github.com/peterbourgon/diskv@v2.0.1+incompatible/compression.go (about)

     1  package diskv
     2  
     3  import (
     4  	"compress/flate"
     5  	"compress/gzip"
     6  	"compress/zlib"
     7  	"io"
     8  )
     9  
    10  // Compression is an interface that Diskv uses to implement compression of
    11  // data. Writer takes a destination io.Writer and returns a WriteCloser that
    12  // compresses all data written through it. Reader takes a source io.Reader and
    13  // returns a ReadCloser that decompresses all data read through it. You may
    14  // define these methods on your own type, or use one of the NewCompression
    15  // helpers.
    16  type Compression interface {
    17  	Writer(dst io.Writer) (io.WriteCloser, error)
    18  	Reader(src io.Reader) (io.ReadCloser, error)
    19  }
    20  
    21  // NewGzipCompression returns a Gzip-based Compression.
    22  func NewGzipCompression() Compression {
    23  	return NewGzipCompressionLevel(flate.DefaultCompression)
    24  }
    25  
    26  // NewGzipCompressionLevel returns a Gzip-based Compression with the given level.
    27  func NewGzipCompressionLevel(level int) Compression {
    28  	return &genericCompression{
    29  		wf: func(w io.Writer) (io.WriteCloser, error) { return gzip.NewWriterLevel(w, level) },
    30  		rf: func(r io.Reader) (io.ReadCloser, error) { return gzip.NewReader(r) },
    31  	}
    32  }
    33  
    34  // NewZlibCompression returns a Zlib-based Compression.
    35  func NewZlibCompression() Compression {
    36  	return NewZlibCompressionLevel(flate.DefaultCompression)
    37  }
    38  
    39  // NewZlibCompressionLevel returns a Zlib-based Compression with the given level.
    40  func NewZlibCompressionLevel(level int) Compression {
    41  	return NewZlibCompressionLevelDict(level, nil)
    42  }
    43  
    44  // NewZlibCompressionLevelDict returns a Zlib-based Compression with the given
    45  // level, based on the given dictionary.
    46  func NewZlibCompressionLevelDict(level int, dict []byte) Compression {
    47  	return &genericCompression{
    48  		func(w io.Writer) (io.WriteCloser, error) { return zlib.NewWriterLevelDict(w, level, dict) },
    49  		func(r io.Reader) (io.ReadCloser, error) { return zlib.NewReaderDict(r, dict) },
    50  	}
    51  }
    52  
    53  type genericCompression struct {
    54  	wf func(w io.Writer) (io.WriteCloser, error)
    55  	rf func(r io.Reader) (io.ReadCloser, error)
    56  }
    57  
    58  func (g *genericCompression) Writer(dst io.Writer) (io.WriteCloser, error) {
    59  	return g.wf(dst)
    60  }
    61  
    62  func (g *genericCompression) Reader(src io.Reader) (io.ReadCloser, error) {
    63  	return g.rf(src)
    64  }