slice填充

区块链底层使用merkle tree，需要对数据([]byte)进行填充等操作。 本文封装了这些操作。

源码结构：

root@jack-VirtualBox:~/test/slice# tree
.
├── go.mod
├── go.sum
├── main.go
├── misc
│   └── util.go
└── tt1 directory, 5 files
root@jack-VirtualBox:~/test/slice#

main.go

package mainimport ("fmt""tt/misc"
)func main() {fmt.Println("vim-go")by := misc.Bytes{'h', 'e', 'l', 'l', 'o'}fmt.Println(string(by))// 字节 -> 0xddddddd十六进制字符串hby, err := by.MarshalText()if err == nil {fmt.Println(string(hby))}newby := &misc.Bytes{}err = newby.UnmarshalText(hby)if err == nil {fmt.Println(string(*newby))}// 深拷贝字节切片dd := []byte("hello jack")ds := misc.CopyBytes(dd)fmt.Printf("%s, %s, %p, %p\r\n", string(ds), string(dd), ds, dd)// 随机打乱字节切片的数据misc.Shuffle(dd)fmt.Println(string(dd))misc.Shuffle(ds)fmt.Println(string(ds))// 左对齐填充容器as := []byte("hello jack")aa := misc.RightPadBytes(as, 100)fmt.Println("-------测试右填充")fmt.Println(as, "\r\n", aa)// 右对齐填充容器kk := misc.LeftPadBytes(as, 300)fmt.Println("-------测试左填充")fmt.Println(as, "\r\n", kk)
}

misc/util.go

package miscimport ("encoding/hex""errors""math/rand""reflect""time"lru "github.com/hashicorp/golang-lru"
)// Bytes is a array byte that is converted to hex string display format when marshal
type Bytes []byte// Has0xPrefix returns true if input start with 0x, otherwise false
func Has0xPrefix(input string) bool {return len(input) >= 2 && input[0] == '0' && (input[1] == 'x' || input[1] == 'X')
}// BytesToHex encodes b as a hex string with 0x prefix.
func BytesToHex(b []byte) string {enc := make([]byte, len(b)*2+2)copy(enc, "0x")hex.Encode(enc[2:], b)return string(enc)
}// HexToBytes decodes a hex string with 0x prefix.
func HexToBytes(input string) ([]byte, error) {if len(input) == 0 {return nil, errors.New("empty hex string")}// MissingPrefixif !Has0xPrefix(input) {return nil, errors.New("empty hex string")}b, err := hex.DecodeString(input[2:])if err != nil {return nil, err}return b, nil
}// MarshalText implement the TextMarshaler interface
func (b Bytes) MarshalText() ([]byte, error) {if len(b) == 0 {return nil, nil}hex := BytesToHex(b)return []byte(hex), nil
}// UnmarshalText implement the TextUnmarshaler interface
func (b *Bytes) UnmarshalText(hex []byte) error {if len(hex) == 0 {return nil}arrayByte, err := HexToBytes(string(hex))if err != nil {return err}*b = arrayBytereturn nil
}// CopyBytes copies and returns a new bytes from the specified source bytes.
func CopyBytes(src []byte) []byte {if src == nil {return nil}dest := make([]byte, len(src))copy(dest, src)return dest
}// MustNewCache creates a LRU cache with specified size. Panics on any error.
func MustNewCache(size int) *lru.Cache {cache, err := lru.New(size)if err != nil {panic(err) // error occurs only when size <= 0.}return cache
}// Shuffle shuffles items in slice
func Shuffle(slice interface{}) {rv := reflect.ValueOf(slice)swap := reflect.Swapper(slice)length := rv.Len()for i := length - 1; i > 0; i-- {rand.Seed(time.Now().UnixNano())j := rand.Intn(i + 1)swap(i, j)}
}// 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
}

执行结果：

root@jack-VirtualBox:~/test/slice# ./tt 
vim-go
hello
0x68656c6c6f
hello
hello jack, hello jack, 0xc000014130, 0xc000014120
jc hkealol
halclekjo 
-------测试右填充
[104 101 108 108 111 32 106 97 99 107] [104 101 108 108 111 32 106 97 99 107 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
-------测试左填充
[104 101 108 108 111 32 106 97 99 107] [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 104 101 108 108 111 32 106 97 99 107]
root@jack-VirtualBox:~/test/slice#

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