Add crc64, constructors

keys/ecc.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"hash/crc32"
+	"hash/crc64"
 )
 
 // ECC is used for anything that calculates an error-correcting code
@@ -33,6 +34,18 @@ type CRC32 struct {
 
 var _ ECC = &CRC32{}
 
+func NewIEEECRC32() *CRC32 {
+	return &CRC32{Poly: crc32.IEEE}
+}
+
+func NewCastagnoliCRC32() *CRC32 {
+	return &CRC32{Poly: crc32.Castagnoli}
+}
+
+func NewKoopmanCRC32() *CRC32 {
+	return &CRC32{Poly: crc32.Koopman}
+}
+
 func (c *CRC32) AddECC(input []byte) []byte {
 	table := c.getTable()
 
@@ -71,3 +84,58 @@ func (c *CRC32) getTable() *crc32.Table {
 	}
 	return c.table
 }
+
+// CRC64 does the ieee crc64 polynomial check
+type CRC64 struct {
+	Poly  uint64
+	table *crc64.Table
+}
+
+var _ ECC = &CRC64{}
+
+func NewISOCRC64() *CRC64 {
+	return &CRC64{Poly: crc64.ISO}
+}
+
+func NewECMACRC64() *CRC64 {
+	return &CRC64{Poly: crc64.ECMA}
+}
+
+func (c *CRC64) AddECC(input []byte) []byte {
+	table := c.getTable()
+
+	// get crc and convert to some bytes...
+	crc := crc64.Checksum(input, table)
+	check := make([]byte, crc64.Size)
+	binary.BigEndian.PutUint64(check, crc)
+
+	// append it to the input
+	output := append(input, check...)
+	return output
+}
+
+func (c *CRC64) CheckECC(input []byte) ([]byte, error) {
+	table := c.getTable()
+
+	if len(input) <= crc64.Size {
+		return nil, errors.New("input too short, no checksum present")
+	}
+	cut := len(input) - crc64.Size
+	data, check := input[:cut], input[cut:]
+	crc := binary.BigEndian.Uint64(check)
+	calc := crc64.Checksum(data, table)
+	if crc != calc {
+		return nil, errors.New("Checksum does not match")
+	}
+	return data, nil
+}
+
+func (c *CRC64) getTable() *crc64.Table {
+	if c.table == nil {
+		if c.Poly == 0 {
+			c.Poly = crc64.ISO
+		}
+		c.table = crc64.MakeTable(c.Poly)
+	}
+	return c.table
+}

keys/ecc_test.go

@@ -1,7 +1,6 @@
 package keys
 
 import (
-	"hash/crc32"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -13,7 +12,14 @@ import (
 func TestECCPasses(t *testing.T) {
 	assert := assert.New(t)
 
-	checks := []ECC{NoECC{}, &CRC32{}, &CRC32{Poly: crc32.Castagnoli}}
+	checks := []ECC{
+		NoECC{},
+		NewIEEECRC32(),
+		NewCastagnoliCRC32(),
+		NewKoopmanCRC32(),
+		NewISOCRC64(),
+		NewECMACRC64(),
+	}
 
 	for _, check := range checks {
 		for i := 0; i < 2000; i++ {
@@ -22,7 +28,7 @@ func TestECCPasses(t *testing.T) {
 
 			checked := check.AddECC(data)
 			res, err := check.CheckECC(checked)
-			if assert.Nil(err, "%v: %+v", check, err) {
+			if assert.Nil(err, "%#v: %+v", check, err) {
 				assert.Equal(data, res, "%v", check)
 			}
 		}
@@ -33,7 +39,13 @@ func TestECCPasses(t *testing.T) {
 func TestECCFails(t *testing.T) {
 	assert := assert.New(t)
 
-	checks := []ECC{&CRC32{}, &CRC32{Poly: crc32.Castagnoli}}
+	checks := []ECC{
+		NewIEEECRC32(),
+		NewCastagnoliCRC32(),
+		NewKoopmanCRC32(),
+		NewISOCRC64(),
+		NewECMACRC64(),
+	}
 
 	attempts := 2000