Golang implementation of BASE64 encryption

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Base64 encryption is an encryption method that we often see, such as the verification process of ESMTP and the Internet transmission of binary files.

Base64 encryption method is a relatively simple one, the encoding process is the original text in accordance with every 6bit (remember, is "bit") for a set of the original to replace, because 6bit can represent the range of values in 0~63 (2 of the 6-square, A total of 64), so you can map the 6bit value with a character descriptor of length 64.

This mapping table is usually A-Z, A-Z, 0-9 Plus + and/two symbols, or "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789+/".

However, before the encryption, we have to solve a problem, that is, a character is usually a byte (byte), Byte is 8bit, but the time of encryption is in accordance with every 6bit units, then how to encrypt it?

In fact, Base64 encoding is done in a group of three bytes, so that three bytes is 24bit, then 24bit÷6bit = 4 (characters), so that after Base64 encryption, every 3 characters will be encrypted to 4 characters. In other words, if normal, the original text after being Base64 encrypted is 3/4 longer than the original.

Of course, this "normal" situation, then if the length of the original text is not a multiple of 3 this abnormal situation should do?

If the length of the original text is not more than 3 integers, then the "=" number is used to populate it. For example, if the last 1 characters, not enough 3, then at the end of the cipher add two "=", if the last remaining 1 characters, at the end of the cipher add a "=".

Again, is to fill the problem of the bit, such as if the last 1 characters left, then the 1 characters only 8bit, so that the first 6bit encoding after only 2bit, encryption on the way to continue. So to fill the insufficient bits with a zero, here is an example to understand:

Now to encode the "ABCDE" base64, then only the "de" is left after the first three characters are encrypted, and the 2 binary representation of the two characters is

"01100100 01100101", a total of 16 bits, if you want to Base64 encryption, you must refill two 0 for "01100100 01100101".

This will be a 6 integer multiple, can be successfully completed encryption. Don't forget to add a "=" when you're done encrypting it.

Here is the implementation code, if there is an error, please leave a message:

Func EncodeBase64 (Plain string) (cipher string) {Const key string = " abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789+/"var (length int = len (plain) Loop_time int = Le ngth/3left int = length% 3bytes_catnate int32index int) for I: = 0; i < loop_time; i++ {bytes_catnate = Int32 (Plain[index]) <<16 + int32 (Plain[index+1]) <<8 + int32 (Plain[index+2]) Index + = 3cipher + = string (key[(bytes_catnate>>18) &0x3f]) cipher + = string (key[(bytes_catnate>>12) &0x3f] ) Cipher + = string (key[(bytes_catnate>>6) &0x3f]) cipher + = string (key[bytes_catnate&0x3f])}if left = = 1 { Bytes_catnate = Int32 (Plain[index]) << 4cipher + = string (key[(bytes_catnate>>6) &0x3f]) cipher + = string (key[bytes_catnate&0x3f]) cipher + = "="}if left = = 2 {bytes_catnate = (int32 (Plain[index]) <<8 + int32 (plain[ INDEX+1])) << 2cipher + = string (key[(bytes_catnate>>12) &0x3f]) cipher + = string (key[(bytes_catnate >>6) &0x3f]) cipher + = string (key[bytes_catnate&0x3f]) cipher + = "="}return cipher} 

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