From: Shark8 <onewingedshark@gmail.com>
Subject: Unchecked_Conversion vs Address-overlaying
Date: Sun, 26 May 2013 16:34:54 -0700 (PDT)
Date: 2013-05-26T16:34:54-07:00 [thread overview]
Message-ID: <6bbc35cb-18ed-4efc-b1ec-6c41dcc0256c@googlegroups.com> (raw)
I recently had to make a dump-function for a collection of bytes and was wondering if the method I chose (address-overlaying) was better than using Unchecked_Conversion or not.
------------------------------
-- The private type BLOB designates some collection of memory-data;
-- it is actually an access to a storage-array [of Storage-Elements].
-- It's sized to the Cell_Size that all the other types are given so
-- that they can be wrapped in a record and that pushed onto a stack.
Type BLOB is Not Null Access All System.Storage_Elements.Storage_Array
with
Size => Cell_Size;
-- Returns a hex-dump of the given BLOB.
Function Image( Item : BLOB ) Return String is
Use System, System.Storage_Elements;
-- Our undervalued friend, the Nybble and the Byte, as well
-- as a type that serves as a collection of bytes.
Subtype Nybble is Interfaces.Unsigned_8 Range 16#0#..16#F#;
Subtype Byte is Interfaces.Unsigned_8;
Type Byte_String is Array(Positive Range <>) of Byte;
-- Return a Hex Character for any given Nybble.
Function Nybble_to_Hex( Input : Nybble ) Return Character is
subtype Decimal is Nybble range 0..9;
Base : Constant Interfaces.Unsigned_8:=
( if Input in Decimal then Character'Pos('0')
else Character'Pos('A') - 10 );
begin
Return Character'Val( Base + Input );
End Nybble_To_Hex;
-- Return the string that is the hex-values for
-- the high- and low-nybbles of the given byte.
Function Image( Item : Byte ) Return String is
begin
Return ( 1 => Nybble_to_Hex(Item / 16), -- High
2 => Nybble_to_Hex(Item mod 16) ); -- Low
End Image;
-- Given a Byte_String return the string containing its Nybbles.
Function Image( Item : Byte_String ) return String is
begin
Case Item'Length is
when 0 => Return "";
when 1 => Return Image(Item(Item'First));
when others =>
declare
Head : String Renames Image(Item(Item'First));
subtype Tail_Range is Positive Range
Positive'Succ(Item'First)..Item'Last;
Tail : String Renames Image(Item(Tail_Range));
begin
Return Head & Tail;
end;
end case;
End Image;
-- Calculate the length of the BLOB, in bytes.
Length : Constant Natural:= (Item'Length*Storage_Array'Component_Size)
/ Byte'Object_Size;
Pragma Warnings(Off);
-- Create an overlayed, non-initializing variable of the proper size.
Image_String : Byte_String(1..Length)
with Import, Convention => Ada, Address => Item.All'Address;
Pragma Warnings(On);
begin
-- Return the image of that overlay.
Return Image(Image_String);
end Image;
next reply other threads:[~2013-05-26 23:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-26 23:34 Shark8 [this message]
2013-05-27 2:33 ` Unchecked_Conversion vs Address-overlaying Jeffrey Carter
2013-05-27 4:37 ` Per Sandberg
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox