Base64加密解密算法的C/C++代码实现

来源：互联网发布：西门子plc编程视频教程编辑：程序博客网时间：2024/05/21 09:14

这个Base64是从Live555的代码里面提取出来的，请大家放心使用吧。

Base64的加密解密的算法和原理我就不想说了。。。。，网上有很多介绍原理的文章。

这个算法有啥好处呢？为什么我们要用它？

Base64算法不是为了防止内容被人破解而使用的算法，因为破解Base64太容易了，就是简单的字符替换。

Base64还有个不好的地方，就是加密后，长度会变成。

那我们为何还要使用Base64 呢？因为Base64可以把乱七八糟的二进制转化为字符串，这个特性在很多地方很有用。

Base64.h 头文件

Base64.cpp 文件

/**********This library is free software; you can redistribute it and/or modify it underthe terms of the GNU Lesser General Public License as published by theFree Software Foundation; either version 2.1 of the License, or (at youroption) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)This library is distributed in the hope that it will be useful, but WITHOUTANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESSFOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License formore details.You should have received a copy of the GNU Lesser General Public Licensealong with this library; if not, write to the Free Software Foundation, Inc.,51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA**********/// "liveMedia"// Copyright (c) 1996-2010 Live Networks, Inc. All rights reserved.// Base64 encoding and decoding// implementation#include "base64.h"#include <string.h>static char base64DecodeTable[256];char* strDup(char const* str) {if (str == NULL) return NULL;size_t len = strlen(str) + 1;char* copy = new char[len];if (copy != NULL) {memcpy(copy, str, len);}return copy;}char* strDupSize(char const* str) {if (str == NULL) return NULL;size_t len = strlen(str) + 1;char* copy = new char[len];return copy;}static void initBase64DecodeTable(){ int i; for (i = 0; i < 256; ++i) base64DecodeTable[i] = (char)0x80; // default value: invalid for (i = 'A'; i <= 'Z'; ++i) base64DecodeTable[i] = 0 + (i - 'A'); for (i = 'a'; i <= 'z'; ++i) base64DecodeTable[i] = 26 + (i - 'a'); for (i = '0'; i <= '9'; ++i) base64DecodeTable[i] = 52 + (i - '0'); base64DecodeTable[(unsigned char)'+'] = 62; base64DecodeTable[(unsigned char)'/'] = 63; base64DecodeTable[(unsigned char)'='] = 0;}unsigned char* base64Decode(char* in, unsigned int& resultSize, bool trimTrailingZeros) { static bool haveInitedBase64DecodeTable = false; if (!haveInitedBase64DecodeTable) { initBase64DecodeTable(); haveInitedBase64DecodeTable = true; } unsigned char* out = (unsigned char*)strDupSize(in); // ensures we have enough space int k = 0; int const jMax = strlen(in) - 3; // in case "in" is not a multiple of 4 bytes (although it should be) for (int j = 0; j < jMax; j += 4) { char inTmp[4], outTmp[4]; for (int i = 0; i < 4; ++i) { inTmp[i] = in[i+j]; outTmp[i] = base64DecodeTable[(unsigned char)inTmp[i]]; if ((outTmp[i]&0x80) != 0) outTmp[i] = 0; // pretend the input was 'A' } out[k++] = (outTmp[0]<<2) | (outTmp[1]>>4); out[k++] = (outTmp[1]<<4) | (outTmp[2]>>2); out[k++] = (outTmp[2]<<6) | outTmp[3]; } if (trimTrailingZeros) { while (k > 0 && out[k-1] == '/0') --k; } resultSize = k; unsigned char* result = new unsigned char[resultSize]; memmove(result, out, resultSize); delete[] out; return result;}static const char base64Char[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";char* base64Encode(char const* origSigned, unsigned origLength) { unsigned char const* orig = (unsigned char const*)origSigned; // in case any input bytes have the MSB set if (orig == NULL) return NULL; unsigned const numOrig24BitValues = origLength/3; bool havePadding = origLength > numOrig24BitValues*3; bool havePadding2 = origLength == numOrig24BitValues*3 + 2; unsigned const numResultBytes = 4*(numOrig24BitValues + havePadding); char* result = new char[numResultBytes+1]; // allow for trailing '/0' // Map each full group of 3 input bytes into 4 output base-64 characters: unsigned i; for (i = 0; i < numOrig24BitValues; ++i) { result[4*i+0] = base64Char[(orig[3*i]>>2)&0x3F]; result[4*i+1] = base64Char[(((orig[3*i]&0x3)<<4) | (orig[3*i+1]>>4))&0x3F]; result[4*i+2] = base64Char[((orig[3*i+1]<<2) | (orig[3*i+2]>>6))&0x3F]; result[4*i+3] = base64Char[orig[3*i+2]&0x3F]; } // Now, take padding into account. (Note: i == numOrig24BitValues) if (havePadding) { result[4*i+0] = base64Char[(orig[3*i]>>2)&0x3F]; if (havePadding2){ result[4*i+1] = base64Char[(((orig[3*i]&0x3)<<4) | (orig[3*i+1]>>4))&0x3F]; result[4*i+2] = base64Char[(orig[3*i+1]<<2)&0x3F]; } else { result[4*i+1] = base64Char[((orig[3*i]&0x3)<<4)&0x3F]; result[4*i+2] = '='; } result[4*i+3] = '='; } result[numResultBytes] = '/0'; return result;}