107 lines
2.6 KiB
Go
107 lines
2.6 KiB
Go
//go:build (linux || darwin || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
|
|
|
|
package vfs
|
|
|
|
import (
|
|
"os"
|
|
"time"
|
|
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
func osGetSharedLock(file *os.File) _ErrorCode {
|
|
// Test the PENDING lock before acquiring a new SHARED lock.
|
|
if lock, _ := osGetLock(file, _PENDING_BYTE, 1); lock == unix.F_WRLCK {
|
|
return _BUSY
|
|
}
|
|
// Acquire the SHARED lock.
|
|
return osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
|
|
}
|
|
|
|
func osGetReservedLock(file *os.File) _ErrorCode {
|
|
// Acquire the RESERVED lock.
|
|
return osWriteLock(file, _RESERVED_BYTE, 1, 0)
|
|
}
|
|
|
|
func osGetPendingLock(file *os.File, block bool) _ErrorCode {
|
|
var timeout time.Duration
|
|
if block {
|
|
timeout = -1
|
|
}
|
|
// Acquire the PENDING lock.
|
|
return osWriteLock(file, _PENDING_BYTE, 1, timeout)
|
|
}
|
|
|
|
func osGetExclusiveLock(file *os.File, wait bool) _ErrorCode {
|
|
var timeout time.Duration
|
|
if wait {
|
|
timeout = time.Millisecond
|
|
}
|
|
// Acquire the EXCLUSIVE lock.
|
|
return osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, timeout)
|
|
}
|
|
|
|
func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
|
|
if state >= LOCK_EXCLUSIVE {
|
|
// Downgrade to a SHARED lock.
|
|
if rc := osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0); rc != _OK {
|
|
// In theory, the downgrade to a SHARED cannot fail because another
|
|
// process is holding an incompatible lock. If it does, this
|
|
// indicates that the other process is not following the locking
|
|
// protocol. If this happens, return _IOERR_RDLOCK. Returning
|
|
// BUSY would confuse the upper layer.
|
|
return _IOERR_RDLOCK
|
|
}
|
|
}
|
|
// Release the PENDING and RESERVED locks.
|
|
return osUnlock(file, _PENDING_BYTE, 2)
|
|
}
|
|
|
|
func osReleaseLock(file *os.File, _ LockLevel) _ErrorCode {
|
|
// Release all locks.
|
|
return osUnlock(file, 0, 0)
|
|
}
|
|
|
|
func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
|
|
// Test the RESERVED lock.
|
|
lock, rc := osGetLock(file, _RESERVED_BYTE, 1)
|
|
return lock == unix.F_WRLCK, rc
|
|
}
|
|
|
|
func osGetLock(file *os.File, start, len int64) (int16, _ErrorCode) {
|
|
lock := unix.Flock_t{
|
|
Type: unix.F_WRLCK,
|
|
Start: start,
|
|
Len: len,
|
|
}
|
|
if unix.FcntlFlock(file.Fd(), unix.F_GETLK, &lock) != nil {
|
|
return 0, _IOERR_CHECKRESERVEDLOCK
|
|
}
|
|
return lock.Type, _OK
|
|
}
|
|
|
|
func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
|
|
if err == nil {
|
|
return _OK
|
|
}
|
|
if errno, ok := err.(unix.Errno); ok {
|
|
switch errno {
|
|
case
|
|
unix.EACCES,
|
|
unix.EAGAIN,
|
|
unix.EBUSY,
|
|
unix.EINTR,
|
|
unix.ENOLCK,
|
|
unix.EDEADLK,
|
|
unix.ETIMEDOUT:
|
|
return _BUSY
|
|
case unix.EPERM:
|
|
return _PERM
|
|
}
|
|
if errno == unix.EWOULDBLOCK && unix.EWOULDBLOCK != unix.EAGAIN {
|
|
return _BUSY
|
|
}
|
|
}
|
|
return def
|
|
}
|