package shachain import ( "encoding/hex" "github.com/btcsuite/btcd/chaincfg/chainhash" ) // getBit return bit on index at position. func getBit(index index, position uint8) uint8 { return uint8((uint64(index) >> position) & 1) } func getPrefix(index index, position uint8) uint64 { // + -------------------------- + // | № | value | mask | return | // + -- + ----- + ---- + ------ + // | 63 | 1 | 0 | 0 | // | 62 | 0 | 0 | 0 | // | 61 | 1 | 0 | 0 | // .... // | 4 | 1 | 0 | 0 | // | 3 | 1 | 0 | 0 | // | 2 | 1 | 1 | 1 | <--- position // | 1 | 0 | 1 | 0 | // | 0 | 1 | 1 | 1 | // + -- + ----- + ---- + ------ + var zero uint64 mask := (zero - 1) - uint64((1<<position)-1) return (uint64(index) & mask) } // countTrailingZeros counts number of trailing zero bits, this function is // used to determine the number of element bucket. func countTrailingZeros(index index) uint8 { var zeros uint8 for ; zeros < maxHeight; zeros++ { if getBit(index, zeros) != 0 { break } } return zeros } // hashFromString takes a hex-encoded string as input and creates an instance of // chainhash.Hash. The chainhash.NewHashFromStr function not suitable because // it reverse the given hash. func hashFromString(s string) (*chainhash.Hash, error) { // Return an error if hash string is too long. if len(s) > chainhash.MaxHashStringSize { return nil, chainhash.ErrHashStrSize } // Hex decoder expects the hash to be a multiple of two. if len(s)%2 != 0 { s = "0" + s } // Convert string hash to bytes. buf, err := hex.DecodeString(s) if err != nil { return nil, err } hash, err := chainhash.NewHash(buf) if err != nil { return nil, err } return hash, nil }