Stop using fuseshim.Buffer.

fuseops/common_op.go

@@ -19,9 +19,8 @@ import (
 	"log"
 	"reflect"
 	"strings"
-	"unsafe"
 
-	"github.com/jacobsa/fuse/internal/fusekernel"
+	"github.com/jacobsa/fuse/internal/buffer"
 	"github.com/jacobsa/fuse/internal/fuseshim"
 	"github.com/jacobsa/reqtrace"
 	"golang.org/x/net/context"
@@ -32,12 +31,12 @@ import (
 type internalOp interface {
 	Op
 
-	// Create a response message for the kernel, with leading pading for a
-	// fusekernel.OutHeader struct.
+	// Create a response message for the kernel, leaving the leading
+	// fusekernel.OutHeader untouched.
 	//
-	// Special case: a return value of nil means that the kernel is not expecting
-	// a response.
-	kernelResponse() []byte
+	// Special case: a zero return value means that the kernel is not expecting a
+	// response.
+	kernelResponse() (b buffer.Buffer)
 }
 
 // A function that sends a reply message back to the kernel for the request
@@ -143,16 +142,17 @@ func (o *commonOp) Respond(err error) {
 	// If successful, we ask the op for an appopriate response to the kernel, and
 	// it is responsible for leaving room for the fusekernel.OutHeader struct.
 	// Otherwise, create our own.
-	var msg []byte
+	var b buffer.Buffer
 	if err == nil {
-		msg = o.op.kernelResponse()
+		b = o.op.kernelResponse()
 	} else {
-		msg = fuseshim.NewBuffer(0)
+		b = buffer.New(0)
 	}
 
 	// Fill in the header if a reply is needed.
+	msg := b.Bytes()
 	if msg != nil {
-		h := (*fusekernel.OutHeader)(unsafe.Pointer(&msg[0]))
+		h := b.OutHeader()
 		h.Unique = o.fuseID
 		h.Len = uint32(len(msg))
 		if err != nil {

fuseops/ops.go

@@ -20,8 +20,8 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/jacobsa/fuse/internal/buffer"
 	"github.com/jacobsa/fuse/internal/fusekernel"
-	"github.com/jacobsa/fuse/internal/fuseshim"
 	"golang.org/x/net/context"
 )
 
@@ -88,13 +88,12 @@ func (o *LookUpInodeOp) ShortDesc() (desc string) {
 	return
 }
 
-func (o *LookUpInodeOp) kernelResponse() (msg []byte) {
+func (o *LookUpInodeOp) kernelResponse() (b buffer.Buffer) {
 	size := fusekernel.EntryOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(size)
-	out := (*fusekernel.EntryOut)(buf.Alloc(size))
+	b = buffer.New(size)
+	out := (*fusekernel.EntryOut)(b.Grow(size))
 	convertChildInodeEntry(&o.Entry, out)
 
-	msg = buf
 	return
 }
 
@@ -124,14 +123,13 @@ func (o *GetInodeAttributesOp) DebugString() string {
 		o.Attributes.DebugString())
 }
 
-func (o *GetInodeAttributesOp) kernelResponse() (msg []byte) {
+func (o *GetInodeAttributesOp) kernelResponse() (b buffer.Buffer) {
 	size := fusekernel.AttrOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(size)
-	out := (*fusekernel.AttrOut)(buf.Alloc(size))
+	b = buffer.New(size)
+	out := (*fusekernel.AttrOut)(b.Grow(size))
 	out.AttrValid, out.AttrValidNsec = convertExpirationTime(o.AttributesExpiration)
 	convertAttributes(o.Inode, &o.Attributes, &out.Attr)
 
-	msg = buf
 	return
 }
 
@@ -159,14 +157,13 @@ type SetInodeAttributesOp struct {
 	AttributesExpiration time.Time
 }
 
-func (o *SetInodeAttributesOp) kernelResponse() (msg []byte) {
+func (o *SetInodeAttributesOp) kernelResponse() (b buffer.Buffer) {
 	size := fusekernel.AttrOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(size)
-	out := (*fusekernel.AttrOut)(buf.Alloc(size))
+	b = buffer.New(size)
+	out := (*fusekernel.AttrOut)(b.Grow(size))
 	out.AttrValid, out.AttrValidNsec = convertExpirationTime(o.AttributesExpiration)
 	convertAttributes(o.Inode, &o.Attributes, &out.Attr)
 
-	msg = buf
 	return
 }
 
@@ -219,7 +216,7 @@ type ForgetInodeOp struct {
 	N uint64
 }
 
-func (o *ForgetInodeOp) kernelResponse() (msg []byte) {
+func (o *ForgetInodeOp) kernelResponse() (b buffer.Buffer) {
 	// No response.
 	return
 }
@@ -262,13 +259,12 @@ func (o *MkDirOp) ShortDesc() (desc string) {
 	return
 }
 
-func (o *MkDirOp) kernelResponse() (msg []byte) {
+func (o *MkDirOp) kernelResponse() (b buffer.Buffer) {
 	size := fusekernel.EntryOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(size)
-	out := (*fusekernel.EntryOut)(buf.Alloc(size))
+	b = buffer.New(size)
+	out := (*fusekernel.EntryOut)(b.Grow(size))
 	convertChildInodeEntry(&o.Entry, out)
 
-	msg = buf
 	return
 }
 
@@ -315,17 +311,16 @@ func (o *CreateFileOp) ShortDesc() (desc string) {
 	return
 }
 
-func (o *CreateFileOp) kernelResponse() (msg []byte) {
+func (o *CreateFileOp) kernelResponse() (b buffer.Buffer) {
 	eSize := fusekernel.EntryOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(eSize + unsafe.Sizeof(fusekernel.OpenOut{}))
+	b = buffer.New(eSize + unsafe.Sizeof(fusekernel.OpenOut{}))
 
-	e := (*fusekernel.EntryOut)(buf.Alloc(eSize))
+	e := (*fusekernel.EntryOut)(b.Grow(eSize))
 	convertChildInodeEntry(&o.Entry, e)
 
-	oo := (*fusekernel.OpenOut)(buf.Alloc(unsafe.Sizeof(fusekernel.OpenOut{})))
+	oo := (*fusekernel.OpenOut)(b.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
 	oo.Fh = uint64(o.Handle)
 
-	msg = buf
 	return
 }
 
@@ -362,13 +357,12 @@ func (o *CreateSymlinkOp) ShortDesc() (desc string) {
 	return
 }
 
-func (o *CreateSymlinkOp) kernelResponse() (msg []byte) {
+func (o *CreateSymlinkOp) kernelResponse() (b buffer.Buffer) {
 	size := fusekernel.EntryOutSize(o.protocol)
-	buf := fuseshim.NewBuffer(size)
-	out := (*fusekernel.EntryOut)(buf.Alloc(size))
+	b = buffer.New(size)
+	out := (*fusekernel.EntryOut)(b.Grow(size))
 	convertChildInodeEntry(&o.Entry, out)
 
-	msg = buf
 	return
 }
 
@@ -424,8 +418,8 @@ type RenameOp struct {
 	NewName   string
 }
 
-func (o *RenameOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *RenameOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -445,8 +439,8 @@ type RmDirOp struct {
 	Name   string
 }
 
-func (o *RmDirOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *RmDirOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -465,8 +459,8 @@ type UnlinkOp struct {
 	Name   string
 }
 
-func (o *UnlinkOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *UnlinkOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -497,12 +491,11 @@ type OpenDirOp struct {
 	Handle HandleID
 }
 
-func (o *OpenDirOp) kernelResponse() (msg []byte) {
-	buf := fuseshim.NewBuffer(unsafe.Sizeof(fusekernel.OpenOut{}))
-	out := (*fusekernel.OpenOut)(buf.Alloc(unsafe.Sizeof(fusekernel.OpenOut{})))
+func (o *OpenDirOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(unsafe.Sizeof(fusekernel.OpenOut{}))
+	out := (*fusekernel.OpenOut)(b.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
 	out.Fh = uint64(o.Handle)
 
-	msg = buf
 	return
 }
 
@@ -596,9 +589,9 @@ type ReadDirOp struct {
 	Data []byte
 }
 
-func (o *ReadDirOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(uintptr(len(o.Data)))
-	msg = append(msg, o.Data...)
+func (o *ReadDirOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(uintptr(len(o.Data)))
+	b.Append(o.Data)
 	return
 }
 
@@ -619,8 +612,8 @@ type ReleaseDirHandleOp struct {
 	Handle HandleID
 }
 
-func (o *ReleaseDirHandleOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *ReleaseDirHandleOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -650,12 +643,11 @@ type OpenFileOp struct {
 	Handle HandleID
 }
 
-func (o *OpenFileOp) kernelResponse() (msg []byte) {
-	buf := fuseshim.NewBuffer(unsafe.Sizeof(fusekernel.OpenOut{}))
-	out := (*fusekernel.OpenOut)(buf.Alloc(unsafe.Sizeof(fusekernel.OpenOut{})))
+func (o *OpenFileOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(unsafe.Sizeof(fusekernel.OpenOut{}))
+	out := (*fusekernel.OpenOut)(b.Grow(unsafe.Sizeof(fusekernel.OpenOut{})))
 	out.Fh = uint64(o.Handle)
 
-	msg = buf
 	return
 }
 
@@ -688,9 +680,9 @@ type ReadFileOp struct {
 	Data []byte
 }
 
-func (o *ReadFileOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(uintptr(len(o.Data)))
-	msg = append(msg, o.Data...)
+func (o *ReadFileOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(uintptr(len(o.Data)))
+	b.Append(o.Data)
 	return
 }
 
@@ -764,12 +756,11 @@ type WriteFileOp struct {
 	Data []byte
 }
 
-func (o *WriteFileOp) kernelResponse() (msg []byte) {
-	buf := fuseshim.NewBuffer(unsafe.Sizeof(fusekernel.WriteOut{}))
-	out := (*fusekernel.WriteOut)(buf.Alloc(unsafe.Sizeof(fusekernel.WriteOut{})))
+func (o *WriteFileOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(unsafe.Sizeof(fusekernel.WriteOut{}))
+	out := (*fusekernel.WriteOut)(b.Grow(unsafe.Sizeof(fusekernel.WriteOut{})))
 	out.Size = uint32(len(o.Data))
 
-	msg = buf
 	return
 }
 
@@ -797,8 +788,8 @@ type SyncFileOp struct {
 	Handle HandleID
 }
 
-func (o *SyncFileOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *SyncFileOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -857,8 +848,8 @@ type FlushFileOp struct {
 	Handle HandleID
 }
 
-func (o *FlushFileOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *FlushFileOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -879,8 +870,8 @@ type ReleaseFileHandleOp struct {
 	Handle HandleID
 }
 
-func (o *ReleaseFileHandleOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(0)
+func (o *ReleaseFileHandleOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(0)
 	return
 }
 
@@ -897,7 +888,7 @@ func (o *unknownOp) ShortDesc() (desc string) {
 	return
 }
 
-func (o *unknownOp) kernelResponse() (msg []byte) {
+func (o *unknownOp) kernelResponse() (b buffer.Buffer) {
 	panic(fmt.Sprintf("Should never get here for unknown op: %s", o.ShortDesc()))
 }
 
@@ -916,9 +907,9 @@ type ReadSymlinkOp struct {
 	Target string
 }
 
-func (o *ReadSymlinkOp) kernelResponse() (msg []byte) {
-	msg = fuseshim.NewBuffer(uintptr(len(o.Target)))
-	msg = append(msg, o.Target...)
+func (o *ReadSymlinkOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(uintptr(len(o.Target)))
+	b.AppendString(o.Target)
 	return
 }
 
@@ -937,11 +928,10 @@ type InternalStatFSOp struct {
 	commonOp
 }
 
-func (o *InternalStatFSOp) kernelResponse() (msg []byte) {
-	buf := fuseshim.NewBuffer(unsafe.Sizeof(fusekernel.StatfsOut{}))
-	buf.Alloc(unsafe.Sizeof(fusekernel.StatfsOut{}))
+func (o *InternalStatFSOp) kernelResponse() (b buffer.Buffer) {
+	b = buffer.New(unsafe.Sizeof(fusekernel.StatfsOut{}))
+	b.Grow(unsafe.Sizeof(fusekernel.StatfsOut{}))
 
-	msg = buf
 	return
 }
 
@@ -951,6 +941,6 @@ type InternalInterruptOp struct {
 	FuseID uint64
 }
 
-func (o *InternalInterruptOp) kernelResponse() (msg []byte) {
+func (o *InternalInterruptOp) kernelResponse() (b buffer.Buffer) {
 	panic("Shouldn't get here.")
 }

internal/buffer/buffer.go

+// Copyright 2015 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package buffer
+
+import (
+	"reflect"
+	"unsafe"
+
+	"github.com/jacobsa/fuse/internal/fusekernel"
+)
+
+// Buffer provides a mechanism for constructing a single contiguous fuse
+// message from multiple segments, where the first segment is always a
+// fusekernel.OutHeader message.
+//
+// Must be created with New. Exception: the zero value has Bytes() == nil.
+type Buffer struct {
+	slice []byte
+}
+
+// Create a new buffer whose initial contents are a zeroed fusekernel.OutHeader
+// message, and with room enough to grow by extra bytes.
+func New(extra uintptr) (b Buffer) {
+	const headerSize = unsafe.Sizeof(fusekernel.OutHeader{})
+	b.slice = make([]byte, headerSize, headerSize+extra)
+	return
+}
+
+// Return a pointer to the header at the start of the buffer.
+func (b *Buffer) OutHeader() (h *fusekernel.OutHeader) {
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&b.slice))
+	h = (*fusekernel.OutHeader)(unsafe.Pointer(sh.Data))
+	return
+}
+
+// Grow the buffer by the supplied number of bytes, returning a pointer to the
+// start of the new segment. The sum of the arguments given to Grow must not
+// exceed the argument given to New when creating the buffer.
+func (b *Buffer) Grow(size uintptr) (p unsafe.Pointer) {
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&b.slice))
+	p = unsafe.Pointer(sh.Data + uintptr(sh.Len))
+	b.slice = b.slice[:len(b.slice)+int(size)]
+	return
+}
+
+// Equivalent to growing by the length of p, then copying p into the new segment.
+func (b *Buffer) Append(p []byte) {
+	sh := reflect.SliceHeader{
+		Data: uintptr(b.Grow(uintptr(len(p)))),
+		Len:  len(p),
+		Cap:  len(p),
+	}
+
+	copy(*(*[]byte)(unsafe.Pointer(&sh)), p)
+}
+
+// Equivalent to growing by the length of s, then copying s into the new segment.
+func (b *Buffer) AppendString(s string) {
+	sh := reflect.SliceHeader{
+		Data: uintptr(b.Grow(uintptr(len(s)))),
+		Len:  len(s),
+		Cap:  len(s),
+	}
+
+	copy(*(*[]byte)(unsafe.Pointer(&sh)), s)
+}
+
+// Return a reference to the current contents of the buffer.
+func (b *Buffer) Bytes() []byte {
+	return b.slice
+}