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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/* $Rev$ $Date$ */
/**
* A cache component implementation which memoizes the value of function
* applications, keyed by the function arguments, in a key/value cache passed
* as a reference.
*
* This is useful if your functions are idempotent and applied many times to
* the same arguments. The results can then be retrieved quickly from the
* cache without actually applying the function.
*/
#include "string.hpp"
#include "function.hpp"
#include "list.hpp"
#include "value.hpp"
#include "monad.hpp"
namespace tuscany {
namespace memocache {
/**
* Memoize the value of a function application in a cache.
*/
const failable<value> memoize(const list<value>& params, const lambda<value(const list<value>&)> relay, const lambda<value(const list<value>&)> cache) {
debug(params, "memocache::memoize::params");
// Lookup memoized value from cache
const value val = cache(mklist<value>("get", params));
if (!isNil(val)) {
debug(val, "memocache::memoize::cached");
return val;
}
// Apply the given function
const value res = relay(params);
debug(res, "memocache::memoize::res");
// Store the result value in the cache
cache(mklist<value>("put", params, res));
return res;
}
}
}
extern "C" {
const tuscany::value apply(const tuscany::list<tuscany::value>& params) {
const tuscany::value func(car(params));
if (func == "start" || func == "stop")
return tuscany::mkfailure<tuscany::value>();
const tuscany::list<tuscany::value> rev = tuscany::reverse(params);
return tuscany::memocache::memoize(tuscany::reverse(tuscany::cddr(rev)), tuscany::cadr(rev), tuscany::car(rev));
}
}
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