请教怎么将一个字符串两两解析成十六进制值存入一个字节中

int __stdcall CrnHexToByte(LPCSTR lpInBuf, LPBYTE lpOutBuf)
{
    size_t uInLen;
    uInLen = strlen(lpInBuf);

    int nResult = 0;
    if (uInLen < 2) return nResult;

    BYTE c;
    for (size_t i = 0; i < uInLen; i += 2)
    {
        // 输出高4位
        c = lpInBuf[i];
        if (c >= '0' && c <= '9') lpOutBuf[nResult] = (c - '0') << 4;
        else if (c >= 'A' && c <= 'F') lpOutBuf[nResult] = (c - 'A' + 10) << 4;

        // 输出低4位
        c = lpInBuf[i + 1];
        if (c >= '0' && c <= '9') lpOutBuf[nResult++] |= (c - '0');
        else if (c >= 'A' && c <= 'F') lpOutBuf[nResult++] |= (c - 'A' + 10);
    }

    return nResult;
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    char sz[] = "4A9000";
    unsigned char bt[3];

    int n = CrnHexToByte(sz, bt);
    Caption = n;
}

------解决方案--------------------
大概是这样的

C/C++ code

int ReadHexStr(const char *szSrc, unsigned char *pucOutput) {
    const char *pch = szSrc;
    int nCount;

    int snChar = 0;
    while ( *szSrc != 0 ) {
        unsigned char ucValue;
        switch ( *szSrc ) {
        case '0' :
        case '1' :
        case '2' :
        case '3' :
        case '4' :
        case '5' :
        case '6' :
        case '7' :
        case '8' :
        case '9' :
            ucValue = *szSrc - '0';
            break;
        case 'A' :
        case 'B' :
        case 'C' :
        case 'D' :
        case 'E' :
        case 'F' :
            ucValue = *szSrc - 'A' + 10;
            break;
        case 'a' :
        case 'b' :
        case 'c' :
        case 'd' :
        case 'e' :
        case 'f' :
            ucValue = *szSrc - 'a' + 10;
            break;
        default :
            assert(false);
        }
        nCount = snChar / 2;
        if ( snChar++ % 2 == 0 )
            pucOutput[nCount] = ucValue;
        else
            pucOutput[nCount] = pucOutput[nCount] << 4 + ucValue;
    }

    nCount = (snChar + 1) / 2;
    pucOutput[nCount] = '\0';

    return nCount;
}