Shared memory API.

vfs/adiantum/hbsh.go

@@ -27,18 +27,19 @@ func (h *hbshVFS) OpenParams(name string, flags vfs.OpenFlag, params url.Values)
 	// Encrypt everything except super journals.
 	if flags&vfs.OPEN_SUPER_JOURNAL == 0 {
 		var key []byte
-		if t, ok := params["key"]; ok {
+		if name == "" {
+			key = h.hbsh.KDF("") // Temporary files get a random key.
+		} else if t, ok := params["key"]; ok {
 			key = []byte(t[0])
 		} else if t, ok := params["hexkey"]; ok {
 			key, _ = hex.DecodeString(t[0])
 		} else if t, ok := params["textkey"]; ok {
 			key = h.hbsh.KDF(t[0])
-		} else if name == "" {
-			key = h.hbsh.KDF("")
 		}
 
 		if hbsh = h.hbsh.HBSH(key); hbsh == nil {
-			return nil, flags, sqlite3.NOTADB
+			// Can't open without a valid key.
+			return nil, flags, sqlite3.CANTOPEN
 		}
 	}
 
@@ -51,6 +52,7 @@ func (h *hbshVFS) OpenParams(name string, flags vfs.OpenFlag, params url.Values)
 		file, flags, err = h.Open(name, flags)
 	}
 	if err != nil || hbsh == nil || flags&vfs.OPEN_MEMORY != 0 {
+		// Error, or no encryption (super journals, memory files).
 		return file, flags, err
 	}
 	return &hbshFile{File: file, hbsh: hbsh}, flags, err
@@ -72,8 +74,8 @@ func (h *hbshFile) ReadAt(p []byte, off int64) (n int, err error) {
 	min := (off) &^ (blockSize - 1)                                 // round down
 	max := (off + int64(len(p)) + blockSize - 1) &^ (blockSize - 1) // round up
 
+	// Read one block at a time.
 	for ; min < max; min += blockSize {
-		// Read full block.
 		m, err := h.File.ReadAt(h.block[:], min)
 		if m != blockSize {
 			return n, err
@@ -98,20 +100,24 @@ func (h *hbshFile) WriteAt(p []byte, off int64) (n int, err error) {
 	min := (off) &^ (blockSize - 1)                                 // round down
 	max := (off + int64(len(p)) + blockSize - 1) &^ (blockSize - 1) // round up
 
+	// Write one block at a time.
 	for ; min < max; min += blockSize {
 		binary.LittleEndian.PutUint64(h.tweak[:], uint64(min))
 		data := h.block[:]
 
 		if off > min || len(p[n:]) < blockSize {
-			// Read full block.
+			// Partial block write: read-update-write.
 			m, err := h.File.ReadAt(h.block[:], min)
 			if m != blockSize {
 				if err != io.EOF {
 					return n, err
 				}
-				// Writing past the EOF.
-				// A partially written block is corrupt,
-				// and also considered to be past the EOF.
+				// Writing past the EOF:
+				// We're either appending an entirely new block,
+				// or the final block was only partially written.
+				// A partially written block can't be decripted,
+				// and is as good as corrupt.
+				// Either way, zero pad the file to the next block size.
 				clear(data)
 			}
 
@@ -124,7 +130,6 @@ func (h *hbshFile) WriteAt(p []byte, off int64) (n int, err error) {
 		t := copy(data, p[n:])
 		h.hbsh.Encrypt(h.block[:], h.tweak[:])
 
-		// Write full block.
 		m, err := h.File.WriteAt(h.block[:], min)
 		if m != blockSize {
 			return n, err
@@ -155,9 +160,11 @@ func (h *hbshFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
 		vfs.IOCAP_BATCH_ATOMIC)
 }
 
-// This is needed for shared memory.
-func (h *hbshFile) Unwrap() vfs.File {
-	return h.File
+func (h *hbshFile) SharedMemory() vfs.SharedMemory {
+	if shm, ok := h.File.(vfs.FileSharedMemory); ok {
+		return shm.SharedMemory()
+	}
+	return nil
 }
 
 // Wrap optional methods.

vfs/api.go

@@ -1,7 +1,12 @@
 // Package vfs wraps the C SQLite VFS API.
 package vfs
 
-import "net/url"
+import (
+	"context"
+	"net/url"
+
+	"github.com/tetratelabs/wazero/api"
+)
 
 // A VFS defines the interface between the SQLite core and the underlying operating system.
 //
@@ -129,3 +134,18 @@ type FileBatchAtomicWrite interface {
 	CommitAtomicWrite() error
 	RollbackAtomicWrite() error
 }
+
+// FileSharedMemory extends File to possibly implement shared memory.
+// It's OK for SharedMemory to return nil.
+type FileSharedMemory interface {
+	File
+	SharedMemory() SharedMemory
+}
+
+// SharedMemory is a shared memory implementation.
+// This cannot be externally implemented.
+type SharedMemory interface {
+	shmMap(context.Context, api.Module, int32, int32, bool) (uint32, error)
+	shmLock(int32, int32, _ShmFlag) error
+	shmUnmap(bool)
+}

vfs/file.go

@@ -1,7 +1,6 @@
 package vfs
 
 import (
-	"context"
 	"errors"
 	"io"
 	"io/fs"
@@ -12,7 +11,6 @@ import (
 	"syscall"
 
 	"github.com/ncruces/go-sqlite3/util/osutil"
-	"github.com/tetratelabs/wazero/api"
 )
 
 type vfsOS struct{}
@@ -215,9 +213,3 @@ func (f *vfsFile) PowersafeOverwrite() bool        { return f.psow }
 func (f *vfsFile) PersistentWAL() bool             { return f.keepWAL }
 func (f *vfsFile) SetPowersafeOverwrite(psow bool) { f.psow = psow }
 func (f *vfsFile) SetPersistentWAL(keepWAL bool)   { f.keepWAL = keepWAL }
-
-type fileShm interface {
-	shmMap(context.Context, api.Module, int32, int32, bool) (uint32, error)
-	shmLock(int32, int32, _ShmFlag) error
-	shmUnmap(bool)
-}

vfs/shm.go

@@ -33,6 +33,8 @@ const (
 	_SHM_DMS   = _SHM_BASE + _SHM_NLOCK
 )
 
+func (f *vfsFile) SharedMemory() SharedMemory { return f }
+
 func (f *vfsFile) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, error) {
 	// Ensure size is a multiple of the OS page size.
 	if int(size)&(unix.Getpagesize()-1) != 0 {

vfs/vfs.go

@@ -171,8 +171,10 @@ func vfsOpen(ctx context.Context, mod api.Module, pVfs, zPath, pFile uint32, fla
 		util.WriteUint32(mod, pOutFlags, uint32(flags))
 	}
 	if pOutVFS != 0 && util.CanMapFiles(ctx) {
-		if _, ok := util.Unwrap(file).(fileShm); ok {
-			util.WriteUint32(mod, pOutVFS, 1)
+		if f, ok := file.(FileSharedMemory); ok {
+			if f.SharedMemory() != nil {
+				util.WriteUint32(mod, pOutVFS, 1)
+			}
 		}
 	}
 	vfsFileRegister(ctx, mod, pFile, file)
@@ -366,7 +368,7 @@ func vfsShmBarrier(ctx context.Context, mod api.Module, pFile uint32) {
 }
 
 func vfsShmMap(ctx context.Context, mod api.Module, pFile uint32, iRegion, szRegion int32, bExtend, pp uint32) _ErrorCode {
-	file := util.Unwrap(vfsFileGet(ctx, mod, pFile)).(fileShm)
+	file := vfsFileGet(ctx, mod, pFile).(FileSharedMemory).SharedMemory()
 	p, err := file.shmMap(ctx, mod, iRegion, szRegion, bExtend != 0)
 	if err != nil {
 		return vfsErrorCode(err, _IOERR_SHMMAP)
@@ -376,13 +378,13 @@ func vfsShmMap(ctx context.Context, mod api.Module, pFile uint32, iRegion, szReg
 }
 
 func vfsShmLock(ctx context.Context, mod api.Module, pFile uint32, offset, n int32, flags _ShmFlag) _ErrorCode {
-	file := util.Unwrap(vfsFileGet(ctx, mod, pFile)).(fileShm)
+	file := vfsFileGet(ctx, mod, pFile).(FileSharedMemory).SharedMemory()
 	err := file.shmLock(offset, n, flags)
 	return vfsErrorCode(err, _IOERR_SHMLOCK)
 }
 
 func vfsShmUnmap(ctx context.Context, mod api.Module, pFile, bDelete uint32) _ErrorCode {
-	file := util.Unwrap(vfsFileGet(ctx, mod, pFile)).(fileShm)
+	file := vfsFileGet(ctx, mod, pFile).(FileSharedMemory).SharedMemory()
 	file.shmUnmap(bDelete != 0)
 	return _OK
 }