github.com/zuoyebang/bitalosdb@v1.1.1-0.20240516111551-79a8c4d8ce20/bitree/bdb/bdb_unix.go (about)

     1  // Copyright 2021 The Bitalosdb author(hustxrb@163.com) and other contributors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  //go:build !windows && !plan9 && !solaris && !aix
    16  
    17  package bdb
    18  
    19  import (
    20  	"syscall"
    21  	"time"
    22  	"unsafe"
    23  
    24  	"github.com/cockroachdb/errors"
    25  	"golang.org/x/sys/unix"
    26  )
    27  
    28  func flock(db *DB, exclusive bool, timeout time.Duration) error {
    29  	var t time.Time
    30  	if timeout != 0 {
    31  		t = time.Now()
    32  	}
    33  	fd := db.file.Fd()
    34  	flag := syscall.LOCK_NB
    35  	if exclusive {
    36  		flag |= syscall.LOCK_EX
    37  	} else {
    38  		flag |= syscall.LOCK_SH
    39  	}
    40  	for {
    41  		err := syscall.Flock(int(fd), flag)
    42  		if err == nil {
    43  			return nil
    44  		} else if err != syscall.EWOULDBLOCK {
    45  			return err
    46  		}
    47  
    48  		if timeout != 0 && time.Since(t) > timeout-flockRetryTimeout {
    49  			return ErrTimeout
    50  		}
    51  
    52  		time.Sleep(flockRetryTimeout)
    53  	}
    54  }
    55  
    56  func funlock(db *DB) error {
    57  	return syscall.Flock(int(db.file.Fd()), syscall.LOCK_UN)
    58  }
    59  
    60  func mmap(db *DB, sz int) error {
    61  	b, err := unix.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED|db.MmapFlags)
    62  	if err != nil {
    63  		return err
    64  	}
    65  
    66  	err = unix.Madvise(b, syscall.MADV_RANDOM)
    67  	if err != nil && err != syscall.ENOSYS {
    68  		return errors.Wrap(err, "madvise err")
    69  	}
    70  
    71  	db.dataref = b
    72  	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
    73  	db.datasz = sz
    74  	return nil
    75  }
    76  
    77  func munmap(db *DB) error {
    78  	if db.dataref == nil {
    79  		return nil
    80  	}
    81  
    82  	err := unix.Munmap(db.dataref)
    83  	db.dataref = nil
    84  	db.data = nil
    85  	db.datasz = 0
    86  	return err
    87  }