9fdf4b24b5
buffer_input_stream is a simple input_stream wrapping a single temporary_buffer. prepended_input_stream suits for the case when some data has been read into a buffer and the rest is still in a stream. It accepts a buffer and a data_source and first reads from the buffer and then, when it ends, proceeds reading from the data_source. Signed-off-by: Vladimir Krivopalov <vladimir@scylladb.com>
64 lines
2.0 KiB
C++
64 lines
2.0 KiB
C++
/*
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* Copyright (C) 2017 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "prepended_input_stream.hh"
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using namespace seastar;
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class prepended_data_source_impl : public data_source_impl {
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private:
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temporary_buffer<char> _buf;
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data_source _ds;
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public:
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prepended_data_source_impl(temporary_buffer<char>&& buf, data_source&& ds)
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: _buf(std::move(buf)), _ds(std::move(ds))
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{}
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prepended_data_source_impl(prepended_data_source_impl&&) = default;
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prepended_data_source_impl& operator=(prepended_data_source_impl&&) = default;
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virtual future<temporary_buffer<char>> get() override {
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if (_buf) {
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return make_ready_future<temporary_buffer<char>>(std::move(_buf));
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}
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return _ds.get();
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}
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virtual future<temporary_buffer<char>> skip(uint64_t n) {
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if (n < _buf.size()) {
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_buf.trim_front(n);
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return make_ready_future<temporary_buffer<char>>(std::move(_buf));
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} else {
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n -= _buf.size();
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_buf = {};
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if (n > 0) {
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return _ds.skip(n);
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} else {
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return _ds.get();
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}
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}
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}
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};
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input_stream<char> make_prepended_input_stream(temporary_buffer<char>&& buf, data_source&& ds) {
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auto impl = std::make_unique<prepended_data_source_impl>(std::move(buf), std::move(ds));
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return input_stream<char>{data_source{std::move(impl)}};
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}
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