--- /dev/null
+/*
+** 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(). All dynamically allocatable memory is
+** contained in a static array, mem.aPool[]. The size of this
+** fixed memory pool is SQLITE_MEMORY_SIZE bytes.
+**
+** This version of the memory allocation subsystem is used if
+** and only if SQLITE_MEMORY_SIZE is defined.
+**
+** $Id: mem3.c,v 1.1 2007/10/19 17:47:25 drh Exp $
+*/
+
+/*
+** This version of the memory allocator is used only when
+** SQLITE_MEMORY_SIZE is defined.
+*/
+#if defined(SQLITE_MEMORY_SIZE)
+#include "sqliteInt.h"
+
+/*
+** Maximum size (in Mem3Blocks) of a "small" chunk.
+*/
+#define MX_SMALL 10
+
+
+/*
+** Number of freelist hash slots
+*/
+#define N_HASH 61
+
+/*
+** A memory allocation (also called a "chunk") consists of two or
+** more blocks where each block is 8 bytes. The first 8 bytes are
+** a header that is not returned to the user.
+**
+** A chunk is two or more blocks that is either checked out or
+** free. The first block has format u.hdr. u.hdr.size is the
+** size of the allocation in blocks if the allocation is free.
+** If the allocation is checked out, u.hdr.size is the negative
+** of the size. Similarly, u.hdr.prevSize is the size of the
+** immediately previous allocation.
+**
+** We often identify a chunk by its index in mem.aPool[]. When
+** this is done, the chunk index refers to the second block of
+** the chunk. In this way, the first chunk has an index of 1.
+** A chunk index of 0 means "no such chunk" and is the equivalent
+** of a NULL pointer.
+**
+** The second block of free chunks is of the form u.list. The
+** two fields form a double-linked list of chunks of related sizes.
+** Pointers to the head of the list are stored in mem.aiSmall[]
+** for smaller chunks and mem.aiHash[] for larger chunks.
+**
+** The second block of a chunk is user data if the chunk is checked
+** out.
+*/
+typedef struct Mem3Block Mem3Block;
+struct Mem3Block {
+ union {
+ struct {
+ int prevSize; /* Size of previous chunk in Mem3Block elements */
+ int size; /* Size of current chunk in Mem3Block elements */
+ } hdr;
+ struct {
+ int next; /* Index in mem.aPool[] of next free chunk */
+ int prev; /* Index in mem.aPool[] of previous free chunk */
+ } list;
+ } u;
+};
+
+/*
+** All of the static variables used by this module are collected
+** into a single structure named "mem". This is to keep the
+** static variables organized and to reduce namespace pollution
+** when this module is combined with other in the amalgamation.
+*/
+static struct {
+ /*
+ ** The alarm callback and its arguments. The mem.mutex lock will
+ ** be held while the callback is running. Recursive calls into
+ ** the memory subsystem are allowed, but no new callbacks will be
+ ** issued. The alarmBusy variable is set to prevent recursive
+ ** callbacks.
+ */
+ sqlite3_int64 alarmThreshold;
+ void (*alarmCallback)(void*, sqlite3_int64,int);
+ void *alarmArg;
+ int alarmBusy;
+
+ /*
+ ** Mutex to control access to the memory allocation subsystem.
+ */
+ sqlite3_mutex *mutex;
+
+ /*
+ ** Current allocation and high-water mark.
+ */
+ sqlite3_int64 nowUsed;
+ sqlite3_int64 mxUsed;
+
+ /*
+ ** iMaster is the index of the master chunk. Most new allocations
+ ** occur off of this chunk. szMaster is the size (in Mem3Blocks)
+ ** of the current master. iMaster is 0 if there is not master chunk.
+ ** The master chunk is not in either the aiHash[] or aiSmall[].
+ */
+ int iMaster;
+ int szMaster;
+
+ /*
+ ** Array of lists of free blocks according to the block size
+ ** for smaller chunks, or a hash on the block size for larger
+ ** chunks.
+ */
+ int aiSmall[MX_SMALL-1]; /* For sizes 2 through MX_SMALL, inclusive */
+ int aiHash[N_HASH]; /* For sizes MX_SMALL+1 and larger */
+
+ /*
+ ** Memory available for allocation
+ */
+ Mem3Block aPool[SQLITE_MEMORY_SIZE/sizeof(Mem3Block)+2];
+} mem;
+
+/*
+** Unlink the chunk at mem.aPool[i] from list it is currently
+** on. *pRoot is the list that i is a member of.
+*/
+static void unlinkChunkFromList(int i, int *pRoot){
+ int next = mem.aPool[i].u.list.next;
+ int prev = mem.aPool[i].u.list.prev;
+ if( prev==0 ){
+ *pRoot = next;
+ }else{
+ mem.aPool[prev].u.list.next = next;
+ }
+ if( next ){
+ mem.aPool[next].u.list.prev = prev;
+ }
+ mem.aPool[i].u.list.next = 0;
+ mem.aPool[i].u.list.prev = 0;
+}
+
+/*
+** Unlink the chunk at index i from
+** whatever list is currently a member of.
+*/
+static void unlinkChunk(int i){
+ int size, hash;
+ size = mem.aPool[i-1].u.hdr.size;
+ assert( size==mem.aPool[i+size-1].u.hdr.prevSize );
+ assert( size>=2 );
+ if( size <= MX_SMALL ){
+ unlinkChunkFromList(i, &mem.aiSmall[size-2]);
+ }else{
+ hash = size % N_HASH;
+ unlinkChunkFromList(i, &mem.aiHash[hash]);
+ }
+}
+
+/*
+** Link the chunk at mem.aPool[i] so that is on the list rooted
+** at *pRoot.
+*/
+static void linkChunkIntoList(int i, int *pRoot){
+ mem.aPool[i].u.list.next = *pRoot;
+ mem.aPool[i].u.list.prev = 0;
+ if( *pRoot ){
+ mem.aPool[*pRoot].u.list.prev = i;
+ }
+ *pRoot = i;
+}
+
+/*
+** Link the chunk at index i into either the appropriate
+** small chunk list, or into the large chunk hash table.
+*/
+static void linkChunk(int i){
+ int size, hash;
+ size = mem.aPool[i-1].u.hdr.size;
+ assert( size==mem.aPool[i+size-1].u.hdr.prevSize );
+ assert( size>=2 );
+ if( size <= MX_SMALL ){
+ linkChunkIntoList(i, &mem.aiSmall[size-2]);
+ }else{
+ hash = size % N_HASH;
+ linkChunkIntoList(i, &mem.aiHash[hash]);
+ }
+}
+
+/*
+** Enter the mutex mem.mutex. Allocate it if it is not already allocated.
+**
+** Also: Initialize the memory allocation subsystem the first time
+** this routine is called.
+*/
+static void enterMem(void){
+ if( mem.mutex==0 ){
+ mem.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM);
+ mem.aPool[0].u.hdr.size = SQLITE_MEMORY_SIZE/8;
+ mem.aPool[SQLITE_MEMORY_SIZE/8].u.hdr.prevSize = SQLITE_MEMORY_SIZE/8;
+ mem.iMaster = 1;
+ mem.szMaster = SQLITE_MEMORY_SIZE/8;
+ }
+ sqlite3_mutex_enter(mem.mutex);
+}
+
+/*
+** Return the amount of memory currently checked out.
+*/
+sqlite3_int64 sqlite3_memory_used(void){
+ sqlite3_int64 n;
+ enterMem();
+ n = mem.nowUsed;
+ sqlite3_mutex_leave(mem.mutex);
+ return n;
+}
+
+/*
+** Return the maximum amount of memory that has ever been
+** checked out since either the beginning of this process
+** or since the most recent reset.
+*/
+sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
+ sqlite3_int64 n;
+ enterMem();
+ n = mem.mxUsed;
+ if( resetFlag ){
+ mem.mxUsed = mem.nowUsed;
+ }
+ sqlite3_mutex_leave(mem.mutex);
+ return n;
+}
+
+/*
+** Change the alarm callback
+*/
+int sqlite3_memory_alarm(
+ void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
+ void *pArg,
+ sqlite3_int64 iThreshold
+){
+ enterMem();
+ mem.alarmCallback = xCallback;
+ mem.alarmArg = pArg;
+ mem.alarmThreshold = iThreshold;
+ sqlite3_mutex_leave(mem.mutex);
+ return SQLITE_OK;
+}
+
+/*
+** Trigger the alarm
+*/
+static void sqlite3MemsysAlarm(int nByte){
+ void (*xCallback)(void*,sqlite3_int64,int);
+ sqlite3_int64 nowUsed;
+ void *pArg;
+ if( mem.alarmCallback==0 || mem.alarmBusy ) return;
+ mem.alarmBusy = 1;
+ xCallback = mem.alarmCallback;
+ nowUsed = mem.nowUsed;
+ pArg = mem.alarmArg;
+ sqlite3_mutex_leave(mem.mutex);
+ xCallback(pArg, nowUsed, nByte);
+ sqlite3_mutex_enter(mem.mutex);
+ mem.alarmBusy = 0;
+}
+
+/*
+** Return the size of an outstanding allocation, in bytes. The
+** size returned includes the 8-byte header overhead. This only
+** works for chunks that are currently checked out.
+*/
+static int internal_size(void *p){
+ Mem3Block *pBlock = (Mem3Block*)p;
+ assert( pBlock[-1].u.hdr.size<0 );
+ return -pBlock[-1].u.hdr.size*8;
+}
+
+/*
+** Chunk i is a free chunk that has been unlinked. Adjust its
+** size parameters for check-out and return a pointer to the
+** user portion of the chunk.
+*/
+static void *checkOutChunk(int i, int nBlock){
+ assert( mem.aPool[i-1].u.hdr.size==nBlock );
+ assert( mem.aPool[i+nBlock-1].u.hdr.prevSize==nBlock );
+ mem.aPool[i-1].u.hdr.size = -nBlock;
+ mem.aPool[i+nBlock-1].u.hdr.prevSize = -nBlock;
+ return &mem.aPool[i];
+}
+
+/*
+** Carve a piece off of the end of the mem.iMaster free chunk.
+** Return a pointer to the new allocation. Or, if the master chunk
+** is not large enough, return 0.
+*/
+static void *internal_from_master(int nBlock){
+ assert( mem.szMaster>=nBlock );
+ if( nBlock>=mem.szMaster-1 ){
+ /* Use the entire master */
+ void *p = checkOutChunk(mem.iMaster, mem.szMaster);
+ mem.iMaster = 0;
+ mem.szMaster = 0;
+ return p;
+ }else{
+ /* Split the master block. Return the tail. */
+ int newi;
+ newi = mem.iMaster + mem.szMaster - nBlock;
+ assert( newi > mem.iMaster+1 );
+ mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = -nBlock;
+ mem.aPool[newi-1].u.hdr.size = -nBlock;
+ mem.szMaster -= nBlock;
+ mem.aPool[newi-1].u.hdr.prevSize = mem.szMaster;
+ mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
+ return (void*)&mem.aPool[newi];
+ }
+}
+
+/*
+** *pRoot is the head of a list of free chunks of the same size
+** or same size hash. In other words, *pRoot is an entry in either
+** mem.aiSmall[] or mem.aiHash[].
+**
+** This routine examines all entries on the given list and tries
+** to coalesce each entries with adjacent free chunks.
+**
+** If it sees a chunk that is larger than mem.iMaster, it replaces
+** the current mem.iMaster with the new larger chunk. In order for
+** this mem.iMaster replacement to work, the master chunk must be
+** linked into the hash tables. That is not the normal state of
+** affairs, of course. The calling routine must link the master
+** chunk before invoking this routine, then must unlink the (possibly
+** changed) master chunk once this routine has finished.
+*/
+static void mergeChunks(int *pRoot){
+ int iNext, prev, size, i;
+
+ for(i=*pRoot; i>0; i=iNext){
+ iNext = mem.aPool[i].u.list.next;
+ size = mem.aPool[i-1].u.hdr.size;
+ assert( size>0 );
+ if( mem.aPool[i-1].u.hdr.prevSize>0 ){
+ unlinkChunkFromList(i, pRoot);
+ prev = i - mem.aPool[i-1].u.hdr.prevSize;
+ assert( prev>=0 );
+ if( prev==iNext ){
+ iNext = mem.aPool[prev].u.list.next;
+ }
+ unlinkChunk(prev);
+ size = i + size - prev;
+ mem.aPool[prev-1].u.hdr.size = size;
+ mem.aPool[prev+size-1].u.hdr.prevSize = size;
+ linkChunk(prev);
+ i = prev;
+ }
+ if( size>mem.szMaster ){
+ mem.iMaster = i;
+ mem.szMaster = size;
+ }
+ }
+}
+
+/*
+** Return a block of memory of at least nBytes in size.
+** Return NULL if unable.
+*/
+static void *internal_malloc(int nByte){
+ int i;
+ int nBlock;
+
+ assert( sizeof(Mem3Block)==8 );
+ if( nByte<=0 ){
+ nBlock = 2;
+ }else{
+ nBlock = (nByte + 15)/8;
+ }
+ assert( nBlock >= 2 );
+
+ /* STEP 1:
+ ** Look for an entry of the correct size in either the small
+ ** chunk table or in the large chunk hash table. This is
+ ** successful most of the time (about 9 times out of 10).
+ */
+ if( nBlock <= MX_SMALL ){
+ i = mem.aiSmall[nBlock-2];
+ if( i>0 ){
+ unlinkChunkFromList(i, &mem.aiSmall[nBlock-2]);
+ return checkOutChunk(i, nBlock);
+ }
+ }else{
+ int hash = nBlock % N_HASH;
+ for(i=mem.aiHash[hash]; i>0; i=mem.aPool[i].u.list.next){
+ if( mem.aPool[i-1].u.hdr.size==nBlock ){
+ unlinkChunkFromList(i, &mem.aiHash[hash]);
+ return checkOutChunk(i, nBlock);
+ }
+ }
+ }
+
+ /* STEP 2:
+ ** Try to satisfy the allocation by carving a piece off of the end
+ ** of the master chunk. This step usually works if step 1 fails.
+ */
+ if( mem.szMaster>=nBlock ){
+ return internal_from_master(nBlock);
+ }
+
+
+ /* STEP 3:
+ ** Loop through the entire memory pool. Coalesce adjacent free
+ ** chunks. Recompute the master chunk as the largest free chunk.
+ ** Then try again to satisfy the allocation by carving a piece off
+ ** of the end of the master chunk. This step happens very
+ ** rarely (we hope!)
+ */
+ if( mem.iMaster ){
+ linkChunk(mem.iMaster);
+ mem.iMaster = 0;
+ mem.szMaster = 0;
+ }
+ for(i=0; i<N_HASH; i++){
+ mergeChunks(&mem.aiHash[i]);
+ }
+ for(i=0; i<MX_SMALL-1; i++){
+ mergeChunks(&mem.aiSmall[i]);
+ }
+ if( mem.szMaster ){
+ unlinkChunk(mem.iMaster);
+ if( mem.szMaster>=nBlock ){
+ return internal_from_master(nBlock);
+ }
+ }
+
+ /* If none of the above worked, then we fail. */
+ return 0;
+}
+
+/*
+** Free an outstanding memory allocation.
+*/
+void internal_free(void *pOld){
+ Mem3Block *p = (Mem3Block*)pOld;
+ int i;
+ int size;
+ assert( p>mem.aPool && p<&mem.aPool[SQLITE_MEMORY_SIZE/8] );
+ i = p - mem.aPool;
+ size = -mem.aPool[i-1].u.hdr.size;
+ assert( size>=2 );
+ assert( mem.aPool[i+size-1].u.hdr.prevSize==-size );
+ mem.aPool[i-1].u.hdr.size = size;
+ mem.aPool[i+size-1].u.hdr.prevSize = size;
+ linkChunk(i);
+
+ /* Try to expand the master using the newly freed chunk */
+ if( mem.iMaster ){
+ while( mem.aPool[mem.iMaster-1].u.hdr.prevSize>0 ){
+ size = mem.aPool[mem.iMaster-1].u.hdr.prevSize;
+ mem.iMaster -= size;
+ mem.szMaster += size;
+ unlinkChunk(mem.iMaster);
+ mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
+ mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
+ }
+ while( mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size>0 ){
+ unlinkChunk(mem.iMaster+mem.szMaster);
+ mem.szMaster += mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.size;
+ mem.aPool[mem.iMaster-1].u.hdr.size = mem.szMaster;
+ mem.aPool[mem.iMaster+mem.szMaster-1].u.hdr.prevSize = mem.szMaster;
+ }
+ }
+}
+
+/*
+** Allocate nBytes of memory
+*/
+void *sqlite3_malloc(int nBytes){
+ sqlite3_int64 *p = 0;
+ if( nBytes>0 ){
+ enterMem();
+ if( mem.alarmCallback!=0 && mem.nowUsed+nBytes>=mem.alarmThreshold ){
+ sqlite3MemsysAlarm(nBytes);
+ }
+ p = internal_malloc(nBytes);
+ if( p==0 ){
+ sqlite3MemsysAlarm(nBytes);
+ p = internal_malloc(nBytes);
+ }
+ if( p ){
+ mem.nowUsed += internal_size(p);
+ if( mem.nowUsed>mem.mxUsed ){
+ mem.mxUsed = mem.nowUsed;
+ }
+ }
+ sqlite3_mutex_leave(mem.mutex);
+ }
+ return (void*)p;
+}
+
+/*
+** Free memory.
+*/
+void sqlite3_free(void *pPrior){
+ if( pPrior==0 ){
+ return;
+ }
+ assert( mem.mutex!=0 );
+ sqlite3_mutex_enter(mem.mutex);
+ mem.nowUsed -= internal_size(pPrior);
+ internal_free(pPrior);
+ sqlite3_mutex_leave(mem.mutex);
+}
+
+/*
+** Change the size of an existing memory allocation
+*/
+void *sqlite3_realloc(void *pPrior, int nBytes){
+ int nOld;
+ void *p;
+ if( pPrior==0 ){
+ return sqlite3_malloc(nBytes);
+ }
+ if( nBytes<=0 ){
+ sqlite3_free(pPrior);
+ return 0;
+ }
+ assert( mem.mutex!=0 );
+ sqlite3_mutex_enter(mem.mutex);
+ nOld = internal_size(pPrior);
+ if( mem.alarmCallback!=0 && mem.nowUsed+nBytes-nOld>=mem.alarmThreshold ){
+ sqlite3MemsysAlarm(nBytes-nOld);
+ }
+ p = internal_malloc(nBytes);
+ if( p==0 ){
+ sqlite3MemsysAlarm(nBytes);
+ p = internal_malloc(nBytes);
+ if( p==0 ){
+ return 0;
+ }
+ }
+ if( nOld<nBytes ){
+ memcpy(p, pPrior, nOld);
+ }else{
+ memcpy(p, pPrior, nBytes);
+ }
+ internal_free(pPrior);
+ mem.nowUsed += internal_size(p)-nOld;
+ if( mem.nowUsed>mem.mxUsed ){
+ mem.mxUsed = mem.nowUsed;
+ }
+ sqlite3_mutex_leave(mem.mutex);
+ return p;
+}
+
+/*
+** Open the file indicated and write a log of all unfreed memory
+** allocations into that log.
+*/
+void sqlite3_memdebug_dump(const char *zFilename){
+#ifdef SQLITE_DEBUG
+ FILE *out;
+ int i, j, size;
+ 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;
+ }
+ }
+ enterMem();
+ fprintf(out, "CHUNKS:\n");
+ for(i=1; i<=SQLITE_MEMORY_SIZE/8; i+=size){
+ size = mem.aPool[i-1].u.hdr.size;
+ if( size>=-1 && size<=1 ){
+ fprintf(out, "%p size error\n", &mem.aPool[i]);
+ assert( 0 );
+ break;
+ }
+ if( mem.aPool[i+(size<0?-size:size)-1].u.hdr.prevSize!=size ){
+ fprintf(out, "%p tail size does not match\n", &mem.aPool[i]);
+ assert( 0 );
+ break;
+ }
+ if( size<0 ){
+ size = -size;
+ fprintf(out, "%p %6d bytes checked out\n", &mem.aPool[i], size*8-8);
+ }else{
+ fprintf(out, "%p %6d bytes free%s\n", &mem.aPool[i], size*8-8,
+ i==mem.iMaster ? " **master**" : "");
+ }
+ }
+ for(i=0; i<MX_SMALL-1; i++){
+ if( mem.aiSmall[i]==0 ) continue;
+ fprintf(out, "small(%2d):", i);
+ for(j = mem.aiSmall[i]; j>0; j=mem.aPool[j].u.list.next){
+ fprintf(out, " %p(%d)", &mem.aPool[j], mem.aPool[j-1].u.hdr.size*8-8);
+ }
+ fprintf(out, "\n");
+ }
+ for(i=0; i<N_HASH; i++){
+ if( mem.aiHash[i]==0 ) continue;
+ fprintf(out, "hash(%2d):", i);
+ for(j = mem.aiHash[i]; j>0; j=mem.aPool[j].u.list.next){
+ fprintf(out, " %p(%d)", &mem.aPool[j], mem.aPool[j-1].u.hdr.size*8-8);
+ }
+ fprintf(out, "\n");
+ }
+ fprintf(out, "master=%d\n", mem.iMaster);
+ fprintf(out, "nowUsed=%lld\n", mem.nowUsed);
+ fprintf(out, "mxUsed=%lld\n", mem.mxUsed);
+ sqlite3_mutex_leave(mem.mutex);
+ if( out==stdout ){
+ fflush(stdout);
+ }else{
+ fclose(out);
+ }
+#endif
+}
+
+
+#endif /* !SQLITE_MEMORY_SIZE */
projects / thirdparty / sqlite.git / commitdiff
