Android Question How to write an array of floats to a File

[GiovanniPolese]

Hi to All. Maybe it is a silly question, but I don't see a way to write an array of floats to the disk. The File object doesn't contain a method for this. The need for using low level functions is related to efficiency. I'll describe the problem first, to explain from where the need of low level I/O functions arises.
I have a map with objects of the folllowing type:

Type VertexData(changed As Boolean, vertexList As List, vertexArray() As Float, beginIndices(4) As Int, endIndices(4) As Int)

I save/load this maps with RandomAccessFile.

'
' mData is a Map  with key "color" and value  a VertexData object
'
'
private Sub UtSave(raf As RandomAccessFile,mData As Map,pos As Long) As Long
    
    raf.WriteInt(mData.Size,pos)            ' cannot use directly  raf.WriteObject(mData,true,pos); App is compiled but crashes saying that mData contains "primitives" 
    pos=pos+4                                      ' so I save the map size and each component 
    For Each color As Int In mData.Keys  ' 
        raf.WriteInt(color,pos)
        pos=pos+4
        raf.WriteObject(mData.Get(color),True,pos)  '  mData.Get(color) is a VertexData object
        pos=raf.CurrentPosition
    Next
    return pos
end sub
'' calling function
'
pos=UtSave(raf,ldata.pointMap,pos)
'

The problem arises because vertexArray is huge and the App takes minutes to save/load various tens of Mb, most of them floats contained in the vertexArray of each vertexData object. My idea was to use FILE object, but It only allows to write/read bytes arrays, Lists, Maps etc, and of course, it doesn't manage the whole Map of vertexData objects...
Thanks in advance for any hint

 

[Sagenut]

You need to convert your map to bytes with B4XSerializator.Convertobjecttobytes and save the file as bytes.
Then you will read it back to a map with Convertbytestoobject.
I can't make you an example because I am not in front of pc.
But at least you have a hint what to search in the forum.

 

[GiovanniPolese]

You need to convert your map to bytes with B4XSerializator.Convertobjecttobytes and save the file as bytes.
Then you will read it back to a map with Convertbytestoobject.
I can't make you an example because I am not in front of pc.
But at least you have a hint what to search in the forum.

Thanks, but it seems that Serializator fails to convert the whole map too, as long as the B4XWriteObject fails. Topics are related. As a matter of fact, my vertexData object, which is a component of the Map, is a custom object containing one list, one array of floats and two arrays of ints. I guess that this is the reason of failure. Anyway, I am finding an apparently efficient solution. As a matter of fact, I think that using File is anyway much faster than using RandomAccesFile. Therefore I am converting the arrays to lists (with AddAll which is very useful). Then I save the List with File.WriteList. It seems an acceptable solution. Same work is done in 4 secs instead of 38 sec. Of course, as a C/C++ programmer I would like to work at lower level to achieve maximum speed, but maybe what I am doing is enough. The fact is that I really have big data, forced to be in Arrays because they feed OpenGL engine. Thanks for attention.

 

[Sagenut]

Took from another thread

Dim serializator As B4XSerializator
Dim byte_array as byte()=serializator.ConvertObjectToBytes(YourMapHere)
Dim out As OutputStream=File.OpenOutput(File.DirApp,"aaa_test_serializzazione.txt",False)
out.WriteBytes(byte_array,0,byte_array.Length)
out.Close

 

[GiovanniPolese]

Dim byte_array as byte()=serializator.ConvertObjectToBytes(YourMapHere)

As I wrote in previous message, if I try to convert the Map, App crashes with:

java.lang.RuntimeException: java.lang.RuntimeException: java.lang.RuntimeException: This method does not support arrays of primitives.

At this point, I have leaved up ... this the beginning of my problems... My Map object cannot be converted ..

 

[Sagenut]

Try converting the array into List if possible.

 

[GiovanniPolese]

Try converting the array into List if possible.

Yes. It is what I am doing. See my first reply to you. Much probably I will resolve the problem by myself, now. The doubt still remain whether there could be a more efficient solution. Maybe using native Java etc.. Thanks for your attention.