Hi,

I have the following snippet in a JSON file.

================
"Settings": {
"SQLDir": "d:\data"
}

================

When I load the complete JSON file using FPC's jsonparser.pp unit I get a parser error.

"Invalid character at line 6, pos 16: 'd' "

It seems like it is trying to interpret the field data value like a C/C++ escape sequence. eg: \n meaning NewLine

I such escape sequence processing a JSON standard? Can I tell the JSON parser to treat data as-is, without any interpretation?

Regards,
Graeme

Just to be clear regarding the problem.

If I change my JSON file so the data values reads...

"d:/data"

instead of the original: "d:\data"

...then FPC's JSON parser has no problem.

So it seems the FPC JSON parser doesn't like DOS\Windows paths as data values. Surely any JSON parser shouldn't try and interpret the data stored in a JSON file?

ps:
I'm using FPC 2.6.4 under Windows 32bit.

Regards,
Graeme

Hi,

Graeme Geldenhuys wrote

It seems like it is trying to interpret the field data value like a C/C++ escape sequence. eg: \n meaning NewLine I such escape sequence processing a JSON standard?

Yes. See:
http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf

Figure 5.

Can I tell the JSON parser to treat data as-is, without any interpretation?

That is probably a bad idea, as it goes against JSON standards. Basically the JSON you're trying to feed it is invalid. Fix the JSON, don't try to force the parser to work it around.

Charlie

Graeme Geldenhuys wrote

So it seems the FPC JSON parser doesn't like DOS\Windows paths as data values.

I guess the alternative (in case \<something> is supposed to be interpreted as an escape sequence) is to store my DOS\Windows paths with forward slashes like UNIX, then use SetDirSeparators() in my program to fix the resulting string.

eg "d:/data"

Regards,
Graeme

Karoly Balogh wrote

> Is such escape sequence processing a JSON standard? Yes. See: http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf

Ah, thanks for confirming that. I see now the relevant JSON standards information regarding a string value is as follows:

==================================
string
""
" chars "
chars
char
char chars
char
any-Unicode-character-
except-"-or-\-or-
control-character
\"
\\
\/
\b
\f
\n
\r
\t
\u four-hex-digits
==================================

That is probably a bad idea, as it goes against JSON standards. Basically the JSON you're trying to feed it is invalid. Fix the JSON, don't try to force the parser to work it around.

Thanks, I'll use forward slashes instead and then SetDirSeparators() in my code after reading in those values.

Looking into the fpjson.pp unit I see the following two functions...

Function StringToJSONString(const S : TJSONStringType) : TJSONStringType;
Function JSONStringToString(const S : TJSONStringType) : TJSONStringType;

Which does all those conversions for you too. Good to know! ;-)

Regards,
Graeme

Does it work if you try "d:\\data"?

g.

geneb wrote

Does it work if you try "d:\\data"?

Yes. My problem was I didn't realise the JSON standard supports escaped sequences.

My program is only reading from the JSON file at this point, not writing. The JSON file is manually created with a text editor. So to be on the safe side, I now implemented my code to support both "d:/data" and "d:\\data" string data formats.

Regards,
Graeme