Initial cloud-services repo - gateway service + pkg modules
This commit is contained in:
Chris Rai
68
pkg/utils/vod/crc.go
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68
pkg/utils/vod/crc.go
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package vod
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import (
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"encoding/binary"
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"github.com/sigurn/crc8"
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)
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func NewVODHelper(lengthInCRC bool,
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crcInLength bool,
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lengthInLength bool) VODHelper {
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return VODHelper{
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table: crc8.MakeTable(crc8.Params{
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Poly: 0x1D,
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Init: 0,
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RefIn: false,
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RefOut: false,
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XorOut: 0,
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Check: 0,
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Name: "CEC-8 VOD",
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}),
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lengthInCRC: lengthInCRC,
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crcInLength: crcInLength,
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lengthInLength: lengthInLength,
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}
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}
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type VODHelper struct {
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table *crc8.Table
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lengthInCRC bool
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crcInLength bool
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lengthInLength bool
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}
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// Given a list of bytes, we calculate our custom CRC-8 on it, then prepend the length and postpend the crc in place of last byte
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// So 0x01 0x02 0x00 -> 0x00 0x05 0x01 0x02 0x00 0xCRC-8(0x01 0x02 0x00)
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// If you have an existing VOD that you are modifying, this function expects you to have removed the length and the crc
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func (v *VODHelper) AddLengthAndCRC(data []byte) []byte {
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// first 2 bytes are length including length bytes
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length := make([]byte, 2)
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lengthPlus := 0
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if v.crcInLength { // No
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lengthPlus += 1
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}
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if v.lengthInLength { // Yes
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lengthPlus += 2
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}
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binary.BigEndian.PutUint16(length, uint16(len(data)+lengthPlus))
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var crc byte
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if v.lengthInCRC { // no
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data = append(length, data...)
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// calculate crc on data only
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crc = v.GenerateCRC(data)
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} else { // yes
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// calculate crc on data only
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crc = v.GenerateCRC(data)
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data = append(length, data...)
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}
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data = append(data, crc)
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return data
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}
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func (v *VODHelper) GenerateCRC(data []byte) byte {
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crc := crc8.Checksum(data, v.table)
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return crc
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}
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133
pkg/utils/vod/crc_test.go
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133
pkg/utils/vod/crc_test.go
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package vod
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import (
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"bytes"
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"encoding/binary"
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"encoding/hex"
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"testing"
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)
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func TestCustomCRC(t *testing.T) {
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inputString := "2301084000000101012200010101010001010101000000000000000000FF7EFF7F000101010101000101010100010001010101000101010100000000000000000000000000010101000100000100010101000201010101000101020101000101010200010101010101010101000101000100010001010101010101010101010000000000000100000101020101010101010000000000000000FFFFFF0000000201010202000101"
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inputB, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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p := NewVODHelper(false, false, false)
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output := p.GenerateCRC(inputB)
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if output != 0x5F {
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t.Fail()
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}
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}
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func TestDoesMatchReport(t *testing.T) {
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reported := "00A92301084000000101012200010101010001010101000000000000000000FF7EFF7F000101010101000101010100010001010101000101010100000000000000000000000000010101000100000100010101000201010101000101020101000101010200010101010101010101000101000100010001010101010101010101010000000000000100000101020101010101010000000000000000FFFFFF00000002010102020001015F"
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reportedBytes, err := hex.DecodeString(reported)
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if err != nil {
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t.Error(err)
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}
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inputBytes := reportedBytes[2 : len(reportedBytes)-1]
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p := NewVODHelper(false, false, true)
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outputBytes := p.AddLengthAndCRC(inputBytes)
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if len(reportedBytes) != len(outputBytes) {
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t.Logf("Lengths did not match %d %d", len(reportedBytes), len(outputBytes))
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t.Fail()
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}
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if !bytes.Equal(outputBytes, reportedBytes) {
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t.Log("input and output did not match")
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t.Fail()
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}
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}
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func TestLengthOfFinal(t *testing.T) {
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inputString := "2EF1110102030405060708091011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798990001020304050607080910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626399"
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inputB, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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// Expect the length to be increased by 2 from pre-pending length
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p := NewVODHelper(false, false, true)
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output := p.AddLengthAndCRC(inputB)
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if len(output) != len(inputB)+3 {
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t.Logf("Expected a final length of %d but got %d", len(inputB)+3, len(output))
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t.Fail()
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}
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length := binary.BigEndian.Uint16(output[:2])
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// Don't include crc with length
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if int64(length) != int64(len(output)-1) {
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t.Logf("The calculated length does not match actual length %d %d", int64(length), int64(len(output)-1))
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t.Fail()
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}
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}
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func TestCRCCorrect(t *testing.T) {
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inputString := "00112233"
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inputB, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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// Expect the length to be increased by 2 from pre-pending length
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p := NewVODHelper(false, true, false)
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output := p.GenerateCRC(inputB)
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secondStep := append(inputB, output)
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output2 := p.GenerateCRC(secondStep)
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if output2 != 0x00 {
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t.Fail()
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}
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}
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func TestCRCCorrect2(t *testing.T) {
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inputString := "00112233"
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inputB, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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// Expect the length to be increased by 2 from pre-pending length
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p := NewVODHelper(false, false, false)
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output := p.AddLengthAndCRC(inputB)
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// Chopping out length
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output = output[2:]
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output2 := p.GenerateCRC(output)
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if output2 != 0x00 {
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t.Fail()
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}
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}
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func TestCRCTotalZero(t *testing.T) {
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p := NewVODHelper(false, false, true)
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inputString := "030405060708091011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798990001020304050607080910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626399"
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inputB, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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crc := p.GenerateCRC(inputB)
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if crc != 0x00 {
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t.Fail()
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}
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}
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func TestCRCAndLengthSame(t *testing.T) {
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inputString := "01012301084000000101012200010101010001010101000000000000000000FF7EFF7F000101010101000101010100010001010101000101010100000000000000000000000000010101000100000100010101000201010101000101020101000101010200010101010101010101000101000100010001010101010101010101010000000000000100000101020101010101010000000000000000FFFFFF000101020101020200010100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000BA"
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inputBytes, err := hex.DecodeString(inputString)
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if err != nil {
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t.Error(err)
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}
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//Removing the length and the CRC
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p := NewVODHelper(false, false, true)
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choppedInput := inputBytes[2 : len(inputBytes)-1]
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choppedInput = p.AddLengthAndCRC(choppedInput)
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if !bytes.Equal(inputBytes, choppedInput) {
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t.Log("CRC and length not calculated as expected")
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t.Fail()
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}
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}
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