From: Olivier Scalbert <olivier.scalbert@algosyn.com>
Subject: Re: Load an object from a file
Date: Fri, 03 Apr 2009 17:19:21 +0200
Date: 2009-04-03T17:19:21+02:00 [thread overview]
Message-ID: <49d628f5$0$2865$ba620e4c@news.skynet.be> (raw)
In-Reply-To: <443d72ca-5bbd-46a3-84c6-e8bd984e5b80@k41g2000yqh.googlegroups.com>
Thanks Ludovic,
One more question:
with:
type u2 is new Integer;
type cp_info is new Integer;
type Constant_Pool_Array is array (Positive range <>) of cp_info;
type Interfaces_Array is array (Positive range <>) of u2;
type Class_File
(constant_pool_count,
interfaces_count,
fields_count,
methods_count,
attributes_count : u2)
is record
constant_pool : Constant_Pool_Array (2 .. constant_pool_count);
interfaces : Interfaces_Array (1 .. interfaces_count);
end record;
I have an error: expected type "Standard.Integer", in the 2 last lines.
If I replace the line:
"attributes_count : u2" by
"attributes_count : Integer"
then compile is Ok !
Don't know how to cleanly solve ...
Olivier
Ludovic Brenta wrote:
> I would create a record type with one discriminant for each array,
> like so:
>
> type Constant_Pool_Array is array (Positive range <>) of cp_info;
> type Interfaces_Array is array (Positive range <>) of u2;
> -- etc.
>
> type Class_File
> (constant_pool_count,
> interfaces_count,
> fields_count,
> methods_count,
> attributes_count : u2)
> is record
> ...
> constant_pool : Constant_Pool_Array (2 .. constant_pool_count);
> ...
> interfaces : Interfaces_Array (1 .. interfaces_count);
> ... etc.
> end record;
>
>> Also how can I fill this array ?
>
> You would normally simply call the predefined Class_File'Read but this
> wouldn't work since the order of the components in type Class_File
> does not match the order in the file. So, you'd specify your own Read:
>
> function Input(
> Stream : not null access Ada.Streams.Root_Stream_Type'Class)
> return Class_File); -- see RM 13.13(22) and following
> for Class_File'Input use Input; -- as per RM 13.13(38/2)
>
> function Input(
> Stream : not null access Ada.Streams.Root_Stream_Type'Class)
> return Class_File)
> is
> Constant_Pool_Count : u2;
> type Constant_Pool_Array_Access is access Constant_Pool_Array;
> procedure Free is new Ada.Unchecked_Deallocation
> (Constant_Pool_Array, Constant_Pool_Array_Access);
> Constant_Pool : Constant_Pool_Array_Access;
> begin
> ...
> u2'Read (Stream, Constant_Pool_Count);
> Constant_Pool := new Constant_Pool_Array (1 .. Constant_Pool - 1);
> Constant_Pool_Array'Read (Stream, Constant_Pool.all);
> ...
>
> After reading all members, construct the result:
>
> declare
> Result : Class_File
> (constant_pool_count => Constant_Pool_Count,
> interfaces_count => Interfaces_Count,
> fields_count => Fields_Count,
> methods_count => Methods_Count,
> attributes_count => Attricutes_Count);
> begin
> Result.Constant_Pool := Constant_Pool.all;
> ...
> Free (Constant_Pool);
> ...
> return Result;
> end;
> end Input;
>
> You can also eliminate the use of access types and dynamic allocation
> and deallocation by nesting declare blocks, e.g.
>
> u2'Read (Stream, Constant_Pool_Count);
> declare
> Constant_Pool : Constant_Pool_Array (1 .. Constant_Pool_Count);
> begin
> Constant_Pool_Array'Read (Stream, Constant_Pool);
> ...
> u2'Read (Stream, Interfaces_Count);
> declare
> Interfaces : Interfaces_Count_Array (1 .. Interfaces_Count);
> begin
> ...
> end;
> end;
>
> HTH
>
> --
> Ludovic Brenta.
next prev parent reply other threads:[~2009-04-03 15:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-03 12:01 Load an object from a file Olivier Scalbert
2009-04-03 13:07 ` Niklas Holsti
2009-04-03 13:37 ` Ludovic Brenta
2009-04-03 15:19 ` Olivier Scalbert [this message]
2009-04-03 16:08 ` Georg Bauhaus
2009-04-03 16:22 ` Ludovic Brenta
2009-04-03 16:41 ` Olivier Scalbert
2009-04-03 16:46 ` Adam Beneschan
2009-04-03 20:22 ` Ludovic Brenta
2009-04-09 20:32 ` Olivier Scalbert
2009-04-09 21:22 ` Ludovic Brenta
2009-04-09 22:22 ` Olivier Scalbert
2009-04-19 13:08 ` Olivier Scalbert
2009-04-19 19:52 ` Ludovic Brenta
2009-04-19 20:27 ` Gautier
2009-04-03 13:41 ` Thomas Løcke
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