neoneo-go/pkg/util/io.go

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package util
import (
"bytes"
"encoding/binary"
"errors"
"io"
)
// Variable length integer, can be encoded to save space according to the value typed.
// len 1 uint8
// len 3 0xfd + uint16
// len 5 0xfe = uint32
// len 9 0xff = uint64
// For more information about this:
// https://github.com/neo-project/neo/wiki/Network-Protocol
// ReadVarUint reads a variable unsigned integer and returns it as a uint64.
func ReadVarUint(r io.Reader) uint64 {
var b uint8
binary.Read(r, binary.LittleEndian, &b)
if b == 0xfd {
var v uint16
binary.Read(r, binary.LittleEndian, &v)
return uint64(v)
}
if b == 0xfe {
var v uint32
binary.Read(r, binary.LittleEndian, &v)
return uint64(v)
}
if b == 0xff {
var v uint64
binary.Read(r, binary.LittleEndian, &v)
return v
}
return uint64(b)
}
// WriteVarUint writes a variable unsigned integer.
func WriteVarUint(w io.Writer, val uint64) error {
if val < 0 {
return errors.New("value out of range")
}
if val < 0xfd {
binary.Write(w, binary.LittleEndian, uint8(val))
return nil
}
if val < 0xFFFF {
binary.Write(w, binary.LittleEndian, byte(0xfd))
binary.Write(w, binary.LittleEndian, uint16(val))
return nil
}
if val < 0xFFFFFFFF {
binary.Write(w, binary.LittleEndian, byte(0xfe))
binary.Write(w, binary.LittleEndian, uint32(val))
return nil
}
binary.Write(w, binary.LittleEndian, byte(0xff))
binary.Write(w, binary.LittleEndian, val)
return nil
}
// ReadVarBytes reads a variable length byte array.
func ReadVarBytes(r io.Reader) ([]byte, error) {
n := ReadVarUint(r)
b := make([]byte, n)
if err := binary.Read(r, binary.LittleEndian, b); err != nil {
return nil, err
}
return b, nil
}
// ReadVarString reads a variable length string.
func ReadVarString(r io.Reader) (string, error) {
b, err := ReadVarBytes(r)
return string(b), err
}
// WriteVarString writes a variable length string.
func WriteVarString(w io.Writer, s string) error {
return WriteVarBytes(w, []byte(s))
}
// WriteVarBytes writes a variable length byte array.
func WriteVarBytes(w io.Writer, b []byte) error {
if err := WriteVarUint(w, uint64(len(b))); err != nil {
return err
}
return binary.Write(w, binary.LittleEndian, b)
}
// Read2000Uint256Hashes attempt to read 2000 Uint256 hashes from
// the given byte array.
func Read2000Uint256Hashes(b []byte) ([]Uint256, error) {
r := bytes.NewReader(b)
lenHashes := ReadVarUint(r)
hashes := make([]Uint256, lenHashes)
if err := binary.Read(r, binary.LittleEndian, hashes); err != nil {
return nil, err
}
return hashes, nil
}