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//go:build sqlite3_dotlk
package vfs
import (
"errors"
"io/fs"
"os"
"sync"
"github.com/ncruces/go-sqlite3/internal/dotlk"
)
var (
// +checklocks:vfsDotLocksMtx
vfsDotLocks = map[string]*vfsDotLocker{}
vfsDotLocksMtx sync.Mutex
)
type vfsDotLocker struct {
shared int // +checklocks:vfsDotLocksMtx
pending *os.File // +checklocks:vfsDotLocksMtx
reserved *os.File // +checklocks:vfsDotLocksMtx
}
func osGetSharedLock(file *os.File) error {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
if locker == nil {
if err := dotlk.TryLock(name + ".lock"); err != nil {
if errors.Is(err, fs.ErrExist) {
return _BUSY // Another process has the lock.
}
return sysError{err, _IOERR_LOCK}
}
locker = &vfsDotLocker{}
vfsDotLocks[name] = locker
}
if locker.pending != nil {
return _BUSY
}
locker.shared++
return nil
}
func osGetReservedLock(file *os.File) error {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
if locker == nil {
return _IOERR_LOCK
}
if locker.reserved != nil && locker.reserved != file {
return _BUSY
}
locker.reserved = file
return nil
}
func osGetExclusiveLock(file *os.File, _ *LockLevel) error {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
if locker == nil {
return _IOERR_LOCK
}
if locker.pending != nil && locker.pending != file {
return _BUSY
}
locker.pending = file
if locker.shared > 1 {
return _BUSY
}
return nil
}
func osDowngradeLock(file *os.File, _ LockLevel) error {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
if locker == nil {
return _IOERR_UNLOCK
}
if locker.reserved == file {
locker.reserved = nil
}
if locker.pending == file {
locker.pending = nil
}
return nil
}
func osReleaseLock(file *os.File, state LockLevel) error {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
if locker == nil {
return _IOERR_UNLOCK
}
if locker.shared == 1 {
if err := dotlk.Unlock(name + ".lock"); err != nil {
return sysError{err, _IOERR_UNLOCK}
}
delete(vfsDotLocks, name)
}
if locker.reserved == file {
locker.reserved = nil
}
if locker.pending == file {
locker.pending = nil
}
locker.shared--
return nil
}
func osCheckReservedLock(file *os.File) (bool, error) {
vfsDotLocksMtx.Lock()
defer vfsDotLocksMtx.Unlock()
name := file.Name()
locker := vfsDotLocks[name]
return locker != nil && locker.reserved != nil, nil
}
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