[rfc][icedtea-web] c-properties-miniparser now escape most (all except multiline?) escape sequences

[Jacob Wisor]

On 12/18/2015 at 04:12 PM Jiri Vanek wrote:
> SSIA
>
> how about 1.6 ? Backport?

This code is supposed to work on manifest files in JAR files and property, files 
right?

> +void IcedTeaPluginUtilities::escape(std::string& str) {
> +    std::string result = "";
> +    for(unsigned int i = 0; i<str.length(); i++) {

I don't think you want to calculate the length() of str on every loop.

> +//        fprintf(stdout, "%s\n", result.c_str());
> +        bool processed = false;
> +        char c1 = str[i];
> +        if (c1 == '\\') {
> +            if (i<str.length()-1) {

Same goes here for calculating the length of str on every loop.

> +                char c2 = str[i+1];
> +                if (c2 == '=' || c2 == '\\' || c2 == ':') {
> +                    result+=c2;
> +                    i++;
> +                    processed = true;
> +                }
> +                if (c2 == 't') {
> +                    result+='\t';
> +                    i++;
> +                    processed = true;
> +                }
> +                if (c2 == 'n') {
> +                    result+='\n';
> +                    i++;
> +                    processed = true;
> +                }
> +                if (c2 == 'r') {
> +                    result+='\r';
> +                    i++;
> +                    processed = true;
> +                }

I suppose a cascading "if else" structure would be more efficient here.

> +
> +            }
> +        }
> +    if (!processed){
> +        result+=c1;
> +    }
> +    }
> +   str=result;
> +}
For one, please fix the formatting and remove trailing white spaces at the end 
of lines.

Second, is this really a good way to do escape sequence processing in C/C++? I'd 
say that regex substitution and selection is the way to go here. Yes, I am aware 
that the standard C/C++ libraries do not support regex. However, this plug-in 
implementation is designed and supposed to run on POSIX systems, which does 
support regex since eons. But, before you rush off and start thinking that Perl 
or Python regex implementations/libraries was meant here or they may be a great 
idea: no they are not. Implementing this should not require a huge additional 
dependency, even if this code uses only a small portion of that dependency and 
possibly has a shorter launching time than a full Java VM.
regex.h, regcomp(), regexec(), regerror(), and regfree() should be your friends.

With regards to portability, unfortunately, Windows does not natively support 
regex (because it was never intended to be POSIX compliant). However, .NET, 
Visual Basic and JScript scripting hosts do support regex. Of course, .NET is 
out of the game but the Windows Scripting Host has become a default Windows 
component of the NT family of products since Windows 2000 (and as a service pack 
for Windows NT 4). And, since the Windows plug-in cannot share all native code 
with the POSIX plug-in for other reasons as well, it is only natural to go "the 
Windows way" where necessary. I do not intend to support anything earlier than 
Windows 2000, so it should be possible and safe to tap into the Windows 
Scripting Host for native regex capability, should regex become a necessity on 
Windows. The Windows Scripting Host has a relatively short launching time 
despite its long name. ;-)

Regards,

Jacob