On Thu, 24 Feb 2011, LacaK wrote:
Hi,
I am writting here to discuss bug
http://bugs.freepascal.org/view.php?id=17268
(I do not want reopen bug and writte there because I am not sure about my
arguments)
IMHO root of problem is in different definition of TFieldDef.Size and
TField.Size
Documentation says, that
1. TFieldDef.Size should be "For string and byte fields, *Size* is the number
of bytes reserved "
http://docwiki.embarcadero.com/VCL/en/DB.TFieldDef.Size
2. TField.Size should be "the maximum number of characters in the string"
(for ftString and I guess that also for ftWideString)
http://docwiki.embarcadero.com/VCL/en/DB.TField.Size
http://docwiki.embarcadero.com/VCL/en/DB.TStringField.Size
And now let's go look into fields.inc:
1. Function TFieldDef.CreateField copies Result.Size:=FSize (so
TField.Size:=TFieldDef.Size)
2. function TStringField.GetDataSize returns for ftString ... Size+1
3. function TWideStringField.GetDataSize returns for ftWideString ... (Size +
1) * 2
Points 2,3 are clear Size is expected to be number of characters, DataSize
number of bytes.
But point 1 says, that TFieldDef.Size and TField.Size should be the same
And now let's go look into bufdataset.pas:
4. function TCustomBufDataset.GetFieldSize works with TFieldDef and returns
number of bytes needed in record buffer
case FieldDef.DataType of
ftString, ftGuid, ftFixedChar: result := FieldDef.Size + 1;
ftFixedWideChar, ftWideString:result := (FieldDef.Size + 1)*2;
...
So also here we can see, that FieldDef.Size is expected to be number of
characters not bytes.
So IMHO logical conclusion will be say, that TFieldDef.Size for string fields
has same menaing as Field.Size, so it is number of characters
Correct, if you assume 1 char = 1 byte.
(so documentation is wrong in this case ... also fast test in Delphi shows,
that FieldDef.Size=Field.Size=number of characters)
Your story is confusing to me. Where do you see a problem ?
Do you see an implementation problem or a documentation problem ?
Note that nowhere in the documentation pages you mention, widestrings are
mentioned (which is convenient, since that's where 1 char <> 1 byte).
Michael.
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