------------------------------------------------------------------------------ -- GNAT COMPILER COMPONENTS -- -- -- -- G N A T . R E W R I T E _ D A T A -- -- -- -- S p e c -- -- -- -- Copyright (C) 2014-2024, 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 3, 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. -- -- -- -- As a special exception under Section 7 of GPL version 3, you are granted -- -- additional permissions described in the GCC Runtime Library Exception, -- -- version 3.1, as published by the Free Software Foundation. -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- This package can be used to rewrite data on the fly. All occurrences of a -- string (named pattern) will be replaced by another string. -- It is not necessary to load all data in memory and so this package can be -- used for large data chunks like disk files for example. The pattern is -- a standard string and not a regular expression. -- There is no dynamic allocation in the implementation. -- For example, to replace all occurrences of "Gnat" with "GNAT": -- Rewriter : Buffer := Create (Pattern => "Gnat", Value => "GNAT"); -- The output procedure that will receive the rewritten data: -- procedure Do (Data : Stream_Element_Array) is -- begin -- -- end Do; -- Then: -- Write (Rewriter, "Let's talk about Gnat compiler", Do'Access); -- Write (Rewriter, "Gnat is an Ada compiler", Do'Access); -- Flush (Rewriter, Do'Access); -- Another possible usage is to specify a method to get the input data: -- procedure Get -- (Buffer : out Stream_Element_Array; -- Last : out Stream_Element_Offset) -- is -- begin -- -- Last := ... -- Buffer := ... -- end Get; -- Then we can rewrite the whole file with: -- Rewrite (Rewriter, Input => Get'Access, Output => Do'Access); with Ada.Streams; use Ada.Streams; package GNAT.Rewrite_Data is type Buffer (<>) is limited private; type Buffer_Ref is access all Buffer; function Create (Pattern, Value : String; Size : Stream_Element_Offset := 1_024) return Buffer; -- Create a rewrite buffer. Pattern is the string to be rewritten as Value. -- Size represents the size of the internal buffer used to store the data -- ready to be output. A larger buffer may improve the performance, as the -- Output routine (see Write, Rewrite below) will be called only when this -- buffer is full. Note that Size cannot be lower than Pattern'Length, and -- if this is the case, then Size value is set to Pattern'Length. function Size (B : Buffer) return Natural; -- Returns the current size of the buffer (count of Stream_Array_Element) procedure Flush (B : in out Buffer; Output : not null access procedure (Data : Stream_Element_Array)); -- Call Output for all remaining data in the buffer. The buffer is -- reset and ready for another use after this call. procedure Reset (B : in out Buffer); pragma Inline (Reset); -- Clear all data in buffer, B is ready for another use. Note that this is -- not needed after a Flush. Note: all data remaining in Buffer is lost. procedure Write (B : in out Buffer; Data : Stream_Element_Array; Output : not null access procedure (Data : Stream_Element_Array)); -- Write Data into the buffer, call Output for any prepared data. Flush -- must be called when the last piece of Data as been sent in the Buffer. procedure Rewrite (B : in out Buffer; Input : not null access procedure (Buffer : out Stream_Element_Array; Last : out Stream_Element_Offset); Output : not null access procedure (Data : Stream_Element_Array)); -- Read data from Input, rewrite it, and then call Output. When there is -- no more data to be read from Input, Last must be set to 0. Before -- leaving this routine, call Flush above to send all remaining data to -- Output. procedure Link (From : in out Buffer; To : Buffer_Ref); -- Link two rewrite buffers. That is, all data sent to From buffer will be -- rewritten and then passed to the To rewrite buffer. private type Buffer (Size, Size_Pattern, Size_Value : Stream_Element_Offset) is limited record Pos_C : Stream_Element_Offset; -- last valid element in Current Pos_B : Stream_Element_Offset; -- last valid element in Buffer Next : Buffer_Ref; -- A link to another rewriter if any Buffer : Stream_Element_Array (1 .. Size); -- Fully prepared/rewritten data waiting to be output Current : Stream_Element_Array (1 .. Size_Pattern); -- Current data checked, this buffer contains every piece of data -- starting with the pattern. It means that at any point: -- Current (1 .. Pos_C) = Pattern (1 .. Pos_C). Pattern : Stream_Element_Array (1 .. Size_Pattern); -- The pattern to look for Value : Stream_Element_Array (1 .. Size_Value); -- The value the pattern is replaced by end record; end GNAT.Rewrite_Data;