1 files changed, 85 insertions, 0 deletions
diff --git a/src/seastar/demos/line_count_demo.cc b/src/seastar/demos/line_count_demo.cc
new file mode 100644
index 000000000..eab4609ec
--- /dev/null
+++ b/src/seastar/demos/line_count_demo.cc
@@ -0,0 +1,85 @@
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  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.
+ */
+/*
+ * Copyright (C) 2015 Cloudius Systems, Ltd.
+ */
+
+// Demonstration of file_input_stream.  Don't expect stellar performance
+// since no read-ahead or caching is done yet.
+
+#include <seastar/core/fstream.hh>
+#include <seastar/core/seastar.hh>
+#include <seastar/core/app-template.hh>
+#include <seastar/core/shared_ptr.hh>
+#include <fmt/printf.h>
+#include <algorithm>
+#include <iostream>
+
+using namespace seastar;
+
+struct reader {
+public:
+    reader(file f)
+            : is(make_file_input_stream(std::move(f), file_input_stream_options{1 << 16, 1})) {
+    }
+
+    input_stream<char> is;
+    size_t count = 0;
+
+    // for input_stream::consume():
+    using unconsumed_remainder = std::optional<temporary_buffer<char>>;
+    future<unconsumed_remainder> operator()(temporary_buffer<char> data) {
+        if (data.empty()) {
+            return make_ready_future<unconsumed_remainder>(std::move(data));
+        } else {
+            count += std::count(data.begin(), data.end(), '\n');
+            // FIXME: last line without \n?
+            return make_ready_future<unconsumed_remainder>();
+        }
+    }
+};
+
+int main(int ac, char** av) {
+    app_template app;
+    namespace bpo = boost::program_options;
+    app.add_positional_options({
+        { "file", bpo::value<std::string>(), "File to process", 1 },
+    });
+    return app.run(ac, av, [&app] {
+        auto fname = app.configuration()["file"].as<std::string>();
+        return open_file_dma(fname, open_flags::ro).then([] (file f) {
+            auto r = make_shared<reader>(std::move(f));
+            return r->is.consume(*r).then([r] {
+               fmt::print("{:d} lines\n", r->count);
+               return r->is.close().then([r] {});
+            });
+        }).then_wrapped([] (future<> f) -> future<int> {
+            try {
+                f.get();
+                return make_ready_future<int>(0);
+            } catch (std::exception& ex) {
+                std::cout << ex.what() << "\n";
+                return make_ready_future<int>(1);
+            } catch (...) {
+                std::cout << "unknown exception\n";
+                return make_ready_future<int>(1);
+            }
+        });
+    });
+}
+