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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.
*/
/* $Rev$ $Date$ */
#ifndef tuscany_cache_hpp
#define tuscany_cache_hpp
/**
* Simple cache monad implementation.
*/
#include <sys/stat.h>
#include <string>
#include "value.hpp"
#include "monad.hpp"
namespace tuscany {
namespace cache {
/**
* Cached monad. Used to represent a value that can be cached.
* To get the value in the monad, just cast it to the value type.
*/
template<typename V> class cached {
public:
cached() : mtime(0) {
}
cached(const lambda<V()>& lvalue, const lambda<unsigned long()> ltime) : lvalue(lvalue), ltime(ltime), mtime(0) {
}
cached(const lambda<V()>& lvalue, const lambda<unsigned long()> ltime, const unsigned long mtime, const V& v) : lvalue(lvalue), ltime(ltime), mtime(mtime), v(v) {
}
cached(const cached<V>& c) : lvalue(c.lvalue), ltime(c.ltime), mtime(c.mtime), v(c.v) {
}
operator const V() const {
return v;
}
const cached<V>& operator=(const cached<V>& c) {
if(this == &c)
return *this;
this->lvalue = c.lvalue;
this->ltime = c.ltime;
this->mtime = c.mtime;
this->v = c.v;
return *this;
}
const bool operator!=(const cached<V>& m) const {
return !this->operator==(m);
}
const bool operator==(const cached<V>& m) const {
if (this == &m)
return true;
return mtime == m.mtime && v == m.v;
}
private:
lambda<V()> lvalue;
lambda<time_t()> ltime;
unsigned long mtime;
V v;
template<typename X> friend const cached<X> latest(const cached<X>& c);
template<typename X> friend std::ostream& operator<<(std::ostream& out, const cached<X>& c);
};
/**
* Write a cached monad to a stream.
*/
template<typename V> std::ostream& operator<<(std::ostream& out, const cached<V>& c) {
out << c.v;
return out;
}
/**
* Returns the latest value of a cached monad.
*/
template<typename V> const cached<V> latest(const cached<V>& c) {
unsigned long nt = c.ltime();
if (nt == c.mtime)
return c;
return cached<V>(c.lvalue, c.ltime, nt, c.lvalue());
}
/**
* Returns the latest modification time of a file.
*/
const unsigned long latestFileTime(const std::string& path) {
struct stat st;
int rc = stat(path.c_str(), &st);
if (rc < 0)
return 0;
return st.st_mtim.tv_nsec;
}
}
}
#endif /* tuscany_cache_hpp */
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