SQLite

/*
** 2004 April 6
**
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.655 2009/07/07 11:39:59 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

  if( NEVER(wrFlag && pBt->readOnly) ){
    return SQLITE_READONLY;
  }
  if( iTable==1 && pagerPagecount(pBt)==0 ){
    return SQLITE_EMPTY;
  }

  pCur->pgnoRoot = (Pgno)iTable;
  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]);
  if( rc!=SQLITE_OK ){
    assert( pCur->apPage[0]==0 );
    return rc;
  }

  /* Now that no other errors can occur, finish filling in the BtCursor
  ** variables and link the cursor into the BtShared list.  */


  pCur->pKeyInfo = pKeyInfo;
  pCur->pBtree = p;
  pCur->pBt = pBt;
  pCur->wrFlag = (u8)wrFlag;
  pCur->pNext = pBt->pCursor;
  if( pCur->pNext ){
    pCur->pNext->pPrev = pCur;

  }

  if( pCur->iPage>=0 ){
    int i;
    for(i=1; i<=pCur->iPage; i++){
      releasePage(pCur->apPage[i]);
    }

  }else{
    if( 
      SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]))
    ){
      pCur->eState = CURSOR_INVALID;
      return rc;
    }










  }

  pRoot = pCur->apPage[0];
  assert( pRoot->pgno==pCur->pgnoRoot );
  pCur->iPage = 0;
  pCur->aiIdx[0] = 0;
  pCur->info.nSize = 0;
  pCur->atLast = 0;
  pCur->validNKey = 0;

  if( pRoot->nCell==0 && !pRoot->leaf ){
    Pgno subpage;

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.869 2009/07/03 16:25:07 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test

  KeyInfo *pKeyInfo;
  int p2;
  int iDb;
  int wrFlag;
  Btree *pX;
  VdbeCursor *pCur;
  Db *pDb;
  int flags;

  nField = 0;
  pKeyInfo = 0;
  p2 = pOp->p2;
  iDb = pOp->p3;
  assert( iDb>=0 && iDb<db->nDb );
  assert( (p->btreeMask & (1<<iDb))!=0 );

  assert( pOp->p1>=0 );
  pCur = allocateCursor(p, pOp->p1, nField, iDb, 1);
  if( pCur==0 ) goto no_mem;
  pCur->nullRow = 1;
  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
  pCur->pKeyInfo = pKeyInfo;

  switch( rc ){
    case SQLITE_OK: {
      flags = sqlite3BtreeFlags(pCur->pCursor);

      /* Sanity checking.  Only the lower four bits of the flags byte should
      ** be used.  Bit 3 (mask 0x08) is unpredictable.  The lower 3 bits
      ** (mask 0x07) should be either 5 (intkey+leafdata for tables) or
      ** 2 (zerodata for indices).  If these conditions are not met it can
      ** only mean that we are dealing with a corrupt database file.
      ** Note:  All of the above is checked already in sqlite3BtreeCursor().
      */


      assert( (flags & 0xf0)==0 );
      assert( (flags & 0x07)==5 || (flags & 0x07)==2 );

      pCur->isTable = (flags & BTREE_INTKEY)!=0 ?1:0;
      pCur->isIndex = (flags & BTREE_ZERODATA)!=0 ?1:0;
      /* If P4==0 it means we are expected to open a table.  If P4!=0 then
      ** we expect to be opening an index.  If this is not what happened,
      ** then the database is corrupt
      */
      if( (pCur->isTable && pOp->p4type==P4_KEYINFO)
       || (pCur->isIndex && pOp->p4type!=P4_KEYINFO) ){
        rc = SQLITE_CORRUPT_BKPT;
        goto abort_due_to_error;
      }
      break;
    }
    case SQLITE_EMPTY: {




      pCur->isTable = pOp->p4type!=P4_KEYINFO;
      pCur->isIndex = !pCur->isTable;
      pCur->pCursor = 0;
      rc = SQLITE_OK;
      break;
    }
    default: {
      assert( rc!=SQLITE_BUSY );  /* Busy conditions detected earlier */
      goto abort_due_to_error;
    }
  }
  break;
}

/* Opcode: OpenEphemeral P1 P2 * P4 *
**
** Open a new cursor P1 to a transient table.
** The cursor is always opened read/write even if