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Comment:Further simplifications to sqlite3VdbeMemSetStr().
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SHA3-256: 1d212957079a2caa30f3c9d80f43464781bc9634c2b5181a5814efbddae31711
User & Date: drh 2019-02-08 17:28:20
Context
2019-02-08
22:34
Small performance improvement and size reduction for pageFindSlot() - the routine in btree.c that locates a free slot for a cell on a btree page. check-in: 1969372a user: drh tags: trunk
20:55
Use a fast compiler-provided memory barrier exclusively, if such a memory barrier is available. Leaf check-in: df66fec9 user: drh tags: faster-memory-barrier
17:28
Further simplifications to sqlite3VdbeMemSetStr(). check-in: 1d212957 user: drh tags: trunk
15:59
Change the sqlite3VdbeMemGrow() routine so that it no longer guarantees a minimum size of 32 bytes. That minimum is no longer required, and without the extra check for the minimum size, the routine runs faster. check-in: 5c499da8 user: drh tags: trunk
Changes
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Changes to src/vdbemem.c.

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    iLimit = SQLITE_MAX_LENGTH;
  }
  flags = (enc==0?MEM_Blob:MEM_Str);
  if( nByte<0 ){
    assert( enc!=0 );
    if( enc==SQLITE_UTF8 ){
      nByte = 0x7fffffff & (int)strlen(z);
      if( nByte>iLimit ) nByte = iLimit+1;
    }else{
      for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
    }
    flags |= MEM_Term;
  }

  /* The following block sets the new values of Mem.z and Mem.xDel. It
  ** also sets a flag in local variable "flags" to indicate the memory
  ** management (one of MEM_Dyn or MEM_Static).
  */
  if( xDel==SQLITE_TRANSIENT ){
    int nAlloc = nByte;
    if( flags&MEM_Term ){
      nAlloc += (enc==SQLITE_UTF8?1:2);
    }
    if( nByte>iLimit ){
      return SQLITE_TOOBIG;
    }
    testcase( nAlloc==0 );
    testcase( nAlloc==31 );
    testcase( nAlloc==32 );
    if( sqlite3VdbeMemClearAndResize(pMem, MAX(nAlloc,32)) ){
      return SQLITE_NOMEM_BKPT;
    }
    memcpy(pMem->z, z, nAlloc);
  }else if( xDel==SQLITE_DYNAMIC ){
    sqlite3VdbeMemRelease(pMem);
    pMem->zMalloc = pMem->z = (char *)z;
    pMem->szMalloc = sqlite3DbMallocSize(pMem->db, pMem->zMalloc);
  }else{
    sqlite3VdbeMemRelease(pMem);
    pMem->z = (char *)z;




    pMem->xDel = xDel;
    flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);

  }

  pMem->n = nByte;
  pMem->flags = flags;
  pMem->enc = (enc==0 ? SQLITE_UTF8 : enc);

#ifndef SQLITE_OMIT_UTF16







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    iLimit = SQLITE_MAX_LENGTH;
  }
  flags = (enc==0?MEM_Blob:MEM_Str);
  if( nByte<0 ){
    assert( enc!=0 );
    if( enc==SQLITE_UTF8 ){
      nByte = 0x7fffffff & (int)strlen(z);

    }else{
      for(nByte=0; nByte<=iLimit && (z[nByte] | z[nByte+1]); nByte+=2){}
    }
    flags |= MEM_Term;
  }

  /* The following block sets the new values of Mem.z and Mem.xDel. It
  ** also sets a flag in local variable "flags" to indicate the memory
  ** management (one of MEM_Dyn or MEM_Static).
  */
  if( xDel==SQLITE_TRANSIENT ){
    u32 nAlloc = nByte;
    if( flags&MEM_Term ){
      nAlloc += (enc==SQLITE_UTF8?1:2);
    }
    if( nByte>iLimit ){
      return SQLITE_TOOBIG;
    }
    testcase( nAlloc==0 );
    testcase( nAlloc==31 );
    testcase( nAlloc==32 );
    if( sqlite3VdbeMemClearAndResize(pMem, (int)MAX(nAlloc,32)) ){
      return SQLITE_NOMEM_BKPT;
    }
    memcpy(pMem->z, z, nAlloc);




  }else{
    sqlite3VdbeMemRelease(pMem);
    pMem->z = (char *)z;
    if( xDel==SQLITE_DYNAMIC ){
      pMem->zMalloc = pMem->z;
      pMem->szMalloc = sqlite3DbMallocSize(pMem->db, pMem->zMalloc);
    }else{
      pMem->xDel = xDel;
      flags |= ((xDel==SQLITE_STATIC)?MEM_Static:MEM_Dyn);
    }
  }

  pMem->n = nByte;
  pMem->flags = flags;
  pMem->enc = (enc==0 ? SQLITE_UTF8 : enc);

#ifndef SQLITE_OMIT_UTF16