Re: wide_string and assertions

[Martin Krischik <krischik@users.sourceforge.net>]

Georg Bauhaus wrote:

> Randy Brukardt <randy@rrsoftware.com> wrote:
> : "Georg Bauhaus" <sb463ba@l1-hrz.uni-duisburg.de> wrote in message
> 
> :> In an assert(x, y), y has to be static. So I guess for y I
> :> will have to play tricks and use UTF-8 coding of static
> :> String values?
> : 
> : Yes.
> 
> OK. (Though I find it a bit inconsistent from some
> point of view not to be able to express failure descriptions
> in a language that is understood by local operators.)
> 
> : As far as demand goes, you're the first person to mention it to my
> : knowledge -- which is suggests that the demand is low. :-)
> 
> How do that do these things in China? Does anyone have some
> experience?
>  
> :    raise Assert_Error with To_UTF_8 ("Wide_Wide_String");
> : so that might be preferable for this purpose.
> 
> Yes. This is what I'm currently doing with Wide_String and
> Raise_Exception.
> 
> 
> : (But you'll probably have to
> : write the function yourself; there doesn't seem to be much support for
> : including such functions in the Standard.)
> 
> (It would be great if someone who know about surrogate characters could
> check the following. Martin, is this similar to your function?)

As I said the functions are based on the Unicode part of XML/Ada. Not point
reinventing the Wheel.

XML/Ada is based on:

   type Unicode_Char is mod 2**32;

   subtype Utf8_String is String;

   subtype Utf16_String is String;
   subtype Utf16_LE_String is Utf16_String;
   subtype Utf16_BE_String is Utf16_String;

   subtype Utf32_String is String;
   subtype Utf32_LE_String is Utf32_String;
   subtype Utf32_BE_String is Utf32_String;

Wide Strings are normaly not part if this. However my extension alows:

   function From_Utf32
     (Str : Unicode.CES.Utf32.Utf32_LE_String)
      return Wide_String;

   --
   --  Return a new utf32-encoded string, from a standard Ada string.
   --
   function To_Utf32
     (Str : Wide_String)
      return Unicode.CES.Utf32.Utf32_LE_String;

   ------------------------------------------
   -- Conversion to and from 8bit-encoding --
   ------------------------------------------

   --
   --  Return a new string, from 8 bit String encoded in codeset.
   --
   function From_Codeset (
      Str : in String;
      Codeset : in String)
   return
      Wide_String;

   --
   --  Return a new 8 bit String encoded in codeset.
   --
   function To_Codeset (
      Str : in Wide_String;
      Codeset : in String)
   return
      String;

   -------------------------------------------
   -- Conversion to and from UTF-8 encoding --
   -------------------------------------------

   --
   --  Return a new string, from 8 bit String encoded in codeset.
   --
   function From_UTF8 (
      Str : in String)
   return
      Wide_String;

   --
   --  Return a new 8 bit String encoded in codeset.
   --
   function To_UTF8 (
      Str : in Wide_String)
   return
      String;

>    function to_UTF8_String
>      (s: Wide_String; substitute: Character := '#') return String is

No substitution. An exception is raised if it does not fit. If this is a
proble you might be better of raising a Utf32_String.

>       result: String(1.. 4 * s'length);
>       --  Unicode has at most 4 bytes for a UTF-8 encoded character

XML/Ada encodes full 32bit that is up to 6 UTF-8 bytes. In an other
discussion we allready figured out that this is not realy needed.

With Regards

Martin
-- 
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