Synopsis:

       value=xtoi(hex_str)                

Arguments:

       hex_str - The hexadecimal string to convert to a decimal integer

Description:  Converts the hexadecimal value in the string hex_str to a decimal integer.

For Example:

       // Returns 255

       value=xtoi("FF");

       // Returns 11

       value=xtoi("b");

Returns: Returns the decimal integer equivalent of the hexadecimal number passed in the hex_str argument.