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vfs.go
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vfs.go
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package filesystem
// this file defines the virtual file system to provide consistent file access APIs
import (
"fmt"
"io"
)
type OptionName string
var (
Option = make(map[OptionName]string)
)
type FileLocation struct {
Location string
}
type VirtualFile interface {
io.ReaderAt
io.ReadCloser
Size() int64
}
type VirtualFileSystem interface {
Accept(*FileLocation) bool
Open(*FileLocation) (VirtualFile, error)
List(*FileLocation) ([]*FileLocation, error)
IsDir(*FileLocation) bool
}
var (
fileSystems = []VirtualFileSystem{
&LocalFileSystem{},
&HdfsFileSystem{},
&S3FileSystem{},
}
)
func Set(name OptionName, value string) {
Option[name] = value
}
func Open(filepath string) (VirtualFile, error) {
fileLocation := &FileLocation{filepath}
for _, fs := range fileSystems {
if fs.Accept(fileLocation) {
return fs.Open(fileLocation)
}
}
return nil, fmt.Errorf("Unknown file %s", filepath)
}
func List(filepath string) ([]*FileLocation, error) {
fileLocation := &FileLocation{filepath}
for _, fs := range fileSystems {
if fs.Accept(fileLocation) {
return fs.List(fileLocation)
}
}
return nil, fmt.Errorf("Unknown file %s", filepath)
}
func IsDir(filepath string) bool {
fileLocation := &FileLocation{filepath}
for _, fs := range fileSystems {
if fs.Accept(fileLocation) {
return fs.IsDir(fileLocation)
}
}
return false
}