go-ethereum/ethutil/bytes.go

package ethutil

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"math/big"
	"strings"
)

// Number to bytes
//
// Returns the number in bytes with the specified base
func NumberToBytes(num interface{}, bits int) []byte {
	buf := new(bytes.Buffer)
	err := binary.Write(buf, binary.BigEndian, num)
	if err != nil {
		fmt.Println("NumberToBytes failed:", err)
	}

	return buf.Bytes()[buf.Len()-(bits/8):]
}

// Bytes to number
//
// Attempts to cast a byte slice to a unsigned integer
func BytesToNumber(b []byte) uint64 {
	var number uint64

	// Make sure the buffer is 64bits
	data := make([]byte, 8)
	data = append(data[:len(b)], b...)

	buf := bytes.NewReader(data)
	err := binary.Read(buf, binary.BigEndian, &number)
	if err != nil {
		fmt.Println("BytesToNumber failed:", err)
	}

	return number
}

// Read variable int
//
// Read a variable length number in big endian byte order
func ReadVarint(reader *bytes.Reader) (ret uint64) {
	if reader.Len() == 8 {
		var num uint64
		binary.Read(reader, binary.BigEndian, &num)
		ret = uint64(num)
	} else if reader.Len() == 4 {
		var num uint32
		binary.Read(reader, binary.BigEndian, &num)
		ret = uint64(num)
	} else if reader.Len() == 2 {
		var num uint16
		binary.Read(reader, binary.BigEndian, &num)
		ret = uint64(num)
	} else {
		var num uint8
		binary.Read(reader, binary.BigEndian, &num)
		ret = uint64(num)
	}

	return ret
}

// Binary length
//
// Returns the true binary length of the given number
func BinaryLength(num int) int {
	if num == 0 {
		return 0
	}

	return 1 + BinaryLength(num>>8)
}

// Copy bytes
//
// Returns an exact copy of the provided bytes
func CopyBytes(b []byte) (copiedBytes []byte) {
	copiedBytes = make([]byte, len(b))
	copy(copiedBytes, b)

	return
}

func IsHex(str string) bool {
	l := len(str)
	return l >= 4 && l%2 == 0 && str[0:2] == "0x"
}

func Bytes2Hex(d []byte) string {
	return hex.EncodeToString(d)
}

func Hex2Bytes(str string) []byte {
	h, _ := hex.DecodeString(str)
	return h
}

func StringToByteFunc(str string, cb func(str string) []byte) (ret []byte) {
	if len(str) > 1 && str[0:2] == "0x" && !strings.Contains(str, "\n") {
		ret = Hex2Bytes(str[2:])
	} else {
		ret = cb(str)
	}

	return
}

func FormatData(data string) []byte {
	if len(data) == 0 {
		return nil
	}
	// Simple stupid
	d := new(big.Int)
	if data[0:1] == "\"" && data[len(data)-1:] == "\"" {
		return RightPadBytes([]byte(data), 32)
	} else if len(data) > 1 && data[:2] == "0x" {
		d.SetBytes(Hex2Bytes(data[2:]))
	} else {
		d.SetString(data, 0)
	}

	return BigToBytes(d, 256)
}

func RightPadBytes(slice []byte, l int) []byte {
	if l < len(slice) {
		return slice
	}

	padded := make([]byte, l)
	copy(padded[0:len(slice)], slice)

	return padded
}

func LeftPadBytes(slice []byte, l int) []byte {
	if l < len(slice) {
		return slice
	}

	padded := make([]byte, l)
	copy(padded[l-len(slice):], slice)

	return padded
}