/*+
−
** 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.+
−
*/+
−
#include "sqliteInt.h"+
−
#include "vdbeInt.h"+
−
+
−
/*+
−
** 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(int nEntry){+
−
  FifoPage *pPage;+
−
  if( nEntry>32767 ){+
−
    nEntry = 32767;+
−
  }+
−
  pPage = (FifoPage*)sqlite3_malloc( 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){+
−
  memset(pFifo, 0, sizeof(*pFifo));+
−
}+
−
+
−
/*+
−
** 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(20);+
−
    if( pPage==0 ){+
−
      return SQLITE_NOMEM;+
−
    }+
−
  }else if( pPage->iWrite>=pPage->nSlot ){+
−
    pPage->pNext = allocateFifoPage(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;+
−
    sqlite3_free(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;+
−
    sqlite3_free(pPage);+
−
  }+
−
  sqlite3VdbeFifoInit(pFifo);+
−
}+
−