//template params：N number digits. S start position//sample data {0x12, 0x34, 0x56, 0x78, 0x9F} if (N=4,S=1) then result = 2345template <int N,int S=0>class bcd_to_int{public:static int parse(char* src){static_assert(sizeof(int)==4, "int must be 4 byte");static_assert(N <= 10,"int not exceed 10 digits");static_assert(S==1 || S==0, "S int [0,1]");char buff[N + 1] = { 0 };typedef std::conditional<S%2 == 0, std::true_type, std::false_type>::type is_even_type;parse_helper<N>(src, buff, is_even_type());return boost::lexical_cast<int>(buff); ;}template<int N>static void parse_helper(char* src, char* buff, std::true_type){buff[0] = ((*src & 0xF0) >> 4) + 0x30;parse_helper<N-1>(src, buff + 1, std::false_type());}template<>static void parse_helper<0>(char* src, char* buff, std::true_type){}template<int N>static void parse_helper(char* src, char* buff,std::false_type){buff[0] = (*src & 0x0F) + 0x30;parse_helper<N-1>(src + 1, buff + 1, std::true_type());}template<>static void parse_helper<0>(char* src, char* buff,std::false_type){}};int main(){char src[] = { 0x89,0x89,0x89,0x89,0x89 };int ret = bcd_to_int<9>::parse(src); //999999999//bcd_to_int<10>::parse(src); will throw errorret = bcd_to_int<3,1>::parse(src); //989return 0;}
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