#include <stdio.h>
#include <unistd.h>
#include <string.h>

//字串轉換成16進位制
inline char *CharArrayToHexString(char* pOut, const int nMaxLen, const char* pInput, const int nInLen)
{
    const char* chHexList = "0123456789ABCDEF";
    int nIndex = 0;
    int i=0, j=0;
    for (i=0, j=0;i<nInLen;i++, j+=2)
    {
        nIndex = (pInput[i] & 0xf);
        pOut[i*2+1] = chHexList[nIndex];
        nIndex = ((pInput[i]>>4) & 0xf);
        pOut[i*2] = chHexList[nIndex];
    }
    return pOut;
}

//16進位制轉換成字串 方法1
inline char *HexStringToCharArray(char* pOut, const char* pInput, const int nInLen)
{
    int i=0;
    int tc;    
    for (i = 0; i < nInLen/2 ; i++)
    {
        sscanf(pInput+i*2, "%02X", (unsigned int*)(pOut+i));
    }
    pOut[i] = '\0';
    return pOut;
}

//16進位制轉換成字串 方法2
char a2x(char ch)
{
    switch(ch)
    {
    case '1':
        return 1;
    case '2':
        return 2;
    case '3':
        return 3;
    case '4':
        return 4;
    case '5':
        return 5;
    case '6':
        return 6;
    case '7':
        return 7;
    case '8':
        return 8;
    case '9':
        return 9;
    case 'A':
    case 'a':
        return 10;
    case 'B':
    case 'b':
        return 11;
    case 'C':
    case 'c':
        return 12;
    case 'D':
    case 'd':
        return 13;
    case 'E':
    case 'e':
        return 14;
    case 'F':
    case 'f':
        return 15;
    default:
        break;;
    }
 
    return 0;
}
 

int main()
{
 char szTmp[9] = "99990198";
 char szHex[20] = {0};
 char szAfter[9] = {0};
 int i = 0;
 memset(szAfter, 0, sizeof(szAfter));

 int nLen = strnlen(szTmp, sizeof(szTmp));

 CharArrayToHexString(szHex, (int)sizeof(szHex), szTmp, nLen);
 nLen = 2*nLen;
 szHex[nLen] = '\0';
 printf("szHex:%s \n\n", szHex);
 
#if 1
 HexStringToCharArray(szAfter, szHex, nLen);
#else  
 while(szHex[i])
 {
  szAfter[i >> 1] = (a2x(szHex[i]) << 4) | a2x(szHex[i + 1]);
  i += 2;
 }
 szAfter[i >> 1] = '\0';
#endif
 printf("szAfter:%s \n\n", szAfter);

 return 0;
}