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