myvtm/Framework/Common/base64File.hpp

/** 该文件目前未在信创设备上使用 [Gifur@2022614]*/

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
using namespace std;

#define ERROR_INVALID_ARG -1
#define ERROR_INVALID_OP  -2
#define ERROR_INVALID_SYN -3
#define ERROR_OPEN_FILE   -4
#define OPERATION_SUCCESS 0


const char base64_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";


int encode64(FILE* input_file, std::string &output_file) {
    //Variables Declaration
    int decode_buffer = 0;
    int byteCount = 1; int temp;
    char raw_byte = 0; char out_byte = 0;

    //Read  and encode
    while (fread(&raw_byte, sizeof(char), 1, input_file)) {
        temp = raw_byte & ~(-1 << 8);
        decode_buffer = (decode_buffer << 8) + temp;

        if (byteCount % 3 == 0) { //Every 3 byte -> 4 base64 char
            for (temp = 0; temp < 4; temp++) {
                out_byte = base64_table[(decode_buffer >> (6 * (3 - temp)) & 0x3F)];
                output_file.push_back(out_byte);
            }
            decode_buffer = 0;
        }
        byteCount++;
    }

    if (byteCount % 3) { //If padding is needed
        for (temp = 0; temp < byteCount % 3; temp++)
            decode_buffer = (decode_buffer << 8); //Fill the missing 1 or 2 byte

        for (temp = 0; temp < 4 - (byteCount % 3); temp++) { //If fill 1 byte -> Get 3 char; if fill 2 byte -> get 2 char => 4-fill_no
            out_byte = base64_table[(decode_buffer >> (6 * (3 - temp)) & 0x3F)];
            output_file.push_back(out_byte);
        }
        for (temp = 0; temp < byteCount % 3; temp++)
            output_file.push_back('=');
    }

    return OPERATION_SUCCESS;
}

int decode64(std::string input_file, FILE* output_file) {
    int decode_buffer = 0;
    int byteCount = 1; int paddingCount = 0; int i;
    char raw_byte = 0; char resolved_byte = 0; unsigned char temp;

    //Read and decode
    while (fread(&raw_byte, sizeof(char), 1, output_file)) {
        if (raw_byte == '=') { //If a padding is encountered
            raw_byte = 'A'; //Turn it into 0
            paddingCount++;
        }

        //Decode the character
        const char* pt = strchr(base64_table, (unsigned char)raw_byte);

        if (!pt) {//Unable to resolve character
            return ERROR_INVALID_SYN;
        }

        resolved_byte = pt - base64_table;
        resolved_byte = resolved_byte & ~(-1 << 6); //Mask the byte to ensure all the bit except the last 6 is zero
        decode_buffer = (decode_buffer << 6) + resolved_byte;

        if (byteCount % 4 == 0) { //Every 4 base64 char -> 3 byte
            for (i = 0; i < 3 - paddingCount; i++) {
                temp = (decode_buffer >> (8 * (2 - i))) & ~(-1 << 8);

                fwrite(&temp, sizeof(char), 1, output_file);
            }

            decode_buffer = 0;
        }

        byteCount++;
    }

    return OPERATION_SUCCESS;
}