BASE64 coding principle and Golang code invocation

I. Introduction to the Concept

Base64 is a representation of binary data based on 64 printable characters. Because of 2^6=64, every 6 bits is a unit, corresponding to a printable character. 3 bytes have 24 bits, corresponding to 4 Base64 units, 3 bytes can be represented by 4 printable characters. It can be used as the transmission encoding for e-mail. The printable characters in Base64 include the letter A-Z, A-Z, the number 0-9, which is 62 characters in total, and two printable symbols that differ from one system to another.

Base64 is often used to represent, transmit, and store some binary data in situations where text data is normally processed.

Two. Code calls

The code base provided in Golang can be called directly to implement BASE64 encoding and decoding, which provides encoding (and decoding) of data in both formats

const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"

From Golang source Base64.go

1. Standard data (ENCODESTD)

    msg := "Mac"    //编码    base64EncodedString := base64.StdEncoding.EncodeToString([]byte(msg))    fmt.Println("Base64编码后:", base64EncodedString)    //解码    base64DecodedByte, err := base64.StdEncoding.DecodeString(base64EncodedString)    if err != nil {        log.Panic(err)    }    fmt.Println("Base64解码后的字节数组:", base64DecodedByte)    fmt.Println("Base64解码后:", string(base64DecodedByte))

Return to print results

Base64编码后: TWFjBase64解码后的字节数组: [77 97 99]Base64解码后: Mac

2.URL data (Encodeurl)

msgUrl :="http://www.google.com"    base64UrlEncodedString :=base64.URLEncoding.EncodeToString([]byte(msgUrl))    fmt.Println("Base64编码后:", base64UrlEncodedString)    base64UrlDecodedByte,err := base64.URLEncoding.DecodeString(base64UrlEncodedString)    if err !=nil {        log.Panic(err)    }    fmt.Println("Base64解码后的字节数组:", base64UrlDecodedByte)    fmt.Println("Base64解码后:", string(base64UrlDecodedByte))

Return to print results

Base64编码后: aHR0cDovL3d3dy5nb29nbGUuY29tBase64解码后的字节数组: [104 116 116 112 58 47 47 119 119 119 46 103 111 111 103 108 101 46 99 111 109]Base64解码后: http://www.google.com

Three. Coding principle

1. Convert each character to ASCII encoding (10 binary)

fmt.Println([]byte(msg)) //[77 97 99]

2. Turn the 10 binary code into a 2-in-binary encoding

Padded 8-bit:

3. Divide the 2 binary encoding by 6-bit group

010011 010110 000101 100011

4. Turn to 10 binary number

010011 ==> 1x2^0 + 1x2^1 + 0 + 0 + 1x2^4 = 19

010110 ==> 0 + 1x2^1 + 1x2^2 + 0 + 1x2^4 = 22

000101 ==> 1x2^0 + 0 + 1 x 2^2 + 0 + 0 + 0 = 5

100011 ==> 1x2^0 + 1x2^1 + 0 + 0 + 0 + 1x2^5 = 35

5. Use decimal numbers as indexes to find characters from BASE64 encoded tables

19 对应 T22 对应 W5  对应 F35 对应 j (注意是小写)

Attention

• If the text is 3 characters, it is exactly encoded as 4 characters long (3 8 = 4 6)
• If the text is 2 characters, it is encoded as 3 characters and the tail is padded with a "="
• If the text is 1 characters, it is encoded as 2 characters and the tail is padded with two "="