63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
#pragma once
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///@file IO buffer abstraction for use by buffered IO types.
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#include <cstddef>
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#include <memory>
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#include <span>
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namespace nix {
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/**
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* A single-threaded read/write IO buffer of fixed size. Adding data to the write side
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* of the buffer makes it available to the read buffer, consuming it from the read side
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* makes it available for future writes. Once the buffer is full no further data may be
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* added, once it is empty no further data can be removed.
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*/
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class IoBuffer
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{
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size_t bufSize, bufBegin{0}, bufUsed{0};
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std::unique_ptr<char[]> buffer;
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public:
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explicit IoBuffer(size_t bufSize = 32ul * 1024) : bufSize(bufSize) {}
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size_t size() const
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{
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return bufSize;
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}
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size_t used() const
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{
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return bufUsed;
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}
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/**
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* Return a subspan of the buffer that contains valid data. The returned
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* span might not cover the entire buffer if `used() > 0`. All reads must be
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* followed by a call to `consumed()` to remove bytes from the read buffer
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* and make them available for use by the write buffer.
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*/
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std::span<const char> getReadBuffer();
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/**
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* Mark the first `size` bytes of the read buffer as consumed. `size` may
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* not exceed `used()`, but may exceed `getReadBuffer().size()`.
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*/
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void consumed(size_t size);
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/**
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* Return a subspan of the buffer that may be written into. The returned
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* span may not cover the entire buffer if `used() > 0`. All writes must be
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* followed by calls to `added(n)` to mark the written bytes as readable.
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*/
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std::span<char> getWriteBuffer();
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/**
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* Mark the first `size` bytes of the write buffer as readable. `size` may
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* not exceed `size() - used()`, but may exceed `getWriteBuffer().size()`.
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*/
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void added(size_t size);
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};
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}
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