_FREE)==0 );
+
+ iLogsize = mem5.aCtrl[iBlock] & CTRL_LOGSIZE;
+ size = 1<<iLogsize;
+ assert( iBlock+size-1<(u32)mem5.nBlock );
+
+ mem5.aCtrl[iBlock] |= CTRL_FREE;
+ mem5.aCtrl[iBlock+size-1] |= CTRL_FREE;
+
+#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
+ assert( mem5.currentCount>0 );
+ assert( mem5.currentOut>=(size*mem5.szAtom) );
+ mem5.currentCount--;
+ mem5.currentOut -= size*mem5.szAtom;
+ assert( mem5.currentOut>0 || mem5.currentCount==0 );
+ assert( mem5.currentCount>0 || mem5.currentOut==0 );
+#endif
+
+ mem5.aCtrl[iBlock] = CTRL_FREE | iLogsize;
+ while( ALWAYS(iLogsize<LOGMAX) ){
+ int iBuddy;
+ if( (iBlock>>iLogsize) & 1 ){
+ iBuddy = iBlock - size;
+ assert( iBuddy>=0 );
+ }else{
+ iBuddy = iBlock + size;
+ if( iBuddy>=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;
+ }
+
+#ifdef SQLITE_DEBUG
+ /* Overwrite freed memory with the 0x55 bit pattern to verify that it is
+ ** not used after being freed */
+ memset(&mem5.zPool[iBlock*mem5.szAtom], 0x55, size);
+#endif
+
+ 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.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.
+*/
+static void memsys5Free(void *pPrior){
+ assert( pPrior!=0 );
+ memsys5Enter();
+ memsys5FreeUnsafe(pPrior);
+ memsys5Leave();
+}
+
+/*
+** Change the size of an existing memory allocation.
+**
+** The outer layer memory allocator prevents this routine from
+** being called with pPrior==0.
+**
+** nBytes is always a value obtained from a prior call to
+** memsys5Round(). Hence nBytes is always a non-negative power
+** of two. If nBytes==0 that means that an oversize allocation
+** (an allocation larger than 0x40000000) was requested and this
+** routine should return 0 without freeing pPrior.
+*/
+static void *memsys5Realloc(void *pPrior, int nBytes){
+ int nOld;
+ void *p;
+ assert( pPrior!=0 );
+ assert( (nBytes&(nBytes-1))==0 ); /* EV: R-46199-30249 */
+ assert( nBytes>=0 );
+ if( nBytes==0 ){
+ return 0;
+ }
+ nOld = memsys5Size(pPrior);
+ if( nBytes<=nOld ){
+ return pPrior;
+ }
+ p = memsys5Malloc(nBytes);
+ if( p ){
+ memcpy(p, pPrior, nOld);
+ memsys5Free(pPrior);
+ }
+ return p;
+}
+
+/*
+** Round up a request size to the next valid allocation size. If
+** the allocation is too large to be handled by this allocation system,
+** return 0.
+**
+** All allocations must be a power of two and must be expressed by a
+** 32-bit signed integer. Hence the largest allocation is 0x40000000
+** or 1073741824 bytes.
+*/
+static int memsys5Roundup(int n){
+ int iFullSz;
+ if( n<=mem5.szAtom*2 ){
+ if( n<=mem5.szAtom ) return mem5.szAtom;
+ return mem5.szAtom*2;
+ }
+ if( n>0x10000000 ){
+ if( n>0x40000000 ) return 0;
+ if( n>0x20000000 ) return 0x40000000;
+ return 0x20000000;
+ }
+ for(iFullSz=mem5.szAtom*8; iFullSz<n; iFullSz *= 4);
+ if( (iFullSz/2)>=(i64)n ) return iFullSz/2;
+ return iFullSz;
+}
+
+/*
+** Return the ceiling of the logarithm base 2 of iValue.
+**
+** Examples: memsys5Log(1) -> 0
+** memsys5Log(2) -> 1
+** memsys5Log(4) -> 2
+** memsys5Log(5) -> 3
+** memsys5Log(8) -> 3
+** memsys5Log(9) -> 4
+*/
+static int memsys5Log(int iValue){
+ int iLog;
+ for(iLog=0; (iLog<(int)((sizeof(int)*8)-1)) && (1<<iLog)<iValue; iLog++);
+ return iLog;
+}
+
+/*
+** Initialize the memory allocator.
+**
+** This routine is not threadsafe. The caller must be holding a mutex
+** to prevent multiple threads from entering at the same time.
+*/
+static int memsys5Init(void *NotUsed){
+ int ii; /* Loop counter */
+ int nByte; /* Number of bytes of memory available to this allocator */
+ u8 *zByte; /* Memory usable by this allocator */
+ int nMinLog; /* Log base 2 of minimum allocation size in bytes */
+ int iOffset; /* An offset into mem5.aCtrl[] */
+
+ UNUSED_PARAMETER(NotUsed);
+
+ /* For the purposes of this routine, disable the mutex */
+ mem5.mutex = 0;
+
+ /* The size of a Mem5Link object must be a power of two. Verify that
+ ** this is case.
+ */
+ assert( (sizeof(Mem5Link)&(sizeof(Mem5Link)-1))==0 );
+
+ nByte = sqlite3GlobalConfig.nHeap;
+ zByte = (u8*)sqlite3GlobalConfig.pHeap;
+ assert( zByte!=0 ); /* sqlite3_config() does not allow otherwise */
+
+ /* boundaries on sqlite3GlobalConfig.mnReq are enforced in sqlite3_config() */
+ nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);
+ mem5.szAtom = (1<<nMinLog);
+ while( (int)sizeof(Mem5Link)>mem5.szAtom ){
+ mem5.szAtom = mem5.szAtom << 1;
+ }
+
+ mem5.nBlock = (nByte / (mem5.szAtom+sizeof(u8)));
+ mem5.zPool = zByte;
+ mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.szAtom];
+
+ 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);
+ }
+
+ /* If a mutex is required for normal operation, allocate one */
+ if( sqlite3GlobalConfig.bMemstat==0 ){
+ mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
+ }
+
+ return SQLITE_OK;
+}
+
+/*
+** Deinitialize this module.
+*/
+static void memsys5Shutdown(void *NotUsed){
+ UNUSED_PARAMETER(NotUsed);
+ mem5.mutex = 0;
+ return;
+}
+
+#ifdef SQLITE_TEST
+/*
+** Open the file indicated and write a log of all unfreed memory
+** allocations into that log.
+*/
+void sqlite3Memsys5Dump(const char *zFilename){
+ 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.szAtom);
+ 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.szAtom << 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 */
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