This package implements generic CRC calculations up to 64 bits wide. It aims to be fairly fast and fairly complete, allowing users to match pretty much any CRC algorithm used in the wild by choosing appropriate Parameters. This obviously includes all popular CRC algorithms, such as CRC64-ISO, CRC64-ECMA, CRC32, CRC32C, CRC16, CCITT, XMODEM and many others. See http://reveng.sourceforge.net/crc-catalogue/ for a good list of CRC algorithms and their parameters.

This package has been largely inspired by Ross Williams' 1993 paper "A Painless Guide to CRC Error Detection Algorithms".

Added missing 8, 16, and 32 bit algorithms.

To install, simply execute:

go get github.com/snksoft/crc 

or:

go get gopkg.in/snksoft/crc.v1 

Using crc is easy. Here is an example of calculating a CCITT crc.

package main import ( "fmt" "github.com/snksoft/crc" ) func main() { data := "123456789" ccittCrc := crc.CalculateCRC(crc.CCITT, []byte(data)) fmt.Printf("CRC is 0x%04X\n", ccittCrc) // prints "CRC is 0x29B1" }

For larger data, table driven implementation is faster. Note that crc.Hash implements hash.Hash interface, so you can use it instead if you want.
Here is how to use it:

package main import ( "fmt" "github.com/snksoft/crc" ) func main() { data := "123456789" hash := crc.NewHash(crc.XMODEM) xmodemCrc := hash.CalculateCRC([]byte(data)) fmt.Printf("CRC is 0x%04X\n", xmodemCrc) // prints "CRC is 0x31C3" // You can also reuse hash instance for another crc calculation // And if data is too big, you may feed it in chunks hash.Reset() // Discard crc data accumulated so far hash.Update([]byte("123456789")) // feed first chunk hash.Update([]byte("01234567890")) // feed next chunk xmodemCrc2 := hash.CRC() // gets CRC of whole data "12345678901234567890" fmt.Printf("CRC is 0x%04X\n", xmodemCrc2) // prints "CRC is 0x2C89" }

In this version I have separated actual CRC caclulations and Hash interface implementation. New Table type incorporates table based implementation which can be used without creating a Hash instance. The main difference is that Table instances are essentially immutable once initialized. This greatly simplifies concurrent use as Table instances can be safely used in concurrent applications without tricky copying or synchronization. The downside is, however, that feeding data in multiple chunks becomes a bit more verbose (as you essentially maintain intermediate crc in your code and keep feeding it back to subsequent calls). So, you might prefer one or the other depending on situation at hand and personal preferences. You even can ask a Hash instance for a Table instance it uses internally and then use both in parallel without recalculating the crc table.

Anyway, here is how to use a Table directly.

package main import ( "fmt" "github.com/snksoft/crc" ) func main() { data := []byte("123456789") // create a Table crcTable := crc.NewTable(crc.XMODEM) // Simple calculation all in one go xmodemCrc := crcTable.CalculateCRC(data) fmt.Printf("CRC is 0x%04X\n", xmodemCrc) // prints "CRC is 0x31C3" // You can also reuse same Table for another crc calculation // or even calculate multiple crc in parallel using same Table crc1 := crcTable.InitCrc() crc1 = crcTable.UpdateCrc(crc1, []byte("1234567890")) // feed first chunk to first crc crc2 := crcTable.InitCrc() crc2 = crcTable.UpdateCrc(crc2, data) // feed first chunk to second crc crc1 = crcTable.UpdateCrc(crc1, []byte("1234567890")) // feed second chunk to first crc // Now finish calcuation for both crc1 = crcTable.CRC(crc1) crc2 = crcTable.CRC(crc2) fmt.Printf("CRC is 0x%04X\n", crc1) // prints "CRC is 0x2C89" fmt.Printf("CRC is 0x%04X\n", crc2) // prints "CRC is 0x31C3" }

Beware that Hash instance is not thread safe. If you want to do parallel CRC calculations (and actually need it to be Hash, not Table), then either use NewHash() to create multiple Hash instances or simply make a copy of Hash whehever you need it. Latter option avoids recalculating CRC table, but keep in mind that NewHash() returns a pointer, so simple assignement will point to the same instance. Use either

hash2 := &crc.Hash{} *hash2 = *hash

or simply

var hash2 = *hash