79 lines
1.8 KiB
C++
79 lines
1.8 KiB
C++
// #todo maybe overload >> operators insted of read()
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#pragma once
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#include "record.hpp"
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#include <istream>
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#include <optional>
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#include <vector>
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class Reader {
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private:
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std::vector<Record> read_buffer;
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std::istream& input_stream;
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size_t buffer_size;
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size_t total_reads_count;
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int last_element_idx; // last valid element in buffer
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int current_idx; // current reading position
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// returns true if at least one record was returned
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bool refill_buffer()
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{
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last_element_idx = -1;
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current_idx = 0;
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for (size_t i = 0; i < buffer_size; i++) {
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if (!(input_stream >> read_buffer[i])) {
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break;
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}
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last_element_idx = i;
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}
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return last_element_idx >= 0;
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}
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public:
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explicit Reader(std::istream& input_stream, size_t buffer_size = 8)
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: read_buffer(buffer_size)
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, input_stream(input_stream)
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, buffer_size(buffer_size)
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, total_reads_count(0)
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, last_element_idx(-1)
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, current_idx(0)
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{
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}
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std::optional<Record> read()
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{
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if (current_idx > last_element_idx) {
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bool read_new_items = refill_buffer();
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if (!read_new_items) {
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return std::nullopt;
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}
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}
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Record record = read_buffer[current_idx];
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current_idx++;
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total_reads_count++;
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return record;
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}
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size_t total_reads() const
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{
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return total_reads_count;
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}
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// #todo remove if not used in the end
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// bool has_more() const
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// {
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// return current_idx <= last_element_idx || !input_stream.eof();
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// }
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// void reset()
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// {
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// input_stream.clear();
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// input_stream.seekg(0);
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// last_element_idx = -1;
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// current_idx = 0;
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// total_reads_count = 0;
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// }
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};
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