求助！！！程序运行出现问题

[feng_ye2015]

程序运行出现0x0043ac50 处未处理的异常: 0xC0000005: 读取位置 0x00000008 时发生访问冲突

程序如下：
CString Base64Decode(LPCTSTR lpszSrc)
{
ASSERT(lpszSrc != NULL && AfxIsValidString(lpszSrc));
const unsigned int BASE64_DECODE_TABLE[256] = {
255, 255, 255, 255, 255, 255, 255, 255, // 00 - 07
255, 255, 255, 255, 255, 255, 255, 255, // 08 - 15
255, 255, 255, 255, 255, 255, 255, 255, // 16 - 23
255, 255, 255, 255, 255, 255, 255, 255, // 24 - 31
255, 255, 255, 255, 255, 255, 255, 255, // 32 - 39
255, 255, 255, 62, 255, 255, 255, 63, // 40 - 47
52, 53, 54, 55, 56, 57, 58, 59, // 48 - 55
60, 61, 255, 255, 255, 255, 255, 255, // 56 - 63
255, 0, 1, 2, 3, 4, 5, 6, // 64 - 71
7, 8, 9, 10, 11, 12, 13, 14, // 72 - 79
15, 16, 17, 18, 19, 20, 21, 22, // 80 - 87
23, 24, 25, 255, 255, 255, 255, 255, // 88 - 95
255, 26, 27, 28, 29, 30, 31, 32, // 96 - 103
33, 34, 35, 36, 37, 38, 39, 40, // 104 - 111
41, 42, 43, 44, 45, 46, 47, 48, // 112 - 119
49, 50, 51, 255, 255, 255, 255, 255, // 120 - 127
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255 };


const int nSrcCount=(int)_tcslen(lpszSrc);
int nSize=nSrcCount/4*3;
if(lpszSrc[nSrcCount-1]=='=')
nSize--;
if(lpszSrc[nSrcCount-2]=='=')
nSize--;
char* pOutBuffer=new char[nSize+3];
ZeroMemory(pOutBuffer,nSize+3);
LPCTSTR pInBuffer=lpszSrc;
UINT iTest,iPack;
for(int i=0;i<nSize/3 ;i++)
{
for(int j=0;j<4;j++)
{
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
//InPtr++;
if (iTest == 0xFF)
{
j--;
continue; //读到255非法字符
}
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
pOutBuffer[2] = iPack;
iPack = iPack >> 8;
pOutBuffer[1] = iPack;
iPack = iPack >> 8;
pOutBuffer[0] = iPack;
//准备写入后3位
pOutBuffer+= 3; iPack = 0;

}
switch(nSize%3)
{
case 1:
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
if (iTest != 0xFF)
{
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
if (iTest != 0xFF)
{
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
iPack = iPack >> 4;
pOutBuffer[0] = iPack;
pOutBuffer++;
break;
case 2:
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
if (iTest != 0xFF)
{
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
if (iTest != 0xFF)
{
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
iTest = BASE64_DECODE_TABLE[*pInBuffer++]; // Read from InputBuffer.
if (iTest != 0xFF)
{
iPack = iPack << 6 ;
iPack = iPack | iTest ;
}
iPack = iPack >> 2;
pOutBuffer[1] = iPack;
iPack = iPack >> 8;
pOutBuffer[0] = iPack;
pOutBuffer+=2;
break;
default:
break;
}
pOutBuffer-=nSize;
CString strDecode=pOutBuffer;
delete pOutBuffer;
return strDecode;
}

[赵4老师]

崩溃的时候在弹出的对话框按相应按钮进入调试，按Alt+7键查看Call Stack即“调用堆栈”里面从上到下列出的对应从里层到外层的函数调用历史。双击某一行可将光标定位到此次调用的源代码或汇编指令处，看不懂时双击下一行，直到能看懂为止。

[zgl7903]

越界访问的可能性很大 int nSize=nSrcCount*3/4; 浮点型的先后顺序影响不大（除非移除），但是整形的结果不一样 如 n=11 n*3/4=8 n/4*3=6 可以打开 atlenc.h 看看 是源码

[feng_ye2015]

up.......