106 lines
3.0 KiB
Go
106 lines
3.0 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fuseutil
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import (
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"syscall"
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"unsafe"
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"github.com/jacobsa/fuse/fuseops"
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)
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type DirentType uint32
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const (
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DT_Unknown DirentType = 0
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DT_Socket DirentType = syscall.DT_SOCK
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DT_Link DirentType = syscall.DT_LNK
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DT_File DirentType = syscall.DT_REG
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DT_Block DirentType = syscall.DT_BLK
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DT_Directory DirentType = syscall.DT_DIR
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DT_Char DirentType = syscall.DT_CHR
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DT_FIFO DirentType = syscall.DT_FIFO
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)
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// A struct representing an entry within a directory file, describing a child.
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// See notes on fuseops.ReadDirOp and on WriteDirent for details.
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type Dirent struct {
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// The (opaque) offset within the directory file of the entry following this
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// one. See notes on fuseops.ReadDirOp.Offset for details.
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Offset fuseops.DirOffset
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// The inode of the child file or directory, and its name within the parent.
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Inode fuseops.InodeID
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Name string
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// The type of the child. The zero value (DT_Unknown) is legal, but means
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// that the kernel will need to call GetAttr when the type is needed.
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Type DirentType
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}
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// Write the supplied directory entry intto the given buffer in the format
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// expected in fuseops.ReadFileOp.Data, returning the number of bytes written.
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// Return zero if the entry would not fit.
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func WriteDirent(buf []byte, d Dirent) (n int) {
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// We want to write bytes with the layout of fuse_dirent
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// (http://goo.gl/BmFxob) in host order. The struct must be aligned according
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// to FUSE_DIRENT_ALIGN (http://goo.gl/UziWvH), which dictates 8-byte
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// alignment.
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type fuse_dirent struct {
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ino uint64
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off uint64
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namelen uint32
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type_ uint32
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name [0]byte
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}
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const direntAlignment = 8
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const direntSize = 8 + 8 + 4 + 4
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// Compute the number of bytes of padding we'll need to maintain alignment
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// for the next entry.
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var padLen int
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if len(d.Name)%direntAlignment != 0 {
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padLen = direntAlignment - (len(d.Name) % direntAlignment)
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}
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// Do we have enough room?
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totalLen := direntSize + len(d.Name) + padLen
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if totalLen > len(buf) {
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return n
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}
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// Write the header.
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de := fuse_dirent{
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ino: uint64(d.Inode),
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off: uint64(d.Offset),
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namelen: uint32(len(d.Name)),
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type_: uint32(d.Type),
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}
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n += copy(buf[n:], (*[direntSize]byte)(unsafe.Pointer(&de))[:])
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// Write the name afterward.
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n += copy(buf[n:], d.Name)
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// Add any necessary padding.
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if padLen != 0 {
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var padding [direntAlignment]byte
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n += copy(buf[n:], padding[:padLen])
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}
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return n
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}
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