Question

I want to do some caching in my project.

Let my API is int foo(int a, float b, float c, int d, char e)

Now in my project, there is lot of calls to above time consuming API with repeating values of a, b, c ,d and e. Now I want to store return value of this function with these arguments as keys.

suppose my call sequence is

foo(23, 3.45, 4.5, 90, 'd') // returns 1000, so I need to store it in cache as (23,3.45, 4.5, 90, 'd')->1000

foo(30, 1.2, 3.5, 100, 'e') // returns 2000, so I need to store it in cache as (30, 1.2, 3.5, 100, 'e')->2000

foo(23, 3.45, 4.5, 90, 'd') // No need to call this API, I just check in my cache value associated with    
//(23, 3.45, 4.5, 90, 'd'), which is already stored as 1000

What should be best strategy to implement above in C++? which data structure would be best to make cache table?

Answer 1

If you can use boost, look at boost::unordered_map, otherwise you can use a std::map. You will have to provide functor to generate the key.