Precomputin the CRC32 lookup table

CRC32lookupTable.m

    calculateCRClookup = (divident)=>
    let
       // move divident byte into MSB of 32Bit CRC
       curByte = Number.BitwiseShiftLeft(divident,24) 
    in 
       List.Accumulate({0..7}, 
                      curByte, 
                      (_curByte,_)=>
                             let 
                              // if MSB set, shift left and XOR with polynomial = 0x4C11DB7
                                 then_clause = Number.BitwiseXor(Number.BitwiseShiftLeft(_curByte,1),0x4C11DB7),
                             // else shift one bit left
                                 else_clause = Number.BitwiseShiftLeft(_curByte,1)
                             in  //if MSB set
                                 if Number.BitwiseAnd(_curByte,0x80000000)<>0 then then_clause else else_clause ),
    // precompute CRC32 lookup table
    CRC_table  	= List.Generate(()=>[count=0,crc=0], each [count]<256, // iterate over all possible input byte values 0-255
                                each  [count = [count]+1, crc = calculateCRClookup(count) ], each [crc])