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//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
package vfs
import (
"context"
"io"
"os"
"sync"
"github.com/tetratelabs/wazero/api"
"golang.org/x/sys/unix"
"github.com/ncruces/go-sqlite3/internal/util"
)
type vfsShmFile struct {
*os.File
info os.FileInfo
refs int // +checklocks:vfsShmFilesMtx
lock [_SHM_NLOCK]int16 // +checklocks:Mutex
sync.Mutex
}
var (
// +checklocks:vfsShmFilesMtx
vfsShmFiles []*vfsShmFile
vfsShmFilesMtx sync.Mutex
)
type vfsShm struct {
*vfsShmFile
path string
lock [_SHM_NLOCK]bool
regions []*util.MappedRegion
}
func (s *vfsShm) Close() error {
if s.vfsShmFile == nil {
return nil
}
vfsShmFilesMtx.Lock()
defer vfsShmFilesMtx.Unlock()
// Unlock everything.
s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
// Decrease reference count.
if s.vfsShmFile.refs > 0 {
s.vfsShmFile.refs--
s.vfsShmFile = nil
return nil
}
err := s.File.Close()
for i, g := range vfsShmFiles {
if g == s.vfsShmFile {
vfsShmFiles[i] = nil
s.vfsShmFile = nil
return err
}
}
panic(util.AssertErr())
}
func (s *vfsShm) shmOpen() _ErrorCode {
if s.vfsShmFile != nil {
return _OK
}
// Always open file read-write, as it will be shared.
f, err := os.OpenFile(s.path,
unix.O_RDWR|unix.O_CREAT|unix.O_NOFOLLOW, 0666)
if err != nil {
return _CANTOPEN
}
// Closes file if it's not nil.
defer func() { f.Close() }()
fi, err := f.Stat()
if err != nil {
return _IOERR_FSTAT
}
vfsShmFilesMtx.Lock()
defer vfsShmFilesMtx.Unlock()
// Find a shared file, increase the reference count.
for _, g := range vfsShmFiles {
if g != nil && os.SameFile(fi, g.info) {
s.vfsShmFile = g
g.refs++
return _OK
}
}
// Lock and truncate the file.
// The lock is only released by closing the file.
if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
return rc
}
if err := f.Truncate(0); err != nil {
return _IOERR_SHMOPEN
}
// Add the new shared file.
s.vfsShmFile = &vfsShmFile{
File: f,
info: fi,
}
f = nil // Don't close the file.
for i, g := range vfsShmFiles {
if g == nil {
vfsShmFiles[i] = s.vfsShmFile
return _OK
}
}
vfsShmFiles = append(vfsShmFiles, s.vfsShmFile)
return _OK
}
func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
// Ensure size is a multiple of the OS page size.
if int(size)&(unix.Getpagesize()-1) != 0 {
return 0, _IOERR_SHMMAP
}
if rc := s.shmOpen(); rc != _OK {
return 0, rc
}
// Check if file is big enough.
o, err := s.Seek(0, io.SeekEnd)
if err != nil {
return 0, _IOERR_SHMSIZE
}
if n := (int64(id) + 1) * int64(size); n > o {
if !extend {
return 0, _OK
}
if osAllocate(s.File, n) != nil {
return 0, _IOERR_SHMSIZE
}
}
r, err := util.MapRegion(ctx, mod, s.File, int64(id)*int64(size), size, false)
if err != nil {
return 0, _IOERR_SHMMAP
}
s.regions = append(s.regions, r)
return r.Ptr, _OK
}
func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
s.Lock()
defer s.Unlock()
switch {
case flags&_SHM_UNLOCK != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
if s.vfsShmFile.lock[i] == 0 {
panic(util.AssertErr())
}
if s.vfsShmFile.lock[i] <= 0 {
s.vfsShmFile.lock[i] = 0
} else {
s.vfsShmFile.lock[i]--
}
s.lock[i] = false
}
}
case flags&_SHM_SHARED != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
panic(util.AssertErr())
}
if s.vfsShmFile.lock[i]+1 <= 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
s.vfsShmFile.lock[i]++
s.lock[i] = true
}
case flags&_SHM_EXCLUSIVE != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
panic(util.AssertErr())
}
if s.vfsShmFile.lock[i] != 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
s.vfsShmFile.lock[i] = -1
s.lock[i] = true
}
default:
panic(util.AssertErr())
}
return _OK
}
func (s *vfsShm) shmUnmap(delete bool) {
if s.vfsShmFile == nil {
return
}
// Unmap regions.
for _, r := range s.regions {
r.Unmap()
}
s.regions = nil
// Close the file.
if delete {
os.Remove(s.path)
}
s.Close()
}
func (s *vfsShm) shmBarrier() {
s.Lock()
//lint:ignore SA2001 memory barrier.
s.Unlock()
}
|
