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92 lines
2.3 KiB
Go
92 lines
2.3 KiB
Go
// Package stream provides a way to read and write to a synchronous buffered pipe, with multiple reader support.
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package stream
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import (
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"errors"
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"sync"
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)
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// ErrRemoving is returned when requesting a Reader on a Stream which is being Removed.
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var ErrRemoving = errors.New("cannot open a new reader while removing file")
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// Stream is used to concurrently Write and Read from a File.
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type Stream struct {
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grp sync.WaitGroup
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b *broadcaster
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file File
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fs FileSystem
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removing chan struct{}
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}
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// New creates a new Stream from the StdFileSystem with Name "name".
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func New(name string) (*Stream, error) {
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return NewStream(name, StdFileSystem)
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}
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// NewStream creates a new Stream with Name "name" in FileSystem fs.
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func NewStream(name string, fs FileSystem) (*Stream, error) {
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f, err := fs.Create(name)
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sf := &Stream{
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file: f,
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fs: fs,
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b: newBroadcaster(),
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removing: make(chan struct{}),
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}
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sf.inc()
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return sf, err
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}
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// Name returns the name of the underlying File in the FileSystem.
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func (s *Stream) Name() string { return s.file.Name() }
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// Write writes p to the Stream. It's concurrent safe to be called with Stream's other methods.
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func (s *Stream) Write(p []byte) (int, error) {
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defer s.b.Broadcast()
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s.b.Lock()
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defer s.b.Unlock()
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return s.file.Write(p)
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}
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// Close will close the active stream. This will cause Readers to return EOF once they have
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// read the entire stream.
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func (s *Stream) Close() error {
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defer s.dec()
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defer s.b.Close()
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s.b.Lock()
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defer s.b.Unlock()
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return s.file.Close()
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}
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// Remove will block until the Stream and all its Readers have been Closed,
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// at which point it will delete the underlying file. NextReader() will return
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// ErrRemoving if called after Remove.
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func (s *Stream) Remove() error {
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close(s.removing)
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s.grp.Wait()
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return s.fs.Remove(s.file.Name())
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}
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// NextReader will return a concurrent-safe Reader for this stream. Each Reader will
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// see a complete and independent view of the stream, and can Read will the stream
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// is written to.
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func (s *Stream) NextReader() (*Reader, error) {
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s.inc()
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select {
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case <-s.removing:
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s.dec()
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return nil, ErrRemoving
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default:
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}
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file, err := s.fs.Open(s.file.Name())
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if err != nil {
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s.dec()
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return nil, err
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}
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return &Reader{file: file, s: s}, nil
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}
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func (s *Stream) inc() { s.grp.Add(1) }
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func (s *Stream) dec() { s.grp.Done() }
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