C代码在查找方面与c++不同

我有以下代码块(不是我写的)，它执行映射并将ASCII字符重新编码为EBCDIC。

// Variables.
CodeHeader* tchpLoc = {};
...
memset(tchpLoc->m_ucpEBCDCMap, 0xff, 256);
for (i = 0; i < 256; i++) {
    if (tchpLoc->m_ucpASCIIMap[i] != 0xff) {
        ucTmp2 = i;
        asc2ebn(&ucTmp1, &ucTmp2, 1);
        tchpLoc->m_ucpEBCDCMap[ucTmp1] = tchpLoc->m_ucpASCIIMap[i];
    }
}

CodeHeader定义为

typedef struct {
    ...
    UCHAR* m_ucpASCIIMap; 
    UCHAR* m_ucpEBCDCMap; 
} CodeHeader;

和似乎给我带来问题的方法是

void asc2ebn(char* szTo, char* szFrom, int nChrs)
{
    while (nChrs--)
        *szTo++ = ucpAtoe[(*szFrom++) & 0xff];
}

[注:unsigned char数组ucpAtoe[256]在题末复制，以供参考]。

现在，我有一个旧的C应用程序和我的c++ 11转换并行运行，这两个代码编写了一个巨大的.bin文件，并且有一个微小的差异，我已经跟踪到上面的代码。这两个代码的情况是

...
    if (tchpLoc->m_ucpASCIIMap[i] != 0xff) {
        ucTmp2 = i;
        asc2ebn(&ucTmp1, &ucTmp2, 1);
        tchpLoc->m_ucpEBCDCMap[ucTmp1] = tchpLoc->m_ucpASCIIMap[i];
    }

进入i = 32, asc2ebn方法返回ucTmp1作为64或'@' 用于C和c++变体 great。下一项是i = 48，对于这个值，asc2ebn方法返回ucTmp1作为240或'ð', c++代码返回ucTmp1作为-16或'ð'。我的问题是为什么这个查找/转换为产生不同的结果正好相同的输入和查找数组(复制如下)?

在这种情况下，旧的C代码被认为是正确的，所以我希望c++对这个查找/转换产生相同的结果。谢谢你的宝贵时间。

static UCHAR ucpAtoe[256] = {
    'x00','x01','x02','x03','x37','x2d','x2e','x2f',/*00-07*/
    'x16','x05','x25','x0b','x0c','x0d','x0e','x0f',/*08-0f*/
    'x10','x11','x12','xff','x3c','x3d','x32','xff',/*10-17*/
    'x18','x19','x3f','x27','x22','x1d','x35','x1f',/*18-1f*/
    'x40','x5a','x7f','x7b','x5b','x6c','x50','xca',/*20-27*/
    'x4d','x5d','x5c','x4e','x6b','x60','x4b','x61',/*28-2f*/
    'xf0','xf1','xf2','xf3','xf4','xf5','xf6','xf7',/*30-37*/
    'xf8','xf9','x7a','x5e','x4c','x7e','x6e','x6f',/*38-3f*/
    'x7c','xc1','xc2','xc3','xc4','xc5','xc6','xc7',/*40-47*/
    'xc8','xc9','xd1','xd2','xd3','xd4','xd5','xd6',/*48-4f*/
    'xd7','xd8','xd9','xe2','xe3','xe4','xe5','xe6',/*50-57*/
    'xe7','xe8','xe9','xad','xe0','xbd','xff','x6d',/*58-5f*/
    'x79','x81','x82','x83','x84','x85','x86','x87',/*60-67*/
    'x88','x89','x91','x92','x93','x94','x95','x96',/*68-6f*/
    'x97','x98','x99','xa2','xa3','xa4','xa5','xa6',/*70-77*/
    'xa7','xa8','xa9','xc0','x6a','xd0','xa1','xff',/*78-7f*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*80-87*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*88-8f*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*90-97*/
    'xff','xff','xff','x4a','xff','xff','xff','xff',/*98-9f*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*a0-a7*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*a8-af*/
    'xff','xff','xff','x4f','xff','xff','xff','xff',/*b0-b7*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*b8-bf*/
    'xff','xff','xff','xff','xff','x8f','xff','xff',/*c0-c7*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*c8-cf*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*d0-d7*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*d8-df*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*e0-e7*/
    'xff','xff','xff','xff','xff','xff','xff','xff',/*e8-ef*/
    'xff','xff','xff','x8c','xff','xff','xff','xff',/*f0-f7*/
    'xff','xff','xff','xff','xff','xff','xff','xff' };