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|
//go:build sqlite3_dotlk
package vfs
import (
"context"
"errors"
"io/fs"
"os"
"sync"
"github.com/ncruces/go-sqlite3/internal/util"
"github.com/tetratelabs/wazero/api"
)
type vfsShmBuffer struct {
shared [][_WALINDEX_PGSZ]byte
refs int // +checklocks:vfsShmBuffersMtx
lock [_SHM_NLOCK]int16 // +checklocks:Mutex
sync.Mutex
}
var (
// +checklocks:vfsShmBuffersMtx
vfsShmBuffers = map[string]*vfsShmBuffer{}
vfsShmBuffersMtx sync.Mutex
)
type vfsShm struct {
*vfsShmBuffer
mod api.Module
alloc api.Function
free api.Function
path string
shadow [][_WALINDEX_PGSZ]byte
ptrs []uint32
stack [1]uint64
lock [_SHM_NLOCK]bool
}
func (s *vfsShm) Close() error {
if s.vfsShmBuffer == nil {
return nil
}
vfsShmBuffersMtx.Lock()
defer vfsShmBuffersMtx.Unlock()
// Unlock everything.
s.shmLock(0, _SHM_NLOCK, _SHM_UNLOCK)
// Decrease reference count.
if s.vfsShmBuffer.refs > 0 {
s.vfsShmBuffer.refs--
s.vfsShmBuffer = nil
return nil
}
err := os.Remove(s.path)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return _IOERR_UNLOCK
}
delete(vfsShmBuffers, s.path)
s.vfsShmBuffer = nil
return nil
}
func (s *vfsShm) shmOpen() _ErrorCode {
if s.vfsShmBuffer != nil {
return _OK
}
vfsShmBuffersMtx.Lock()
defer vfsShmBuffersMtx.Unlock()
// Find a shared buffer, increase the reference count.
if g, ok := vfsShmBuffers[s.path]; ok {
s.vfsShmBuffer = g
g.refs++
return _OK
}
// Create a directory on disk to ensure only this process
// uses this path to register a shared memory.
err := os.Mkdir(s.path, 0777)
if errors.Is(err, fs.ErrExist) {
return _BUSY
}
if err != nil {
return _IOERR_LOCK
}
// Add the new shared buffer.
s.vfsShmBuffer = &vfsShmBuffer{}
vfsShmBuffers[s.path] = s.vfsShmBuffer
return _OK
}
func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _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()
// 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)...)
s.shadow[0][4] = 1 // force invalidation
}
// Allocate local memory.
for int(id) >= len(s.ptrs) {
s.stack[0] = uint64(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, uint32(s.stack[0]), _WALINDEX_PGSZ))
s.ptrs = append(s.ptrs, uint32(s.stack[0]))
}
return s.ptrs[id], _OK
}
func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
s.Lock()
defer s.Unlock()
switch {
case flags&_SHM_LOCK != 0:
defer s.shmAcquire()
case flags&_SHM_EXCLUSIVE != 0:
s.shmRelease()
}
switch {
case flags&_SHM_UNLOCK != 0:
for i := offset; i < offset+n; i++ {
if s.lock[i] {
if s.vfsShmBuffer.lock[i] == 0 {
panic(util.AssertErr())
}
if s.vfsShmBuffer.lock[i] <= 0 {
s.vfsShmBuffer.lock[i] = 0
} else {
s.vfsShmBuffer.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.vfsShmBuffer.lock[i]+1 <= 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
s.vfsShmBuffer.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.vfsShmBuffer.lock[i] != 0 {
return _BUSY
}
}
for i := offset; i < offset+n; i++ {
s.vfsShmBuffer.lock[i] = -1
s.lock[i] = true
}
default:
panic(util.AssertErr())
}
return _OK
}
func (s *vfsShm) shmUnmap(delete bool) {
if s.vfsShmBuffer == nil {
return
}
defer s.Close()
s.Lock()
s.shmRelease()
defer s.Unlock()
for _, p := range s.ptrs {
s.stack[0] = uint64(p)
if err := s.free.CallWithStack(context.Background(), s.stack[:]); err != nil {
panic(err)
}
}
s.ptrs = nil
s.shadow = nil
}
|
