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package babyjub
import ( "bytes" "encoding/hex" "fmt" "math/big" "strings"
"github.com/dchest/blake512" // I have personally reviewed that this module doesn't do anything suspicious
)
// SwapEndianness swaps the endianness of the value encoded in xs. If xs is
// Big-Endian, the result will be Little-Endian and viceversa.
func SwapEndianness(xs []byte) []byte { ys := make([]byte, len(xs)) for i, b := range xs { ys[len(xs)-1-i] = b } return ys }
// BigIntLEBytes encodes a big.Int into an array in Little-Endian.
func BigIntLEBytes(v *big.Int) [32]byte { le := SwapEndianness(v.Bytes()) res := [32]byte{} copy(res[:], le) return res }
// SetBigIntFromLEBytes sets the value of a big.Int from a Little-Endian
// encoded value.
func SetBigIntFromLEBytes(v *big.Int, leBuf []byte) *big.Int { beBuf := SwapEndianness(leBuf) return v.SetBytes(beBuf) }
// Blake512 performs the blake-512 hash over the buffer m. Note that this is
// the original blake from the SHA3 competition and not the new blake2 version.
func Blake512(m []byte) []byte { h := blake512.New() h.Write(m[:]) return h.Sum(nil) }
// Hex is a byte slice type that can be marshalled and unmarshaled in hex
type Hex []byte
// MarshalText encodes buf as hex
func (buf Hex) MarshalText() ([]byte, error) { return []byte(hex.EncodeToString(buf)), nil }
// String encodes buf as hex
func (buf Hex) String() string { return hex.EncodeToString(buf) }
// HexEncode encodes an array of bytes into a string in hex.
func HexEncode(bs []byte) string { return fmt.Sprintf("0x%s", hex.EncodeToString(bs)) }
// HexDecode decodes a hex string into an array of bytes.
func HexDecode(h string) ([]byte, error) { if strings.HasPrefix(h, "0x") { h = h[2:] } return hex.DecodeString(h) }
// HexDecodeInto decodes a hex string into an array of bytes (dst), verifying
// that the decoded array has the same length as dst.
func HexDecodeInto(dst []byte, h []byte) error { if bytes.HasPrefix(h, []byte("0x")) { h = h[2:] } if len(h)/2 != len(dst) { return fmt.Errorf("expected %v bytes in hex string, got %v", len(dst), len(h)/2) } n, err := hex.Decode(dst, h) if err != nil { return err } else if n != len(dst) { return fmt.Errorf("expected %v bytes when decoding hex string, got %v", len(dst), n) } return nil }
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