B4J Question Concatenate Byte Arrays

[barx]

Hi,

I have put this in b4j as it is what I am currently working in, but I'm sure it will be same for b4a.

I get some data through serial. I need to pluck out certain bytes and use them as part of a larger byte array stream later. So I do:

Dim mask() As Byte = Array As Byte(serial(9), serial(10), serial(11), serial(12), serial(13), serial(14), serial(15), serial(16), serial(17), serial(18))

This works fine.
As I said I then need to build a larger stream to send back out by concatenating, but I cannot seem to get it to work.

I have tried a few things including

astream.Write(Array As Byte(0x55, 0xaa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x0a, mask))

and

astream.Write(Array As Byte(0x55, 0xaa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x0a) & mask)

 

[stevel05]

You could try this : https://www.b4x.com/android/forum/threads/jslbytearraybuffer.39092/

 

[stevel05]

Although if you don't need to build a new array, would it not work sending two arrays:

astream.Write(Array As Byte(0x55, 0xaa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x0a))

astream.Write(mask)

 

[barx]

Although if you don't need to build a new array, would it not work sending two arrays:

astream.Write(Array As Byte(0x55, 0xaa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x0a))

astream.Write(mask)

I don't think it will work as it is 1 command> I don't have control of the other side.

Also, a note. I need to do this in a fashion that will also be possible in b4r as the project is eventually destined for a ESP8266 board. This (b4j) is just the testing stage.

Thanks so far

 

[stevel05]

Ah OK, I don't know what is avallable underlying B4r. The only way I can think of to do it using only arrays is to Dim the array big enough to hold all of the data and copy each byte from both arrays into the correct position.

Dim arr1() As Byte = Array As Byte(0x55, 0xaa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x0a)
    'Dim arr2() As Byte =  Array As Byte(serial(9), serial(10), serial(11), serial(12), serial(13), serial(14), serial(15), serial(16), serial(17), serial(18))
    Dim arr2() As Byte = Array As Byte(0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a)

    Dim arr(arr1.Length + arr2.Length) As Byte
    For i = 0 To arr1.length -1
        arr(i) = arr1(i)
    Next
    For j = 0 To arr2.length - 1
        arr(i+j) = arr2(j)
    Next

    For i = 0 To arr.Length - 1
        Log(arr(i))
    Next

That should work on all flavours, but it creates a new array which may be an issue if memory is tight and the arrays are large.

 

[stevel05]

Apparently B4r has a joinbytes keyword : https://www.b4x.com/android/forum/threads/strings-and-bytes.66729/#content

So you could emulate that using a sub in B4j for testing

 

[Erel]

You can use ByteConverter.ArrayCopy to copy arrays of bytes. It will be faster.

I recommend you to go over this code: https://www.b4x.com/android/forum/threads/b4x-class-mjpeg-decoder.73702/#content
It copies the data to a large buffer and uses a global variable to mark the data length. There is also code to "trim" the array. This means that it removes a complete message from the array and move all the other data to the beginning of the array.

 

[barx]

You can use ByteConverter.ArrayCopy to copy arrays of bytes. It will be faster.

I recommend you to go over this code: https://www.b4x.com/android/forum/threads/b4x-class-mjpeg-decoder.73702/#content
It copies the data to a large buffer and uses a global variable to mark the data length. There is also code to "trim" the array. This means that it removes a complete message from the array and move all the other data to the beginning of the array.

I was looking at that Erel but couldn't see anything that suggested ByteConverter was supported by b4r.

I suppose even if it isn't, I can change to the JoinBytes as suggested by @stevel05 above.

cheers

 

[Erel]

It is better to start a new thread for this in B4R forum. Arduino is very different.