cpp_cached

cpp_cached is a collection of data caching schemes:

• memory LRU
• disk one file per object
• sqlite backend
• postgresql backend
• rocksdb backend
• a combination of two of the previous caches (usually mem first)

use

caches are key/value stores

they all conform to the following interface

// c is some cache object
// o some object of class O
// key is at least a std::string_view
// fn is a function returning an O
c.set(key,o);
bool b = c.has(key);
if (b)
	o = c.get(key);
// this line
auto oo = c.get(key,fn);
// is equivalent to
O ooo = c.has(key) ? c.get(key) : fn();

The concept is_a_cache checks that an object conforms to the cache interface.