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]]

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.

 

[John Ztwin]

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

 

[Jon Skeet [C# MVP]]

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

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

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

 

[Arne Vajhøj]

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(res, @"\\u([0-9A-F]{4})");
for(int i = 0; i < reg.Count; i++) {
res = res.Replace(reg.Groups[0].Value, "" +
(char)int.Parse(reg.Groups[1].Value, NumberStyles.HexNumber));
}
return res;
}

Arne

 

[Michael Justin]

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