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#include "rotating_file.h" 
#include "file.h" 
#include "record.h" 
 
#include <util/string/builder.h>
#include <util/system/fstat.h> 
#include <util/system/rwlock.h> 
#include <util/system/fs.h> 
#include <util/system/atomic.h> 
#include <util/generic/string.h> 
 
/* 
 * rotating file log 
 * if Size_ > MaxSizeBytes
 *    Path.(N-1) -> Path.N
 *    Path.(N-2) -> Path.(N-1)
 *    ...
 *    Path.1     -> Path.2
 *    Path       -> Path.1
 */ 
class TRotatingFileLogBackend::TImpl { 
public: 
    inline TImpl(const TString& path, const ui64 maxSizeBytes, const ui32 rotatedFilesCount)
        : Log_(path)
        , Path_(path)
        , MaxSizeBytes_(maxSizeBytes)
        , Size_(TFileStat(Path_).Size)
        , RotatedFilesCount_(rotatedFilesCount)
    {
        Y_ENSURE(RotatedFilesCount_ != 0);
    }

    inline void WriteData(const TLogRecord& rec) { 
        if (static_cast<ui64>(AtomicGet(Size_)) > MaxSizeBytes_) { 
            TWriteGuard guard(Lock_); 
            if (static_cast<ui64>(AtomicGet(Size_)) > MaxSizeBytes_) { 
                TString newLogPath(TStringBuilder{} << Path_ << "." << RotatedFilesCount_);
                for (size_t fileId = RotatedFilesCount_ - 1; fileId; --fileId) {
                    TString oldLogPath(TStringBuilder{} << Path_ << "." << fileId);
                    NFs::Rename(oldLogPath, newLogPath);
                    newLogPath = oldLogPath;
                }
                NFs::Rename(Path_, newLogPath);
                Log_.ReopenLog(); 
                AtomicSet(Size_, 0); 
            } 
        } 
        TReadGuard guard(Lock_); 
        Log_.WriteData(rec); 
        AtomicAdd(Size_, rec.Len); 
    } 
 
    inline void ReopenLog() { 
        TWriteGuard guard(Lock_); 
 
        Log_.ReopenLog(); 
        AtomicSet(Size_, TFileStat(Path_).Size);
    } 
 
private: 
    TRWMutex Lock_; 
    TFileLogBackend Log_; 
    const TString Path_;
    const ui64 MaxSizeBytes_; 
    TAtomic Size_; 
    const ui32 RotatedFilesCount_;
}; 
 
TRotatingFileLogBackend::TRotatingFileLogBackend(const TString& path, const ui64 maxSizeByte, const ui32 rotatedFilesCount)
    : Impl_(new TImpl(path, maxSizeByte, rotatedFilesCount))
{
}

TRotatingFileLogBackend::~TRotatingFileLogBackend() { 
} 
 
void TRotatingFileLogBackend::WriteData(const TLogRecord& rec) { 
    Impl_->WriteData(rec); 
} 
 
void TRotatingFileLogBackend::ReopenLog() { 
    TAtomicSharedPtr<TImpl> copy = Impl_; 
    if (copy) { 
        copy->ReopenLog(); 
    } 
}