base64.hpp

//
//  base64.hpp
//  Neo4j-cpp-driver
//
//  Created by skyblue on 2017/7/9.
//  Copyright © 2017年 skyblue. All rights reserved.
//

#ifndef base64_hpp
#define base64_hpp

#include <string>

namespace neo4jDriver
{
    const char kBase64Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz"
    "0123456789+/";
    
    class Base64
    {
    public:
        static bool Encode(const std::string &in, std::string *out) {
            int i = 0, j = 0;
            size_t enc_len = 0;
            unsigned char a3[3];
            unsigned char a4[4];
            
            out->resize(EncodedLength(in));
            
            int input_len = in.size();
            std::string::const_iterator input = in.begin();
            
            while (input_len--) {
                a3[i++] = *(input++);
                if (i == 3) {
                    a3_to_a4(a4, a3);
                    
                    for (i = 0; i < 4; i++) {
                        (*out)[enc_len++] = kBase64Alphabet[a4[i]];
                    }
                    
                    i = 0;
                }
            }
            
            if (i) {
                for (j = i; j < 3; j++) {
                    a3[j] = '\0';
                }
                
                a3_to_a4(a4, a3);
                
                for (j = 0; j < i + 1; j++) {
                    (*out)[enc_len++] = kBase64Alphabet[a4[j]];
                }
                
                while ((i++ < 3)) {
                    (*out)[enc_len++] = '=';
                }
            }
            
            return (enc_len == out->size());
        }
        
        static bool Encode(const char *input, size_t input_length, char *out, size_t out_length) {
            int i = 0, j = 0;
            char *out_begin = out;
            unsigned char a3[3];
            unsigned char a4[4];
            
            size_t encoded_length = EncodedLength(input_length);
            
            if (out_length < encoded_length) return false;
            
            while (input_length--) {
                a3[i++] = *input++;
                if (i == 3) {
                    a3_to_a4(a4, a3);
                    
                    for (i = 0; i < 4; i++) {
                        *out++ = kBase64Alphabet[a4[i]];
                    }
                    
                    i = 0;
                }
            }
            
            if (i) {
                for (j = i; j < 3; j++) {
                    a3[j] = '\0';
                }
                
                a3_to_a4(a4, a3);
                
                for (j = 0; j < i + 1; j++) {
                    *out++ = kBase64Alphabet[a4[j]];
                }
                
                while ((i++ < 3)) {
                    *out++ = '=';
                }
            }
            
            return (out == (out_begin + encoded_length));
        }
        
        static bool Decode(const std::string &in, std::string *out) {
            int i = 0, j = 0;
            size_t dec_len = 0;
            unsigned char a3[3];
            unsigned char a4[4];
            
            int input_len = in.size();
            std::string::const_iterator input = in.begin();
            
            out->resize(DecodedLength(in));
            
            while (input_len--) {
                if (*input == '=') {
                    break;
                }
                
                a4[i++] = *(input++);
                if (i == 4) {
                    for (i = 0; i <4; i++) {
                        a4[i] = b64_lookup(a4[i]);
                    }
                    
                    a4_to_a3(a3,a4);
                    
                    for (i = 0; i < 3; i++) {
                        (*out)[dec_len++] = a3[i];
                    }
                    
                    i = 0;
                }
            }
            
            if (i) {
                for (j = i; j < 4; j++) {
                    a4[j] = '\0';
                }
                
                for (j = 0; j < 4; j++) {
                    a4[j] = b64_lookup(a4[j]);
                }
                
                a4_to_a3(a3,a4);
                
                for (j = 0; j < i - 1; j++) {
                    (*out)[dec_len++] = a3[j];
                }
            }
            
            return (dec_len == out->size());
        }
        
        static bool Decode(const char *input, size_t input_length, char *out, size_t out_length) {
            int i = 0, j = 0;
            char *out_begin = out;
            unsigned char a3[3];
            unsigned char a4[4];
            
            size_t decoded_length = DecodedLength(input, input_length);
            
            if (out_length < decoded_length) return false;
            
            while (input_length--) {
                if (*input == '=') {
                    break;
                }
                
                a4[i++] = *(input++);
                if (i == 4) {
                    for (i = 0; i <4; i++) {
                        a4[i] = b64_lookup(a4[i]);
                    }
                    
                    a4_to_a3(a3,a4);
                    
                    for (i = 0; i < 3; i++) {
                        *out++ = a3[i];
                    }
                    
                    i = 0;
                }
            }
            
            if (i) {
                for (j = i; j < 4; j++) {
                    a4[j] = '\0';
                }
                
                for (j = 0; j < 4; j++) {
                    a4[j] = b64_lookup(a4[j]);
                }
                
                a4_to_a3(a3,a4);
                
                for (j = 0; j < i - 1; j++) {
                    *out++ = a3[j];
                }
            }
            
            return (out == (out_begin + decoded_length));
        }
        
        static int DecodedLength(const char *in, size_t in_length) {
            int numEq = 0;
            
            const char *in_end = in + in_length;
            while (*--in_end == '=') ++numEq;
            
            return ((6 * in_length) / 8) - numEq;
        }
        
        static int DecodedLength(const std::string &in) {
            int numEq = 0;
            int n = in.size();
            
            for (std::string::const_reverse_iterator it = in.rbegin(); *it == '='; ++it) {
                ++numEq;
            }
            
            return ((6 * n) / 8) - numEq;
        }
        
        inline static int EncodedLength(size_t length) {
            return (length + 2 - ((length + 2) % 3)) / 3 * 4;
        }
        
        inline static int EncodedLength(const std::string &in) {
            return EncodedLength(in.length());
        }
        
        inline static void StripPadding(std::string *in) {
            while (!in->empty() && *(in->rbegin()) == '=') in->resize(in->size() - 1);
        }
        
    private:
        static inline void a3_to_a4(unsigned char * a4, unsigned char * a3) {
            a4[0] = (a3[0] & 0xfc) >> 2;
            a4[1] = ((a3[0] & 0x03) << 4) + ((a3[1] & 0xf0) >> 4);
            a4[2] = ((a3[1] & 0x0f) << 2) + ((a3[2] & 0xc0) >> 6);
            a4[3] = (a3[2] & 0x3f);
        }
        
        static inline void a4_to_a3(unsigned char * a3, unsigned char * a4) {
            a3[0] = (a4[0] << 2) + ((a4[1] & 0x30) >> 4);
            a3[1] = ((a4[1] & 0xf) << 4) + ((a4[2] & 0x3c) >> 2);
            a3[2] = ((a4[2] & 0x3) << 6) + a4[3];
        }
        
        static inline unsigned char b64_lookup(unsigned char c) {
            if(c >='A' && c <='Z') return c - 'A';
            if(c >='a' && c <='z') return c - 71;
            if(c >='0' && c <='9') return c + 4;
            if(c == '+') return 62;
            if(c == '/') return 63;
            return 255;
        }
    };
}

#endif /* base64_hpp */