register.go

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package zip
     6  
     7  import (
     8  	"compress/flate"
     9  	"errors"
    10  	"io"
    11  	"sync"
    12  )
    13  
    14  // A Compressor returns a new compressing writer, writing to w.
    15  // The WriteCloser's Close method must be used to flush pending data to w.
    16  // The Compressor itself must be safe to invoke from multiple goroutines
    17  // simultaneously, but each returned writer will be used only by
    18  // one goroutine at a time.
    19  type Compressor func(w io.Writer) (io.WriteCloser, error)
    20  
    21  // A Decompressor returns a new decompressing reader, reading from r.
    22  // The [io.ReadCloser]'s Close method must be used to release associated resources.
    23  // The Decompressor itself must be safe to invoke from multiple goroutines
    24  // simultaneously, but each returned reader will be used only by
    25  // one goroutine at a time.
    26  type Decompressor func(r io.Reader) io.ReadCloser
    27  
    28  var flateWriterPool sync.Pool
    29  
    30  func newFlateWriter(w io.Writer) io.WriteCloser {
    31  	fw, ok := flateWriterPool.Get().(*flate.Writer)
    32  	if ok {
    33  		fw.Reset(w)
    34  	} else {
    35  		fw, _ = flate.NewWriter(w, 5)
    36  	}
    37  	return &pooledFlateWriter{fw: fw}
    38  }
    39  
    40  type pooledFlateWriter struct {
    41  	mu sync.Mutex // guards Close and Write
    42  	fw *flate.Writer
    43  }
    44  
    45  func (w *pooledFlateWriter) Write(p []byte) (n int, err error) {
    46  	w.mu.Lock()
    47  	defer w.mu.Unlock()
    48  	if w.fw == nil {
    49  		return 0, errors.New("Write after Close")
    50  	}
    51  	return w.fw.Write(p)
    52  }
    53  
    54  func (w *pooledFlateWriter) Close() error {
    55  	w.mu.Lock()
    56  	defer w.mu.Unlock()
    57  	var err error
    58  	if w.fw != nil {
    59  		err = w.fw.Close()
    60  		flateWriterPool.Put(w.fw)
    61  		w.fw = nil
    62  	}
    63  	return err
    64  }
    65  
    66  var flateReaderPool sync.Pool
    67  
    68  func newFlateReader(r io.Reader) io.ReadCloser {
    69  	fr, ok := flateReaderPool.Get().(io.ReadCloser)
    70  	if ok {
    71  		fr.(flate.Resetter).Reset(r, nil)
    72  	} else {
    73  		fr = flate.NewReader(r)
    74  	}
    75  	return &pooledFlateReader{fr: fr}
    76  }
    77  
    78  type pooledFlateReader struct {
    79  	mu sync.Mutex // guards Close and Read
    80  	fr io.ReadCloser
    81  }
    82  
    83  func (r *pooledFlateReader) Read(p []byte) (n int, err error) {
    84  	r.mu.Lock()
    85  	defer r.mu.Unlock()
    86  	if r.fr == nil {
    87  		return 0, errors.New("Read after Close")
    88  	}
    89  	return r.fr.Read(p)
    90  }
    91  
    92  func (r *pooledFlateReader) Close() error {
    93  	r.mu.Lock()
    94  	defer r.mu.Unlock()
    95  	var err error
    96  	if r.fr != nil {
    97  		err = r.fr.Close()
    98  		flateReaderPool.Put(r.fr)
    99  		r.fr = nil
   100  	}
   101  	return err
   102  }
   103  
   104  var (
   105  	compressors   sync.Map // map[uint16]Compressor
   106  	decompressors sync.Map // map[uint16]Decompressor
   107  )
   108  
   109  func init() {
   110  	compressors.Store(Store, Compressor(func(w io.Writer) (io.WriteCloser, error) { return &nopCloser{w}, nil }))
   111  	compressors.Store(Deflate, Compressor(func(w io.Writer) (io.WriteCloser, error) { return newFlateWriter(w), nil }))
   112  
   113  	decompressors.Store(Store, Decompressor(io.NopCloser))
   114  	decompressors.Store(Deflate, Decompressor(newFlateReader))
   115  }
   116  
   117  // RegisterDecompressor allows custom decompressors for a specified method ID.
   118  // The common methods [Store] and [Deflate] are built in.
   119  func RegisterDecompressor(method uint16, dcomp Decompressor) {
   120  	if _, dup := decompressors.LoadOrStore(method, dcomp); dup {
   121  		panic("decompressor already registered")
   122  	}
   123  }
   124  
   125  // RegisterCompressor registers custom compressors for a specified method ID.
   126  // The common methods [Store] and [Deflate] are built in.
   127  func RegisterCompressor(method uint16, comp Compressor) {
   128  	if _, dup := compressors.LoadOrStore(method, comp); dup {
   129  		panic("compressor already registered")
   130  	}
   131  }
   132  
   133  func compressor(method uint16) Compressor {
   134  	ci, ok := compressors.Load(method)
   135  	if !ok {
   136  		return nil
   137  	}
   138  	return ci.(Compressor)
   139  }
   140  
   141  func decompressor(method uint16) Decompressor {
   142  	di, ok := decompressors.Load(method)
   143  	if !ok {
   144  		return nil
   145  	}
   146  	return di.(Decompressor)
   147  }
   148
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