Re: [Vala] string <-> bytes conversion in Vala

[Sandino Flores Moreno <tigrux gmail com>]

Problem with casting string to/from char*is that in utf8, some
characters are actually two-byte sized.

That's why glib has a specialized API for dealing with utf8, like the
function g_utf8_find_next_char.



On Wed, Dec 29, 2010 at 5:59 PM, Anatol Pomozov
<anatol pomozov gmail com> wrote:
> On Wed, Dec 29, 2010 at 3:51 PM, Anatol Pomozov
> <anatol pomozov gmail com> wrote:
> > Hi
> >
> > On Thu, Dec 23, 2010 at 12:37 AM, Anatol Pomozov
> > <anatol pomozov gmail com> wrote:
> > > Hi,
> > >
> > > I manipulate with strings in my application such as storing/reading
> > > to/from binary files. And I need to convert a string to/from array of
> > > bytes. What is the best way of doing it in Vala?
> > >
> > > Looking into string class http://valadoc.org/glib-2.0/string.html I
> > > see a method called string#to_utf8() that converts string to array of
> > > chars. But I cannot find any other methods.
> > >
> > > So I have 2 questions:
> > >  - How to convert a string to array of chars in encoding different
> > > from UTF8. Something like this one
> > > http://download.oracle.com/javase/6/docs/api/java/lang/String.html#getBytes(java.nio.charset.Charset)
> > >  - How to convert array of chars/uint8 back to string? Like this one
> > > http://download.oracle.com/javase/6/docs/api/java/lang/String.html#String(byte[],
> > > java.nio.charset.Charset)
> >
> > I think I found a way to convert string to bytes in Vala. Actually it
> > is as simple as casting string to char* and back. Under the hood
> > strings in vala is just a pointer to char.
> >
> > Here is an example that shows it:
> >
> >  string hello = "abcd";
> >  char* ch = (char*) hello;
> >  stdout.printf("%c\n", ch[1]); // Second char, that is 'b'
>
> It actually produces an interesting effect. You *can* change content
> of a string (that are claimed as immutable)
>
>  string hello = "abcd";
>  char* ch = (char*) hello;
>  ch[0] = 'z';
>  stdout.printf(hello); // Prints 'zbcd'
>
> PS Casting string to/from char* is an interesting technique and worth
> mention about it in the tutorial.
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