Base64用途
1.用于对SOHO级路由器（网关设备）管理员帐户密码的加密
2.流媒体网站对于播放的流媒体文件的路径的加密
3.迅雷等下载软件对下载链接地址的加密
Base64算法
Base64编码要求把3个8位字节（3*8=24）转化为4个6位的字节（4*6=24），之后在6位的前面补两个0，形成8位一个字节的形式。
Base64类
函数：
unsigned int CreateMatchingEncodingBuffer (unsigned int p_InputByteCount, char** p_ppEncodingBuffer);
创建匹配于编码的缓存空间。参数：1输入字节数，2进行编码需要的缓存空间；返回值：缓存空间大小。
unsigned int CreateMatchingDecodingBuffer (char* p_pInputBufferString, char** p_ppDecodingBuffer);
创建匹配于解码的缓存空间。参数：1解码对象缓存，2进行解码需要的缓存空间；返回值：缓存空间大小。
void EncodeBuffer (char* p_pInputBuffer, unsigned int p_InputBufferLength, char* p_pOutputBufferString);
进行编码。参数：1明文，2明文长度，3密文输出。
unsigned int DecodeBuffer (char* p_pInputBufferString, char* p_pOutputBuffer);
进行解码。参数：1密文，2明文；返回值：明文长度
C++实现：
头文件：
View Code
/************************************************ * * * CBase64.h * * Base 64 de- and encoding class * * * * ============================================ * * * * This class was written on 28.05.2003 * * by Jan Raddatz [jan-raddatz@web.de] * * * * ============================================ * * * * Copyright (c) by Jan Raddatz * * This class was published @ codeguru.com * * 28.05.2003 * * * ************************************************/ #pragma once #include <afx.h> #include <stdlib.h> #include <math.h> #include <memory.h> const static unsigned int MAX_LINE_LENGTH = 76; const static char BASE64_ALPHABET [64] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', // 0 - 9 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', // 10 - 19 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', // 20 - 29 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 30 - 39 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', // 40 - 49 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', // 50 - 59 '8', '9', '+', '/' // 60 - 63 }; const static char BASE64_DEALPHABET [128] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0 - 9 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 10 - 19 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20 - 29 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 30 - 39 0, 0, 0, 62, 0, 0, 0, 63, 52, 53, // 40 - 49 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, // 50 - 59 0, 61, 0, 0, 0, 0, 1, 2, 3, 4, // 60 - 69 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, // 70 - 79 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, // 80 - 89 25, 0, 0, 0, 0, 0, 0, 26, 27, 28, // 90 - 99 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // 100 - 109 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, // 110 - 119 49, 50, 51, 0, 0, 0, 0, 0 // 120 - 127 }; enum { UNABLE_TO_OPEN_INPUT_FILE, UNABLE_TO_OPEN_OUTPUT_FILE, UNABLE_TO_CREATE_OUTPUTBUFFER }; class CBase64 { public: CBase64 (); unsigned int CalculateRecquiredEncodeOutputBufferSize (unsigned int p_InputByteCount); unsigned int CalculateRecquiredDecodeOutputBufferSize (char* p_pInputBufferString); void EncodeByteTriple (char* p_pInputBuffer, unsigned int InputCharacters, char* p_pOutputBuffer); unsigned int DecodeByteQuartet (char* p_pInputBuffer, char* p_pOutputBuffer); void EncodeBuffer (char* p_pInputBuffer, unsigned int p_InputBufferLength, char*p_pOutputBufferString); unsigned int DecodeBuffer (char* p_pInputBufferString, char* p_pOutputBuffer); unsigned int CreateMatchingEncodingBuffer (unsigned int p_InputByteCount, char** p_ppEncodingBuffer); unsigned int CreateMatchingDecodingBuffer (char* p_pInputBufferString, char** p_ppDecodingBuffer); unsigned int EncodeFile (char* p_pSourceFileName, char* p_pEncodedFileName); unsigned int DecodeFile (char* p_pSourceFileName, char* p_pDecodedFileName); };
cpp文件：
View Code
/************************************************ * * * CBase64.cpp * * Base 64 de- and encoding class * * * * ============================================ * * * * This class was written on 28.05.2003 * * by Jan Raddatz [jan-raddatz@web.de] * * * * ============================================ * * * * Copyright (c) by Jan Raddatz * * This class was published @ codeguru.com * * 28.05.2003 * * * ************************************************/ #include "stdafx.h" #include "CBase64.h" CBase64::CBase64 () { } unsigned int CBase64::CalculateRecquiredEncodeOutputBufferSize (unsigned int p_InputByteCount) { div_t result = div (p_InputByteCount, 3); unsigned int RecquiredBytes = 0; if (result.rem == 0) { // Number of encoded characters RecquiredBytes = result.quot * 4; // CRLF -> "\r\n" each 76 characters result = div (RecquiredBytes, 76); RecquiredBytes += result.quot * 2; // Terminating null for the Encoded String RecquiredBytes += 1; return RecquiredBytes; } else { // Number of encoded characters RecquiredBytes = result.quot * 4 + 4; // CRLF -> "\r\n" each 76 characters result = div (RecquiredBytes, 76); RecquiredBytes += result.quot * 2; // Terminating null for the Encoded String RecquiredBytes += 1; return RecquiredBytes; } } unsigned int CBase64::CalculateRecquiredDecodeOutputBufferSize (char* p_pInputBufferString) { unsigned int BufferLength = strlen (p_pInputBufferString); div_t result = div (BufferLength, 4); if (p_pInputBufferString [BufferLength - 1] != '=') { return result.quot * 3; } else { if (p_pInputBufferString [BufferLength - 2] == '=') { return result.quot * 3 - 2; } else { return result.quot * 3 - 1; } } } void CBase64::EncodeByteTriple (char* p_pInputBuffer, unsigned int InputCharacters, char* p_pOutputBuffer) { unsigned int mask = 0xfc000000; unsigned int buffer = 0; char* temp = (char*) &buffer; temp [3] = p_pInputBuffer [0]; if (InputCharacters > 1) temp [2] = p_pInputBuffer [1]; if (InputCharacters > 2) temp [1] = p_pInputBuffer [2]; switch (InputCharacters) { case 3: { p_pOutputBuffer [0] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [1] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [2] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [3] = BASE64_ALPHABET [(buffer & mask) >> 26]; break; } case 2: { p_pOutputBuffer [0] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [1] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [2] = BASE64_ALPHABET [(buffer & mask) >> 26]; p_pOutputBuffer [3] = '='; break; } case 1: { p_pOutputBuffer [0] = BASE64_ALPHABET [(buffer & mask) >> 26]; buffer = buffer << 6; p_pOutputBuffer [1] = BASE64_ALPHABET [(buffer & mask) >> 26]; p_pOutputBuffer [2] = '='; p_pOutputBuffer [3] = '='; break; } } } unsigned int CBase64::DecodeByteQuartet (char* p_pInputBuffer, char* p_pOutputBuffer) { unsigned int buffer = 0; if (p_pInputBuffer[3] == '=') { if (p_pInputBuffer[2] == '=') { buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[0]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[1]]) << 6; buffer = buffer << 14; char* temp = (char*) &buffer; p_pOutputBuffer [0] = temp [3]; return 1; } else { buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[0]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[1]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[2]]) << 6; buffer = buffer << 8; char* temp = (char*) &buffer; p_pOutputBuffer [0] = temp [3]; p_pOutputBuffer [1] = temp [2]; return 2; } } else { buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[0]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[1]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[2]]) << 6; buffer = (buffer | BASE64_DEALPHABET [p_pInputBuffer[3]]) << 6; buffer = buffer << 2; char* temp = (char*) &buffer; p_pOutputBuffer [0] = temp [3]; p_pOutputBuffer [1] = temp [2]; p_pOutputBuffer [2] = temp [1]; return 3; } return -1; } void CBase64::EncodeBuffer(char* p_pInputBuffer, unsigned int p_InputBufferLength, char* p_pOutputBufferString) { unsigned int FinishedByteQuartetsPerLine = 0; unsigned int InputBufferIndex = 0; unsigned int OutputBufferIndex = 0; memset (p_pOutputBufferString, 0, CalculateRecquiredEncodeOutputBufferSize (p_InputBufferLength)); while (InputBufferIndex < p_InputBufferLength) { if (p_InputBufferLength - InputBufferIndex <= 2) { FinishedByteQuartetsPerLine ++; EncodeByteTriple (p_pInputBuffer + InputBufferIndex, p_InputBufferLength - InputBufferIndex, p_pOutputBufferString + OutputBufferIndex); break; } else { FinishedByteQuartetsPerLine++; EncodeByteTriple (p_pInputBuffer + InputBufferIndex, 3, p_pOutputBufferString + OutputBufferIndex); InputBufferIndex += 3; OutputBufferIndex += 4; } if (FinishedByteQuartetsPerLine == 19) { p_pOutputBufferString [OutputBufferIndex ] = '\r'; p_pOutputBufferString [OutputBufferIndex+1] = '\n'; p_pOutputBufferString += 2; FinishedByteQuartetsPerLine = 0; } } } unsigned int CBase64::DecodeBuffer (char* p_pInputBufferString, char* p_pOutputBuffer) { unsigned int InputBufferIndex = 0; unsigned int OutputBufferIndex = 0; unsigned int InputBufferLength = strlen (p_pInputBufferString); char ByteQuartet [4]; while (InputBufferIndex < InputBufferLength) { for (int i = 0; i < 4; i++) { ByteQuartet [i] = p_pInputBufferString [InputBufferIndex]; // Ignore all characters except the ones in BASE64_ALPHABET if ((ByteQuartet [i] >= 48 && ByteQuartet [i] <= 57) || (ByteQuartet [i] >= 65 && ByteQuartet [i] <= 90) || (ByteQuartet [i] >= 97 && ByteQuartet [i] <= 122) || ByteQuartet [i] == '+' || ByteQuartet [i] == '/' || ByteQuartet [i] == '=') { } else { // Invalid character i--; } InputBufferIndex++; } OutputBufferIndex += DecodeByteQuartet (ByteQuartet, p_pOutputBuffer + OutputBufferIndex); } // OutputBufferIndex gives us the next position of the next decoded character // inside our output buffer and thus represents the number of decoded characters // in our buffer. return OutputBufferIndex; } unsigned int CBase64::CreateMatchingEncodingBuffer (unsigned int p_InputByteCount, char** p_ppEncodingBuffer) { unsigned int Size = CalculateRecquiredEncodeOutputBufferSize (p_InputByteCount); (*p_ppEncodingBuffer) = (char*) malloc (Size); memset (*p_ppEncodingBuffer, 0, Size); return Size; } unsigned int CBase64::CreateMatchingDecodingBuffer (char* p_pInputBufferString, char** p_ppDecodingBuffer) { unsigned int Size = CalculateRecquiredDecodeOutputBufferSize (p_pInputBufferString); (*p_ppDecodingBuffer) = (char*) malloc (Size+1); memset (*p_ppDecodingBuffer, 0, Size+1); return Size+1; } unsigned int CBase64::EncodeFile (char* p_pSourceFileName, char* p_pEncodedFileName) { CFile InputFile; CFile OutputFile; if (!InputFile.Open (p_pSourceFileName, CFile::modeRead)) return UNABLE_TO_OPEN_INPUT_FILE; if (!OutputFile.Open (p_pEncodedFileName, CFile::modeCreate|CFile::modeWrite)) return UNABLE_TO_OPEN_OUTPUT_FILE; char InputBuffer [19 * 3]; char* pOutputBuffer; CreateMatchingEncodingBuffer (sizeof (InputBuffer), &pOutputBuffer); if (pOutputBuffer == 0) return UNABLE_TO_CREATE_OUTPUTBUFFER; unsigned int ReadBytes = 0; while ((ReadBytes = InputFile.Read (InputBuffer, sizeof (InputBuffer))) != 0) { EncodeBuffer (InputBuffer, ReadBytes, pOutputBuffer); OutputFile.Write (pOutputBuffer, strlen (pOutputBuffer)); } OutputFile.Flush (); OutputFile.Close (); InputFile.Close (); return 0; } unsigned int CBase64::DecodeFile (char* p_pSourceFileName, char* p_pDecodedFileName) { CStdioFile InputFile; CFile OutputFile; if (!InputFile.Open (p_pSourceFileName, CFile::modeRead)) return UNABLE_TO_OPEN_INPUT_FILE; if (!OutputFile.Open (p_pDecodedFileName, CFile::modeCreate|CFile::modeWrite)) return UNABLE_TO_OPEN_OUTPUT_FILE; CString InputBuffer; char OutputBuffer[64]; unsigned int ReadBytes = 0; while ((ReadBytes = InputFile.ReadString (InputBuffer)) != 0) { InputBuffer.Remove ('\r'); InputBuffer.Remove ('\n'); unsigned int DecodedBytes = DecodeBuffer ((LPTSTR) (LPCTSTR) InputBuffer, OutputBuffer); OutputFile.Write (&OutputBuffer [0], DecodedBytes); } OutputFile.Flush (); OutputFile.Close (); InputFile.Close (); return 0; }
参考：
1.Base64-维基百科（http://zh.wikipedia.org/wiki/Base64）
2.BASE 64 Decoding and Encoding Class (http://www.codeguru.com/cpp/cpp/algorithms/article.php/c5099)