BPHYS files spécifications I've been trying to write out particles cache files from Houdini to Blender.

I successfully exported a sequence of bphys file, which Blender loads fine. the code is roughly ( in python ): 

    dataType = 1
    nParticles = npoints
    data = struct.pack("8c","B","P","H","Y","S","I","C","S")
    data += struct.pack("III",dataType,nParticles,31) # I don't understand that 31 ...

    for i in range(nParticles):        
        #index 
        data += struct.pack('I',idList[i]) 
        #Location
        data += struct.pack('fff',positionList[i][0], positionList[i][2]*-1, positionList[i][1]) 
        #Velocity
        data += struct.pack('fff',velocityList[i][0], velocityList[i][2]*-1, velocityList[i][1]) 
        #Rotation
        data += struct.pack('ffff',0.0,0.0,0.0,0.0) ## no values for now
        #Avelocity
        data += struct.pack('fff',5.0,10.0,0.5) ## no values for now


This code runs for every frame in the animation.
Lastly, I write the very first bphys file ( with 6 padded zeros) "filename_000000_00.bphys" , containing a list of all the particles 'times' in the simulation, with the good header data.

dataType = 1
nParticles = len(particlesList)
data = struct.pack("8c","B","P","H","Y","S","I","C","S")
data += struct.pack("III",dataType,nParticles,64)

for particle in particlesList:    
    data += struct.pack('fff', particle['birth'], particle['death'], particle['lifetime'])


Now, that's a good first step. Althought I haven't been able to see any Angular velocity in blender; Location and Velocity are read fine.

One of the key parameters I would love to export from Houdini, is the scale parameter. But I have no idea how to add this value to the bphys file. 
I tried to add a float to the "collection" , of course it doesn't work.  I must have to change something in the header. This "31" value seems to correspond to the amount of data per particles. 
There seems to be a lot of different possible values for this parameter. How can I find some informations about that ? ( if possible without having to dive into C++ source code, which I tried )

I feel like I'm almost there 

I need some light ^^
not sure if you found a solution, but here is python script, that reads and writes  bphys data

https://blenderartists.org/forum/showthread.php?318831-Point-Cache-Doctor-script

via phonybone 
and here is nice solution via kram1032

Can I access the particle system through Python to build custom simulations?