Reading Unicode escape sequences from File

[John Ztwin]

Hello,

I have a file that contains ordinary text and some special charaters in
Unicode escape sequences (\uxxxx).

When I read the file using e.g. StreamReader Unicode escape sequences are
not converted to their character representation. They are shown excatly same
way than in file. Literals in C# code's variables are shown corretly.

Can anyone tell how to read Unicode escape sequences from file so that they
are presented like literals?

Thanks,

[Jon Skeet [C# MVP]]

Re: Reading Unicode escape sequences from File

John Ztwin <John.z@mail.co mwrote:

I have a file that contains ordinary text and some special charaters in
Unicode escape sequences (\uxxxx).
>
When I read the file using e.g. StreamReader Unicode escape sequences are
not converted to their character representation.

No, I wouldn't expect them to be. That's done by the C# compiler - it
would be a big mistake for it to be done by StreamReader.

They are shown excatly same
way than in file. Literals in C# code's variables are shown corretly.
>
Can anyone tell how to read Unicode escape sequences from file so that they
are presented like literals?

You basically need to parse the text you've read, just like the C#
compiler does. You can search for \u fairly easily, then take the next
four digits, complain if they're not all hex, convert the hex to a
char, then replace the whole section with the character value.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[John Ztwin]

Re: Reading Unicode escape sequences from File

A little bit more work than in Java if I remember right,
Thanks for reply!

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:MPG.22c611 1d826f19f2da2@m snews.microsoft .com...

John Ztwin <John.z@mail.co mwrote:

>I have a file that contains ordinary text and some special charaters in
>Unicode escape sequences (\uxxxx).
>>
>When I read the file using e.g. StreamReader Unicode escape sequences are
>not converted to their character representation.

>
No, I wouldn't expect them to be. That's done by the C# compiler - it
would be a big mistake for it to be done by StreamReader.
>

>They are shown excatly same
>way than in file. Literals in C# code's variables are shown corretly.
>>
>Can anyone tell how to read Unicode escape sequences from file so that
>they
>are presented like literals?

>
You basically need to parse the text you've read, just like the C#
compiler does. You can search for \u fairly easily, then take the next
four digits, complain if they're not all hex, convert the hex to a
char, then replace the whole section with the character value.
>
--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[Jon Skeet [C# MVP]]

Re: Reading Unicode escape sequences from File

John Ztwin <John.z@mail.co mwrote:

A little bit more work than in Java if I remember right,

Well, not if you use the normal BufferedReader and InputStreamRead er in
Java.

Java's Properties class will do the unescaping for properties files,
but it isn't general purpose.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Re: Reading Unicode escape sequences from File

John Ztwin wrote:

I have a file that contains ordinary text and some special charaters in
Unicode escape sequences (\uxxxx).
>
When I read the file using e.g. StreamReader Unicode escape sequences are
not converted to their character representation. They are shown excatly same
way than in file. Literals in C# code's variables are shown corretly.
>
Can anyone tell how to read Unicode escape sequences from file so that they
are presented like literals?

You will need to make a text replace.

Example code:

public static string U2U(string s)
{
string res = s;
MatchCollection reg = Regex.Matches(r es, @"\\u([0-9A-F]{4})");
for(int i = 0; i < reg.Count; i++) {
res = res.Replace(reg[i].Groups[0].Value, "" +
(char)int.Parse (reg[i].Groups[1].Value, NumberStyles.He xNumber));
}
return res;
}

Arne

[Michael Justin]

Re: Reading Unicode escape sequences from File

John Ztwin wrote:

I have a file that contains ordinary text and some special charaters in
Unicode escape sequences (\uxxxx).

If the file always uses \u then there is no risk. However, some
standards (like the C# spec) allow \U (uppercase) escape sequences:

unicode-escape-sequence:
\u hex-digit hex-digit hex-digit hex-digit
\U hex-digit hex-digit hex-digit hex-digit hex-digit
hex-digit hex-digit hex-digit

http://msdn.microsoft.com/en-us/library/aa664812.aspx

Best regards
--
Michael Justin
SCJP, SCJA
betasoft - Software for Delphiâ„¢ and for the Javaâ„¢ platform
http://www.mikejustin.com - http://www.betabeans.de