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

请问如何将一个字符串两两解析成十六进制值存入一个字节中
如字符串“4A9000”
请问如何将它转换成十六进制数：0x4A, 0x90, 0x00，从而使得这三个能分别存入字节数组中呢？
即是 unsigned char ch[3];
ch[0] = 0x4A;
ch[1] = 0x90;
ch[2] = 0x00;


[解决办法]

C/C++ code

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;}
[解决办法]
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;}