A CRC will not generate a checksum! A CRC generates a 'Cyclic Redundancy Check' whereas a checksum is generated from the sum of the values. You probably know this but it is always wise to use the correct terms to avoid confusion.

Raj is also right in pointing you to the web. There are two main methods for CRC generation/checking: table driven or looped. Table driven is faster but chews up memory due to the table whereas looped is smaller but executes slower.