| // Licensed to the Apache Software Foundation (ASF) under one or more |
| // contributor license agreements. See the NOTICE file distributed with |
| // this work for additional information regarding copyright ownership. |
| // The ASF licenses this file to You 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 filesystem contains an extensible file system abstraction. It allows |
| // various kinds of storage systems to be used uniformly, notably through textio. |
| package filesystem |
| |
| import ( |
| "context" |
| "fmt" |
| "io" |
| "strings" |
| |
| "github.com/apache/beam/sdks/go/pkg/beam/internal/errors" |
| ) |
| |
| var registry = make(map[string]func(context.Context) Interface) |
| |
| // Register registers a file system backend under the given scheme. For |
| // example, "hdfs" would be registered a HFDS file system and HDFS paths used |
| // transparently. |
| func Register(scheme string, fs func(context.Context) Interface) { |
| if _, ok := registry[scheme]; ok { |
| panic(fmt.Sprintf("scheme %v already registered", scheme)) |
| } |
| registry[scheme] = fs |
| } |
| |
| // New returns a new Interface for the given file path's scheme. |
| func New(ctx context.Context, path string) (Interface, error) { |
| scheme := getScheme(path) |
| mkfs, ok := registry[scheme] |
| if !ok { |
| return nil, errors.Errorf("file system scheme %v not registered for %v", scheme, path) |
| } |
| return mkfs(ctx), nil |
| } |
| |
| // Interface is a filesystem abstraction that allows beam io sources and sinks |
| // to use various underlying storage systems transparently. |
| type Interface interface { |
| io.Closer |
| |
| // List expands a patten to a list of filenames. |
| List(ctx context.Context, glob string) ([]string, error) |
| |
| // OpenRead opens a file for reading. |
| OpenRead(ctx context.Context, filename string) (io.ReadCloser, error) |
| // OpenRead opens a file for writing. If the file already exist, it will be |
| // overwritten. |
| OpenWrite(ctx context.Context, filename string) (io.WriteCloser, error) |
| // Size returns the size of a file in bytes. |
| Size(ctx context.Context, filename string) (int64, error) |
| } |
| |
| func getScheme(path string) string { |
| if index := strings.Index(path, "://"); index > 0 { |
| return path[:index] |
| } |
| return "default" |
| } |
| |
| // ValidateScheme panics if the given path's scheme does not have a |
| // corresponding file system registered. |
| func ValidateScheme(path string) { |
| if strings.TrimSpace(path) == "" { |
| panic("empty file glob provided") |
| } |
| scheme := getScheme(path) |
| if _, ok := registry[scheme]; !ok { |
| panic(fmt.Sprintf("filesystem scheme %v not registered", scheme)) |
| } |
| } |