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ea97e07ed7
While serialization vector it is sometimes required to rollback some of the serialized elements. vector_position is the equivalent to the bytes_ostream position struct. It holds information about the current position in a serialized vector, the position in the bufffer and the current number of elements serialized. It will allow to rollback to the current point. Signed-off-by: Amnon Heiman <amnon@scylladb.com> Message-Id: <1456041750-1505-2-git-send-email-amnon@scylladb.com>
95 lines
2.5 KiB
C++
95 lines
2.5 KiB
C++
/*
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* Copyright 2016 ScylaDB
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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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#pragma once
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#include "bytes_ostream.hh"
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namespace ser {
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// frame represents a place holder for object size which will be known later
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struct place_holder {
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bytes_ostream::place_holder<size_type> ph;
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place_holder(bytes_ostream::place_holder<size_type> ph) : ph(ph) { }
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void set(bytes_ostream& out, bytes_ostream::size_type v) {
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auto stream = ph.get_stream();
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serialize(stream, v);
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}
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};
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struct frame : public place_holder {
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bytes_ostream::size_type offset;
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frame(bytes_ostream::place_holder<size_type> ph, bytes_ostream::size_type offset)
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: place_holder(ph), offset(offset) { }
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void end(bytes_ostream& out) {
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set(out, out.size() - offset);
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}
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};
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struct vector_position {
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bytes_ostream::position pos;
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size_type count;
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};
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//empty frame, behave like a place holder, but is used when no place holder is needed
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struct empty_frame {
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void end(bytes_ostream&) {}
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empty_frame() = default;
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empty_frame(const frame&){}
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};
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inline place_holder start_place_holder(bytes_ostream& out) {
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auto size_ph = out.write_place_holder<size_type>();
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return { size_ph};
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}
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inline frame start_frame(bytes_ostream& out) {
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auto offset = out.size();
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auto size_ph = out.write_place_holder<size_type>();
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return frame { size_ph, offset };
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}
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template<typename T>
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inline void skip(seastar::simple_input_stream& v, boost::type<T>) {
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deserialize(v, boost::type<T>());
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}
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template<>
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inline void skip(seastar::simple_input_stream& v, boost::type<sstring>) {
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v.skip(deserialize(v, boost::type<size_type>()));
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}
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template<typename T>
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inline void skip(seastar::simple_input_stream& v, boost::type<std::vector<T>>) {
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auto ln = deserialize(v, boost::type<size_type>());
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for (size_type i = 0; i < ln; i++) {
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skip(v, boost::type<T>());
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}
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}
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}
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