c5f61666d3
Our input_stream::consume() mechanism allows feeding data from an input stream into a consumer, piece by piece, until the consumer doesn't want any more. It currently assumed the input can block (when reading from disk), but the consumption is assumed to be immediate. This patch adds support for blocking in the consumption function: The consumer now returns a future which it promises to fulfill after consuming the given buffer. This patch goes further by somewhat simplifying (?) the interface of the consumer. Instead of receiving a mysterious "done" lambda the consumer is supposed to call when done (doesn't want any more input), the consumer now returns a future<optional<temporary_buffer<char>>, which means: 1. The future is fulfilled when the consumer is done with this buffer and either wants more - or wants to stop. 2. If the consumer wants to stop, it returns the *remaining* part of the buffer it didn't want to process (this will be pushed back into the input stream). 3. If the consumer is not done, and wants to consume more, it returns an unset optional. Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
78 lines
2.6 KiB
C++
78 lines
2.6 KiB
C++
/*
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* This file is open source software, licensed to you under the terms
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* of the Apache License, Version 2.0 (the "License"). See the NOTICE file
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* distributed with this work for additional information regarding copyright
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* ownership. You may not use this file except in compliance with the License.
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*
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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/*
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* Copyright (C) 2015 Cloudius Systems, Ltd.
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*/
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// Demonstration of file_input_stream. Don't expect stellar performance
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// since no read-ahead or caching is done yet.
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#include "core/fstream.hh"
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#include "core/app-template.hh"
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#include "core/shared_ptr.hh"
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#include "core/reactor.hh"
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#include <algorithm>
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struct reader {
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reader(file f) : is(make_file_input_stream(
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make_lw_shared<file>(std::move(f)), 0, 4096)) {}
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input_stream<char> is;
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size_t count = 0;
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// for input_stream::consume():
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using unconsumed_remainder = std::experimental::optional<temporary_buffer<char>>;
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future<unconsumed_remainder> operator()(temporary_buffer<char> data) {
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if (data.empty()) {
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return make_ready_future<unconsumed_remainder>(std::move(data));
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} else {
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count += std::count(data.begin(), data.end(), '\n');
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// FIXME: last line without \n?
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return make_ready_future<unconsumed_remainder>();
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}
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}
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};
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int main(int ac, char** av) {
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app_template app;
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namespace bpo = boost::program_options;
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app.add_positional_options({
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{ "file", bpo::value<std::string>(), "File to process", 1 },
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});
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app.run(ac, av, [&app] {
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auto fname = app.configuration()["file"].as<std::string>();
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engine().open_file_dma(fname, open_flags::ro).then([] (file f) {
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auto r = make_shared<reader>(std::move(f));
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r->is.consume(*r).then([r] {
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print("%d lines\n", r->count);
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});
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}).then_wrapped([] (future<> f) {
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try {
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f.get();
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engine().exit(0);
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} catch (std::exception& ex) {
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std::cout << ex.what() << "\n";
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engine().exit(1);
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} catch (...) {
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std::cout << "unknown exception\n";
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engine().exit(0);
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}
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});
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});
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}
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