CVS difference for ais/ai-00301.txt

Differences between 1.1 and version 1.2
Log of other versions for file ais/ai-00301.txt

--- ais/ai-00301.txt	2002/06/14 23:48:56	1.1
+++ ais/ai-00301.txt	2002/07/23 01:05:25	1.2
@@ -765,3 +765,153 @@
 
 ****************************************************************
 
+From: Robert Dewar
+Sent: Saturday, June 22, 2002  6:30 AM
+
+> Implementation advice: the Put and Put_Line operations should be implemented
+> such that no extra copy of the string data occurs.
+
+The Ada RM is no place to put in requests for some particular optimization
+that you want to see. How to spend time and effort in improving performance
+of various language constructs is between vendors and the marketplace.
+
+This partciular IA is ill advised in my opinion in any case, but for sure
+IA of this type does not belong.
+
+****************************************************************
+
+From: Robert Dewar
+Sent: Saturday, June 22, 2002  7:17 AM
+
+> Compiler writers do not deliberately try to make their products
+> inefficient.  Of course they cut corners to save money.  So what they
+> need is pressure from paying customers, so they can set their
+> optimization priorities right.
+
+It is not a matter of cutting corners even. A simple implementation that
+does an extra copy may be far superior to a complex one that does an
+extra copy if the time for the extra copy is negligible in the entire
+context of performance requirements.
+
+****************************************************************
+
+From: Robert A. Duff
+Sent: Saturday, June 22, 2002  11:55 AM
+
+> It is not a matter of cutting corners even.
+
+Well, perhaps "cutting corners" is a somewhat rude choice of words.
+
+>... A simple implementation that
+> does an extra copy may be far superior to a complex one that does an
+> extra copy if the time for the extra copy is negligible in the entire
+> context of performance requirements.
+
+I think you're missing a "not" in the above sentence.  Amusing typo.  ;-)
+
+Anyway, you and I obviously agree that the kind of optimization advice
+being discussed does not belong in the RM.
+
+****************************************************************
+
+From: Robert Dewar
+Sent: Sunday, June 23, 2002  6:33 AM
+
+Here is a package that we provide with GNAT that we have found useful for
+solving some of these problems
+
+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT RUNTIME COMPONENTS                          --
+--                                                                          --
+--            A D A . S T R I N G S . U N B O U N D E D . A U X             --
+--                                                                          --
+--                                 S p e c                                  --
+--                                                                          --
+--                            $Revision: 1.2 $                              --
+--                                                                          --
+--          Copyright (C) 1992-1998, Free Software Foundation, Inc.         --
+--                                                                          --
+-- GNAT is free software;  you can  redistribute it  and/or modify it under --
+-- terms of the  GNU General Public License as published  by the Free Soft- --
+-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
+-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
+-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
+-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
+-- for  more details.  You should have  received  a copy of the GNU General --
+-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
+-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
+-- MA 02111-1307, USA.                                                      --
+--                                                                          --
+-- As a special exception,  if other files  instantiate  generics from this --
+-- unit, or you link  this unit with other files  to produce an executable, --
+-- this  unit  does not  by itself cause  the resulting  executable  to  be --
+-- covered  by the  GNU  General  Public  License.  This exception does not --
+-- however invalidate  any other reasons why  the executable file  might be --
+-- covered by the  GNU Public License.                                      --
+--                                                                          --
+-- GNAT was originally developed  by the GNAT team at  New York University. --
+-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+--                                                                          --
+------------------------------------------------------------------------------
+
+--  This child package of Ada.Strings.Unbounded provides some specialized
+--  access functions which are intended to allow more efficient use of the
+--  facilities of Ada.Strings.Unbounded, particularly by other layered
+--  utilities (such as GNAT.Patterns).
+
+package Ada.Strings.Unbounded.Aux is
+pragma Preelaborate (Aux);
+
+   function Get_String (U  : Unbounded_String) return String_Access;
+   pragma Inline (Get_String);
+   --  This function returns the internal string pointer used in the
+   --  representation of an unbounded string. There is no copy involved,
+   --  so the value obtained references the same string as the original
+   --  unbounded string. The characters of this string may not be modified
+   --  via the returned pointer, and are valid only as long as the original
+   --  unbounded string is not modified. Violating either of these two
+   --  rules results in erroneous execution.
+   --
+   --  This function is much more efficient than the use of To_String
+   --  since it avoids the need to copy the string. The lower bound of the
+   --  referenced string returned by this call is always one.
+
+   procedure Set_String (UP : in out Unbounded_String; S : String);
+   pragma Inline (Set_String);
+   --  This function sets the string contents of the referenced unbounded
+   --  string to the given string value. It is significantly more efficient
+   --  than the use of To_Unbounded_String with an assignment, since it
+   --  avoids the necessity of messing with finalization chains. The lower
+   --  bound of the string S is not required to be one.
+
+   procedure Set_String (UP : in out Unbounded_String; S : String_Access);
+   pragma Inline (Set_String);
+   --  This version of Set_String takes a string access value, rather than a
+   --  string. The lower bound of the string value is required to be one, and
+   --  this requirement is not checked.
+
+end Ada.Strings.Unbounded.Aux;
+
+
+----------------------
+-- REVISION HISTORY --
+----------------------
+
+--  ----------------------------
+--  revision 1.1
+--  date: 1997/01/25 15:24:52;  author: dewar;  state: Exp;
+--  Initial revision
+--  ----------------------------
+--  revision 1.2
+--  date: 1997/01/26 20:31:05;  author: dewar;
+--  Add pragma Inline for Set_String
+--  (Set_String): New version taking a String_Access value
+--  ----------------------------
+--  revision 1.3
+--  date: 1998/04/27 12:14:21;  author: dewar;
+--  Remove unused withs
+--  Add missing copyright line to header
+--  ----------------------------
+--  New changes after this line.  Each line starts with: "--  "
+

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