SQLite

**
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** of the code in this file is, therefore, important.  See other comments
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**
** $Id: vdbe.c,v 1.529 2006/01/13 17:12:01 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  int p2 = pOp->p2;  /* column number to retrieve */
  Cursor *pC = 0;    /* The VDBE cursor */
  char *zRec;        /* Pointer to complete record-data */
  BtCursor *pCrsr;   /* The BTree cursor */
  u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
  u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
  u32 nField;        /* number of fields in the record */

  int len;           /* The length of the serialized data for the column */


  int i;             /* Loop counter */
  char *zData;       /* Part of the record being decoded */
  Mem sMem;          /* For storing the record being decoded */

  sMem.flags = 0;
  assert( p1<p->nCursor );
  pTos++;

  /* Read and parse the table header.  Store the results of the parse
  ** into the record header cache fields of the cursor.
  */
  if( pC && pC->cacheStatus==p->cacheCtr ){
    aType = pC->aType;
    aOffset = pC->aOffset;
  }else{
    u8 *zIdx;        /* Index into header */
    u8 *zEndHdr;     /* Pointer to first byte after the header */
    u32 offset;      /* Offset into the data */
    int avail;       /* Number of bytes of available data */
    if( pC && pC->aType ){
      aType = pC->aType;
    }else{
      aType = sqliteMallocRaw( 2*nField*sizeof(aType) );
    }
    aOffset = &aType[nField];
    if( aType==0 ){

      if( avail>=payloadSize ){
        zRec = zData;
        pC->aRow = (u8*)zData;
      }else{
        pC->aRow = 0;
      }
    }
    zIdx = (u8 *)GetVarint((u8*)zData, offset);


    /* The KeyFetch() or DataFetch() above are fast and will get the entire
    ** record header in most cases.  But they will fail to get the complete
    ** record header if the record header does not fit on a single page
    ** in the B-Tree.  When that happens, use sqlite3VdbeMemFromBtree() to
    ** acquire the complete header text.
    */
    if( !zRec && avail<offset ){
      rc = sqlite3VdbeMemFromBtree(pCrsr, 0, offset, pC->isIndex, &sMem);
      if( rc!=SQLITE_OK ){
        goto op_column_out;
      }
      zData = sMem.z;
    }
    zEndHdr = (u8 *)zData + offset;
    zIdx = zData + (int)zIdx;

    /* Scan the header and use it to fill in the aType[] and aOffset[]
    ** arrays.  aType[i] will contain the type integer for the i-th
    ** column and aOffset[i] will contain the offset from the beginning
    ** of the record to the start of the data for the i-th column
    */


    for(i=0; i<nField; i++){
      if( zIdx<zEndHdr ){
        aOffset[i] = offset;
        zIdx += GetVarint(zIdx, aType[i]);
        offset += sqlite3VdbeSerialTypeLen(aType[i]);

      }else{



        /* If i is less that nField, then there are less fields in this
        ** record than SetNumColumns indicated there are columns in the
        ** table. Set the offset for any extra columns not present in
        ** the record to 0. This tells code below to push a NULL onto the
        ** stack instead of deserializing a value from the record.
        */

        aOffset[i] = 0;
      }
    }
    Release(&sMem);
    sMem.flags = MEM_Null;

    /* If we have read more header data than was contained in the header,
    ** or if the end of the last field appears to be past the end of the
    ** record, then we must be dealing with a corrupt database.
    */
    if( zIdx>zEndHdr || offset>payloadSize ){
      rc = SQLITE_CORRUPT_BKPT;
      goto op_column_out;
    }

    /* Remember all aType and aColumn information if we have a cursor
    ** to remember it in. */
    if( pC ){