问题描述
嘿，所有，我目前正试图编写一个编译时字符串加密（使用'字符串'和'加密'相当宽松）lib。
我到目前为止如下：
// Cacluate在编译时的窄字符串长度
template< char ... ArgsT>
struct CountArgs
{
template< char ... ArgsInnerT> struct Counter;
template< char Cur，char ... Tail>
struct Counter< Cur，Tail ...>
{
static unsigned long const Value = Counter< Tail ...> :: Value + 1;
};
template< char Cur>
struct Counter< Cur>
{
static unsigned long const Value = 1;
};
static unsigned long const Value = Counter< ArgsT ...> :: Value;
};
//'在编译时加密窄字符串
template< char ... Chars>
struct EncryptCharsA
{
static const char Value [CountArgs< Chars ...> :: Value + 1];
};
template< char ... Chars>
char const EncryptCharsA< Chars ...> :: Value [CountArgs< Chars ...> :: Value + 1] =
{
Chars ...
};
但是我不知道如何对字符执行操作，数组。我只想对每个字符执行一个简单的操作（例如'（（（c ^ 0x12）^ 0x55）+ 1）'其中c是字符）。
感谢所有。
如果你只是想一次操作一个字符，它的容易：
template< char c& struct add_three {
enum {value = c + 3};
};
template< char ... Chars> struct EncryptCharsA {
static const char value [sizeof ...（Chars）+ 1];
};
template< char ... Chars>
char const EncryptCharsA< Chars ...> :: value [sizeof ...（Chars）+ 1] = {
add_three< Chars> :: value ...
};
int main（）{
std :: cout< EncryptCharsA<'A'，'B'，'C'> :: value< std :: endl;
//打印DEF
}
注意 CountArgs 是多余的（这就是 sizeof ... ），并且这使用。
要使转换依赖于前面的结果，一个选项是递归地使用字符，一次一个，逐步构建新模板：
模板< char ... P> struct StringBuilder {
template< char C> struct add_char {
typedef StringBuilder< P ...，C>类型;
};
static const char value [sizeof ...（P）+1];
};
template< char ... P> const char StringBuilder< P ...> :: value [sizeof ...（P）+1] = {
P ...
};
template< class B，char ...> struct EncryptImpl;
template< class B，char Seed，char Head，char ... Tail>
struct EncryptImpl< B，Seed，Head，Tail ...> {
static const char next = Head + Seed; //或任何
typedef typename EncryptImpl<
typename B :: template add_char< next> :: type，
next，Tail ...
> :: type type;
};
template< class B，char Seed> struct EncryptImpl< B，Seed> {
typedef B type;
};
template< char ... P> struct Encrypt {
typedef typename EncryptImpl< StringBuilder<>，0，P ...> :: type type;
};
Hey all, I'm currently trying to write a compile-time string encryption (using the words 'string' and 'encryption' quite loosely) lib.
What I have so far is as follows:
// Cacluate narrow string length at compile-time
template <char... ArgsT>
struct CountArgs
{
template <char... ArgsInnerT> struct Counter;
template <char Cur, char... Tail>
struct Counter<Cur, Tail...>
{
static unsigned long const Value = Counter<Tail...>::Value + 1;
};
template <char Cur>
struct Counter<Cur>
{
static unsigned long const Value = 1;
};
static unsigned long const Value = Counter<ArgsT...>::Value;
};
// 'Encrypt' narrow string at compile-time
template <char... Chars>
struct EncryptCharsA
{
static const char Value[CountArgs<Chars...>::Value + 1];
};
template<char... Chars>
char const EncryptCharsA<Chars...>::Value[CountArgs<Chars...>::Value + 1] =
{
Chars...
};
However I can't figure out how to perform operations on the characters as I expand them into the static array. I'd just like to execute a simple operation on each character (e.g. '(((c ^ 0x12) ^ 0x55) + 1)' where c is the character).
A shove in the right direction would be greatly appreciated.
Thanks all.
If you just want to operate on one character at a time its easy:
template<char c> struct add_three {
enum { value = c+3 };
};
template <char... Chars> struct EncryptCharsA {
static const char value[sizeof...(Chars) + 1];
};
template<char... Chars>
char const EncryptCharsA<Chars...>::value[sizeof...(Chars) + 1] = {
add_three<Chars>::value...
};
int main() {
std::cout << EncryptCharsA<'A','B','C'>::value << std::endl;
// prints "DEF"
}
Note that CountArgs is redundant (that's what sizeof... is for) and that this uses element-wise transformation of the elements in a parameter-pack.
To make the transformation dependent on previous results, one option would be to consume the characters recursively, one at a time, and incrementally build a new template from that:
template<char... P> struct StringBuilder {
template<char C> struct add_char {
typedef StringBuilder<P..., C> type;
};
static const char value[sizeof...(P)+1];
};
template<char... P> const char StringBuilder<P...>::value[sizeof...(P)+1] = {
P...
};
template<class B, char...> struct EncryptImpl;
template<class B, char Seed, char Head, char... Tail>
struct EncryptImpl<B, Seed, Head, Tail...> {
static const char next = Head + Seed; // or whatever
typedef typename EncryptImpl<
typename B::template add_char<next>::type,
next, Tail...
>::type type;
};
template<class B, char Seed> struct EncryptImpl<B, Seed> {
typedef B type;
};
template<char... P> struct Encrypt {
typedef typename EncryptImpl<StringBuilder<>, 0, P...>::type type;
};
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