1.stdEncoding：标准的base64编码

type Encoding struct {

encode [64]byte

decodeMap [256]byte

padChar rune

strict bool

}

const (

StdPadding rune = '=' // Standard padding character

NoPadding rune = -1 // No padding

)

const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"

// NewEncoding returns a new padded Encoding defined by the given alphabet,

// which must be a 64-byte string that does not contain the padding character

// or CR / LF ('\r', '\n').

// The resulting Encoding uses the default padding character ('='),

// which may be changed or disabled via WithPadding.

func NewEncoding(encoder string) *Encoding {

if len(encoder) != 64 {

panic("encoding alphabet is not 64-bytes long")

}

for i := 0; i < len(encoder); i++ {

if encoder[i] == '\n' || encoder[i] == '\r' {

panic("encoding alphabet contains newline character")

}

}

e := new(Encoding)

e.padChar = StdPadding

copy(e.encode[:], encoder)

for i := 0; i < len(e.decodeMap); i++ {

e.decodeMap[i] = 0xFF

}

for i := 0; i < len(encoder); i++ {

e.decodeMap[encoder[i]] = byte(i)

}

return e

}

// StdEncoding is the standard base64 encoding, as defined in

// RFC 4648.

var StdEncoding = NewEncoding(encodeStd)

// URLEncoding is the alternate base64 encoding defined in RFC 4648.

// It is typically used in URLs and file names.

var URLEncoding = NewEncoding(encodeURL)

// EncodeToString returns the base64 encoding of src.

func (enc *Encoding) EncodeToString(src []byte) string {

buf := make([]byte, enc.EncodedLen(len(src)))

enc.Encode(buf, src)

return string(buf)

}

示例

d := "This is a golang test."

encodedContent := base64.StdEncoding.EncodeToString([]byte(d))

fmt.Println(encodedContent)

sourceContent,_ := base64.StdEncoding.DecodeString(encodedContent)

fmt.Println(string(sourceContent))

Output:

VGhpcyBpcyBhIGdvbGFuZyB0ZXN0Lg==

This is a golang test.