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by Jens Richnow >> Thu, 22 Jun 2000 0:08:44 GMT

Hi,

for some encoding/decoding routines I need to do lots of bitwise AND operations of two Integers. Since JADE does not have a Byte primitive type and the Binary gives a hexadecimal representation in 4 byte blocks, I ventured to write some methods to achieve this bitwise AND operation. This, however, required four method calls (actually three without the initiating method) and some string manipulations. Therefore, the encoding/decoding of large strings requires some time in JADE. I attach the methods I just below and wonder whether somebody has a better idea with handling bytes and bits in JADE and do operations with them.

Cheers

Jens

The first method sits on the Binary primitive type and the other three can be tested using JadeScript by running the ::bits() method.

Binary::asByte():String updating; //========================================================================== // Purpose: Converts a byte to its binary representation, e.g., 0101010. // Return: Binary representation as String type.
// Created: 21 June 2000 by Jens //========================================================================== vars count :Integer;
byte :Integer;
bits :String;begin

byte := self[1:1].Integer;
foreach count in 7 to 0 step -1 do
if (2 ^ count) <= byte then
bits := bits & "1";
byte := byte - (2 ^ count);
else
bits := bits & "0";
endif;
endforeach;
return bits;
end;

bits() updating; //========================================================================== // Purpose: Converts two Integers in the byte representation and
intiates a
// bitwise comparison.
// Created: 25 May 2000 by Jens. //========================================================================== vars bin1, bin2 :Binary;
int1, int2 :Integer;
str1, str2, str3 :String;begin

read int1;
read int2;
bin1 := int1.Binary;
bin2 := int2.Binary;
str1 := bin1.asByte();
str2 := bin2.asByte();
write str1 & Tab & "= " & bitToInteger(str1).String;
write str2 & Tab & "= " & bitToInteger(str2).String & CrLf;
str3 := bitwiseAND(bin1.asByte, bin2.asByte);
write str3 & Tab & "= " & bitToInteger(str3).String;
end;


bitwiseAND(byte1, byte2:String):String updating; //========================================================================== // Purpose: Bitwise AND comparison of two byte.
// Return: Result.
// Created: 21 June 2000 by Jens //========================================================================== vars bit :Integer;
andBit :String;begin

foreach bit in 1 to 8 do
if byte1[bit:1] = byte2[bit:1] then
if byte1[bit:1] = "1" or byte2[bit:1] = "1" then
andBit := andBit & "1";
else
andBit := andBit & "0";
endif;
else
andBit := andBit & "0";
endif;
endforeach;
return andBit;
end;

byteToInteger(byte:String):Integer updating; //========================================================================== // Purpose: Converts a byte representation to an integer.
// Created: 21 June 2000 by Jens //========================================================================== vars count :Integer;
result :Integer;begin

result := 0;
// Left to right.
foreach count in 1 to 8 do
if count = 1 and byte[count:1] = "1" then
result := result + 128;
elseif count = 2 and byte[count:1] = "1" then
result := result + 64;
elseif count = 3 and byte[count:1] = "1" then
result := result + 32;
elseif count = 4 and byte[count:1] = "1" then
result := result + 16;
elseif count = 5 and byte[count:1] = "1" then
result := result + 8;
elseif count = 6 and byte[count:1] = "1" then
result := result + 4;
elseif count = 7 and byte[count:1] = "1" then
result := result + 2;
elseif count = 8 and byte[count:1] = "1" then
result := result + 1;
endif;
endforeach;
return result;
end;

by Krull >> Thu, 22 Jun 2000 1:13:33 GMT

Hi Jens,

for some encoding/decoding routines I need to do lots of bitwise AND operations of two Integers.

Have you looked at the Integer primitive methods: bitAnd, bitNot, bitOr and BitXor?

Since JADE does not have a Byte primitive
type and the Binary gives a hexadecimal representation in 4 byte blocks,

Yes, since JADE does not have an intrinsic Byte type, each element in a binary variable obtained by subscripting the binary is considered to be an integer by the compiler and interpreter; that means you can use the above Integer bitwise methods directly on each binary element.

by Jens Richnow >> Thu, 22 Jun 2000 1:59:06 GMT

Hi Hugh,

No I havn't before, but did it now. It speeds everything up quite a bit! Sometimes it pays to approach the JADE help from as many angles as possible. So, I had a gooid exercise reinventing the wheel.

Thanks for that

Jens