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// Copyright 2012 The LevelDB-Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package db
import (
"io"
"os"
)
// File is a readable, writable sequence of bytes.
//
// Typically, it will be an *os.File, but test code may choose to substitute
// memory-backed implementations.
type File interface {
io.Closer
io.Reader
io.ReaderAt
io.Writer
Stat() (os.FileInfo, error)
Sync() error
}
// FileSystem is a namespace for files.
//
// The names are filepath names: they may be / separated or \ separated,
// depending on the underlying operating system.
type FileSystem interface {
// Create creates the named file for writing, truncating it if it already
// exists.
Create(name string) (File, error)
// Open opens the named file for reading.
Open(name string) (File, error)
// Remove removes the named file or directory.
Remove(name string) error
// Rename renames a file. It overwrites the file at newname if one exists,
// the same as os.Rename.
Rename(oldname, newname string) error
// MkdirAll creates a directory and all necessary parents. The permission
// bits perm have the same semantics as in os.MkdirAll. If the directory
// already exists, MkdirAll does nothing and returns nil.
MkdirAll(dir string, perm os.FileMode) error
// Lock locks the given file, creating the file if necessary, and
// truncating the file if it already exists. The lock is an exclusive lock
// (a write lock), but locked files should neither be read from nor written
// to. Such files should have zero size and only exist to co-ordinate
// ownership across processes.
//
// A nil Closer is returned if an error occurred. Otherwise, close that
// Closer to release the lock.
//
// On Linux and OSX, a lock has the same semantics as fcntl(2)'s advisory
// locks. In particular, closing any other file descriptor for the same
// file will release the lock prematurely.
//
// Attempting to lock a file that is already locked by the current process
// has undefined behavior.
//
// Lock is not yet implemented on other operating systems, and calling it
// will return an error.
Lock(name string) (io.Closer, error)
// List returns a listing of the given directory. The names returned are
// relative to dir.
List(dir string) ([]string, error)
// Stat returns an os.FileInfo describing the named file.
Stat(name string) (os.FileInfo, error)
}
// DefaultFileSystem is a FileSystem implementation backed by the underlying
// operating system's file system.
var DefaultFileSystem FileSystem = defFS{}
type defFS struct{}
func (defFS) Create(name string) (File, error) {
return os.Create(name)
}
func (defFS) Open(name string) (File, error) {
return os.Open(name)
}
func (defFS) Remove(name string) error {
return os.Remove(name)
}
func (defFS) Rename(oldname, newname string) error {
return os.Rename(oldname, newname)
}
func (defFS) MkdirAll(dir string, perm os.FileMode) error {
return os.MkdirAll(dir, perm)
}
func (defFS) List(dir string) ([]string, error) {
f, err := os.Open(dir)
if err != nil {
return nil, err
}
defer f.Close()
return f.Readdirnames(-1)
}
func (defFS) Stat(name string) (os.FileInfo, error) {
return os.Stat(name)
}
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