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68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
#pragma once
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#include <Common/CounterInFile.h>
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/** Allows to get an auto-increment number, storing it in a file.
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* Intended for rare calls (not designed for performance).
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*/
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class Increment
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{
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public:
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/// path - the name of the file, including the path
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explicit Increment(const std::string & path_) : counter(path_) {}
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/** Get the next number.
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* If the `create_if_need` parameter is not set to true, then
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* the file must already have a number written (if not - create the file manually with zero).
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*
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* To protect against race conditions between different processes, file locks are used.
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* (But when the first file is created, the race condition is possible, so it's better to create the file in advance.)
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*
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* `locked_callback` is called when the counter file is locked. A new value is passed to it.
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* `locked_callback` can be used to do something atomically with the increment of the counter (for example, rename files).
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*/
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template <typename Callback>
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UInt64 get(Callback && locked_callback, bool create_if_need = false)
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{
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return static_cast<UInt64>(counter.add(1, std::forward<Callback>(locked_callback), create_if_need));
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}
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UInt64 get(bool create_if_need = false)
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{
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return getBunch(1, create_if_need);
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}
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/// Peek the next value.
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UInt64 peek(bool create_if_need = false)
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{
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return getBunch(0, create_if_need);
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}
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/** Get the next number and increase the counter by `count`.
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* If the `create_if_need` parameter is not set to true, then
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* the file should already have a number written (if not - create the file manually with zero).
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*
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* To protect against race conditions between different processes, file locks are used.
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* (But when the first file is created, the race condition is possible, so it's better to create the file in advance.)
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*/
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UInt64 getBunch(UInt64 count, bool create_if_need = false)
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{
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return static_cast<UInt64>(counter.add(static_cast<Int64>(count), create_if_need) - count + 1);
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}
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/// Change the path to the file.
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void setPath(std::string path_)
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{
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counter.setPath(path_);
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}
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void fixIfBroken(UInt64 value)
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{
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counter.fixIfBroken(value);
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}
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private:
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CounterInFile counter;
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};
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