Overview
| Comment: | smaz: merge verbatim blocks when it improves compression |
|---|---|
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
90bba135f9523785c21af52085404155 |
| User & Date: | nat on 2016-09-16 19:59:10 |
| Other Links: | manifest | tags |
Context
|
2016-09-17
| ||
| 19:15 | smaz: add functions that return directly the filtered array check-in: f85deca432 user: nat tags: trunk | |
|
2016-09-16
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| 19:59 | smaz: merge verbatim blocks when it improves compression check-in: 90bba135f9 user: nat tags: trunk | |
|
2016-09-14
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| 21:44 |
smaz-tests: make round-trip test really a round-trip
Since there are multiple encoded sequence that decompress into the same original string, it is much more important to check that compressed data really decompress into the original data than to check that it matches exactly the expected byte sequence check-in: e2fbcb314b user: nat tags: trunk | |
Changes
Modified src/natools-smaz.adb from [84a6bd2551] to [860a7091a3].
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Template : in String;
Index : out Ada.Streams.Stream_Element;
Length : out Natural);
function To_String (Data : in Ada.Streams.Stream_Element_Array)
return String;
------------------------------
-- Local Helper Subprograms --
------------------------------
function Dict_Entry
(Dict : in Dictionary;
| > > > | 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 |
Template : in String;
Index : out Ada.Streams.Stream_Element;
Length : out Natural);
function To_String (Data : in Ada.Streams.Stream_Element_Array)
return String;
function Verbatim_Size (Dict : Dictionary; Original_Size : Natural)
return Ada.Streams.Stream_Element_Count;
------------------------------
-- Local Helper Subprograms --
------------------------------
function Dict_Entry
(Dict : in Dictionary;
|
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Result (I) := Character'Val (Data
(Data'First + Ada.Streams.Stream_Element_Offset (I - 1)));
end loop;
end return;
end To_String;
----------------------
-- Public Interface --
----------------------
function Compressed_Upper_Bound
(Dict : in Dictionary;
Input : in String)
| > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | < < < < < < < < | < < < < < | 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 |
Result (I) := Character'Val (Data
(Data'First + Ada.Streams.Stream_Element_Offset (I - 1)));
end loop;
end return;
end To_String;
function Verbatim_Size (Dict : Dictionary; Original_Size : Natural)
return Ada.Streams.Stream_Element_Count
is
Verbatim1_Max_Size : constant Ada.Streams.Stream_Element_Count
:= Ada.Streams.Stream_Element_Count
(Ada.Streams.Stream_Element'Last - Dict.Dict_Last)
- Boolean'Pos (Dict.Variable_Length_Verbatim);
Verbatim2_Max_Size : constant Ada.Streams.Stream_Element_Count
:= Ada.Streams.Stream_Element_Count (Ada.Streams.Stream_Element'Last)
+ Verbatim1_Max_Size;
Remaining : Ada.Streams.Stream_Element_Count
:= Ada.Streams.Stream_Element_Count (Original_Size);
Overhead : Ada.Streams.Stream_Element_Count := 0;
begin
if Dict.Variable_Length_Verbatim then
if Remaining >= Verbatim2_Max_Size then
declare
Full_Blocks : constant Ada.Streams.Stream_Element_Count
:= Remaining / Verbatim2_Max_Size;
begin
Overhead := Overhead + 2 * Full_Blocks;
Remaining := Remaining - Verbatim2_Max_Size * Full_Blocks;
end;
end if;
if Remaining > Verbatim1_Max_Size then
Overhead := Overhead + 2;
Remaining := 0;
end if;
end if;
declare
Full_Blocks : constant Ada.Streams.Stream_Element_Count
:= Remaining / Verbatim1_Max_Size;
begin
Overhead := Overhead + Full_Blocks;
end;
return Overhead + Ada.Streams.Stream_Element_Count (Original_Size);
end Verbatim_Size;
----------------------
-- Public Interface --
----------------------
function Compressed_Upper_Bound
(Dict : in Dictionary;
Input : in String)
return Ada.Streams.Stream_Element_Count is
begin
return Verbatim_Size (Dict, Input'Length);
end Compressed_Upper_Bound;
procedure Compress
(Dict : in Dictionary;
Input : in String;
Output_Buffer : out Ada.Streams.Stream_Element_Array;
|
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(Dict,
Input (Input_Index
.. Natural'Min (Input_Index + Dict.Max_Word_Length - 1,
Input'Last)),
Word,
Length);
end Find_Entry;
begin
Output_Last := Output_Buffer'First - 1;
Find_Entry;
Main_Loop :
while Input_Index in Input'Range loop
Data_In_Dict :
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(Dict,
Input (Input_Index
.. Natural'Min (Input_Index + Dict.Max_Word_Length - 1,
Input'Last)),
Word,
Length);
end Find_Entry;
Previous_Verbatim_Beginning : Natural := 0;
Previous_Verbatim_Last : Ada.Streams.Stream_Element_Offset := 0;
begin
Output_Last := Output_Buffer'First - 1;
Find_Entry;
Main_Loop :
while Input_Index in Input'Range loop
Data_In_Dict :
|
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Verbatim_Scan :
while Length = 0 and Input_Index in Input'Range loop
Input_Index := Input_Index + 1;
Find_Entry;
end loop Verbatim_Scan;
Verbatim_Length := Input_Index - Beginning;
Verbatim_Encode :
while Verbatim_Length > 0 loop
if Dict.Variable_Length_Verbatim
and then Verbatim_Length > Verbatim1_Max_Size
then
Block_Length := Natural'Min
| > > > > > > > > > > > > > | 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 |
Verbatim_Scan :
while Length = 0 and Input_Index in Input'Range loop
Input_Index := Input_Index + 1;
Find_Entry;
end loop Verbatim_Scan;
Verbatim_Length := Input_Index - Beginning;
if Previous_Verbatim_Beginning > 0
and then Output_Last + Verbatim_Size (Dict, Verbatim_Length)
> Previous_Verbatim_Last + Verbatim_Size
(Dict, Input_Index - Previous_Verbatim_Beginning)
then
Beginning := Previous_Verbatim_Beginning;
Output_Last := Previous_Verbatim_Last;
Verbatim_Length := Input_Index - Beginning;
else
Previous_Verbatim_Beginning := Beginning;
Previous_Verbatim_Last := Output_Last;
end if;
Verbatim_Encode :
while Verbatim_Length > 0 loop
if Dict.Variable_Length_Verbatim
and then Verbatim_Length > Verbatim1_Max_Size
then
Block_Length := Natural'Min
|
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