mirror of
https://github.com/triqs/dft_tools
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75 lines
2.5 KiB
C++
75 lines
2.5 KiB
C++
/*******************************************************************************
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*
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* TRIQS: a Toolbox for Research in Interacting Quantum Systems
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*
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* Copyright (C) 2014 by O. Parcollet
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*
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* TRIQS is free software: you can redistribute it and/or modify it under the
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* terms of the GNU General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* TRIQS. If not, see <http://www.gnu.org/licenses/>.
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*
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******************************************************************************/
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#pragma once
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#include <vector>
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#include <functional>
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namespace triqs {
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namespace utility {
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/**
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* A simple buffer for a generator.
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* Given a function, it provides a buffer of this function
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* Advantage :
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* - do not pay the indirection cost at each call, but once every size call.
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* - erase the function type
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* It is a semi-regular type.
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*/
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template <typename R> struct buffered_function {
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/// Default constructor : no function bufferized. () will throw in this state
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buffered_function() = default;
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/** Constructor
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*
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* @tparam Function : type of the function to bufferize
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* @param f : function to bufferize
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* @param size : size of the buffer [optional]
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*/
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template <typename Function> buffered_function(Function f, size_t size = 1000) : buffer(size) {
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refill = [f](buffered_function *bf) mutable { // without the mutable, the () of the lambda object is const, hence f
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for (auto &x : bf->buffer) x = f();
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bf->index = 0;
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};
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refill(this); // first filling of the buffer
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}
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/// Returns the next element. Refills the buffer if necessary.
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R operator()() {
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if (index > buffer.size() - 1) refill(this);
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return buffer[index++];
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}
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/// Returns the future next element, without increasing the index. Refills the buffer if necessary.
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R preview() {
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if (index > buffer.size() - 1) refill(this);
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return buffer[index];
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}
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private:
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size_t index;
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std::vector<R> buffer;
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std::function<void(buffered_function *)> refill; // this refills the buffer and reset index of a buffered_function.
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// NB : cannot capture this in refill because we want the object to be copyable and movable
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};
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}
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}
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