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43 lines
1.4 KiB
C++
43 lines
1.4 KiB
C++
#pragma once
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#include <IO/ReadBufferFromFileBase.h>
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#include <IO/ReadSettings.h>
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#include <Common/PageCache.h>
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namespace DB
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{
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class CachedInMemoryReadBufferFromFile : public ReadBufferFromFileBase
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{
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public:
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/// `in_` must support using external buffer. I.e. we assign its internal_buffer before each next()
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/// call and expect the read data to be put into that buffer.
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/// `in_` should be seekable and should be able to read the whole file from 0 to in_->getFileSize();
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/// if you set `in_`'s read-until-position bypassing CachedInMemoryReadBufferFromFile then
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/// CachedInMemoryReadBufferFromFile will break.
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CachedInMemoryReadBufferFromFile(FileChunkAddress cache_key_, PageCachePtr cache_, std::unique_ptr<ReadBufferFromFileBase> in_, const ReadSettings & settings_);
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String getFileName() const override;
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off_t seek(off_t off, int whence) override;
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off_t getPosition() override;
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size_t getFileOffsetOfBufferEnd() const override;
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bool supportsRightBoundedReads() const override { return true; }
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void setReadUntilPosition(size_t position) override;
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void setReadUntilEnd() override;
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private:
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FileChunkAddress cache_key; // .offset is offset of `chunk` start
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PageCachePtr cache;
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ReadSettings settings;
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std::unique_ptr<ReadBufferFromFileBase> in;
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size_t file_offset_of_buffer_end = 0;
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size_t read_until_position;
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std::optional<PinnedPageChunk> chunk;
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bool nextImpl() override;
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};
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}
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