660 lines
18 KiB
Ada
660 lines
18 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- T R E E _ I O --
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-- --
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-- B o d y --
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-- --
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-- Copyright (C) 1992-2002 Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 2, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING. If not, write --
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-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
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-- Boston, MA 02110-1301, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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with Debug; use Debug;
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with Output; use Output;
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with Unchecked_Conversion;
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package body Tree_IO is
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Debug_Flag_Tree : Boolean := False;
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-- Debug flag for debug output from tree read/write
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-------------------------------------------
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-- Compression Scheme Used for Tree File --
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-------------------------------------------
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-- We don't just write the data directly, but instead do a mild form
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-- of compression, since we expect lots of compressible zeroes and
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-- blanks. The compression scheme is as follows:
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-- 00nnnnnn followed by nnnnnn bytes (non compressed data)
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-- 01nnnnnn indicates nnnnnn binary zero bytes
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-- 10nnnnnn indicates nnnnnn ASCII space bytes
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-- 11nnnnnn bbbbbbbb indicates nnnnnnnn occurrences of byte bbbbbbbb
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-- Since we expect many zeroes in trees, and many spaces in sources,
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-- this compression should be reasonably efficient. We can put in
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-- something better later on.
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-- Note that this compression applies to the Write_Tree_Data and
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-- Read_Tree_Data calls, not to the calls to read and write single
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-- scalar values, which are written in memory format without any
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-- compression.
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C_Noncomp : constant := 2#00_000000#;
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C_Zeros : constant := 2#01_000000#;
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C_Spaces : constant := 2#10_000000#;
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C_Repeat : constant := 2#11_000000#;
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-- Codes for compression sequences
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Max_Count : constant := 63;
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-- Maximum data length for one compression sequence
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-- The above compression scheme applies only to data written with the
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-- Tree_Write routine and read with Tree_Read. Data written using the
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-- Tree_Write_Char or Tree_Write_Int routines and read using the
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-- corresponding input routines is not compressed.
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type Int_Bytes is array (1 .. 4) of Byte;
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for Int_Bytes'Size use 32;
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function To_Int_Bytes is new Unchecked_Conversion (Int, Int_Bytes);
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function To_Int is new Unchecked_Conversion (Int_Bytes, Int);
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----------------------
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-- Global Variables --
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----------------------
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Tree_FD : File_Descriptor;
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-- File descriptor for tree
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Buflen : constant Int := 8_192;
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-- Length of buffer for read and write file data
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Buf : array (Pos range 1 .. Buflen) of Byte;
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-- Read/write file data buffer
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Bufn : Nat;
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-- Number of bytes read/written from/to buffer
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Buft : Nat;
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-- Total number of bytes in input buffer containing valid data. Used only
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-- for input operations. There is data left to be processed in the buffer
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-- if Buft > Bufn. A value of zero for Buft means that the buffer is empty.
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-----------------------
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-- Local Subprograms --
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-----------------------
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procedure Read_Buffer;
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-- Reads data into buffer, setting Bufe appropriately
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function Read_Byte return Byte;
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pragma Inline (Read_Byte);
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-- Returns next byte from input file, raises Tree_Format_Error if none left
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procedure Write_Buffer;
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-- Writes out current buffer contents
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procedure Write_Byte (B : Byte);
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pragma Inline (Write_Byte);
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-- Write one byte to output buffer, checking for buffer-full condition
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-----------------
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-- Read_Buffer --
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-----------------
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procedure Read_Buffer is
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begin
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Buft := Int (Read (Tree_FD, Buf (1)'Address, Integer (Buflen)));
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if Buft = 0 then
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raise Tree_Format_Error;
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else
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Bufn := 0;
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end if;
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end Read_Buffer;
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---------------
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-- Read_Byte --
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---------------
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function Read_Byte return Byte is
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begin
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if Bufn = Buft then
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Read_Buffer;
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end if;
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Bufn := Bufn + 1;
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return Buf (Bufn);
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end Read_Byte;
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--------------------
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-- Tree_Read_Bool --
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--------------------
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procedure Tree_Read_Bool (B : out Boolean) is
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begin
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B := Boolean'Val (Read_Byte);
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if Debug_Flag_Tree then
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if B then
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Write_Str ("True");
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else
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Write_Str ("False");
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end if;
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Write_Eol;
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end if;
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end Tree_Read_Bool;
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--------------------
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-- Tree_Read_Char --
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--------------------
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procedure Tree_Read_Char (C : out Character) is
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begin
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C := Character'Val (Read_Byte);
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting Character = ");
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Write_Char (C);
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Write_Eol;
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end if;
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end Tree_Read_Char;
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--------------------
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-- Tree_Read_Data --
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--------------------
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procedure Tree_Read_Data (Addr : Address; Length : Int) is
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type S is array (Pos) of Byte;
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-- This is a big array, for which we have to suppress the warning
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type SP is access all S;
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function To_SP is new Unchecked_Conversion (Address, SP);
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Data : constant SP := To_SP (Addr);
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-- Data buffer to be read as an indexable array of bytes
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OP : Pos := 1;
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-- Pointer to next byte of data buffer to be read into
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B : Byte;
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C : Byte;
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L : Int;
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begin
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting ");
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Write_Int (Length);
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Write_Str (" data bytes");
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Write_Eol;
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end if;
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-- Verify data length
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Tree_Read_Int (L);
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if L /= Length then
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Write_Str ("==> transmitting, expected ");
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Write_Int (Length);
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Write_Str (" bytes, found length = ");
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Write_Int (L);
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Write_Eol;
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raise Tree_Format_Error;
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end if;
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-- Loop to read data
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while OP <= Length loop
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-- Get compression control character
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B := Read_Byte;
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C := B and 2#00_111111#;
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B := B and 2#11_000000#;
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-- Non-repeat case
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if B = C_Noncomp then
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if Debug_Flag_Tree then
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Write_Str ("==> uncompressed: ");
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Write_Int (Int (C));
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Write_Str (", starting at ");
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Write_Int (OP);
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Write_Eol;
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end if;
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for J in 1 .. C loop
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Data (OP) := Read_Byte;
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OP := OP + 1;
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end loop;
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-- Repeated zeroes
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elsif B = C_Zeros then
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if Debug_Flag_Tree then
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Write_Str ("==> zeroes: ");
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Write_Int (Int (C));
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Write_Str (", starting at ");
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Write_Int (OP);
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Write_Eol;
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end if;
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for J in 1 .. C loop
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Data (OP) := 0;
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OP := OP + 1;
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end loop;
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-- Repeated spaces
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elsif B = C_Spaces then
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if Debug_Flag_Tree then
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Write_Str ("==> spaces: ");
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Write_Int (Int (C));
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Write_Str (", starting at ");
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Write_Int (OP);
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Write_Eol;
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end if;
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for J in 1 .. C loop
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Data (OP) := Character'Pos (' ');
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OP := OP + 1;
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end loop;
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-- Specified repeated character
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else -- B = C_Repeat
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B := Read_Byte;
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if Debug_Flag_Tree then
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Write_Str ("==> other char: ");
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Write_Int (Int (C));
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Write_Str (" (");
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Write_Int (Int (B));
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Write_Char (')');
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Write_Str (", starting at ");
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Write_Int (OP);
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Write_Eol;
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end if;
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for J in 1 .. C loop
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Data (OP) := B;
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OP := OP + 1;
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end loop;
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end if;
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end loop;
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-- At end of loop, data item must be exactly filled
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if OP /= Length + 1 then
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raise Tree_Format_Error;
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end if;
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end Tree_Read_Data;
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--------------------------
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-- Tree_Read_Initialize --
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--------------------------
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procedure Tree_Read_Initialize (Desc : File_Descriptor) is
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begin
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Buft := 0;
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Bufn := 0;
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Tree_FD := Desc;
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Debug_Flag_Tree := Debug_Flag_5;
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end Tree_Read_Initialize;
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-------------------
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-- Tree_Read_Int --
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-------------------
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procedure Tree_Read_Int (N : out Int) is
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N_Bytes : Int_Bytes;
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begin
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for J in 1 .. 4 loop
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N_Bytes (J) := Read_Byte;
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end loop;
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N := To_Int (N_Bytes);
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting Int = ");
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Write_Int (N);
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Write_Eol;
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end if;
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end Tree_Read_Int;
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-------------------
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-- Tree_Read_Str --
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-------------------
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procedure Tree_Read_Str (S : out String_Ptr) is
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N : Nat;
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begin
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Tree_Read_Int (N);
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S := new String (1 .. Natural (N));
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Tree_Read_Data (S.all (1)'Address, N);
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end Tree_Read_Str;
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-------------------------
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-- Tree_Read_Terminate --
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-------------------------
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procedure Tree_Read_Terminate is
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begin
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-- Must be at end of input buffer, so we should get Tree_Format_Error
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-- if we try to read one more byte, if not, we have a format error.
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declare
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B : Byte;
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pragma Warnings (Off, B);
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begin
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B := Read_Byte;
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exception
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when Tree_Format_Error => return;
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end;
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raise Tree_Format_Error;
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end Tree_Read_Terminate;
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---------------------
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-- Tree_Write_Bool --
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---------------------
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procedure Tree_Write_Bool (B : Boolean) is
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begin
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting Boolean = ");
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if B then
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Write_Str ("True");
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else
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Write_Str ("False");
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end if;
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Write_Eol;
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end if;
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Write_Byte (Boolean'Pos (B));
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end Tree_Write_Bool;
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---------------------
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-- Tree_Write_Char --
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---------------------
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procedure Tree_Write_Char (C : Character) is
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begin
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting Character = ");
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Write_Char (C);
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Write_Eol;
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end if;
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Write_Byte (Character'Pos (C));
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end Tree_Write_Char;
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---------------------
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-- Tree_Write_Data --
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---------------------
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procedure Tree_Write_Data (Addr : Address; Length : Int) is
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type S is array (Pos) of Byte;
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-- This is a big array, for which we have to suppress the warning
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type SP is access all S;
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function To_SP is new Unchecked_Conversion (Address, SP);
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Data : constant SP := To_SP (Addr);
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-- Pointer to data to be written, converted to array type
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IP : Pos := 1;
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-- Input buffer pointer, next byte to be processed
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NC : Nat range 0 .. Max_Count := 0;
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-- Number of bytes of non-compressible sequence
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C : Byte;
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procedure Write_Non_Compressed_Sequence;
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-- Output currently collected sequence of non-compressible data
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procedure Write_Non_Compressed_Sequence is
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begin
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if NC > 0 then
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Write_Byte (C_Noncomp + Byte (NC));
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if Debug_Flag_Tree then
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Write_Str ("==> uncompressed: ");
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Write_Int (NC);
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Write_Str (", starting at ");
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Write_Int (IP - NC);
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Write_Eol;
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end if;
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for J in reverse 1 .. NC loop
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Write_Byte (Data (IP - J));
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end loop;
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NC := 0;
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end if;
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end Write_Non_Compressed_Sequence;
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-- Start of processing for Tree_Write_Data
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begin
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting ");
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Write_Int (Length);
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Write_Str (" data bytes");
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Write_Eol;
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end if;
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-- We write the count at the start, so that we can check it on
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-- the corresponding read to make sure that reads and writes match
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Tree_Write_Int (Length);
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-- Conversion loop
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-- IP is index of next input character
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-- NC is number of non-compressible bytes saved up
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loop
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-- If input is completely processed, then we are all done
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if IP > Length then
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Write_Non_Compressed_Sequence;
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return;
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end if;
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-- Test for compressible sequence, must be at least three identical
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-- bytes in a row to be worthwhile compressing.
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if IP + 2 <= Length
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and then Data (IP) = Data (IP + 1)
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and then Data (IP) = Data (IP + 2)
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then
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Write_Non_Compressed_Sequence;
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-- Count length of new compression sequence
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C := 3;
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IP := IP + 3;
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while IP < Length
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and then Data (IP) = Data (IP - 1)
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and then C < Max_Count
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loop
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C := C + 1;
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IP := IP + 1;
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end loop;
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-- Output compression sequence
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if Data (IP - 1) = 0 then
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if Debug_Flag_Tree then
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Write_Str ("==> zeroes: ");
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Write_Int (Int (C));
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Write_Str (", starting at ");
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Write_Int (IP - Int (C));
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Write_Eol;
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end if;
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Write_Byte (C_Zeros + C);
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elsif Data (IP - 1) = Character'Pos (' ') then
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if Debug_Flag_Tree then
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Write_Str ("==> spaces: ");
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Write_Int (Int (C));
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Write_Str (", starting at ");
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Write_Int (IP - Int (C));
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Write_Eol;
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end if;
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Write_Byte (C_Spaces + C);
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else
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if Debug_Flag_Tree then
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Write_Str ("==> other char: ");
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Write_Int (Int (C));
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Write_Str (" (");
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Write_Int (Int (Data (IP - 1)));
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Write_Char (')');
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Write_Str (", starting at ");
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Write_Int (IP - Int (C));
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Write_Eol;
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end if;
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Write_Byte (C_Repeat + C);
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Write_Byte (Data (IP - 1));
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end if;
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-- No compression possible here
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else
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-- Output non-compressed sequence if at maximum length
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if NC = Max_Count then
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Write_Non_Compressed_Sequence;
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end if;
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NC := NC + 1;
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IP := IP + 1;
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end if;
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end loop;
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end Tree_Write_Data;
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---------------------------
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-- Tree_Write_Initialize --
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---------------------------
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procedure Tree_Write_Initialize (Desc : File_Descriptor) is
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begin
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Bufn := 0;
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Tree_FD := Desc;
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Set_Standard_Error;
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Debug_Flag_Tree := Debug_Flag_5;
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end Tree_Write_Initialize;
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--------------------
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-- Tree_Write_Int --
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--------------------
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procedure Tree_Write_Int (N : Int) is
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N_Bytes : constant Int_Bytes := To_Int_Bytes (N);
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begin
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if Debug_Flag_Tree then
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Write_Str ("==> transmitting Int = ");
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Write_Int (N);
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Write_Eol;
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end if;
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for J in 1 .. 4 loop
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Write_Byte (N_Bytes (J));
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end loop;
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end Tree_Write_Int;
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--------------------
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-- Tree_Write_Str --
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--------------------
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procedure Tree_Write_Str (S : String_Ptr) is
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begin
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Tree_Write_Int (S'Length);
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Tree_Write_Data (S (1)'Address, S'Length);
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end Tree_Write_Str;
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--------------------------
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|
-- Tree_Write_Terminate --
|
|
--------------------------
|
|
|
|
procedure Tree_Write_Terminate is
|
|
begin
|
|
if Bufn > 0 then
|
|
Write_Buffer;
|
|
end if;
|
|
end Tree_Write_Terminate;
|
|
|
|
------------------
|
|
-- Write_Buffer --
|
|
------------------
|
|
|
|
procedure Write_Buffer is
|
|
begin
|
|
if Integer (Bufn) = Write (Tree_FD, Buf'Address, Integer (Bufn)) then
|
|
Bufn := 0;
|
|
|
|
else
|
|
Set_Standard_Error;
|
|
Write_Str ("fatal error: disk full");
|
|
OS_Exit (2);
|
|
end if;
|
|
end Write_Buffer;
|
|
|
|
----------------
|
|
-- Write_Byte --
|
|
----------------
|
|
|
|
procedure Write_Byte (B : Byte) is
|
|
begin
|
|
Bufn := Bufn + 1;
|
|
Buf (Bufn) := B;
|
|
|
|
if Bufn = Buflen then
|
|
Write_Buffer;
|
|
end if;
|
|
end Write_Byte;
|
|
|
|
end Tree_IO;
|