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// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package storage
import (
"bytes"
"os"
"sync"
)
const typeShift = 4
// Verify at compile-time that typeShift is large enough to cover all FileType
// values by confirming that 0 == 0.
var _ [0]struct{} = [TypeAll >> typeShift]struct{}{}
type memStorageLock struct {
ms *memStorage
}
func (lock *memStorageLock) Unlock() {
ms := lock.ms
ms.mu.Lock()
defer ms.mu.Unlock()
if ms.slock == lock {
ms.slock = nil
}
return
}
// memStorage is a memory-backed storage.
type memStorage struct {
mu sync.Mutex
slock *memStorageLock
files map[uint64]*memFile
meta FileDesc
}
// NewMemStorage returns a new memory-backed storage implementation.
func NewMemStorage() Storage {
return &memStorage{
files: make(map[uint64]*memFile),
}
}
func (ms *memStorage) Lock() (Locker, error) {
ms.mu.Lock()
defer ms.mu.Unlock()
if ms.slock != nil {
return nil, ErrLocked
}
ms.slock = &memStorageLock{ms: ms}
return ms.slock, nil
}
func (*memStorage) Log(str string) {}
func (ms *memStorage) SetMeta(fd FileDesc) error {
if !FileDescOk(fd) {
return ErrInvalidFile
}
ms.mu.Lock()
ms.meta = fd
ms.mu.Unlock()
return nil
}
func (ms *memStorage) GetMeta() (FileDesc, error) {
ms.mu.Lock()
defer ms.mu.Unlock()
if ms.meta.Zero() {
return FileDesc{}, os.ErrNotExist
}
return ms.meta, nil
}
func (ms *memStorage) List(ft FileType) ([]FileDesc, error) {
ms.mu.Lock()
var fds []FileDesc
for x := range ms.files {
fd := unpackFile(x)
if fd.Type&ft != 0 {
fds = append(fds, fd)
}
}
ms.mu.Unlock()
return fds, nil
}
func (ms *memStorage) Open(fd FileDesc) (Reader, error) {
if !FileDescOk(fd) {
return nil, ErrInvalidFile
}
ms.mu.Lock()
defer ms.mu.Unlock()
if m, exist := ms.files[packFile(fd)]; exist {
if m.open {
return nil, errFileOpen
}
m.open = true
return &memReader{Reader: bytes.NewReader(m.Bytes()), ms: ms, m: m}, nil
}
return nil, os.ErrNotExist
}
func (ms *memStorage) Create(fd FileDesc) (Writer, error) {
if !FileDescOk(fd) {
return nil, ErrInvalidFile
}
x := packFile(fd)
ms.mu.Lock()
defer ms.mu.Unlock()
m, exist := ms.files[x]
if exist {
if m.open {
return nil, errFileOpen
}
m.Reset()
} else {
m = &memFile{}
ms.files[x] = m
}
m.open = true
return &memWriter{memFile: m, ms: ms}, nil
}
func (ms *memStorage) Remove(fd FileDesc) error {
if !FileDescOk(fd) {
return ErrInvalidFile
}
x := packFile(fd)
ms.mu.Lock()
defer ms.mu.Unlock()
if _, exist := ms.files[x]; exist {
delete(ms.files, x)
return nil
}
return os.ErrNotExist
}
func (ms *memStorage) Rename(oldfd, newfd FileDesc) error {
if !FileDescOk(oldfd) || !FileDescOk(newfd) {
return ErrInvalidFile
}
if oldfd == newfd {
return nil
}
oldx := packFile(oldfd)
newx := packFile(newfd)
ms.mu.Lock()
defer ms.mu.Unlock()
oldm, exist := ms.files[oldx]
if !exist {
return os.ErrNotExist
}
newm, exist := ms.files[newx]
if (exist && newm.open) || oldm.open {
return errFileOpen
}
delete(ms.files, oldx)
ms.files[newx] = oldm
return nil
}
func (*memStorage) Close() error { return nil }
type memFile struct {
bytes.Buffer
open bool
}
type memReader struct {
*bytes.Reader
ms *memStorage
m *memFile
closed bool
}
func (mr *memReader) Close() error {
mr.ms.mu.Lock()
defer mr.ms.mu.Unlock()
if mr.closed {
return ErrClosed
}
mr.m.open = false
return nil
}
type memWriter struct {
*memFile
ms *memStorage
closed bool
}
func (*memWriter) Sync() error { return nil }
func (mw *memWriter) Close() error {
mw.ms.mu.Lock()
defer mw.ms.mu.Unlock()
if mw.closed {
return ErrClosed
}
mw.memFile.open = false
return nil
}
func packFile(fd FileDesc) uint64 {
return uint64(fd.Num)<<typeShift | uint64(fd.Type)
}
func unpackFile(x uint64) FileDesc {
return FileDesc{FileType(x) & TypeAll, int64(x >> typeShift)}
}
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