Share memory by copying.

driver/example_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package driver_test
 

tests/bradfitz/sql_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package bradfitz
 

vfs/adiantum/example_test.go

@@ -1,4 +1,4 @@
-//go:build (linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && !sqlite3_nosys
+//go:build ((linux || darwin || windows || freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_nosys) || sqlite3_flock || sqlite3_dotlk
 
 package adiantum_test
 

vfs/shm.go

@@ -1,4 +1,4 @@
-//go:build (darwin || linux || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_noshm || sqlite3_nosys)
+//go:build ((darwin || linux || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_noshm || sqlite3_nosys)) || sqlite3_flock || sqlite3_dotlk
 
 package vfs
 

vfs/shm_bsd.go

@@ -1,4 +1,4 @@
-//go:build (freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_noshm || sqlite3_nosys)
+//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_dotlk || sqlite3_noshm || sqlite3_nosys)) || sqlite3_flock
 
 package vfs
 

vfs/shm_copy.go

@@ -0,0 +1,266 @@
+//go:build sqlite3_dotlk
+
+package vfs
+
+import (
+	"context"
+	"sync"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+	"github.com/tetratelabs/wazero/api"
+)
+
+const _SHM_NLOCK = 8
+
+type vfsShmBuffer struct {
+	path string
+	data []byte
+
+	refs int
+
+	lock [_SHM_NLOCK]int16
+	sync.Mutex
+}
+
+var (
+	vfsShmBuffers    []*vfsShmBuffer
+	vfsShmBuffersMtx sync.Mutex
+)
+
+type vfsShm struct {
+	*vfsShmBuffer
+	mod      api.Module
+	alloc    api.Function
+	free     api.Function
+	path     string
+	shadow   []byte
+	ptrs     []uint32
+	stack    [1]uint64
+	lock     [_SHM_NLOCK]bool
+	size     int32
+	readOnly 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 > 1 {
+		s.vfsShmBuffer.refs--
+		s.vfsShmBuffer = nil
+		return nil
+	}
+
+	for i, g := range vfsShmBuffers {
+		if g == s.vfsShmBuffer {
+			vfsShmBuffers[i] = nil
+			s.vfsShmBuffer = nil
+			return nil
+		}
+	}
+	panic(util.AssertErr())
+}
+
+func (s *vfsShm) shmOpen() {
+	if s.vfsShmBuffer != nil {
+		return
+	}
+
+	vfsShmBuffersMtx.Lock()
+	defer vfsShmBuffersMtx.Unlock()
+
+	// Find a shared buffer, increase the reference count.
+	for _, g := range vfsShmBuffers {
+		if g != nil && s.path == g.path {
+			s.vfsShmBuffer = g
+			g.refs++
+			return
+		}
+	}
+
+	// Add the new shared buffer.
+	s.vfsShmBuffer = &vfsShmBuffer{
+		path: s.path,
+		refs: 1,
+	}
+	for i, g := range vfsShmBuffers {
+		if g == nil {
+			vfsShmBuffers[i] = s.vfsShmBuffer
+			return
+		}
+	}
+	vfsShmBuffers = append(vfsShmBuffers, s.vfsShmBuffer)
+}
+
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+	switch {
+	case s.size == 0:
+		s.size = size
+		s.mod = mod
+		s.free = mod.ExportedFunction("sqlite3_free")
+		s.alloc = mod.ExportedFunction("sqlite3_malloc64")
+	case s.size != size:
+		return 0, _IOERR_SHMMAP
+	}
+
+	s.shmOpen()
+	s.Lock()
+	defer s.Unlock()
+	defer s.shmAcquire()
+
+	n := (int(id) + 1) * int(size)
+
+	if n > len(s.data) {
+		if !extend {
+			return 0, _OK
+		}
+		if s.readOnly {
+			return 0, _IOERR_SHMSIZE
+		}
+		s.data = append(s.data, make([]byte, n-len(s.data))...)
+	}
+
+	if n > len(s.shadow) {
+		s.shadow = append(s.shadow, make([]byte, n-len(s.shadow))...)
+	}
+
+	if 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]), uint64(s.size)))
+		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
+	}
+
+	if s.readOnly {
+		return s.ptrs[id], _READONLY
+	}
+	return s.ptrs[id], _OK
+}
+
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+	s.Lock()
+	defer s.Unlock()
+
+	if flags&_SHM_UNLOCK == 0 {
+		s.shmAcquire()
+	} else {
+		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)
+		}
+	}
+}
+
+func (s *vfsShm) shmBarrier() {
+	s.Lock()
+	s.shmAcquire()
+	s.shmRelease()
+	s.Unlock()
+}
+
+func (s *vfsShm) shmAcquire() {
+	for id, p := range s.ptrs {
+		start := id * int(s.size)
+		stop := start + int(s.size)
+		data := s.data[start:stop]
+		shadow := s.shadow[start:stop]
+		local := util.View(s.mod, p, uint64(s.size))
+		for i, data := range data {
+			if shadow[i] != data {
+				shadow[i] = data
+				local[i] = data
+			}
+		}
+	}
+}
+
+func (s *vfsShm) shmRelease() {
+	for id, p := range s.ptrs {
+		start := id * int(s.size)
+		stop := start + int(s.size)
+		data := s.data[start:stop]
+		shadow := s.shadow[start:stop]
+		local := util.View(s.mod, p, uint64(s.size))
+		for i, local := range local {
+			if shadow[i] != local {
+				shadow[i] = local
+				data[i] = local
+			}
+		}
+	}
+}

vfs/shm_other.go

@@ -1,4 +1,4 @@
-//go:build !(darwin || linux || freebsd || openbsd || netbsd || dragonfly || illumos || sqlite3_flock) || !(386 || arm || amd64 || arm64 || riscv64 || ppc64le) || sqlite3_dotlk || sqlite3_noshm || sqlite3_nosys
+//go:build !(((darwin || linux || freebsd || openbsd || netbsd || dragonfly || illumos) && (386 || arm || amd64 || arm64 || riscv64 || ppc64le) && !(sqlite3_noshm || sqlite3_nosys)) || sqlite3_flock || sqlite3_dotlk)
 
 package vfs