/* Divide the input into three parts, using the values of the first two
* bytes to choose lengths, which generate b1, b2 and b3. Use three bits
* of the third byte to choose signs for the three numbers.
/* Divide the input into three parts, using the values of the first two
* bytes to choose lengths, which generate b1, b2 and b3. Use three bits
* of the third byte to choose signs for the three numbers.