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/*
** 2005 June 16
**
** 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 implements a FIFO queue of rowids used for processing
** UPDATE and DELETE statements.
**
** $Id: vdbefifo.c,v 1.8 2008/07/28 19:34:54 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"
/*
** Constants FIFOSIZE_FIRST and FIFOSIZE_MAX are the initial
** number of entries in a fifo page and the maximum number of
** entries in a fifo page.
*/
#define FIFOSIZE_FIRST (((128-sizeof(FifoPage))/8)+1)
#ifdef SQLITE_MALLOC_SOFT_LIMIT
# define FIFOSIZE_MAX (((SQLITE_MALLOC_SOFT_LIMIT-sizeof(FifoPage))/8)+1)
#else
# define FIFOSIZE_MAX (((262144-sizeof(FifoPage))/8)+1)
#endif
/*
** Allocate a new FifoPage and return a pointer to it. Return NULL if
** we run out of memory. Leave space on the page for nEntry entries.
*/
static FifoPage *allocateFifoPage(sqlite3 *db, int nEntry){
FifoPage *pPage;
if( nEntry>FIFOSIZE_MAX ){
nEntry = FIFOSIZE_MAX;
}
pPage = sqlite3DbMallocRaw(db, sizeof(FifoPage) + sizeof(i64)*(nEntry-1) );
if( pPage ){
pPage->nSlot = nEntry;
pPage->iWrite = 0;
pPage->iRead = 0;
pPage->pNext = 0;
}
return pPage;
}
/*
** Initialize a Fifo structure.
*/
void sqlite3VdbeFifoInit(Fifo *pFifo, sqlite3 *db){
memset(pFifo, 0, sizeof(*pFifo));
pFifo->db = db;
}
/*
** Push a single 64-bit integer value into the Fifo. Return SQLITE_OK
** normally. SQLITE_NOMEM is returned if we are unable to allocate
** memory.
*/
int sqlite3VdbeFifoPush(Fifo *pFifo, i64 val){
FifoPage *pPage;
pPage = pFifo->pLast;
if( pPage==0 ){
pPage = pFifo->pLast = pFifo->pFirst =
allocateFifoPage(pFifo->db, FIFOSIZE_FIRST);
if( pPage==0 ){
return SQLITE_NOMEM;
}
}else if( pPage->iWrite>=pPage->nSlot ){
pPage->pNext = allocateFifoPage(pFifo->db, pFifo->nEntry);
if( pPage->pNext==0 ){
return SQLITE_NOMEM;
}
pPage = pFifo->pLast = pPage->pNext;
}
pPage->aSlot[pPage->iWrite++] = val;
pFifo->nEntry++;
return SQLITE_OK;
}
/*
** Extract a single 64-bit integer value from the Fifo. The integer
** extracted is the one least recently inserted. If the Fifo is empty
** return SQLITE_DONE.
*/
int sqlite3VdbeFifoPop(Fifo *pFifo, i64 *pVal){
FifoPage *pPage;
if( pFifo->nEntry==0 ){
return SQLITE_DONE;
}
assert( pFifo->nEntry>0 );
pPage = pFifo->pFirst;
assert( pPage!=0 );
assert( pPage->iWrite>pPage->iRead );
assert( pPage->iWrite<=pPage->nSlot );
assert( pPage->iRead<pPage->nSlot );
assert( pPage->iRead>=0 );
*pVal = pPage->aSlot[pPage->iRead++];
pFifo->nEntry--;
if( pPage->iRead>=pPage->iWrite ){
pFifo->pFirst = pPage->pNext;
sqlite3DbFree(pFifo->db, pPage);
if( pFifo->nEntry==0 ){
assert( pFifo->pLast==pPage );
pFifo->pLast = 0;
}else{
assert( pFifo->pFirst!=0 );
}
}else{
assert( pFifo->nEntry>0 );
}
return SQLITE_OK;
}
/*
** Delete all information from a Fifo object. Free all memory held
** by the Fifo.
*/
void sqlite3VdbeFifoClear(Fifo *pFifo){
FifoPage *pPage, *pNextPage;
for(pPage=pFifo->pFirst; pPage; pPage=pNextPage){
pNextPage = pPage->pNext;
sqlite3DbFree(pFifo->db, pPage);
}
sqlite3VdbeFifoInit(pFifo, pFifo->db);
}
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