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Comment:smaz_implementations-base_64: rewrite variable-length verbatim code

At some point in the development I changed the base-64 scheme, but failed to propagate it everywhere. Mostly I intend to use only one mode in base-64, and the other one is merely a place-holder, which explains how it got neglected. Now at least it works, even if it's useless.

Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 210677c0612ba94cc105be42f18c5d010cd089f7
User & Date: nat on 2017-01-07 22:53:28
Other Links: manifest | tags
Context
2017-01-27
20:44
tools/timekey: refactor command-line argument processing check-in: f9d3f1aa38 user: nat tags: trunk
2017-01-07
22:53
smaz_implementations-base_64: rewrite variable-length verbatim code

At some point in the development I changed the base-64 scheme, but failed to propagate it everywhere. Mostly I intend to use only one mode in base-64, and the other one is merely a place-holder, which explains how it got neglected. Now at least it works, even if it's useless. check-in: 210677c061 user: nat tags: trunk

2017-01-06
22:44
smaz_tests: add a test for base-64 variable-length verbatim check-in: 3e04c004e7 user: nat tags: trunk
Changes
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Modified src/natools-smaz_implementations-base_64.adb from [1a162cf272] to [de5cce5c1a].

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   begin
      Tools.Next_Digit (Input, Offset, Code);

      if Code <= Last_Code then
         Verbatim_Length := 0;

      elsif Variable_Length_Verbatim then
         if Code < 63 then
         Verbatim_Length := 64 - Natural (Code);
            Verbatim_Length := 63 - Natural (Code);
         else
            Tools.Next_Digit (Input, Offset, Code);
            Verbatim_Length := Natural (Code) + 63 - Natural (Last_Code);
         end if;
         Code := 0;

      elsif Code = 63 then
         Tools.Next_Digit (Input, Offset, Code);
         Verbatim_Length := Natural (Code) * 3 + 3;
         Code := 0;
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     (Input_Length : in Positive;
      Last_Code : in Natools.Smaz_Implementations.Base_64_Tools.Base_64_Digit;
      Variable_Length_Verbatim : in Boolean)
     return Ada.Streams.Stream_Element_Count is
   begin
      if Variable_Length_Verbatim then
         declare
            Largest_Single : constant Positive := 62 - Natural (Last_Code);
            Largest_Run : constant Positive := 63 - Natural (Last_Code);
            Run_Count : constant Positive
            Largest_Run : constant Positive := 64 + Largest_Single;
            Run_Count : constant Natural
              := (Input_Length + Largest_Run - 1) / Largest_Run;
            Last_Run_Size : constant Positive
              := Input_Length - (Run_Count - 1) * Largest_Run;
            Last_Run_Header_Size : constant Ada.Streams.Stream_Element_Count
              := (if Last_Run_Size > Largest_Single then 2 else 1);
         begin
            return Ada.Streams.Stream_Element_Count (Run_Count - 1)
                    * (Tools.Image_Length (Largest_Run) + 1)
                 + Tools.Image_Length (Last_Run_Size) + 1;
            return Ada.Streams.Stream_Element_Count (Run_Count)
                    * (Tools.Image_Length (Largest_Run) + 2)
                 + Tools.Image_Length (Last_Run_Size) + Last_Run_Header_Size;
         end;
      else
         declare
            Largest_Prefix : constant Natural
              := (case Input_Length mod 3 is
                  when 1 => 15 * 3 + 1,
                  when 2 => ((62 - Natural (Last_Code)) * 4 - 1) * 3 + 2,
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      Last_Code : in Natools.Smaz_Implementations.Base_64_Tools.Base_64_Digit;
      Variable_Length_Verbatim : in Boolean)
   is
      Index : Positive := Input'First;
   begin
      if Variable_Length_Verbatim then
         declare
            Largest_Single : constant Positive := 62 - Natural (Last_Code);
            Largest_Run : constant Positive := 63 - Natural (Last_Code);
            Length, Last : Positive;
            Largest_Run : constant Positive := 64 + Largest_Single;
            Length, Last : Natural;
         begin
            while Index in Input'Range loop
               Length := Positive'Min (Largest_Run, Input'Last + 1 - Index);
               Last := Index + Length - 1;
               Output (Offset)
                 := Tools.Image (63 - Tools.Base_64_Digit (Length - 1));
               Offset := Offset + 1;
               Tools.Encode (Input (Index .. Last), Output, Offset);
               Index := Last + 1;

               if Length > Largest_Single then
                  Write_Code (Output, Offset, 63);
                  Write_Code
                    (Output, Offset,
                     Tools.Base_64_Digit (Length - Largest_Single - 1));
               else
                  Write_Code
                    (Output, Offset,
                     Tools.Base_64_Digit (63 - Length));
               end if;

               if Length mod 3 = 1 then
                  Tools.Encode_Single (Input (Index), 0, Output, Offset);
                  Index := Index + 1;
                  Length := Length - 1;
               elsif Length mod 3 = 2 then
                  Tools.Encode_Double
                    (Input (Index .. Index + 1), 0, Output, Offset);
                  Index := Index + 2;
                  Length := Length - 2;
               end if;

               if Length > 0 then
                  Last := Index + Length - 1;
                  Tools.Encode (Input (Index .. Last), Output, Offset);
                  Index := Last + 1;
               end if;
            end loop;
         end;
      else
         if Input'Length mod 3 = 1 then
            declare
               Extra_Blocks : constant Natural
                 := Natural'Min (15, Input'Length / 3);
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