SQLite

*************************************************************************
**
** Memory allocation functions used throughout sqlite.
*/
#include "sqliteInt.h"
#include <stdarg.h>

/*
** There are two general-purpose memory allocators:
**
** Simple:
**
**     sqlite3_malloc
**     sqlite3_free
**     sqlite3_realloc
**     sqlite3Malloc
**     sqlite3MallocSize
**     sqlite3_mprintf
**
** Enhanced:
**
**     sqlite3DbMallocRaw
**     sqlite3DbMallocZero
**     sqlite3DbFree
**     sqlite3DbRealloc
**     sqlite3MPrintf
**     sqlite3DbMalloc
**
** All external allocations use the simple memory allocator.
** The enhanced allocator is used internally only, and is not
** available to extensions or applications.
**
** The enhanced allocator is a wrapper around the simple allocator that
** adds the following capabilities:
**
** (1) Access to lookaside memory associated with a database connection.
**
** (2) The ability to link allocations into a hierarchy with automatic
**     deallocation of all elements of the subhierarchy whenever any
**     element within the hierarchy is deallocated.
**
** The two allocators are incompatible in the sense that allocations that
** originate from the simple allocator must be deallocated using the simple
** deallocator and allocations that originate from the enhanced allocator must
** be deallocated using the enhanced deallocator.  You cannot check-out 
** memory from one allocator then return it to the other.
*/

/*
** The automatic hierarchical deallocation feature of the enhanced allocator
** is implemented by adding an instance of the following structure to the
** header of each enhanced allocation.
**
** In order to preserve alignment, this structure must be a multiple of
** 8 bytes in size.
*/
typedef struct EMemHdr EMemHdr;
struct EMemHdr {
  EMemHdr *pEChild;      /* List of children of this node */
  EMemHdr *pESibling;    /* Other nodes that are children of the same parent */
#ifdef SQLITE_MEMDEBUG
  u32 iEMemMagic;        /* Magic number for sanity checking */
  u32 isAChild;          /* True if this allocate is a child of another */
#endif
};

/*
** Macros for querying and setting debugging fields of the EMemHdr object.
*/
#ifdef SQLITE_MEMDEBUG
# define isValidEMem(E)     ((E)->iEMemMagic==0xc0a43fad)
# define setValidEMem(E)    (E)->iEMemMagic = 0xc0a43fad
# define clearValidEMem(E)  (E)->iEMemMagic = 0x12345678
# define isChildEMem(E)     ((E)->isAChild!=0)
# define setChildEMem(E)    (E)->isAChild = 1
# define clearChildEMem(E)  (E)->isAChild = 0
#else
# define isValidEMem(E)
# define setValidEMem(E)
# define clearValidEMem(E)
# define isChildEMem(E)
# define setChildEMem(E)
# define clearChildEMem(E)
#endif

/*
** This routine runs when the memory allocator sees that the
** total memory allocation is about to exceed the soft heap
** limit.
*/
static void softHeapLimitEnforcer(
  void *NotUsed, 
  sqlite3_int64 NotUsed2,
  int allocSize
){
  UNUSED_PARAMETER2(NotUsed, NotUsed2);
  sqlite3_release_memory(allocSize);
}

/*
** Set the soft heap-size limit for the library. Passing a zero or 
** negative value indicates no limit.
**
** If the total amount of memory allocated (by all threads) exceeds
** the soft heap limit, then sqlite3_release_memory() is invoked to
** try to free up some memory before proceeding.
*/
void sqlite3_soft_heap_limit(int n){
  sqlite3_uint64 iLimit;
  int overage;
  if( n<0 ){
    iLimit = 0;
  }else{

#else
#define isLookaside(A,B) 0
#endif

/*
** Return the size of a memory allocation previously obtained from
** sqlite3Malloc() or sqlite3_malloc().
**
** The size returned is the usable size and does not include any
** bookkeeping overhead or sentinals at the end of the allocation.
*/
int sqlite3MallocSize(void *p){
  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
  assert( !sqlite3MemdebugHasType(p, MEMTYPE_RECURSIVE) );
  return sqlite3GlobalConfig.m.xSize(p);
}
int sqlite3DbMallocSize(sqlite3 *db, void *pObj){
  EMemHdr *p = (EMemHdr*)pObj;
  assert( db==0 || sqlite3_mutex_held(db->mutex) );
  if( p ){
    p--;
    assert( isValidEMem(p) );
  }
  if( isLookaside(db, p) ){
    return db->lookaside.sz - sizeof(EMemHdr);
  }else{
    assert( sqlite3MemdebugHasType(p, MEMTYPE_RECURSIVE) );
    assert( sqlite3MemdebugHasType(p,
             db ? (MEMTYPE_DB|MEMTYPE_HEAP) : MEMTYPE_HEAP) );
    return sqlite3GlobalConfig.m.xSize(p) - sizeof(EMemHdr);
  }
}

/*
** Free memory previously obtained from sqlite3Malloc().
*/
void sqlite3_free(void *p){

  }else{
    sqlite3GlobalConfig.m.xFree(p);
  }
}

/*
** Free memory that might be associated with a particular database
** connection.  All child allocations are also freed.
*/
void sqlite3DbFree(sqlite3 *db, void *pObj){
  EMemHdr *p = (EMemHdr*)pObj;
  assert( db==0 || sqlite3_mutex_held(db->mutex) );
  if( p ) p--;
  while( p ){
    EMemHdr *pNext = p->pESibling;
    assert( isValidEMem(p) );
    if( p->pEChild ) sqlite3DbFree(db, (void*)&p->pEChild[1]);
    if( isLookaside(db, p) ){
      LookasideSlot *pBuf = (LookasideSlot*)p;
      clearValidEMem(p);
      pBuf->pNext = db->lookaside.pFree;
      db->lookaside.pFree = pBuf;
      db->lookaside.nOut--;
    }else{
      assert( sqlite3MemdebugHasType(p, MEMTYPE_RECURSIVE) );
      assert( sqlite3MemdebugHasType(p,
                         db ? (MEMTYPE_DB|MEMTYPE_HEAP) : MEMTYPE_HEAP) );
      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
      clearValidEMem(p);
      sqlite3_free(p);
    }
    p = pNext;
  }
}

/*
** Change the size of an existing memory allocation.
**
** This is the same as sqlite3_realloc() except that it assumes that
** the memory subsystem has already been initialized.
*/
void *sqlite3Realloc(void *pOld, int nBytes){
  int nOld, nNew;
  void *pNew;
  if( pOld==0 ){
    return sqlite3Malloc(nBytes);
  }

**         int *b = (int*)sqlite3DbMallocRaw(db, 200);
**         if( b ) a[10] = 9;
**
** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
** that all prior mallocs (ex: "a") worked too.
*/
void *sqlite3DbMallocRaw(sqlite3 *db, int n){
  EMemHdr *p;
  assert( db==0 || sqlite3_mutex_held(db->mutex) );
  n += sizeof(EMemHdr);
#ifndef SQLITE_OMIT_LOOKASIDE
  if( db ){
    LookasideSlot *pBuf;
    if( db->mallocFailed ){
      return 0;
    }
    if( db->lookaside.bEnabled && n<=db->lookaside.sz
         && (pBuf = db->lookaside.pFree)!=0 ){
      db->lookaside.pFree = pBuf->pNext;
      db->lookaside.nOut++;
      if( db->lookaside.nOut>db->lookaside.mxOut ){
        db->lookaside.mxOut = db->lookaside.nOut;
      }
      p = (EMemHdr*)pBuf;
      goto finish_emalloc_raw;
    }
  }
#else
  if( db && db->mallocFailed ){
    return 0;
  }
#endif
  p = sqlite3Malloc(n);
  if( !p ){
    if( db ) db->mallocFailed = 1;
    return 0;
  }
  sqlite3MemdebugSetType(p, MEMTYPE_RECURSIVE |
            ((db && db->lookaside.bEnabled) ? MEMTYPE_DB : MEMTYPE_HEAP));

finish_emalloc_raw:
  memset(p, 0, sizeof(EMemHdr));
  setValidEMem(p);
  return (void*)&p[1];
}

/*
** Resize the block of memory pointed to by p to n bytes. If the
** resize fails, set the mallocFailed flag in the connection object.
**
** The pOld memory block must not be linked into an allocation hierarchy
** as a child.  It is OK for the allocation to be the root of a hierarchy
** of allocations; the only restriction is that there must be no other
** allocations above the pOld allocation in the hierarchy.  To resize 
** an allocation that is a child within a hierarchy, first
** unlink the allocation, resize it, then relink it.  
*/
void *sqlite3DbRealloc(sqlite3 *db, void *pOld, int n){
  EMemHdr *p = (EMemHdr*)pOld;
  EMemHdr *pNew = 0;
  assert( db!=0 );
  assert( sqlite3_mutex_held(db->mutex) );
  if( db->mallocFailed==0 ){
    if( p==0 ){
      return sqlite3DbMallocRaw(db, n);
    }
    p--;
    assert( isValidEMem(p) );    /* pOld obtained from extended allocator */
    assert( !isChildEMem(p) );   /* pOld must not be a child allocation */
    if( isLookaside(db, p) ){
      if( n+sizeof(EMemHdr)<=db->lookaside.sz ){
        return pOld;
      }
      pNew = sqlite3DbMallocRaw(db, n);
      if( pNew ){
        memcpy(pNew-1, p, db->lookaside.sz);
        setValidEMem(pNew-1);
        sqlite3DbFree(db, pOld);
      }
    }else{
      assert( sqlite3MemdebugHasType(p, MEMTYPE_RECURSIVE) );
      assert( sqlite3MemdebugHasType(p, MEMTYPE_DB|MEMTYPE_HEAP) );
      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
      pNew = sqlite3_realloc(p, n+sizeof(EMemHdr));
      if( !pNew ){
        sqlite3MemdebugSetType(p, MEMTYPE_RECURSIVE|MEMTYPE_HEAP);
        db->mallocFailed = 1;
      }else{
        sqlite3MemdebugSetType(pNew, MEMTYPE_RECURSIVE | 
              (db->lookaside.bEnabled ? MEMTYPE_DB : MEMTYPE_HEAP));
        setValidEMem(pNew);
        pNew++;
      }
    }
  }
  return (void*)pNew;
}

/*
** Attempt to reallocate p.  If the reallocation fails, then free p
** and set the mallocFailed flag in the database connection.
*/
void *sqlite3DbReallocOrFree(sqlite3 *db, void *p, int n){

  zNew = sqlite3DbMallocRaw(db, n+1);
  if( zNew ){
    memcpy(zNew, z, n);
    zNew[n] = 0;
  }
  return zNew;
}

/*
** Link extended allocation nodes such that deallocating the parent
** causes the child to be automatically deallocated.
*/
void sqlite3MemLink(void *pParentObj, void *pChildObj){
  EMemHdr *pParent = (EMemHdr*)pParentObj;
  EMemHdr *pChild = (EMemHdr*)pChildObj;
  if( pParent && pChild ){
    pParent--;
    assert( isValidEMem(pParent) );  /* pParentObj is an extended allocation */ 
    pChild--;
    assert( isValidEMem(pChild) );   /* pChildObj is an extended allocation */
    assert( !isChildEMem(pChild) );  /* pChildObj not a child of another obj */
    pChild->pESibling = pParent->pEChild;
    pParent->pEChild = pChild;
    setChildEMem(pChild);
  }
}

/*
** pChildObj is a child object of pParentObj due to a prior call
** to sqlite3MemLink().  This routine breaks that linkage, making
** pChildObj an independent node that is not a child of any other node.
*/
void sqlite3MemUnlink(void *pParentObj, void *pChildObj){
  EMemHdr *pParent = (EMemHdr*)pParentObj;
  EMemHdr *pChild = (EMemHdr*)pChildObj;
  EMemHdr **pp;

  assert( pParentObj!=0 );
  assert( pChildObj!=0 );
  pParent--;
  assert( isValidEMem(pParent) );  /* pParentObj is an extended allocation */ 
  pChild--;
  assert( isValidEMem(pChild) );   /* pChildObj is an extended allocation */
  assert( isChildEMem(pChild) );   /* pChildObj a child of something */
  for(pp=&pParent->pEChild; (*pp)!=pChild; pp = &(*pp)->pESibling){
    assert( *pp );                /* pChildObj is a child of pParentObj */
    assert( isValidEMem(*pp) );   /* All children of pParentObj are valid */
    assert( isChildEMem(*pp) );   /* All children of pParentObj are children */
  }
  *pp = pChild->pESibling;
  pChild->pESibling = 0;
  clearChildEMem(pChild);
}


/*
** Create a string from the zFromat argument and the va_list that follows.
** Store the string in memory obtained from sqliteMalloc() and make *pz
** point to that string.
*/
void sqlite3SetString(char **pz, sqlite3 *db, const char *zFormat, ...){

void *sqlite3DbMallocRaw(sqlite3*, int);
char *sqlite3DbStrDup(sqlite3*,const char*);
char *sqlite3DbStrNDup(sqlite3*,const char*, int);
void *sqlite3Realloc(void*, int);
void *sqlite3DbReallocOrFree(sqlite3 *, void *, int);
void *sqlite3DbRealloc(sqlite3 *, void *, int);
void sqlite3DbFree(sqlite3*, void*);
void sqlite3MemLink(void *pParent, void *pChild);
void sqlite3MemUnlink(void *pParent, void *pChild);
int sqlite3MallocSize(void*);
int sqlite3DbMallocSize(sqlite3*, void*);
void *sqlite3ScratchMalloc(int);
void sqlite3ScratchFree(void*);
void *sqlite3PageMalloc(int);
void sqlite3PageFree(void*);
void sqlite3MemSetDefault(void);