c++ string 与 char 互转 以及base64

c++ string 与 char 互转

很简单如下

    char bts[5] = {'A','B','C','D','E'};
    printf("%s
",bts);
    //char to string
    std::string strBts = bts;
    std::cout << strBts << std::endl;
    
    //string to char
    char *theBts = (char *)strBts.c_str();
    printf("%s
",theBts);

c++ base64 工具

//
//  base64.h
//  CPPWork
//  from http://stackoverflow.com/questions/180947/base64-decode-snippet-in-c
//  Created by cocoa on 16/8/5.
//  Copyright © 2016年 cc. All rights reserved.
//

#ifndef base64_h
#define base64_h

#include <string>

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len);
std::string base64_decode(std::string const& encoded_string);


#endif /* base64_h */

//
//  base64.cpp
//  CPPWork
//
//  Created by cocoa on 16/8/5.
//  Copyright © 2016年 cc. All rights reserved.
//

#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;
    int j = 0;
    unsigned char char_array_3[3];
    unsigned char 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] = '';
        
        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;
    int j = 0;
    int 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;
}