qfedu-basic-level/day13/LPR/base/base64.h

/**
 * Copyright (c) 2017 Baidu.com, Inc. All Rights Reserved
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 *
 * @author baidu aip
 */
#ifndef __AIP_BASE64_H__
#define __AIP_BASE64_H__

#include <iostream>
#include <string>

namespace aip {
    
    static const std::string base64_chars =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz"
    "0123456789+/";
    
    
    static inline bool is_base64(const char c)
    {
        return (isalnum(c) || (c == '+') || (c == '/'));
    }
    
    std::string base64_encode(const char * 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] = '\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 = (int) 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;  
    }
    
}
#endif