[CynicRus]

Не так давно потребовалось распаковать на Delphi файлик сжатый snappy, в связи с чем и была написана данная функция. Работает как в Delphi так и в Lazarus.

Сжатие мне было не нужно, поэтому я его особо не ковырял.

Код:

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procedure SnappyDecompress(Input: TByteArray; Offset,   Length: integer; var Output: TByteArray); var   i, l, o, c,targetIndex,SourceIndex,targetLength: integer;   function incPP(var AVal: integer): integer; begin   result := AVal;   inc(AVal); end;   begin   sourceIndex:=offset;   targetIndex:=0;   targetLength:=0;   i:=0;   repeat      targetLength := targetLength + (input[sourceIndex] and $7f) shl (incPP(i) * 7);    until ((input[incPP(sourceIndex)] and $80) <> $80);    SetLength(Output,targetLength);    while (sourceIndex < offset + length) do     begin       if(targetIndex >= targetLength) then        raise Exception.Create('Superfluous input data encountered on offset '+IntToStr(sourceIndex));         case (input[sourceIndex] and 3) of          0: begin             l := (input[incPP(sourceIndex)] shr 2) and $3f;                   case l of                    60: begin                        l := input[incPP(sourceIndex)] and $ff;                        inc(l);                        end;                    61:                        begin                        l := input[incPP(sourceIndex)] and $ff;                        l := l or ((input[incPP(sourceIndex)]) and $ff);                        inc(l);                        end;                    62:                        begin                        l := input[incPP(sourceIndex)] and $ff;                        l :=l or ((input[IncPP(sourceIndex)] and $ff) shl 8);                        l :=l or ((input[IncPP(sourceIndex)] and $ff) shl 16);                        inc(l);                        end;                    63:                        begin                        l := input[IncPP(sourceIndex)] and $ff;                        l := l or ((input[IncPP(sourceIndex)] and $ff) shl 8);                        l := l or ((input[IncPP(sourceIndex)] and $ff) shl 16);                        l := l or ((input[IncPP(sourceIndex)] and $ff) shl 24);                        inc(l);                        end                    else                        inc(l);                    end;                    Move(Input[sourceIndex],Output[targetIndex],l);                    sourceIndex := sourceIndex + l;                    targetIndex :=targetIndex + l;                end;           1:              begin                l := 4 + ((input[sourceIndex] shr 2) and 7);                o := (input[IncPP(sourceIndex)] and $e0) shl 3;                o := o or (input[incPP(sourceIndex)] and $ff);                if (l < o) then                 begin                   move(output[targetIndex - o],output[targetIndex],l);                   targetIndex:=targetIndex + l;                 end                  else                 begin                   if (o = 1) then                     begin                      FillChar(Output[targetIndex],l,output[targetIndex-l]);                      targetIndex:= targetIndex + l;                     end                     else                     begin                         while (l > 0) do                           begin                             c:= ifthen( L > o, o, l);                               Move(output[targetIndex-o],output[targetIndex],c);                               targetIndex:= targetIndex + c;                               l:= l - c;                           end;                     end;                 end;                end;              2:               begin               l := ((input[IncPP(sourceIndex)] shr 2) and $3f) + 1;               o := input[IncPP(sourceIndex)] and $ff;               o := o or ((input[IncPP(sourceIndex)] and $ff) shl 8);                if (l < o) then                 begin                   move(output[abs(targetIndex - o)],output[targetIndex],l);                   targetIndex:=targetIndex + l;                 end                  else                 begin                   if (o = 1) then                     begin                      FillChar(Output[targetIndex],l,output[targetIndex-l]);                      targetIndex:= targetIndex + l;                     end                     else                     begin                         while (l > 0) do                           begin                             c:= ifthen( L > o, o, l);                               Move(output[targetIndex-o],output[targetIndex],c);                               targetIndex:= targetIndex + c;                               l:= l - c;                           end;                     end;                 end;                end;               3:                begin               l := ((input[IncPP(sourceIndex)] shr 2) and $3f) + 1;               o := input[IncPP(sourceIndex)] and $ff;               o := o or ((input[IncPP(sourceIndex)] and $ff) shl 8);               o := o or ((input[IncPP(sourceIndex)] and $ff) shl 16);               o := o or ((input[IncPP(sourceIndex)] and $ff) shl 24);                if (l < o) then                 begin                   move(output[targetIndex - o],output[targetIndex],l);                   targetIndex:=targetIndex + l;                 end                  else                 begin                   if (o = 1) then                     begin                      FillChar(Output[targetIndex],l,output[targetIndex-l]);                      targetIndex:= targetIndex + l;                     end                     else                     begin                         while (l > 0) do                           begin                               c:= ifthen( L > o, o, l);                               Move(output[targetIndex-o],output[targetIndex],c);                               targetIndex:= targetIndex + c;                               l:= l - c;                           end;                     end;                 end;                end;            end;        end; end;