Reworking "c things" like static const unsigned char clcidx[19] =

[Hlaaftana]

I don't know why the hex literals above high(int32) are locked into int64 but 
you do not have to parse hex strings here, you can just use an array of int64:
    
    
    var tab: array[16, uint32]
    for i, v in [0x00000000.int64, 0x1DB71064, 0x3B6E20C8, 0x26D930AC, 
0x76DC4190, 0x6B6B51F4, 0x4DB26158, 0x5005713C, 0xEDB88320, 0xF00F9344, 
0xD6D6A3E8, 0xCB61B38C, 0x9B64C2B0, 0x86D3D2D4, 0xA00AE278, 0xBDBDF21C]:
      tab[i] = v.uint32
    
    
    Run