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/*
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** 2005 June 16
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file implements a FIFO queue of rowids used for processing
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** UPDATE and DELETE statements.
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**
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** $Id: vdbefifo.c,v 1.8 2008/07/28 19:34:54 drh Exp $
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*/
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#include "sqliteInt.h"
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#include "vdbeInt.h"
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/*
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** Constants FIFOSIZE_FIRST and FIFOSIZE_MAX are the initial
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** number of entries in a fifo page and the maximum number of
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** entries in a fifo page.
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*/
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#define FIFOSIZE_FIRST (((128-sizeof(FifoPage))/8)+1)
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#ifdef SQLITE_MALLOC_SOFT_LIMIT
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# define FIFOSIZE_MAX (((SQLITE_MALLOC_SOFT_LIMIT-sizeof(FifoPage))/8)+1)
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#else
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# define FIFOSIZE_MAX (((262144-sizeof(FifoPage))/8)+1)
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#endif
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/*
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** Allocate a new FifoPage and return a pointer to it. Return NULL if
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** we run out of memory. Leave space on the page for nEntry entries.
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*/
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static FifoPage *allocateFifoPage(sqlite3 *db, int nEntry){
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FifoPage *pPage;
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if( nEntry>FIFOSIZE_MAX ){
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nEntry = FIFOSIZE_MAX;
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}
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pPage = sqlite3DbMallocRaw(db, sizeof(FifoPage) + sizeof(i64)*(nEntry-1) );
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if( pPage ){
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pPage->nSlot = nEntry;
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pPage->iWrite = 0;
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pPage->iRead = 0;
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pPage->pNext = 0;
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}
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return pPage;
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}
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/*
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** Initialize a Fifo structure.
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*/
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void sqlite3VdbeFifoInit(Fifo *pFifo, sqlite3 *db){
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memset(pFifo, 0, sizeof(*pFifo));
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pFifo->db = db;
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}
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/*
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** Push a single 64-bit integer value into the Fifo. Return SQLITE_OK
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** normally. SQLITE_NOMEM is returned if we are unable to allocate
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** memory.
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*/
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int sqlite3VdbeFifoPush(Fifo *pFifo, i64 val){
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FifoPage *pPage;
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pPage = pFifo->pLast;
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if( pPage==0 ){
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pPage = pFifo->pLast = pFifo->pFirst =
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allocateFifoPage(pFifo->db, FIFOSIZE_FIRST);
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if( pPage==0 ){
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return SQLITE_NOMEM;
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}
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}else if( pPage->iWrite>=pPage->nSlot ){
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pPage->pNext = allocateFifoPage(pFifo->db, pFifo->nEntry);
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if( pPage->pNext==0 ){
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return SQLITE_NOMEM;
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}
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pPage = pFifo->pLast = pPage->pNext;
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}
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pPage->aSlot[pPage->iWrite++] = val;
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pFifo->nEntry++;
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return SQLITE_OK;
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}
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/*
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** Extract a single 64-bit integer value from the Fifo. The integer
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** extracted is the one least recently inserted. If the Fifo is empty
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** return SQLITE_DONE.
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*/
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int sqlite3VdbeFifoPop(Fifo *pFifo, i64 *pVal){
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FifoPage *pPage;
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if( pFifo->nEntry==0 ){
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return SQLITE_DONE;
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}
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assert( pFifo->nEntry>0 );
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pPage = pFifo->pFirst;
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assert( pPage!=0 );
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assert( pPage->iWrite>pPage->iRead );
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assert( pPage->iWrite<=pPage->nSlot );
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assert( pPage->iRead<pPage->nSlot );
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assert( pPage->iRead>=0 );
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*pVal = pPage->aSlot[pPage->iRead++];
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pFifo->nEntry--;
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if( pPage->iRead>=pPage->iWrite ){
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pFifo->pFirst = pPage->pNext;
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sqlite3DbFree(pFifo->db, pPage);
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if( pFifo->nEntry==0 ){
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assert( pFifo->pLast==pPage );
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pFifo->pLast = 0;
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}else{
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assert( pFifo->pFirst!=0 );
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}
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}else{
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assert( pFifo->nEntry>0 );
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}
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return SQLITE_OK;
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}
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/*
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** Delete all information from a Fifo object. Free all memory held
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** by the Fifo.
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*/
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void sqlite3VdbeFifoClear(Fifo *pFifo){
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FifoPage *pPage, *pNextPage;
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for(pPage=pFifo->pFirst; pPage; pPage=pNextPage){
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pNextPage = pPage->pNext;
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sqlite3DbFree(pFifo->db, pPage);
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}
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sqlite3VdbeFifoInit(pFifo, pFifo->db);
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}
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