116 lines
4.6 KiB
C++
116 lines
4.6 KiB
C++
#include <string>
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#include <iostream>
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/**
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* Base64 编码/解码
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* @author liruixing
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*/
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class Base64{
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private:
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std::string _base64_table;
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static const char base64_pad = '=';
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public:
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Base64()
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{
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_base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; /*这是Base64编码使用的标准字典*/
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}
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/**
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* 这里必须是unsigned类型，否则编码中文的时候出错
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*/
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std::string Encode(const unsigned char * str,int bytes) {
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int num = 0,bin = 0,i;
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std::string _encode_result;
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const unsigned char * current;
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current = str;
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while(bytes > 2) {
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_encode_result += _base64_table[current[0] >> 2];
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_encode_result += _base64_table[((current[0] & 0x03) << 4) + (current[1] >> 4)];
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_encode_result += _base64_table[((current[1] & 0x0f) << 2) + (current[2] >> 6)];
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_encode_result += _base64_table[current[2] & 0x3f];
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current += 3;
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bytes -= 3;
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}
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if(bytes > 0)
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{
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_encode_result += _base64_table[current[0] >> 2];
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if(bytes%3 == 1) {
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_encode_result += _base64_table[(current[0] & 0x03) << 4];
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_encode_result += "==";
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} else if(bytes%3 == 2) {
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_encode_result += _base64_table[((current[0] & 0x03) << 4) + (current[1] >> 4)];
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_encode_result += _base64_table[(current[1] & 0x0f) << 2];
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_encode_result += "=";
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}
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}
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return _encode_result;
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}
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std::string Decode(const char *str,int length) {
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//解码表
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const std::int8_t DecodeTable[] =
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{
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -2, -2, -1, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -2, -2, -2,
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-2, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -2, -2, -2, -2, -2,
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-2, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
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};
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int bin = 0,i=0,pos=0;
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std::string _decode_result;
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const char *current = str;
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char ch;
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while( (ch = *current++) != '\0' && length-- > 0 )
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{
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if (ch == base64_pad) { // 当前一个字符是“=”号
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/*
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先说明一个概念：在解码时，4个字符为一组进行一轮字符匹配。
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两个条件：
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1、如果某一轮匹配的第二个是“=”且第三个字符不是“=”，说明这个带解析字符串不合法，直接返回空
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2、如果当前“=”不是第二个字符，且后面的字符只包含空白符，则说明这个这个条件合法，可以继续。
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*/
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if (*current != '=' && (i % 4) == 1) {
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return NULL;
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}
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continue;
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}
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ch = DecodeTable[ch];
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//这个很重要，用来过滤所有不合法的字符
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if (ch < 0 ) { /* a space or some other separator character, we simply skip over */
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continue;
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}
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switch(i % 4)
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{
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case 0:
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bin = ch << 2;
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break;
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case 1:
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bin |= ch >> 4;
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_decode_result += bin;
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bin = ( ch & 0x0f ) << 4;
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break;
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case 2:
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bin |= ch >> 2;
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_decode_result += bin;
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bin = ( ch & 0x03 ) << 6;
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break;
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case 3:
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bin |= ch;
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_decode_result += bin;
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break;
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}
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i++;
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}
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return _decode_result;
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}
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};
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