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memory.go
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memory.go
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// 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 memfs contains a in-memory Beam filesystem. Useful for testing.
package memfs
import (
"bytes"
"context"
"io"
"io/ioutil"
"os"
"sort"
"strings"
"sync"
"github.com/apache/beam/sdks/go/pkg/beam/io/filesystem"
)
func init() {
filesystem.Register("memfs", New)
}
var instance = &fs{m: make(map[string][]byte)}
type fs struct {
m map[string][]byte
mu sync.Mutex
}
// New returns the global memory filesystem.
func New(ctx context.Context) filesystem.Interface {
return instance
}
func (f *fs) Close() error {
return nil
}
func (f *fs) List(ctx context.Context, glob string) ([]string, error) {
f.mu.Lock()
defer f.mu.Unlock()
var ret []string
for k := range f.m {
ret = append(ret, k)
}
sort.Strings(ret)
return ret, nil
}
func (f *fs) OpenRead(ctx context.Context, filename string) (io.ReadCloser, error) {
f.mu.Lock()
defer f.mu.Unlock()
if v, ok := f.m[normalize(filename)]; ok {
return ioutil.NopCloser(bytes.NewReader(v)), nil
}
return nil, os.ErrNotExist
}
func (f *fs) OpenWrite(ctx context.Context, filename string) (io.WriteCloser, error) {
return &commitWriter{key: filename}, nil
}
// Write stores the given key and value in the global store.
func Write(key string, value []byte) {
instance.mu.Lock()
defer instance.mu.Unlock()
cp := make([]byte, len(value))
copy(cp, value)
instance.m[normalize(key)] = cp
}
func normalize(key string) string {
if strings.HasPrefix(key, "memfs://") {
return key
}
return "memfs://" + key
}
type commitWriter struct {
key string
buf bytes.Buffer
}
func (w *commitWriter) Write(p []byte) (n int, err error) {
return w.buf.Write(p)
}
func (w *commitWriter) Close() error {
Write(w.key, w.buf.Bytes())
return nil
}