mirror of
https://github.com/ton-blockchain/ton
synced 2025-03-09 15:40:10 +00:00
73 lines
2 KiB
C++
73 lines
2 KiB
C++
/*
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This file is part of TON Blockchain Library.
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TON Blockchain Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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TON Blockchain Library 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 Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with TON Blockchain Library. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2017-2020 Telegram Systems LLP
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*/
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#pragma once
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#include "td/utils/common.h"
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#include "td/utils/port/FileFd.h"
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#include "td/utils/Slice.h"
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#include "td/utils/Status.h"
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namespace td {
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class BufferedReader {
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public:
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explicit BufferedReader(FileFd &file, size_t buff_size = 8152)
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: file_(file), buff_(buff_size), begin_pos_(0), end_pos_(0) {
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}
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Result<size_t> read(MutableSlice slice) TD_WARN_UNUSED_RESULT;
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private:
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FileFd &file_;
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vector<char> buff_;
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size_t begin_pos_;
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size_t end_pos_;
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};
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inline Result<size_t> BufferedReader::read(MutableSlice slice) {
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size_t available = end_pos_ - begin_pos_;
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if (available >= slice.size()) {
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// have enough data in buffer
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slice.copy_from({&buff_[begin_pos_], slice.size()});
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begin_pos_ += slice.size();
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return slice.size();
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}
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if (available) {
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slice.copy_from({&buff_[begin_pos_], available});
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begin_pos_ += available;
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slice.remove_prefix(available);
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}
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if (slice.size() > buff_.size() / 2) {
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TRY_RESULT(result, file_.read(slice));
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return result + available;
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}
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TRY_RESULT(result, file_.read({&buff_[0], buff_.size()}));
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begin_pos_ = 0;
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end_pos_ = result;
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size_t left = min(end_pos_, slice.size());
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slice.copy_from({&buff_[0], left});
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begin_pos_ = left;
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return left + available;
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}
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} // namespace td
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