Compute the CRC32 checksum of a buffer's worth of data.
the starting checksum for the computation. Use 0 for a new checksum. Use the output of this function for a cumulative checksum.
buffer containing input data
A uint checksum for the provided input data and starting checksum
http://en.wikipedia.org/wiki/Cyclic_redundancy_check
See Implementation
Compute the CRC32 checksum of a buffer's worth of data.