mirror of
https://github.com/superseriousbusiness/gotosocial.git
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129 lines
3.1 KiB
Go
129 lines
3.1 KiB
Go
//go:build linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock || sqlite3_dotlk
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package vfs
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import "github.com/ncruces/go-sqlite3/internal/util"
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// SupportsFileLocking is false on platforms that do not support file locking.
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// To open a database file on those platforms,
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// you need to use the [nolock] or [immutable] URI parameters.
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//
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// [nolock]: https://sqlite.org/uri.html#urinolock
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// [immutable]: https://sqlite.org/uri.html#uriimmutable
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const SupportsFileLocking = true
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const (
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_PENDING_BYTE = 0x40000000
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_RESERVED_BYTE = (_PENDING_BYTE + 1)
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_SHARED_FIRST = (_PENDING_BYTE + 2)
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_SHARED_SIZE = 510
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)
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func (f *vfsFile) Lock(lock LockLevel) error {
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switch {
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case lock != LOCK_SHARED && lock != LOCK_RESERVED && lock != LOCK_EXCLUSIVE:
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// Argument check. SQLite never explicitly requests a pending lock.
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panic(util.AssertErr())
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case f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE:
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// Connection state check.
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panic(util.AssertErr())
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case f.lock == LOCK_NONE && lock > LOCK_SHARED:
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// We never move from unlocked to anything higher than a shared lock.
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panic(util.AssertErr())
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case f.lock != LOCK_SHARED && lock == LOCK_RESERVED:
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// A shared lock is always held when a reserved lock is requested.
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panic(util.AssertErr())
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}
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// If we already have an equal or more restrictive lock, do nothing.
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if f.lock >= lock {
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return nil
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}
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// Do not allow any kind of write-lock on a read-only database.
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if f.readOnly && lock >= LOCK_RESERVED {
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return _IOERR_LOCK
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}
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switch lock {
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case LOCK_SHARED:
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// Must be unlocked to get SHARED.
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if f.lock != LOCK_NONE {
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panic(util.AssertErr())
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}
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if rc := osGetSharedLock(f.File); rc != _OK {
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return rc
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}
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f.lock = LOCK_SHARED
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return nil
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case LOCK_RESERVED:
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// Must be SHARED to get RESERVED.
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if f.lock != LOCK_SHARED {
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panic(util.AssertErr())
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}
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if rc := osGetReservedLock(f.File); rc != _OK {
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return rc
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}
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f.lock = LOCK_RESERVED
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return nil
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case LOCK_EXCLUSIVE:
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// Must be SHARED, RESERVED or PENDING to get EXCLUSIVE.
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if f.lock <= LOCK_NONE || f.lock >= LOCK_EXCLUSIVE {
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panic(util.AssertErr())
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}
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if rc := osGetExclusiveLock(f.File, &f.lock); rc != _OK {
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return rc
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}
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f.lock = LOCK_EXCLUSIVE
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return nil
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default:
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panic(util.AssertErr())
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}
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}
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func (f *vfsFile) Unlock(lock LockLevel) error {
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switch {
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case lock != LOCK_NONE && lock != LOCK_SHARED:
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// Argument check.
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panic(util.AssertErr())
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case f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE:
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// Connection state check.
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panic(util.AssertErr())
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}
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// If we don't have a more restrictive lock, do nothing.
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if f.lock <= lock {
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return nil
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}
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switch lock {
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case LOCK_SHARED:
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rc := osDowngradeLock(f.File, f.lock)
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f.lock = LOCK_SHARED
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return rc
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case LOCK_NONE:
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rc := osReleaseLock(f.File, f.lock)
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f.lock = LOCK_NONE
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return rc
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default:
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panic(util.AssertErr())
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}
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}
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func (f *vfsFile) CheckReservedLock() (bool, error) {
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// Connection state check.
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if f.lock < LOCK_NONE || f.lock > LOCK_EXCLUSIVE {
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panic(util.AssertErr())
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}
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if f.lock >= LOCK_RESERVED {
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return true, nil
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}
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return osCheckReservedLock(f.File)
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}
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