学步园

/* ----------------------------------------------------------
文件名称：BASE64_API.h
功能描述：
	BASE64编码和解码

接口函数：
	Base64_Encode
	Base64_Decode

说明：
	1.	参考openssl-1.0.0。
	2.	改进接口，以使其适应TCHAR字符串。
	3.	修正EVP_DecodeBlock函数解码时未去掉填充字节的缺陷。
 ------------------------------------------------------------ */
#pragma once

#include <windows.h>

#ifdef	__cplusplus
extern "C" {
#endif

/*
功能：将二进制数据转换成BASE64编码字符串
参数说明：
	inputBuffer：要编码的二进制数据
	inputCount：数据长度
	outputBuffer：存储转换后的BASE64编码字符串
返回值：
	 -1：参数错误
	>=0：有效编码长度（字符数）,不包括字符串结束符。
备注：
	等效于openssl中EVP_EncodeBlock函数
*/
INT BASE64_Encode( const BYTE* inputBuffer, INT inputCount, TCHAR* outputBuffer );

/*
功能：将BASE64编码字符串转换为二进制数据
参数说明：
	inputBuffer：BASE64编码字符串
	inputCount：编码长度（字符数）,应该为4的倍数。
	outputBuffer：存储转换后的二进制数据
返回值：
	 -1：参数错误
	 -2：数据错误
	>=0：转换后的字节数
备注：
	等效于openssl中EVP_DecodeBlock函数
*/
INT BASE64_Decode( const TCHAR* inputBuffer, INT inputCount, BYTE* outputBuffer );

#ifdef  __cplusplus
}
#endif

#include "stdafx.h"
#include "BASE64_API.h"

static const CHAR* DATA_BIN2ASCII = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

INT BASE64_Encode( const BYTE* inputBuffer, INT inputCount, TCHAR* outputBuffer )
{
	INT i;
	BYTE b0, b1, b2;

	if( (inputBuffer == NULL) || (inputCount < 0) )
	{
		return -1;	// 参数错误
	}

	if( outputBuffer != NULL )
	{
		for( i = inputCount; i > 0; i -= 3 )
		{
			if( i >= 3 )
			{	// 将3字节数据转换成4个ASCII字符
				b0 = *inputBuffer++;
				b1 = *inputBuffer++;
				b2 = *inputBuffer++;

				*outputBuffer++ = DATA_BIN2ASCII[b0 >> 2];
				*outputBuffer++ = DATA_BIN2ASCII[((b0 << 4) | (b1 >> 4)) & 0x3F];
				*outputBuffer++ = DATA_BIN2ASCII[((b1 << 2) | (b2 >> 6)) & 0x3F];
				*outputBuffer++ = DATA_BIN2ASCII[b2 & 0x3F];
			}
			else
			{
				b0 = *inputBuffer++;
				if( i == 2 )
					b1 = *inputBuffer++; 
				else 
					b1 = 0;

				*outputBuffer++ = DATA_BIN2ASCII[b0 >> 2];
				*outputBuffer++ = DATA_BIN2ASCII[((b0 << 4) | (b1 >> 4)) & 0x3F];
				*outputBuffer++ = (i == 1) ? TEXT('=') : DATA_BIN2ASCII[(b1 << 2) & 0x3F];
				*outputBuffer++ = TEXT('=');
			}
		} // End for i

		*outputBuffer++ = TEXT('\0');	// 添加字符串结束标记
	}

	return ((inputCount + 2) / 3) * 4;	// 返回有效字符个数
}

#define B64_EOLN			0xF0	// 换行\n
#define B64_CR				0xF1	// 回车\r
#define B64_EOF				0xF2	// 连字符-
#define B64_WS				0xE0	// 跳格或者空格（\t、space）
#define B64_ERROR       	0xFF	// 错误字符
#define B64_NOT_BASE64(a)	(((a)|0x13) == 0xF3)

static const BYTE DATA_ASCII2BIN[128] = {
	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xE0,0xF0,0xFF,0xFF,0xF1,0xFF,0xFF,
	0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
	0xE0,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x3E,0xFF,0xF2,0xFF,0x3F,
	0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B,0x3C,0x3D,0xFF,0xFF,0xFF,0x00,0xFF,0xFF,
	0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,
	0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF,
	0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,
	0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0xFF,0xFF,0xFF,0xFF,0xFF
};

INT BASE64_Decode( const TCHAR* inputBuffer, INT inputCount, BYTE* outputBuffer )
{
	INT i, j;
	BYTE b[4];
	TCHAR ch;

	if( (inputBuffer == NULL) || (inputCount < 0) )
	{
		return -1;	// 参数错误
	}

	// 去除头部空白字符
	while( inputCount > 0 )
	{
		ch = *inputBuffer;
		if( (ch < 0) || (ch >= 0x80) )
		{
			return -2;	// 数据错误，不在ASCII字符编码范围内
		}
		else
		{
			if( DATA_ASCII2BIN[ch] == B64_WS )
			{
				inputBuffer++;
				inputCount--;
			}
			else
			{
				break;
			}
		}
	}

	// 去除尾部的空白字符、回车换行字符、连字符
	while( inputCount >= 4 )
	{
		ch = inputBuffer[inputCount - 1];
		if( (ch < 0) || (ch >= 0x80) )
		{
			return -2;	// 数据错误，不在ASCII字符编码范围内
		}
		else
		{
			if( B64_NOT_BASE64(DATA_ASCII2BIN[ch]) )
			{
				inputCount--;
			}
			else
			{
				break;
			}
		}
	}

	// 字符串长度必须为4的倍数
	if( (inputCount % 4) != 0 )
	{
		return -2;	// 数据错误
	}

	if( outputBuffer != NULL )
	{
		for( i = 0; i < inputCount; i += 4 )
		{
			for( j = 0; j < 4; j++ )
			{
				ch = *inputBuffer++;
				if( (ch < 0) || (ch >= 0x80) )
				{
					return -2;	// 数据错误，不在ASCII字符编码范围内
				}
				else
				{
					if( ch == '=' )	// 发现BASE64编码中的填充字符
					{
						break;
					}
					else
					{
						b[j] = DATA_ASCII2BIN[ch];
						if( b[j] & 0x80 )
						{
							return -2;	// 数据错误，无效的Base64编码字符
						}
					}					
				}
			} // End for j

			if( j == 4 )
			{
				*outputBuffer++ = (b[0] << 2) | (b[1] >> 4);
				*outputBuffer++ = (b[1] << 4) | (b[2] >> 2 );
				*outputBuffer++ = (b[2] << 6) | b[3];
			}
			else if( j == 3 )
			{	// 有1个填充字节
				*outputBuffer++ = (b[0] << 2) | (b[1] >> 4);
				*outputBuffer++ = (b[1] << 4) | (b[2] >> 2 );

				return (i >> 2) * 3 + 2;
			}
			else if( j == 2 )
			{	// 有2个填充字节
				*outputBuffer++ = (b[0] << 2) | (b[1] >> 4);

				return (i >> 2) * 3 + 1;
			}
			else
			{
				return -2;	// 数据错误，无效的Base64编码字符
			}			
		}	// End for i
	}

	return (inputCount >> 2) * 3;
}