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Overview
| Comment: | smaz_generic: new package attempting generic Smaz-like compression |
|---|---|
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
4b73acb2a8e38f012c38be461007808f |
| User & Date: | nat 2016-11-13 21:42:05 |
Context
|
2016-11-14
| ||
| 20:19 | smaz_implementations-base_256: component to instantiate standard Smaz check-in: b13d7f70e3 user: nat tags: trunk | |
|
2016-11-13
| ||
| 21:42 | smaz_generic: new package attempting generic Smaz-like compression check-in: 4b73acb2a8 user: nat tags: trunk | |
|
2016-11-12
| ||
| 20:15 | tools/smaz: use variable length verbatim option on built dictionaries check-in: 33d57890f4 user: nat tags: trunk | |
Changes
Added src/natools-smaz_generic.adb.
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------------------------------------------------------------------------------
-- Copyright (c) 2016, Natacha Porté --
-- --
-- Permission to use, copy, modify, and distribute this software for any --
-- purpose with or without fee is hereby granted, provided that the above --
-- copyright notice and this permission notice appear in all copies. --
-- --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. --
------------------------------------------------------------------------------
package body Natools.Smaz_Generic is
use type Ada.Streams.Stream_Element_Offset;
procedure Find_Entry
(Dict : in Dictionary;
Template : in String;
Code : out Dictionary_Code;
Length : out Natural);
-- Try to find the longest entry in Dict that is a prefix of Template,
-- setting Length to 0 when no such entry exists.
function Verbatim_Size
(Dict : in Dictionary;
Length : in Positive)
return Ada.Streams.Stream_Element_Count
is (Verbatim_Size (Length, Dict.Last_Code, Dict.Variable_Length_Verbatim));
-- Wrapper around the formal Verbatim_Size
------------------------------
-- Local Helper Subprograms --
------------------------------
procedure Find_Entry
(Dict : in Dictionary;
Template : in String;
Code : out Dictionary_Code;
Length : out Natural)
is
N : Natural;
Is_Valid : Boolean;
begin
Length := 0;
for Last in reverse Template'Range loop
Is_Valid := False;
N := Dict.Hash (Template (Template'First .. Last));
To_Code :
begin
Code := Dictionary_Code'Val (N);
if Is_Valid_Code (Dict, Code) then
Is_Valid := True;
end if;
exception
when Constraint_Error => null;
end To_Code;
if Is_Valid
and then Dict_Entry (Dict, Code) = Template (Template'First .. Last)
then
Length := 1 + Last - Template'First;
return;
end if;
end loop;
end Find_Entry;
----------------------
-- Public Interface --
----------------------
function Compressed_Upper_Bound
(Dict : in Dictionary;
Input : in String)
return Ada.Streams.Stream_Element_Count is
begin
return Verbatim_Size
(Input'Length, Dict.Last_Code, Dict.Variable_Length_Verbatim);
end Compressed_Upper_Bound;
procedure Compress
(Dict : in Dictionary;
Input : in String;
Output_Buffer : out Ada.Streams.Stream_Element_Array;
Output_Last : out Ada.Streams.Stream_Element_Offset)
is
procedure Find_Current_Entry;
Input_Index : Positive := Input'First;
Length : Natural;
Code : Dictionary_Code;
Output_Index : Ada.Streams.Stream_Element_Offset;
procedure Find_Current_Entry is
begin
Find_Entry
(Dict,
Input (Input_Index
.. Natural'Min (Input_Index + Dict.Max_Word_Length - 1,
Input'Last)),
Code,
Length);
end Find_Current_Entry;
Previous_Verbatim_Beginning : Natural := 0;
Previous_Verbatim_Index : Ada.Streams.Stream_Element_Offset := 0;
begin
Output_Index := Output_Buffer'First;
Find_Current_Entry;
Main_Loop :
while Input_Index in Input'Range loop
Data_In_Dict :
while Length > 0 loop
Write_Code (Output_Buffer, Output_Index, Code);
Input_Index := Input_Index + Length;
exit Main_Loop when Input_Index not in Input'Range;
Find_Current_Entry;
end loop Data_In_Dict;
Verbatim_Block :
declare
Beginning : Positive := Input_Index;
Verbatim_Length : Natural;
begin
Verbatim_Scan :
while Length = 0 and Input_Index in Input'Range loop
Input_Index := Input_Index + 1;
Find_Current_Entry;
end loop Verbatim_Scan;
Verbatim_Length := Input_Index - Beginning;
if Previous_Verbatim_Beginning > 0
and then Output_Index + Verbatim_Size (Dict, Verbatim_Length)
>= Previous_Verbatim_Index + Verbatim_Size
(Dict, Input_Index - Previous_Verbatim_Beginning)
then
Beginning := Previous_Verbatim_Beginning;
Output_Index := Previous_Verbatim_Index;
Verbatim_Length := Input_Index - Beginning;
else
Previous_Verbatim_Beginning := Beginning;
Previous_Verbatim_Index := Output_Index;
end if;
Write_Verbatim
(Output_Buffer, Output_Index,
Input (Beginning .. Input_Index - 1),
Dict.Last_Code, Dict.Variable_Length_Verbatim);
end Verbatim_Block;
end loop Main_Loop;
Output_Last := Output_Index - 1;
end Compress;
function Compress (Dict : in Dictionary; Input : in String)
return Ada.Streams.Stream_Element_Array
is
Result : Ada.Streams.Stream_Element_Array
(1 .. Compressed_Upper_Bound (Dict, Input));
Last : Ada.Streams.Stream_Element_Offset;
begin
Compress (Dict, Input, Result, Last);
return Result (Result'First .. Last);
end Compress;
function Decompressed_Length
(Dict : in Dictionary;
Input : in Ada.Streams.Stream_Element_Array)
return Natural
is
Result : Natural := 0;
Input_Index : Ada.Streams.Stream_Element_Offset := Input'First;
Code : Dictionary_Code;
Verbatim_Length : Natural;
begin
while Input_Index in Input'Range loop
Read_Code
(Input, Input_Index,
Code, Verbatim_Length,
Dict.Last_Code, Dict.Variable_Length_Verbatim);
if Verbatim_Length > 0 then
Skip_Verbatim (Input, Input_Index, Verbatim_Length);
Result := Result + Verbatim_Length;
else
Result := Result + Dict_Entry_Length (Dict, Code);
end if;
end loop;
return Result;
end Decompressed_Length;
procedure Decompress
(Dict : in Dictionary;
Input : in Ada.Streams.Stream_Element_Array;
Output_Buffer : out String;
Output_Last : out Natural)
is
Input_Index : Ada.Streams.Stream_Element_Offset := Input'First;
Code : Dictionary_Code;
Verbatim_Length : Natural;
begin
Output_Last := Output_Buffer'First - 1;
while Input_Index in Input'Range loop
Read_Code
(Input, Input_Index,
Code, Verbatim_Length,
Dict.Last_Code, Dict.Variable_Length_Verbatim);
if Verbatim_Length > 0 then
Read_Verbatim
(Input, Input_Index,
Output_Buffer
(Output_Last + 1 .. Output_Last + Verbatim_Length));
Output_Last := Output_Last + Verbatim_Length;
else
declare
Decoded : constant String := Dict_Entry (Dict, Code);
begin
Output_Buffer (Output_Last + 1 .. Output_Last + Decoded'Length)
:= Decoded;
Output_Last := Output_Last + Decoded'Length;
end;
end if;
end loop;
end Decompress;
function Decompress
(Dict : in Dictionary; Input : in Ada.Streams.Stream_Element_Array)
return String
is
Result : String (1 .. Decompressed_Length (Dict, Input));
Last : Natural;
begin
Decompress (Dict, Input, Result, Last);
pragma Assert (Last = Result'Last);
return Result;
end Decompress;
end Natools.Smaz_Generic;
|
Added src/natools-smaz_generic.ads.
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------------------------------------------------------------------------------
-- Copyright (c) 2016, Natacha Porté --
-- --
-- Permission to use, copy, modify, and distribute this software for any --
-- purpose with or without fee is hereby granted, provided that the above --
-- copyright notice and this permission notice appear in all copies. --
-- --
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES --
-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. --
------------------------------------------------------------------------------
with Ada.Streams;
generic
type Dictionary_Code is (<>);
with procedure Read_Code
(Input : in Ada.Streams.Stream_Element_Array;
Offset : in out Ada.Streams.Stream_Element_Offset;
Code : out Dictionary_Code;
Verbatim_Length : out Natural;
Last_Code : in Dictionary_Code;
Variable_Length_Verbatim : in Boolean);
with procedure Read_Verbatim
(Input : in Ada.Streams.Stream_Element_Array;
Offset : in out Ada.Streams.Stream_Element_Offset;
Output : out String);
with procedure Skip_Verbatim
(Input : in Ada.Streams.Stream_Element_Array;
Offset : in out Ada.Streams.Stream_Element_Offset;
Verbatim_Length : in Positive);
with function Verbatim_Size
(Input_Length : in Positive;
Last_Code : in Dictionary_Code;
Variable_Length_Verbatim : in Boolean)
return Ada.Streams.Stream_Element_Count;
with procedure Write_Code
(Output : in out Ada.Streams.Stream_Element_Array;
Offset : in out Ada.Streams.Stream_Element_Offset;
Code : in Dictionary_Code);
with procedure Write_Verbatim
(Output : in out Ada.Streams.Stream_Element_Array;
Offset : in out Ada.Streams.Stream_Element_Offset;
Input : in String;
Last_Code : in Dictionary_Code;
Variable_Length_Verbatim : in Boolean);
package Natools.Smaz_Generic is
pragma Pure;
type Offset_Array is array (Dictionary_Code range <>) of Positive;
type Dictionary
(Last_Code : Dictionary_Code;
Values_Last : Natural)
is record
Variable_Length_Verbatim : Boolean;
Max_Word_Length : Positive;
Offsets : Offset_Array
(Dictionary_Code'Succ (Dictionary_Code'First) .. Last_Code);
Values : String (1 .. Values_Last);
Hash : not null access function (Value : String) return Natural;
end record
with Dynamic_Predicate =>
(for all Code in Dictionary.Offsets'Range
=> Dictionary.Offsets (Code) in Dictionary.Values'Range)
and then (for all Code in Dictionary_Code'First .. Dictionary.Last_Code
=> Code_Last (Dictionary.Offsets, Code, Dictionary.Values'Last) + 1
- Code_First (Dictionary.Offsets, Code, Dictionary.Values'First)
in 1 .. Dictionary.Max_Word_Length);
function Code_First
(Offsets : in Offset_Array;
Code : in Dictionary_Code;
Fallback : in Positive)
return Positive
is (if Code in Offsets'Range then Offsets (Code) else Fallback);
-- Return the first index of the value for Code in Dictionary.Values
function Code_Last
(Offsets : in Offset_Array;
Code : in Dictionary_Code;
Fallback : in Natural)
return Natural
is (if Dictionary_Code'Succ (Code) in Offsets'Range
then Offsets (Dictionary_Code'Succ (Code)) - 1
else Fallback);
-- Return the value index of the value for Code in Dictionary.Values
function Is_Valid_Code
(Dict : in Dictionary;
Code : in Dictionary_Code)
return Boolean
is (Code in Dictionary_Code'First .. Dict.Last_Code);
-- Return whether Code exists in Dict
function Dict_Entry
(Dict : in Dictionary;
Code : in Dictionary_Code)
return String
is (Dict.Values (Code_First (Dict.Offsets, Code, Dict.Values'First)
.. Code_Last (Dict.Offsets, Code, Dict.Values'Last)))
with Pre => Is_Valid_Code (Dict, Code);
-- Return the string for at the given Index in Dict
function Dict_Entry_Length
(Dict : in Dictionary;
Code : in Dictionary_Code)
return Positive
is (1 + Code_Last (Dict.Offsets, Code, Dict.Values'Last)
- Code_First (Dict.Offsets, Code, Dict.Values'First))
with Pre => Is_Valid_Code (Dict, Code);
-- Return the length of the string for at the given Index in Dict
function Compressed_Upper_Bound
(Dict : in Dictionary;
Input : in String)
return Ada.Streams.Stream_Element_Count;
-- Return the maximum number of bytes needed to encode Input
procedure Compress
(Dict : in Dictionary;
Input : in String;
Output_Buffer : out Ada.Streams.Stream_Element_Array;
Output_Last : out Ada.Streams.Stream_Element_Offset);
-- Encode Input into Output_Buffer
function Compress (Dict : in Dictionary; Input : in String)
return Ada.Streams.Stream_Element_Array;
-- Return an encoded buffer for Input
function Decompressed_Length
(Dict : in Dictionary;
Input : in Ada.Streams.Stream_Element_Array)
return Natural;
-- Return the exact length when Input is decoded
procedure Decompress
(Dict : in Dictionary;
Input : in Ada.Streams.Stream_Element_Array;
Output_Buffer : out String;
Output_Last : out Natural);
-- Decode Input into Output_Buffer
function Decompress
(Dict : in Dictionary; Input : in Ada.Streams.Stream_Element_Array)
return String;
-- Return a decoded buffer for Input
end Natools.Smaz_Generic;
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