#include "string.h"

#define INVALID_VALUE_LXX	((1 << (8 * sizeof(int) -1)) - 1)

/*有符号整型最大值,假设越界将为0, and - is prioty of <<*/

#define A2a(ch) (('a' <= (ch) && (ch) <= 'f') ? (ch) : ((ch) - 'A' + 'a'))

bool is0to9(char ch)

{

	if ('0' <= ch && ch <= '9')

	{

		return true;

	}

	else

	{

		return false;

	}

}

bool isatoF(char ch)

{

	if (('a' <= ch && ch <= 'f') || ('A' < ch && ch <= 'F'))

	{

		return true;

	}

	else

	{

		return false;

	}

}

int a2iLxx(char* ch)

{

	int index = 0;

	int retVal = 0;

	bool flag = false;

	if (NULL == ch)

	{

		return INVALID_VALUE_LXX;

	}

	/*Ox*/

	if ('0' == ch[0] && ('x' == ch[1] || 'X' == ch[1]))

	{

		index = 2;

		for (; ch[index] != '\0'; index++)

		{

			/* x * 2^y == x * 1 << y */

			if (is0to9(ch[index]))

			{

				retVal = (retVal << 4) + ch[index] - '0';

				continue;

			}

			if (isatoF(ch[index]))

			{

				retVal = (retVal << 4) + 10 + A2a(ch[index]) - 'a';

				continue;

			}

			return INVALID_VALUE_LXX;

		}

		return retVal;

	}

	/*10*/

	index = 0;

	if ('-' == ch[0])

	{

		/*负数*/

		flag = true;

		index = 1;

	}

	for (; ch[index] != '\0'; index++)

	{

		if (!is0to9(ch[index]))

		{

			return INVALID_VALUE_LXX;

		}

		retVal = retVal * 10 + ch[index] - '0';

	}

	if (flag)

	{

		return -retVal;

	}

	else

	{

		return retVal;

	}

}

void main()

{

	char ch1[] = "123";

	char ch2[] = "-234";

	char ch3[] = "0";

	char ch4[] = "0x123";

	char ch5[] = "0xff";

	int a = INVALID_VALUE_LXX;

	char d1 = A2a('a');

	char d2 = A2a('B');

	/*调试查看值*/

	a = a2iLxx(ch1);

	a = a2iLxx(ch2);

	a = a2iLxx(ch3);

	a = a2iLxx(ch4);

	a = a2iLxx(ch5);

}