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