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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- T R E E _ I O --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2014, 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 --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Debug; use Debug;
with Output; use Output;
with Unchecked_Conversion;
package body Tree_IO is
Debug_Flag_Tree : Boolean := False;
-- Debug flag for debug output from tree read/write
-------------------------------------------
-- Compression Scheme Used for Tree File --
-------------------------------------------
-- We don't just write the data directly, but instead do a mild form
-- of compression, since we expect lots of compressible zeroes and
-- blanks. The compression scheme is as follows:
-- 00nnnnnn followed by nnnnnn bytes (non compressed data)
-- 01nnnnnn indicates nnnnnn binary zero bytes
-- 10nnnnnn indicates nnnnnn ASCII space bytes
-- 11nnnnnn bbbbbbbb indicates nnnnnnnn occurrences of byte bbbbbbbb
-- Since we expect many zeroes in trees, and many spaces in sources,
-- this compression should be reasonably efficient. We can put in
-- something better later on.
-- Note that this compression applies to the Write_Tree_Data and
-- Read_Tree_Data calls, not to the calls to read and write single
-- scalar values, which are written in memory format without any
-- compression.
C_Noncomp : constant := 2#00_000000#;
C_Zeros : constant := 2#01_000000#;
C_Spaces : constant := 2#10_000000#;
C_Repeat : constant := 2#11_000000#;
-- Codes for compression sequences
Max_Count : constant := 63;
-- Maximum data length for one compression sequence
-- The above compression scheme applies only to data written with the
-- Tree_Write routine and read with Tree_Read. Data written using the
-- Tree_Write_Char or Tree_Write_Int routines and read using the
-- corresponding input routines is not compressed.
type Int_Bytes is array (1 .. 4) of Byte;
for Int_Bytes'Size use 32;
function To_Int_Bytes is new Unchecked_Conversion (Int, Int_Bytes);
function To_Int is new Unchecked_Conversion (Int_Bytes, Int);
----------------------
-- Global Variables --
----------------------
Tree_FD : File_Descriptor;
-- File descriptor for tree
Buflen : constant Int := 8_192;
-- Length of buffer for read and write file data
Buf : array (Pos range 1 .. Buflen) of Byte;
-- Read/write file data buffer
Bufn : Nat;
-- Number of bytes read/written from/to buffer
Buft : Nat;
-- Total number of bytes in input buffer containing valid data. Used only
-- for input operations. There is data left to be processed in the buffer
-- if Buft > Bufn. A value of zero for Buft means that the buffer is empty.
-----------------------
-- Local Subprograms --
-----------------------
procedure Read_Buffer;
-- Reads data into buffer, setting Bufn appropriately
function Read_Byte return Byte;
pragma Inline (Read_Byte);
-- Returns next byte from input file, raises Tree_Format_Error if none left
procedure Write_Buffer;
-- Writes out current buffer contents
procedure Write_Byte (B : Byte);
pragma Inline (Write_Byte);
-- Write one byte to output buffer, checking for buffer-full condition
-----------------
-- Read_Buffer --
-----------------
procedure Read_Buffer is
begin
Buft := Int (Read (Tree_FD, Buf (1)'Address, Integer (Buflen)));
if Buft = 0 then
raise Tree_Format_Error;
else
Bufn := 0;
end if;
end Read_Buffer;
---------------
-- Read_Byte --
---------------
function Read_Byte return Byte is
begin
if Bufn = Buft then
Read_Buffer;
end if;
Bufn := Bufn + 1;
return Buf (Bufn);
end Read_Byte;
--------------------
-- Tree_Read_Bool --
--------------------
procedure Tree_Read_Bool (B : out Boolean) is
begin
B := Boolean'Val (Read_Byte);
if Debug_Flag_Tree then
if B then
Write_Str ("True");
else
Write_Str ("False");
end if;
Write_Eol;
end if;
end Tree_Read_Bool;
--------------------
-- Tree_Read_Char --
--------------------
procedure Tree_Read_Char (C : out Character) is
begin
C := Character'Val (Read_Byte);
if Debug_Flag_Tree then
Write_Str ("==> transmitting Character = ");
Write_Char (C);
Write_Eol;
end if;
end Tree_Read_Char;
--------------------
-- Tree_Read_Data --
--------------------
procedure Tree_Read_Data (Addr : Address; Length : Int) is
type S is array (Pos) of Byte;
-- This is a big array, for which we have to suppress the warning
type SP is access all S;
function To_SP is new Unchecked_Conversion (Address, SP);
Data : constant SP := To_SP (Addr);
-- Data buffer to be read as an indexable array of bytes
OP : Pos := 1;
-- Pointer to next byte of data buffer to be read into
B : Byte;
C : Byte;
L : Int;
begin
if Debug_Flag_Tree then
Write_Str ("==> transmitting ");
Write_Int (Length);
Write_Str (" data bytes");
Write_Eol;
end if;
-- Verify data length
Tree_Read_Int (L);
if L /= Length then
Write_Str ("==> transmitting, expected ");
Write_Int (Length);
Write_Str (" bytes, found length = ");
Write_Int (L);
Write_Eol;
raise Tree_Format_Error;
end if;
-- Loop to read data
while OP <= Length loop
-- Get compression control character
B := Read_Byte;
C := B and 2#00_111111#;
B := B and 2#11_000000#;
-- Non-repeat case
if B = C_Noncomp then
if Debug_Flag_Tree then
Write_Str ("==> uncompressed: ");
Write_Int (Int (C));
Write_Str (", starting at ");
Write_Int (OP);
Write_Eol;
end if;
for J in 1 .. C loop
Data (OP) := Read_Byte;
OP := OP + 1;
end loop;
-- Repeated zeroes
elsif B = C_Zeros then
if Debug_Flag_Tree then
Write_Str ("==> zeroes: ");
Write_Int (Int (C));
Write_Str (", starting at ");
Write_Int (OP);
Write_Eol;
end if;
for J in 1 .. C loop
Data (OP) := 0;
OP := OP + 1;
end loop;
-- Repeated spaces
elsif B = C_Spaces then
if Debug_Flag_Tree then
Write_Str ("==> spaces: ");
Write_Int (Int (C));
Write_Str (", starting at ");
Write_Int (OP);
Write_Eol;
end if;
for J in 1 .. C loop
Data (OP) := Character'Pos (' ');
OP := OP + 1;
end loop;
-- Specified repeated character
else -- B = C_Repeat
B := Read_Byte;
if Debug_Flag_Tree then
Write_Str ("==> other char: ");
Write_Int (Int (C));
Write_Str (" (");
Write_Int (Int (B));
Write_Char (')');
Write_Str (", starting at ");
Write_Int (OP);
Write_Eol;
end if;
for J in 1 .. C loop
Data (OP) := B;
OP := OP + 1;
end loop;
end if;
end loop;
-- At end of loop, data item must be exactly filled
if OP /= Length + 1 then
raise Tree_Format_Error;
end if;
end Tree_Read_Data;
--------------------------
-- Tree_Read_Initialize --
--------------------------
procedure Tree_Read_Initialize (Desc : File_Descriptor) is
begin
Buft := 0;
Bufn := 0;
Tree_FD := Desc;
Debug_Flag_Tree := Debug_Flag_5;
end Tree_Read_Initialize;
-------------------
-- Tree_Read_Int --
-------------------
procedure Tree_Read_Int (N : out Int) is
N_Bytes : Int_Bytes;
begin
for J in 1 .. 4 loop
N_Bytes (J) := Read_Byte;
end loop;
N := To_Int (N_Bytes);
if Debug_Flag_Tree then
Write_Str ("==> transmitting Int = ");
Write_Int (N);
Write_Eol;
end if;
end Tree_Read_Int;
-------------------
-- Tree_Read_Str --
-------------------
procedure Tree_Read_Str (S : out String_Ptr) is
N : Nat;
begin
Tree_Read_Int (N);
S := new String (1 .. Natural (N));
Tree_Read_Data (S.all (1)'Address, N);
end Tree_Read_Str;
-------------------------
-- Tree_Read_Terminate --
-------------------------
procedure Tree_Read_Terminate is
begin
-- Must be at end of input buffer, so we should get Tree_Format_Error
-- if we try to read one more byte, if not, we have a format error.
declare
B : Byte;
pragma Warnings (Off, B);
begin
B := Read_Byte;
exception
when Tree_Format_Error => return;
end;
raise Tree_Format_Error;
end Tree_Read_Terminate;
---------------------
-- Tree_Write_Bool --
---------------------
procedure Tree_Write_Bool (B : Boolean) is
begin
if Debug_Flag_Tree then
Write_Str ("==> transmitting Boolean = ");
if B then
Write_Str ("True");
else
Write_Str ("False");
end if;
Write_Eol;
end if;
Write_Byte (Boolean'Pos (B));
end Tree_Write_Bool;
---------------------
-- Tree_Write_Char --
---------------------
procedure Tree_Write_Char (C : Character) is
begin
if Debug_Flag_Tree then
Write_Str ("==> transmitting Character = ");
Write_Char (C);
Write_Eol;
end if;
Write_Byte (Character'Pos (C));
end Tree_Write_Char;
---------------------
-- Tree_Write_Data --
---------------------
procedure Tree_Write_Data (Addr : Address; Length : Int) is
type S is array (Pos) of Byte;
-- This is a big array, for which we have to suppress the warning
type SP is access all S;
function To_SP is new Unchecked_Conversion (Address, SP);
Data : constant SP := To_SP (Addr);
-- Pointer to data to be written, converted to array type
IP : Pos := 1;
-- Input buffer pointer, next byte to be processed
NC : Nat range 0 .. Max_Count := 0;
-- Number of bytes of non-compressible sequence
C : Byte;
procedure Write_Non_Compressed_Sequence;
-- Output currently collected sequence of non-compressible data
-----------------------------------
-- Write_Non_Compressed_Sequence --
-----------------------------------
procedure Write_Non_Compressed_Sequence is
begin
if NC > 0 then
Write_Byte (C_Noncomp + Byte (NC));
if Debug_Flag_Tree then
Write_Str ("==> uncompressed: ");
Write_Int (NC);
Write_Str (", starting at ");
Write_Int (IP - NC);
Write_Eol;
end if;
for J in reverse 1 .. NC loop
Write_Byte (Data (IP - J));
end loop;
NC := 0;
end if;
end Write_Non_Compressed_Sequence;
-- Start of processing for Tree_Write_Data
begin
if Debug_Flag_Tree then
Write_Str ("==> transmitting ");
Write_Int (Length);
Write_Str (" data bytes");
Write_Eol;
end if;
-- We write the count at the start, so that we can check it on
-- the corresponding read to make sure that reads and writes match
Tree_Write_Int (Length);
-- Conversion loop
-- IP is index of next input character
-- NC is number of non-compressible bytes saved up
loop
-- If input is completely processed, then we are all done
if IP > Length then
Write_Non_Compressed_Sequence;
return;
end if;
-- Test for compressible sequence, must be at least three identical
-- bytes in a row to be worthwhile compressing.
if IP + 2 <= Length
and then Data (IP) = Data (IP + 1)
and then Data (IP) = Data (IP + 2)
then
Write_Non_Compressed_Sequence;
-- Count length of new compression sequence
C := 3;
IP := IP + 3;
while IP < Length
and then Data (IP) = Data (IP - 1)
and then C < Max_Count
loop
C := C + 1;
IP := IP + 1;
end loop;
-- Output compression sequence
if Data (IP - 1) = 0 then
if Debug_Flag_Tree then
Write_Str ("==> zeroes: ");
Write_Int (Int (C));
Write_Str (", starting at ");
Write_Int (IP - Int (C));
Write_Eol;
end if;
Write_Byte (C_Zeros + C);
elsif Data (IP - 1) = Character'Pos (' ') then
if Debug_Flag_Tree then
Write_Str ("==> spaces: ");
Write_Int (Int (C));
Write_Str (", starting at ");
Write_Int (IP - Int (C));
Write_Eol;
end if;
Write_Byte (C_Spaces + C);
else
if Debug_Flag_Tree then
Write_Str ("==> other char: ");
Write_Int (Int (C));
Write_Str (" (");
Write_Int (Int (Data (IP - 1)));
Write_Char (')');
Write_Str (", starting at ");
Write_Int (IP - Int (C));
Write_Eol;
end if;
Write_Byte (C_Repeat + C);
Write_Byte (Data (IP - 1));
end if;
-- No compression possible here
else
-- Output non-compressed sequence if at maximum length
if NC = Max_Count then
Write_Non_Compressed_Sequence;
end if;
NC := NC + 1;
IP := IP + 1;
end if;
end loop;
end Tree_Write_Data;
---------------------------
-- Tree_Write_Initialize --
---------------------------
procedure Tree_Write_Initialize (Desc : File_Descriptor) is
begin
Bufn := 0;
Tree_FD := Desc;
Set_Standard_Error;
Debug_Flag_Tree := Debug_Flag_5;
end Tree_Write_Initialize;
--------------------
-- Tree_Write_Int --
--------------------
procedure Tree_Write_Int (N : Int) is
N_Bytes : constant Int_Bytes := To_Int_Bytes (N);
begin
if Debug_Flag_Tree then
Write_Str ("==> transmitting Int = ");
Write_Int (N);
Write_Eol;
end if;
for J in 1 .. 4 loop
Write_Byte (N_Bytes (J));
end loop;
end Tree_Write_Int;
--------------------
-- Tree_Write_Str --
--------------------
procedure Tree_Write_Str (S : String_Ptr) is
begin
Tree_Write_Int (S'Length);
Tree_Write_Data (S (1)'Address, S'Length);
end Tree_Write_Str;
--------------------------
-- 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;