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Overview
Comment:Small size and performance optimization in the bytecode engine.
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SHA3-256: 3b3e32d4cd07a1d2d1708fffa47819345ae6b39205a9f548280d499c8f481d64
User & Date: drh 2017-09-20 17:49:12
References
2017-09-21
01:04
Revert one performance improvement changes from check-in [3b3e32d4cd07] as it was causing a reference to an uninitialized value. check-in: f8b1c64d user: drh tags: trunk
Context
2017-09-20
18:07
The BLOB returned by sqlite3VdbeMemFromBtree() does not need to be zero-terminated. check-in: e0af9a90 user: drh tags: trunk
17:49
Small size and performance optimization in the bytecode engine. check-in: 3b3e32d4 user: drh tags: trunk
10:47
Improved resolution of large integer values in "CAST(x AS NUMERIC)". check-in: 7f2bd4ff user: drh tags: trunk
Changes
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Changes to src/vdbemem.c.

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int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
#ifndef SQLITE_OMIT_UTF16
  int rc;
#endif
  assert( (pMem->flags&MEM_RowSet)==0 );
  assert( desiredEnc==SQLITE_UTF8 || desiredEnc==SQLITE_UTF16LE
           || desiredEnc==SQLITE_UTF16BE );
  if( !(pMem->flags&MEM_Str) || pMem->enc==desiredEnc ){
    return SQLITE_OK;
  }
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
#ifdef SQLITE_OMIT_UTF16
  return SQLITE_ERROR;
#else

................................................................................
    return sqlite3VdbeMemGrow(pMem, szNew, 0);
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  pMem->z = pMem->zMalloc;
  pMem->flags &= (MEM_Null|MEM_Int|MEM_Real);
  return SQLITE_OK;
}















/*
** Change pMem so that its MEM_Str or MEM_Blob value is stored in
** MEM.zMalloc, where it can be safely written.
**
** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
*/
int sqlite3VdbeMemMakeWriteable(Mem *pMem){
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
  assert( (pMem->flags&MEM_RowSet)==0 );
  if( (pMem->flags & (MEM_Str|MEM_Blob))!=0 ){
    if( ExpandBlob(pMem) ) return SQLITE_NOMEM;
    if( pMem->szMalloc==0 || pMem->z!=pMem->zMalloc ){
      if( sqlite3VdbeMemGrow(pMem, pMem->n + 2, 1) ){
        return SQLITE_NOMEM_BKPT;
      }
      pMem->z[pMem->n] = 0;
      pMem->z[pMem->n+1] = 0;
      pMem->flags |= MEM_Term;
    }
  }
  pMem->flags &= ~MEM_Ephem;
#ifdef SQLITE_DEBUG
  pMem->pScopyFrom = 0;
#endif

................................................................................
  memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
  pMem->n += pMem->u.nZero;
  pMem->flags &= ~(MEM_Zero|MEM_Term);
  return SQLITE_OK;
}
#endif

/*
** It is already known that pMem contains an unterminated string.
** Add the zero terminator.
*/
static SQLITE_NOINLINE int vdbeMemAddTerminator(Mem *pMem){
  if( sqlite3VdbeMemGrow(pMem, pMem->n+2, 1) ){
    return SQLITE_NOMEM_BKPT;
  }
  pMem->z[pMem->n] = 0;
  pMem->z[pMem->n+1] = 0;
  pMem->flags |= MEM_Term;
  return SQLITE_OK;
}

/*
** Make sure the given Mem is \u0000 terminated.
*/
int sqlite3VdbeMemNulTerminate(Mem *pMem){
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
  testcase( (pMem->flags & (MEM_Term|MEM_Str))==(MEM_Term|MEM_Str) );
  testcase( (pMem->flags & (MEM_Term|MEM_Str))==0 );







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int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
#ifndef SQLITE_OMIT_UTF16
  int rc;
#endif
  assert( (pMem->flags&MEM_RowSet)==0 );
  assert( desiredEnc==SQLITE_UTF8 || desiredEnc==SQLITE_UTF16LE
           || desiredEnc==SQLITE_UTF16BE );
  if( pMem->enc==desiredEnc || !(pMem->flags&MEM_Str) ){
    return SQLITE_OK;
  }
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
#ifdef SQLITE_OMIT_UTF16
  return SQLITE_ERROR;
#else

................................................................................
    return sqlite3VdbeMemGrow(pMem, szNew, 0);
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  pMem->z = pMem->zMalloc;
  pMem->flags &= (MEM_Null|MEM_Int|MEM_Real);
  return SQLITE_OK;
}

/*
** It is already known that pMem contains an unterminated string.
** Add the zero terminator.
*/
static SQLITE_NOINLINE int vdbeMemAddTerminator(Mem *pMem){
  if( sqlite3VdbeMemGrow(pMem, pMem->n+2, 1) ){
    return SQLITE_NOMEM_BKPT;
  }
  pMem->z[pMem->n] = 0;
  pMem->z[pMem->n+1] = 0;
  pMem->flags |= MEM_Term;
  return SQLITE_OK;
}

/*
** Change pMem so that its MEM_Str or MEM_Blob value is stored in
** MEM.zMalloc, where it can be safely written.
**
** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
*/
int sqlite3VdbeMemMakeWriteable(Mem *pMem){
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
  assert( (pMem->flags&MEM_RowSet)==0 );
  if( (pMem->flags & (MEM_Str|MEM_Blob))!=0 ){
    if( ExpandBlob(pMem) ) return SQLITE_NOMEM;
    if( pMem->szMalloc==0 || pMem->z!=pMem->zMalloc ){
      int rc = vdbeMemAddTerminator(pMem);
      if( rc ) return rc;




    }
  }
  pMem->flags &= ~MEM_Ephem;
#ifdef SQLITE_DEBUG
  pMem->pScopyFrom = 0;
#endif

................................................................................
  memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
  pMem->n += pMem->u.nZero;
  pMem->flags &= ~(MEM_Zero|MEM_Term);
  return SQLITE_OK;
}
#endif















/*
** Make sure the given Mem is \u0000 terminated.
*/
int sqlite3VdbeMemNulTerminate(Mem *pMem){
  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
  testcase( (pMem->flags & (MEM_Term|MEM_Str))==(MEM_Term|MEM_Str) );
  testcase( (pMem->flags & (MEM_Term|MEM_Str))==0 );