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//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le)) || sqlite3_flock || sqlite3_dotlk
package vfs
import "github.com/ncruces/go-sqlite3/internal/util"
// +checklocks:s.Mutex
func (s *vfsShm) shmMemLock(offset, n int32, flags _ShmFlag) _ErrorCode {
switch {
case flags&_SHM_UNLOCK != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
if s.vfsShmParent.lock[i] <= 0 {
s.vfsShmParent.lock[i] = 0
} else {
s.vfsShmParent.lock[i]--
}
s.lock[i] = false
}
}
case flags&_SHM_SHARED != 0:
for i := offset; i < offset+n; i++ {
if !s.lock[i] &&
s.vfsShmParent.lock[i]+1 <= 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
if !s.lock[i] {
s.vfsShmParent.lock[i]++
s.lock[i] = true
}
}
case flags&_SHM_EXCLUSIVE != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
// SQLite never requests an exclusive lock that it already holds.
panic(util.AssertErr())
}
if s.vfsShmParent.lock[i] != 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
s.vfsShmParent.lock[i] = -1
s.lock[i] = true
}
default:
panic(util.AssertErr())
}
return _OK
}
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