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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 muchany 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. Seehttp://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".

To install, simply execute:

go get github.com/snksoft/crc

or:

go get gopkg.in/snksoft/crc.v1

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

package mainimport ("fmt""github.com/snksoft/crc")funcmain() {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 thatcrc.Hash implementshash.Hash interface, so you can use it instead if you want.
Here is how to use it:

package mainimport ("fmt""github.com/snksoft/crc")funcmain() {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 chunkshash.Reset()// Discard crc data accumulated so farhash.Update([]byte("123456789"))// feed first chunkhash.Update([]byte("01234567890"))// feed next chunkxmodemCrc2:=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. NewTable type incorporates table based implementation which can be used without creating aHash instance. The main difference is thatTable instances are essentially immutable once initialized. This greatly simplifies concurrent use asTable 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 aHash instance for aTable instance it uses internally and then use both in parallel without recalculating the crc table.

Anyway, here is how to use aTable directly.

package mainimport ("fmt""github.com/snksoft/crc")funcmain() {data:= []byte("123456789")// create a TablecrcTable:=crc.NewTable(crc.XMODEM)// Simple calculation all in one goxmodemCrc:=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 Tablecrc1:=crcTable.InitCrc()crc1=crcTable.UpdateCrc(crc1, []byte("1234567890"))// feed first chunk to first crccrc2:=crcTable.InitCrc()crc2=crcTable.UpdateCrc(crc2,data)// feed first chunk to second crccrc1=crcTable.UpdateCrc(crc1, []byte("1234567890"))// feed second chunk to first crc// Now finish calcuation for bothcrc1=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 thatHash instance is not thread safe. If you want to do parallel CRC calculations (and actually need it to beHash, notTable), then either useNewHash() 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 thatNewHash() returns a pointer, so simple assignement will point to the same instance.Use either

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

or simply

varhash2=*hash