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Integrate ecc into word-byte codec

This commit is contained in:
Ethan Frey 2017-06-20 16:10:15 +02:00
parent 0b0e994cd1
commit ad029d1293
2 changed files with 36 additions and 23 deletions
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39
keys/wordcodec.go
View File

@ -21,6 +21,7 @@ type Codec interface {
type WordCodec struct {
words []string
bytes map[string]int
check ECC
}
var _ Codec = WordCodec{}
@ -30,7 +31,13 @@ func NewCodec(words []string) (codec WordCodec, err error) {
return codec, errors.Errorf("Bank must have %d words, found %d", BankSize, len(words))
}
return WordCodec{words: words}, nil
res := WordCodec{
words: words,
// TODO: configure this outside???
check: NewIEEECRC32(),
}
return res, nil
}
func LoadCodec(bank string) (codec WordCodec, err error) {
@ -70,6 +77,7 @@ func getData(filename string) (string, error) {
// given this many bytes, we will produce this many words
func wordlenFromBytes(numBytes int) int {
// 2048 words per bank, which is 2^11.
// 8 bits per byte, and we add +10 so it rounds up
return (8*numBytes + 10) / 11
}
@ -88,8 +96,9 @@ func bytelenFromWords(numWords int) (length int, maybeShorter bool) {
}
// TODO: add checksum
func (c WordCodec) BytesToWords(data []byte) (words []string, err error) {
// 2048 words per bank, which is 2^11.
func (c WordCodec) BytesToWords(raw []byte) (words []string, err error) {
// always add a checksum to the data
data := c.check.AddECC(raw)
numWords := wordlenFromBytes(len(data))
n2048 := big.NewInt(2048)
@ -106,12 +115,6 @@ func (c WordCodec) BytesToWords(data []byte) (words []string, err error) {
}
func (c WordCodec) WordsToBytes(words []string) ([]byte, error) {
// // 2048 words per bank, which is 2^11.
// numWords := (8*len(dest) + 10) / 11
// if numWords != len(words) {
// return errors.New(Fmt("Expected %v words for %v dest bytes", numWords, len(dest)))
// }
l := len(words)
n2048 := big.NewInt(2048)
nData := big.NewInt(0)
@ -131,10 +134,20 @@ func (c WordCodec) WordsToBytes(words []string) ([]byte, error) {
// are lots of leading 0s
dataBytes := nData.Bytes()
outLen, _ := bytelenFromWords(len(words))
output := make([]byte, outLen)
copy(output[outLen-len(dataBytes):], dataBytes)
return output, nil
// copy into the container we have with the expected size
outLen, flex := bytelenFromWords(len(words))
toCheck := make([]byte, outLen)
copy(toCheck[outLen-len(dataBytes):], dataBytes)
// validate the checksum...
output, err := c.check.CheckECC(toCheck)
if flex && err != nil {
// if flex, try again one shorter....
toCheck = toCheck[1:]
output, err = c.check.CheckECC(toCheck)
}
return output, err
}
// GetIndex finds the index of the words to create bytes

20
keys/wordcodec_test.go
View File

@ -54,16 +54,16 @@ func TestEncodeDecode(t *testing.T) {
require.Nil(err, "%+v", err)
cases := [][]byte{
// {7, 8, 9}, // TODO: 3 words -> 3 or 4 bytes
{12, 54, 99, 11}, // TODO: 3 words -> 3 or 4 bytes
{0, 54, 99, 11}, // TODO: 3 words -> 3 or 4 bytes, detect leading 0
{1, 2, 3, 4, 5}, // normal
// {0, 0, 0, 0, 122, 23, 82, 195}, // leading 0s (8 chars, unclear)
{0, 0, 0, 0, 5, 22, 123, 55, 22}, // leading 0s (9 chars, clear)
{22, 44, 55, 1, 13, 0, 0, 0, 0}, // trailing 0s (9 chars, clear)
{0, 5, 253, 2, 0}, // leading and trailing zeros
{255, 196, 172, 234, 192, 255}, // big numbers
// {255, 196, 172, 1, 234, 192, 255}, // big numbers, two length choices
{7, 8, 9}, // TODO: 3 words -> 3 or 4 bytes
{12, 54, 99, 11}, // TODO: 3 words -> 3 or 4 bytes
{0, 54, 99, 11}, // TODO: 3 words -> 3 or 4 bytes, detect leading 0
{1, 2, 3, 4, 5}, // normal
{0, 0, 0, 0, 122, 23, 82, 195}, // leading 0s (8 chars, unclear)
{0, 0, 0, 0, 5, 22, 123, 55, 22}, // leading 0s (9 chars, clear)
{22, 44, 55, 1, 13, 0, 0, 0, 0}, // trailing 0s (9 chars, clear)
{0, 5, 253, 2, 0}, // leading and trailing zeros
{255, 196, 172, 234, 192, 255}, // big numbers
{255, 196, 172, 1, 234, 192, 255}, // big numbers, two length choices
// others?
}