github.com/cheng762/platon-go@v1.8.17-0.20190529111256-7deff2d7be26/common/bytes.go

// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// Package common contains various helper functions.
package common

import (
	"bytes"
	"encoding/binary"
	"encoding/hex"
	"math"
)

// ToHex returns the hex representation of b, prefixed with '0x'.
// For empty slices, the return value is "0x0".
//
// Deprecated: use hexutil.Encode instead.
func ToHex(b []byte) string {
	hex := Bytes2Hex(b)
	if len(hex) == 0 {
		hex = "0"
	}
	return "0x" + hex
}

// FromHex returns the bytes represented by the hexadecimal string s.
// s may be prefixed with "0x".
func FromHex(s string) []byte {
	if len(s) > 1 {
		if s[0:2] == "0x" || s[0:2] == "0X" {
			s = s[2:]
		}
	}
	if len(s)%2 == 1 {
		s = "0" + s
	}
	return Hex2Bytes(s)
}

// CopyBytes returns an exact copy of the provided bytes.
func CopyBytes(b []byte) (copiedBytes []byte) {
	if b == nil {
		return nil
	}
	copiedBytes = make([]byte, len(b))
	copy(copiedBytes, b)

	return
}

// hasHexPrefix validates str begins with '0x' or '0X'.
func hasHexPrefix(str string) bool {
	return len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X')
}

// isHexCharacter returns bool of c being a valid hexadecimal.
func isHexCharacter(c byte) bool {
	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')
}

// isHex validates whether each byte is valid hexadecimal string.
func isHex(str string) bool {
	if len(str)%2 != 0 {
		return false
	}
	for _, c := range []byte(str) {
		if !isHexCharacter(c) {
			return false
		}
	}
	return true
}

// Bytes2Hex returns the hexadecimal encoding of d.
func Bytes2Hex(d []byte) string {
	return hex.EncodeToString(d)
}

// Hex2Bytes returns the bytes represented by the hexadecimal string str.
func Hex2Bytes(str string) []byte {
	h, _ := hex.DecodeString(str)
	return h
}

// Hex2BytesFixed returns bytes of a specified fixed length flen.
func Hex2BytesFixed(str string, flen int) []byte {
	h, _ := hex.DecodeString(str)
	if len(h) == flen {
		return h
	}
	if len(h) > flen {
		return h[len(h)-flen:]
	}
	hh := make([]byte, flen)
	copy(hh[flen-len(h):flen], h)
	return hh
}

// RightPadBytes zero-pads slice to the right up to length l.
func RightPadBytes(slice []byte, l int) []byte {
	if l <= len(slice) {
		return slice
	}

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

	return padded
}

// LeftPadBytes zero-pads slice to the left up to length l.
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
}

func BytesCombine(pBytes ...[]byte) []byte {
	return bytes.Join(pBytes, []byte(""))
}

func Int32ToBytes(n int32) []byte {
	tmp := int32(n)
	bytesBuffer := bytes.NewBuffer([]byte{})
	binary.Write(bytesBuffer, binary.BigEndian, tmp)
	return bytesBuffer.Bytes()
}

func BytesToInt32(b []byte) int32 {
	bytesBuffer := bytes.NewBuffer(b)
	var tmp int32
	binary.Read(bytesBuffer, binary.BigEndian, &tmp)
	return int32(tmp)
}

func Int64ToBytes(n int64) []byte {
	tmp := int64(n)
	bytesBuffer := bytes.NewBuffer([]byte{})
	binary.Write(bytesBuffer, binary.BigEndian, tmp)
	return bytesBuffer.Bytes()
}

func BytesToInt64(b []byte) int64 {
	bytesBuffer := bytes.NewBuffer(b)
	var tmp int64
	binary.Read(bytesBuffer, binary.BigEndian, &tmp)
	return int64(tmp)
}

func Float32ToBytes(float float32) []byte {
	bits := math.Float32bits(float)
	bytes := make([]byte, 4)
	binary.LittleEndian.PutUint32(bytes, bits)
	return bytes
}

func BytesToFloat32(bytes []byte) float32 {
	bits := binary.LittleEndian.Uint32(bytes)
	return math.Float32frombits(bits)
}

func Float64ToBytes(float float64) []byte {
	bits := math.Float64bits(float)
	bytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(bytes, bits)
	return bytes
}

func BytesToFloat64(bytes []byte) float64 {
	bits := binary.LittleEndian.Uint64(bytes)
	return math.Float64frombits(bits)
}

func PaddingLeft(src []byte, bytes int) []byte {
	if len(src) >= bytes {
		return src
	}
	dst := make([]byte, bytes)
	copy(dst, src)
	return reverse(dst)
}

func reverse(s []byte) []byte {
	for i, j := 0, len(s) - 1; i < j; i, j = i + 1, j - 1 {
		s[i], s[j] = s[j], s[i]
	}
	return s
}