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base64加密你一點也不會陌生，Base64是網路上最常見的用於傳輸8Bit位元組程式碼的編碼方式之一，大家可以檢視RFC2045～RFC2049，上面有MIME的詳細規範。Base64編碼可用於在HTTP環境下傳遞較長的標識資訊。

首先介紹介紹一下老本行，C++中是如何進行base64加密解密的，直接上程式碼了：
base64.h

#include <string>

#ifndef _BASE64_H_
#define _BASE64_H_

 __declspec(dllexport)  std::string base64_encode(unsigned
 
 char const*, unsigned int len);
 __declspec(dllexport)  std::string base64_decode(std::string const& s);

#endif

base64.cc

#include "base64.h"
#include <iostream>

static const std::string base64_chars = 
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
 

             "0123456789+/";


static inline bool is_base64(unsigned char c) 
{
  return (isalnum(c) || (c == '+') || (c == '/'));
}

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) 
{
  std::string ret;
  int i = 0, j = 0;
  unsigned char char_array_3[3], char_array_4[4
 
];

  while (in_len--)
    {
    char_array_3[i++] = *(bytes_to_encode++);
    if (i == 3) 
        {
      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
      char_array_4[3] = char_array_3[2] & 0x3f;

      for(i = 0; (i <4) ; i++)
        ret += base64_chars[char_array_4[i]];
      i = 0;
    }
  }

  if (i)
  {
    for(j = i; j < 3; j++)
      char_array_3[j] = '\0';

    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
    char_array_4[3] = char_array_3[2] & 0x3f;

    for (j = 0; (j < i + 1); j++)
      ret += base64_chars[char_array_4[j]];

    while((i++ < 3))
      ret += '=';

  }

  return ret;

}

std::string base64_decode(std::string const& encoded_string) 
{
  int in_len = encoded_string.size();
  int i = 0, j = 0, in_ = 0;
  unsigned char char_array_4[4], char_array_3[3];
  std::string ret;

  while (in_len-- && ( encoded_string[in_] != '=') && is_base64(encoded_string[in_])) 
    {
    char_array_4[i++] = encoded_string[in_]; in_++;
    if (i ==4) {
      for (i = 0; i <4; i++)
        char_array_4[i] = base64_chars.find(char_array_4[i]);

      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
      char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

      for (i = 0; (i < 3); i++)
        ret += char_array_3[i];
      i = 0;
    }
  }

  if (i) 
    {
    for (j = i; j <4; j++)
      char_array_4[j] = 0;

    for (j = 0; j <4; j++)
      char_array_4[j] = base64_chars.find(char_array_4[j]);

    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

    for (j = 0; (j < i - 1); j++) 
            ret += char_array_3[j];
  }

  return ret;
}

下面就進行介紹在golang中如何進行base64加密。

encoding/base64
Package base64 implements base64 encoding as specified by RFC 4648.

StdEncoding
StdEncoding is the standard base64 encoding, as defined in RFC 4648.

NewDecoder

func NewDecoder(enc *Encoding, r io.Reader) io.Reader

NewDecoder constructs a new base64 stream decoder.

EncodeToString

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

EncodeToString returns the base64 encoding of src.

應用：

package main

import (
    "encoding/base64"
    "fmt"
)

func main() {
    s := "heal the world, make it a better place"

    encodeStd := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    s64 := base64.NewEncoding(encodeStd).EncodeToString([]byte(s))
    fmt.Println("base64.NewEncoding(encodeStd).EncodeToString")
    fmt.Println(len(s))
    fmt.Println(len(s64))
    fmt.Println(s)
    fmt.Println(s64)

    s64_std := base64.StdEncoding.EncodeToString([]byte(s))
    fmt.Println("base64.StdEncoding.EncodeToString")
    fmt.Println(len(s))
    fmt.Println(len(s64_std))
    fmt.Println(s)
    fmt.Println(s64_std)
}

輸出結果：
base64.NewEncoding(encodeStd).EncodeToString
38
52
heal the world, make it a better place
aGVhbCB0aGUgd29ybGQsIG1ha2UgaXQgYSBiZXR0ZXIgcGxhY2U=

base64.StdEncoding.EncodeToString
38
52
heal the world, make it a better place
aGVhbCB0aGUgd29ybGQsIG1ha2UgaXQgYSBiZXR0ZXIgcGxhY2U=