}
#endif /* !SQLITE_OMIT_TRACE && SQLITE_ENABLE_IOTRACE */
-/*
-** Allocate space from a fixed size buffer and return a pointer to
-** that space. If insufficient space is available, return NULL.
-**
-** The pBuf parameter is the initial value of a pointer which will
-** receive the new memory. pBuf is normally NULL. If pBuf is not
-** NULL, it means that memory space has already been allocated and that
-** this routine should not allocate any new memory. When pBuf is not
-** NULL simply return pBuf. Only allocate new memory space when pBuf
-** is NULL.
-**
-** nByte is the number of bytes of space needed.
+/* An instance of this object describes bulk memory available for use
+** by subcomponents of a prepared statement. Space is allocated out
+** of a ReusableSpace object by the allocSpace() routine below.
+*/
+struct ReusableSpace {
+ u8 *pSpace; /* Available memory */
+ int nFree; /* Bytes of available memory */
+ int nNeeded; /* Total bytes that could not be allocated */
+};
+
+/* Try to allocate nByte bytes of 8-byte aligned bulk memory for pBuf
+** from the ReusableSpace object. Return a pointer to the allocated
+** memory on success. If insufficient memory is available in the
+** ReusableSpace object, increase the ReusableSpace.nNeeded
+** value by the amount needed and return NULL.
**
-** pFrom points to *pnFrom bytes of available space. New space is allocated
-** from the end of the pFrom buffer and *pnFrom is decremented.
+** If pBuf is not initially NULL, that means that the memory has already
+** been allocated by a prior call to this routine, so just return a copy
+** of pBuf and leave ReusableSpace unchanged.
**
-** *pnNeeded is a counter of the number of bytes of space that have failed
-** to allocate. If there is insufficient space in pFrom to satisfy the
-** request, then increment *pnNeeded by the amount of the request.
+** This allocator is employed to repurpose unused slots at the end of the
+** opcode array of prepared state for other memory needs of the prepared
+** statement.
*/
static void *allocSpace(
- void *pBuf, /* Where return pointer will be stored */
- int nByte, /* Number of bytes to allocate */
- u8 *pFrom, /* Memory available for allocation */
- int *pnFrom, /* IN/OUT: Space available at pFrom */
- int *pnNeeded /* If allocation cannot be made, increment *pnByte */
+ struct ReusableSpace *p, /* Bulk memory available for allocation */
+ void *pBuf, /* Pointer to a prior allocation */
+ int nByte /* Bytes of memory needed */
){
- assert( EIGHT_BYTE_ALIGNMENT(pFrom) );
+ assert( EIGHT_BYTE_ALIGNMENT(p->pSpace) );
if( pBuf==0 ){
nByte = ROUND8(nByte);
- if( nByte <= *pnFrom ){
- *pnFrom -= nByte;
- pBuf = &pFrom[*pnFrom];
+ if( nByte <= p->nFree ){
+ p->nFree -= nByte;
+ pBuf = &p->pSpace[p->nFree];
}else{
- *pnNeeded += nByte;
+ p->nNeeded += nByte;
}
}
assert( EIGHT_BYTE_ALIGNMENT(pBuf) );
int nArg; /* Number of arguments in subprograms */
int nOnce; /* Number of OP_Once instructions */
int n; /* Loop counter */
- int nFree; /* Available free space */
- u8 *zCsr; /* Memory available for allocation */
- int nByte; /* How much extra memory is needed */
+ struct ReusableSpace x; /* Reusable bulk memory */
assert( p!=0 );
assert( p->nOp>0 );
/* For each cursor required, also allocate a memory cell. Memory
** cells (nMem+1-nCursor)..nMem, inclusive, will never be used by
- ** the vdbe program. Instead they are used to allocate space for
+ ** the vdbe program. Instead they are used to allocate memory for
** VdbeCursor/BtCursor structures. The blob of memory associated with
** cursor 0 is stored in memory cell nMem. Memory cell (nMem-1)
** stores the blob of memory associated with cursor 1, etc.
*/
nMem += nCursor;
- /* zCsr will initially point to nFree bytes of unused space at the
- ** end of the opcode array, p->aOp. The computation of nFree is
- ** conservative - it might be smaller than the true number of free
- ** bytes, but never larger. nFree must be a multiple of 8 - it is
- ** rounded down if is not.
+ /* Figure out how much reusable memory is available at the end of the
+ ** opcode array. This extra memory will be reallocated for other elements
+ ** of the prepared statement.
*/
- n = ROUND8(sizeof(Op)*p->nOp); /* Bytes of opcode space used */
- zCsr = &((u8*)p->aOp)[n]; /* Unused opcode space */
- assert( EIGHT_BYTE_ALIGNMENT(zCsr) );
- nFree = ROUNDDOWN8(pParse->szOpAlloc - n); /* Bytes of unused space */
- assert( nFree>=0 );
- if( nFree>0 ){
- memset(zCsr, 0, nFree);
- assert( EIGHT_BYTE_ALIGNMENT(&zCsr[nFree]) );
+ n = ROUND8(sizeof(Op)*p->nOp); /* Bytes of opcode memory used */
+ x.pSpace = &((u8*)p->aOp)[n]; /* Unused opcode memory */
+ assert( EIGHT_BYTE_ALIGNMENT(x.pSpace) );
+ x.nFree = ROUNDDOWN8(pParse->szOpAlloc - n); /* Bytes of unused memory */
+ assert( x.nFree>=0 );
+ if( x.nFree>0 ){
+ memset(x.pSpace, 0, x.nFree);
+ assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) );
}
resolveP2Values(p, &nArg);
}
p->expired = 0;
- /* Memory for registers, parameters, cursor, etc, is allocated in two
- ** passes. On the first pass, we try to reuse unused space at the
+ /* Memory for registers, parameters, cursor, etc, is allocated in one or two
+ ** passes. On the first pass, we try to reuse unused memory at the
** end of the opcode array. If we are unable to satisfy all memory
** requirements by reusing the opcode array tail, then the second
- ** pass will fill in the rest using a fresh allocation.
+ ** pass will fill in the remainder using a fresh memory allocation.
**
** This two-pass approach that reuses as much memory as possible from
- ** the leftover space at the end of the opcode array can significantly
+ ** the leftover memory at the end of the opcode array. This can significantly
** reduce the amount of memory held by a prepared statement.
*/
do {
- nByte = 0;
- p->aMem = allocSpace(p->aMem, nMem*sizeof(Mem), zCsr, &nFree, &nByte);
- p->aVar = allocSpace(p->aVar, nVar*sizeof(Mem), zCsr, &nFree, &nByte);
- p->apArg = allocSpace(p->apArg, nArg*sizeof(Mem*), zCsr, &nFree, &nByte);
- p->apCsr = allocSpace(p->apCsr, nCursor*sizeof(VdbeCursor*),
- zCsr, &nFree, &nByte);
- p->aOnceFlag = allocSpace(p->aOnceFlag, nOnce, zCsr, &nFree, &nByte);
+ x.nNeeded = 0;
+ p->aMem = allocSpace(&x, p->aMem, nMem*sizeof(Mem));
+ p->aVar = allocSpace(&x, p->aVar, nVar*sizeof(Mem));
+ p->apArg = allocSpace(&x, p->apArg, nArg*sizeof(Mem*));
+ p->apCsr = allocSpace(&x, p->apCsr, nCursor*sizeof(VdbeCursor*));
+ p->aOnceFlag = allocSpace(&x, p->aOnceFlag, nOnce);
#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
- p->anExec = allocSpace(p->anExec, p->nOp*sizeof(i64), zCsr, &nFree, &nByte);
+ p->anExec = allocSpace(&x, p->anExec, p->nOp*sizeof(i64));
#endif
- if( nByte ){
- p->pFree = sqlite3DbMallocZero(db, nByte);
- }
- zCsr = p->pFree;
- nFree = nByte;
- }while( nByte && !db->mallocFailed );
+ if( x.nNeeded==0 ) break;
+ x.pSpace = p->pFree = sqlite3DbMallocZero(db, x.nNeeded);
+ x.nFree = x.nNeeded;
+ }while( !db->mallocFailed );
p->nCursor = nCursor;
p->nOnceFlag = nOnce;
projects / thirdparty / sqlite.git / commitdiff
