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//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
}
|
