Regular expressions and hex characters

Archived
1

It’s quite possible I’m doing something wrong, but it appears the \x escape sequence isn’t recognized. Example:

ba = CreateObject("roByteArray")
ba[0] = &hE2
ba[1] = &h80
ba[2] = &h99
str = ba.ToAsciiString()
regex = CreateObject("roRegEx","\xe2","")
print regex.IsMatch(str)

This tries to match the hex byte E2, but the IsMatch() returns false.

-JT

2

i think you are running into issue related to string encoding, likely one of those gets treated as UTF-8. When i try your code on &h12 &h10 &h19 and \x12 it works just fine, probably with everything else in range 0-x7f too.

On your example

BrightScript Debugger> ? len(str)
 1

seems to show you are not getting what you expect (len should be 3)

PS. ok here is what’s going on: bytes e2 80 99 is a single character encoded in utf-8:
in binary, utf8 prefixes marked: (1110)0010 (10)000000 (10)011001
the encoded symbol is: 0010-000000-011001 (bin) or 0x2019 (right-single-quotation-mark)

So this is how it should be reg-ex-ed:

BrightScript Debugger> regex = CreateObject("roRegEx","\x{2019}","")
BrightScript Debugger> ? regex.IsMatch(str)
true

Based on the syntax for Unicode (\u2019 did not work), chances are the library underneath is PCRE

3

Thanks! I knew I was missing something. By the way, the documentation does state that Brightscript uses the PCRE library.

-JT