compressor_cache.go

Documentation: github.com/emicklei/go-restful/v3

     1  package restful
     2  
     3  // Copyright 2015 Ernest Micklei. All rights reserved.
     4  // Use of this source code is governed by a license
     5  // that can be found in the LICENSE file.
     6  
     7  import (
     8  	"compress/gzip"
     9  	"compress/zlib"
    10  )
    11  
    12  // BoundedCachedCompressors is a CompressorProvider that uses a cache with a fixed amount
    13  // of writers and readers (resources).
    14  // If a new resource is acquired and all are in use, it will return a new unmanaged resource.
    15  type BoundedCachedCompressors struct {
    16  	gzipWriters     chan *gzip.Writer
    17  	gzipReaders     chan *gzip.Reader
    18  	zlibWriters     chan *zlib.Writer
    19  	writersCapacity int
    20  	readersCapacity int
    21  }
    22  
    23  // NewBoundedCachedCompressors returns a new, with filled cache,  BoundedCachedCompressors.
    24  func NewBoundedCachedCompressors(writersCapacity, readersCapacity int) *BoundedCachedCompressors {
    25  	b := &BoundedCachedCompressors{
    26  		gzipWriters:     make(chan *gzip.Writer, writersCapacity),
    27  		gzipReaders:     make(chan *gzip.Reader, readersCapacity),
    28  		zlibWriters:     make(chan *zlib.Writer, writersCapacity),
    29  		writersCapacity: writersCapacity,
    30  		readersCapacity: readersCapacity,
    31  	}
    32  	for ix := 0; ix < writersCapacity; ix++ {
    33  		b.gzipWriters <- newGzipWriter()
    34  		b.zlibWriters <- newZlibWriter()
    35  	}
    36  	for ix := 0; ix < readersCapacity; ix++ {
    37  		b.gzipReaders <- newGzipReader()
    38  	}
    39  	return b
    40  }
    41  
    42  // AcquireGzipWriter returns an resettable *gzip.Writer. Needs to be released.
    43  func (b *BoundedCachedCompressors) AcquireGzipWriter() *gzip.Writer {
    44  	var writer *gzip.Writer
    45  	select {
    46  	case writer, _ = <-b.gzipWriters:
    47  	default:
    48  		// return a new unmanaged one
    49  		writer = newGzipWriter()
    50  	}
    51  	return writer
    52  }
    53  
    54  // ReleaseGzipWriter accepts a writer (does not have to be one that was cached)
    55  // only when the cache has room for it. It will ignore it otherwise.
    56  func (b *BoundedCachedCompressors) ReleaseGzipWriter(w *gzip.Writer) {
    57  	// forget the unmanaged ones
    58  	if len(b.gzipWriters) < b.writersCapacity {
    59  		b.gzipWriters <- w
    60  	}
    61  }
    62  
    63  // AcquireGzipReader returns a *gzip.Reader. Needs to be released.
    64  func (b *BoundedCachedCompressors) AcquireGzipReader() *gzip.Reader {
    65  	var reader *gzip.Reader
    66  	select {
    67  	case reader, _ = <-b.gzipReaders:
    68  	default:
    69  		// return a new unmanaged one
    70  		reader = newGzipReader()
    71  	}
    72  	return reader
    73  }
    74  
    75  // ReleaseGzipReader accepts a reader (does not have to be one that was cached)
    76  // only when the cache has room for it. It will ignore it otherwise.
    77  func (b *BoundedCachedCompressors) ReleaseGzipReader(r *gzip.Reader) {
    78  	// forget the unmanaged ones
    79  	if len(b.gzipReaders) < b.readersCapacity {
    80  		b.gzipReaders <- r
    81  	}
    82  }
    83  
    84  // AcquireZlibWriter returns an resettable *zlib.Writer. Needs to be released.
    85  func (b *BoundedCachedCompressors) AcquireZlibWriter() *zlib.Writer {
    86  	var writer *zlib.Writer
    87  	select {
    88  	case writer, _ = <-b.zlibWriters:
    89  	default:
    90  		// return a new unmanaged one
    91  		writer = newZlibWriter()
    92  	}
    93  	return writer
    94  }
    95  
    96  // ReleaseZlibWriter accepts a writer (does not have to be one that was cached)
    97  // only when the cache has room for it. It will ignore it otherwise.
    98  func (b *BoundedCachedCompressors) ReleaseZlibWriter(w *zlib.Writer) {
    99  	// forget the unmanaged ones
   100  	if len(b.zlibWriters) < b.writersCapacity {
   101  		b.zlibWriters <- w
   102  	}
   103  }
   104
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