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|
//go:build sqlite3_dotlk
package vfs
import (
"context"
"errors"
"io/fs"
"sync"
"github.com/tetratelabs/wazero/api"
"github.com/ncruces/go-sqlite3/internal/dotlk"
"github.com/ncruces/go-sqlite3/internal/util"
)
type vfsShmParent struct {
shared [][_WALINDEX_PGSZ]byte
refs int // +checklocks:vfsShmListMtx
lock [_SHM_NLOCK]int8 // +checklocks:Mutex
sync.Mutex
}
var (
// +checklocks:vfsShmListMtx
vfsShmList = map[string]*vfsShmParent{}
vfsShmListMtx sync.Mutex
)
type vfsShm struct {
*vfsShmParent
mod api.Module
alloc api.Function
free api.Function
path string
shadow [][_WALINDEX_PGSZ]byte
ptrs []ptr_t
stack [1]stk_t
lock [_SHM_NLOCK]bool
}
func (s *vfsShm) Close() error {
if s.vfsShmParent == nil {
return nil
}
vfsShmListMtx.Lock()
defer vfsShmListMtx.Unlock()
// Unlock everything.
s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
// Decrease reference count.
if s.vfsShmParent.refs > 0 {
s.vfsShmParent.refs--
s.vfsShmParent = nil
return nil
}
if err := dotlk.Unlock(s.path); err != nil {
return _IOERR_UNLOCK
}
delete(vfsShmList, s.path)
s.vfsShmParent = nil
return nil
}
func (s *vfsShm) shmOpen() _ErrorCode {
if s.vfsShmParent != nil {
return _OK
}
vfsShmListMtx.Lock()
defer vfsShmListMtx.Unlock()
// Find a shared buffer, increase the reference count.
if g, ok := vfsShmList[s.path]; ok {
s.vfsShmParent = g
g.refs++
return _OK
}
// Dead man's switch.
err := dotlk.LockShm(s.path)
if errors.Is(err, fs.ErrExist) {
return _BUSY
}
if err != nil {
return _IOERR_LOCK
}
// Add the new shared buffer.
s.vfsShmParent = &vfsShmParent{}
vfsShmList[s.path] = s.vfsShmParent
return _OK
}
func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (ptr_t, _ErrorCode) {
if size != _WALINDEX_PGSZ {
return 0, _IOERR_SHMMAP
}
if s.mod == nil {
s.mod = mod
s.free = mod.ExportedFunction("sqlite3_free")
s.alloc = mod.ExportedFunction("sqlite3_malloc64")
}
if rc := s.shmOpen(); rc != _OK {
return 0, rc
}
s.Lock()
defer s.Unlock()
defer s.shmAcquire(nil)
// Extend shared memory.
if int(id) >= len(s.shared) {
if !extend {
return 0, _OK
}
s.shared = append(s.shared, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shared)+1)...)
}
// Allocate shadow memory.
if int(id) >= len(s.shadow) {
s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
}
// Allocate local memory.
for int(id) >= len(s.ptrs) {
s.stack[0] = stk_t(size)
if err := s.alloc.CallWithStack(ctx, s.stack[:]); err != nil {
panic(err)
}
if s.stack[0] == 0 {
panic(util.OOMErr)
}
clear(util.View(s.mod, ptr_t(s.stack[0]), _WALINDEX_PGSZ))
s.ptrs = append(s.ptrs, ptr_t(s.stack[0]))
}
s.shadow[0][4] = 1
return s.ptrs[id], _OK
}
func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
s.Lock()
defer s.Unlock()
switch {
case flags&_SHM_LOCK != 0:
defer s.shmAcquire(&rc)
case flags&_SHM_EXCLUSIVE != 0:
s.shmRelease()
}
return s.shmMemLock(offset, n, flags)
}
func (s *vfsShm) shmUnmap(delete bool) {
if s.vfsShmParent == nil {
return
}
defer s.Close()
s.Lock()
s.shmRelease()
defer s.Unlock()
for _, p := range s.ptrs {
s.stack[0] = stk_t(p)
if err := s.free.CallWithStack(context.Background(), s.stack[:]); err != nil {
panic(err)
}
}
s.ptrs = nil
s.shadow = nil
}
|
