mirror of
https://github.com/ncruces/go-sqlite3.git
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99 lines
2.5 KiB
Go
99 lines
2.5 KiB
Go
//go:build (linux || darwin || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys
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package vfs
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import (
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"os"
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"time"
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"golang.org/x/sys/unix"
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)
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// SupportsFileLocking is false on platforms that do not support file locking.
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// To open a database file in one such platform,
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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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func osGetSharedLock(file *os.File) _ErrorCode {
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// Test the PENDING lock before acquiring a new SHARED lock.
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if pending, _ := osCheckLock(file, _PENDING_BYTE, 1); pending {
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return _BUSY
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}
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// Acquire the SHARED lock.
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return osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
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}
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func osGetReservedLock(file *os.File) _ErrorCode {
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// Acquire the RESERVED lock.
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return osWriteLock(file, _RESERVED_BYTE, 1, 0)
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}
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func osGetPendingLock(file *os.File, block bool) _ErrorCode {
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var timeout time.Duration
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if block {
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timeout = -1
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}
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// Acquire the PENDING lock.
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return osWriteLock(file, _PENDING_BYTE, 1, timeout)
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}
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func osGetExclusiveLock(file *os.File, wait bool) _ErrorCode {
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var timeout time.Duration
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if wait {
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timeout = time.Millisecond
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}
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// Acquire the EXCLUSIVE lock.
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return osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, timeout)
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}
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func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
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if state >= LOCK_EXCLUSIVE {
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// Downgrade to a SHARED lock.
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if rc := osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0); rc != _OK {
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// In theory, the downgrade to a SHARED cannot fail because another
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// process is holding an incompatible lock. If it does, this
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// indicates that the other process is not following the locking
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// protocol. If this happens, return _IOERR_RDLOCK. Returning
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// BUSY would confuse the upper layer.
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return _IOERR_RDLOCK
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}
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}
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// Release the PENDING and RESERVED locks.
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return osUnlock(file, _PENDING_BYTE, 2)
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}
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func osReleaseLock(file *os.File, _ LockLevel) _ErrorCode {
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// Release all locks.
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return osUnlock(file, 0, 0)
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}
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func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
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// Test the RESERVED lock.
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return osCheckLock(file, _RESERVED_BYTE, 1)
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}
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func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
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if err == nil {
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return _OK
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}
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if errno, ok := err.(unix.Errno); ok {
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switch errno {
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case
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unix.EACCES,
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unix.EAGAIN,
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unix.EBUSY,
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unix.EINTR,
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unix.ENOLCK,
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unix.EDEADLK,
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unix.ETIMEDOUT:
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return _BUSY
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case unix.EPERM:
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return _PERM
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}
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}
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return def
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}
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