SQLite4  Check-in [e7b52edf68]

**
**   Or, if the column contains tokens from multiple streams, the first
**   varint contains a bitmask indicating which of the streams are present
**   (stored as ((bitmask << 1) | 0x01)). Following the bitmask is a
**   varint containing the number of tokens for each stream present, in
**   ascending order of stream number.
**
**   TODO: The format above is not currently implemented! Instead, there
**   is a simpler place-holder format (which consumes more space).
**
** Global size record:
**   There is a single "global size" record stored in the database. The
**   database key for this record is a single byte - 0x00.
**
**   The data for this record is a series of varint values. The first 
**   varint is the total number of rows in the table. The subsequent
**   varints make up a "row size" record containing the total number of

  KVCursor *pCsr = 0;             /* Cursor used to read global record */
  int rc;

  rc = sqlite4KVStoreOpenCursor(db->aDb[pInfo->iDb].pKV, &pCsr);
  if( rc==SQLITE4_OK ){
    rc = sqlite4KVCursorSeek(pCsr, aKey, nKey, 0);
    if( rc==SQLITE4_NOTFOUND ){
      if( pnRow ){
        int nByte = sizeof(Fts5Size) + sizeof(i64) * pInfo->nCol * nMinStream;
        pSz = sqlite4DbMallocZero(db, nByte);
        if( pSz==0 ){
          rc = SQLITE4_NOMEM;
        }else{
          pSz->aSz = (i64 *)&pSz[1];
          *pnRow = 0;
          rc = SQLITE4_OK;
        }
      }else{
        rc = SQLITE4_CORRUPT_BKPT;
      }
    }else if( rc==SQLITE4_OK ){
      const u8 *aData = 0;
      int nData = 0;
      rc = sqlite4KVCursorData(pCsr, 0, -1, &aData, &nData);
      if( rc==SQLITE4_OK ){
        int iOff = 0;
        int nStream = 0;

        pSz = sqlite4DbMallocZero(db, 
            sizeof(Fts5Size) + sizeof(i64) * pInfo->nCol * nAlloc
        );
        if( pSz==0 ){
          rc = SQLITE4_NOMEM;
        }else{
          int iCol = 0;
          pSz->aSz = (i64 *)&pSz[1];
          pSz->nCol = pInfo->nCol;
          pSz->nStream = nAlloc;
          while( iOff<nData ){
            int i;
            i64 *aSz = &pSz->aSz[iCol*nAlloc];
            for(i=0; i<nStream; i++){
              iOff += sqlite4GetVarint(&aData[iOff], (u64*)&aSz[i]);

  u8 const *aVal; int nVal;       /* List of token instances */
  u8 const *aToken; int nToken;   /* Token for this entry */
  u8 const *aPk; int nPk;         /* Entry primary key blob */
  InstanceList sList;             /* Used to iterate through pVal */
  int nTnum;
  u32 tnum;


  aKey = (const u8 *)sqlite4_value_blob(pKey);
  nKey = sqlite4_value_bytes(pKey);
  aVal = (const u8 *)sqlite4_value_blob(pVal);
  nVal = sqlite4_value_bytes(pVal);

  /* Find the token and primary key blobs for this entry. */
  nTnum = getVarint32(aKey, tnum);
  if( aKey[nTnum]!=0 ){
    aToken = &aKey[nTnum+1];
    nToken = sqlite4Strlen30((const char *)aToken);
    aPk = &aToken[nToken+1];
    nPk = (&aKey[nKey] - aPk);

    fts5InstanceListInit((u8 *)aVal, nVal, &sList);
    while( 0==fts5InstanceListNext(&sList) ){
      i64 v = fts5TermInstanceCksum(
          aPk, nPk, aToken, nToken, sList.iStream, sList.iCol, sList.iOff
          );
      cksum = cksum ^ v;
    }
  }

  *piCksum = cksum;
  return SQLITE4_OK;
}

typedef struct CksumCtx CksumCtx;