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114 lines
3.2 KiB
C++
114 lines
3.2 KiB
C++
#pragma once
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#if defined(__linux__) || defined(__FreeBSD__)
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#include <IO/ReadBufferFromFileBase.h>
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#include <IO/ReadBuffer.h>
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#include <IO/BufferWithOwnMemory.h>
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#include <IO/AIO.h>
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#include <Core/Defines.h>
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#include <Common/CurrentMetrics.h>
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#include <string>
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#include <limits>
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#include <future>
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#include <unistd.h>
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#include <fcntl.h>
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namespace CurrentMetrics
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{
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extern const Metric OpenFileForRead;
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}
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namespace DB
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{
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/** Class for asynchronous data reading.
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*/
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class ReadBufferAIO : public ReadBufferFromFileBase
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{
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public:
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ReadBufferAIO(const std::string & filename_, size_t buffer_size_ = DBMS_DEFAULT_BUFFER_SIZE, int flags_ = -1,
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char * existing_memory_ = nullptr);
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~ReadBufferAIO() override;
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ReadBufferAIO(const ReadBufferAIO &) = delete;
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ReadBufferAIO & operator=(const ReadBufferAIO &) = delete;
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void setMaxBytes(size_t max_bytes_read_);
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off_t getPositionInFile() override { return first_unread_pos_in_file - (working_buffer.end() - pos); }
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std::string getFileName() const override { return filename; }
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int getFD() const override { return fd; }
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private:
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///
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bool nextImpl() override;
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///
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off_t doSeek(off_t off, int whence) override;
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/// Synchronously read the data.
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void synchronousRead();
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/// Get data from an asynchronous request.
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void receive();
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/// Ignore data from an asynchronous request.
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void skip();
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/// Wait for the end of the current asynchronous task.
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bool waitForAIOCompletion();
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/// Prepare the request.
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void prepare();
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/// Prepare for reading a duplicate buffer containing data from
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/// of the last request.
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void finalize();
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private:
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/// Buffer for asynchronous data read operations.
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BufferWithOwnMemory<ReadBuffer> fill_buffer;
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/// Description of the asynchronous read request.
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iocb request{};
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std::future<ssize_t> future_bytes_read;
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const std::string filename;
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/// The maximum number of bytes that can be read.
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size_t max_bytes_read = std::numeric_limits<size_t>::max();
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/// Number of bytes requested.
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size_t requested_byte_count = 0;
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/// The number of bytes read at the last request.
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ssize_t bytes_read = 0;
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/// The total number of bytes read.
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size_t total_bytes_read = 0;
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/// The position of the first unread byte in the file.
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off_t first_unread_pos_in_file = 0;
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/// The starting position of the aligned region of the disk from which the data is read.
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off_t region_aligned_begin = 0;
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/// Left offset to align the region of the disk.
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size_t region_left_padding = 0;
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/// The size of the aligned region of the disk.
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size_t region_aligned_size = 0;
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/// The file descriptor for read.
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int fd = -1;
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/// The buffer to which the received data is written.
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Position buffer_begin = nullptr;
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/// The asynchronous read operation is not yet completed.
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bool is_pending_read = false;
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/// The end of the file is reached.
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bool is_eof = false;
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/// At least one read request was sent.
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bool is_started = false;
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/// Is the operation asynchronous?
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bool is_aio = false;
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/// Did the asynchronous operation fail?
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bool aio_failed = false;
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CurrentMetrics::Increment metric_increment{CurrentMetrics::OpenFileForRead};
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};
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}
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#endif
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