[Win32utils-devel] PathIsURL and frozen strings

Daniel Berger djberg96 at gmail.com
Sat Jul 19 20:04:49 EDT 2008


Park Heesob wrote:
> Hi,
> ----- Original Message ----- 
> From: "Daniel Berger" <djberg96 at gmail.com>
> To: "win32utils-devel" <win32utils-devel at rubyforge.org>
> Sent: Sunday, July 13, 2008 9:37 PM
> Subject: [Win32utils-devel] PathIsURL and frozen strings
> 
> 
>> Hi all,
>>
>> I may have brought this up a long time ago, but I've forgotten. Why does 
>> PathIsURL(path) fail if 'path' is frozen?
>>
>> require 'windows/path'
>> include Windows::Path
>>
>> path = "file://C:\\Documents and Settings\\djberge"
>> PathIsURL(path) # true
>>
>> path.freeze
>> PathIsURL(path) # Boom!
>>
>> TypeError: can't modify frozen string
>>         from (eval):3:in `call'
>>         from (eval):3:in `PathIsURL'
>>         from (irb):9
>>
>> Any ideas? I realize I can just dup the string, but I thought I'd ask.
>>
> In the win32-api, the string type('P') denotes both input and output pointer 
> parameter.
> Thus the string parameter can be modified and must not be frozen.
> In case of pure input string, you can define another parameter type and skip
> rb_str_modify(v_arg) (line #584 of win32/api.c)

After thinking about it some more I'm going to go ahead and add an 'S' 
prototype, which will be for const char* strings. My reasoning is as 
follows:

It's a bit faster. About 25% in a strcpy benchmark I ran.

It means we don't have to worry about buffers in some cases (or will, 
once I redefine the prototypes in windows-pr).

It eliminates the issue I originally mentioned regarding frozen strings.

I think it will simplify certain parts of a port for JRuby or IronRuby.

I'll mark this as a major release, 1.2.0.

Regards,

Dan


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