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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;
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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;
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)
return Ada.Streams.Stream_Element_Count
is
Verbatim1_Max_Size : constant Natural
:= Natural (Ada.Streams.Stream_Element'Last - Dict.Dict_Last)
- Boolean'Pos (Dict.Variable_Length_Verbatim);
Verbatim2_Max_Size : constant Natural
:= Natural (Ada.Streams.Stream_Element'Last)
+ Verbatim1_Max_Size;
begin
if Dict.Variable_Length_Verbatim then
return Ada.Streams.Stream_Element_Count (Input'Length
+ 2 * (Input'Length + Verbatim2_Max_Size - 1) / Verbatim2_Max_Size);
else
return Ada.Streams.Stream_Element_Count (Input'Length
+ (Input'Length + Verbatim1_Max_Size - 1) / Verbatim1_Max_Size);
end if;
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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;
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
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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;
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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