f3eade2f62
Drop the AGPL license in favor of a source-available license. See the blog post [1] for details. [1] https://www.scylladb.com/2024/12/18/why-were-moving-to-a-source-available-license/
99 lines
3.0 KiB
C++
99 lines
3.0 KiB
C++
/*
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* Copyright 2020-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
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*/
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#pragma once
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#include "readers/mutation_reader.hh"
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// A reader which allows to insert a deferring operation before reading.
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// All calls will first wait for a future to resolve, then forward to a given underlying reader.
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class chained_delegating_reader : public mutation_reader::impl {
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std::unique_ptr<mutation_reader> _underlying;
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std::function<future<mutation_reader>()> _populate_reader;
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std::function<void()> _on_destroyed;
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public:
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chained_delegating_reader(schema_ptr s, std::function<future<mutation_reader>()>&& populate, reader_permit permit, std::function<void()> on_destroyed = []{})
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: impl(s, std::move(permit))
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, _populate_reader(std::move(populate))
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, _on_destroyed(std::move(on_destroyed))
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{ }
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chained_delegating_reader(chained_delegating_reader&& rd) = delete;
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~chained_delegating_reader() {
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_on_destroyed();
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}
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virtual future<> fill_buffer() override {
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if (!_underlying) {
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return _populate_reader().then([this] (mutation_reader&& rd) {
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_underlying = std::make_unique<mutation_reader>(std::move(rd));
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return fill_buffer();
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});
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}
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if (is_buffer_full()) {
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return make_ready_future<>();
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}
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return _underlying->fill_buffer().then([this] {
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_end_of_stream = _underlying->is_end_of_stream();
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_underlying->move_buffer_content_to(*this);
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});
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}
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virtual future<> fast_forward_to(position_range pr) override {
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if (!_underlying) {
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return _populate_reader().then([this, pr = std::move(pr)] (mutation_reader&& rd) mutable {
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_underlying = std::make_unique<mutation_reader>(std::move(rd));
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return fast_forward_to(pr);
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});
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}
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_end_of_stream = false;
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clear_buffer();
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return _underlying->fast_forward_to(std::move(pr));
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}
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virtual future<> next_partition() override {
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if (!_underlying) {
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return make_ready_future<>();
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}
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clear_buffer_to_next_partition();
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auto f = make_ready_future<>();
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if (is_buffer_empty()) {
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f = _underlying->next_partition();
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}
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_end_of_stream = _underlying->is_end_of_stream() && _underlying->is_buffer_empty();
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return f;
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}
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virtual future<> fast_forward_to(const dht::partition_range& pr) override {
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if (!_underlying) {
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return _populate_reader().then([this, &pr] (mutation_reader&& rd) mutable {
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_underlying = std::make_unique<mutation_reader>(std::move(rd));
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return fast_forward_to(pr);
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});
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}
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_end_of_stream = false;
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clear_buffer();
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return _underlying->fast_forward_to(pr);
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}
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virtual future<> close() noexcept override {
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if (_underlying) {
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return _underlying->close();
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}
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return make_ready_future<>();
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}
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};
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