github.com/bodgit/sevenzip@v1.5.1/internal/zstd/reader.go (about)

     1  package zstd
     2  
     3  import (
     4  	"errors"
     5  	"io"
     6  	"runtime"
     7  	"sync"
     8  
     9  	"github.com/klauspost/compress/zstd"
    10  )
    11  
    12  //nolint:gochecknoglobals
    13  var zstdReaderPool sync.Pool
    14  
    15  type readCloser struct {
    16  	c io.Closer
    17  	r *zstd.Decoder
    18  }
    19  
    20  func (rc *readCloser) Close() (err error) {
    21  	if rc.c != nil {
    22  		zstdReaderPool.Put(rc.r)
    23  		err = rc.c.Close()
    24  		rc.c, rc.r = nil, nil
    25  	}
    26  
    27  	return
    28  }
    29  
    30  func (rc *readCloser) Read(p []byte) (int, error) {
    31  	if rc.r == nil {
    32  		return 0, errors.New("zstd: Read after Close")
    33  	}
    34  
    35  	return rc.r.Read(p)
    36  }
    37  
    38  // NewReader returns a new Zstandard io.ReadCloser.
    39  func NewReader(_ []byte, _ uint64, readers []io.ReadCloser) (io.ReadCloser, error) {
    40  	if len(readers) != 1 {
    41  		return nil, errors.New("zstd: need exactly one reader")
    42  	}
    43  
    44  	var err error
    45  
    46  	r, ok := zstdReaderPool.Get().(*zstd.Decoder)
    47  	if ok {
    48  		if err = r.Reset(readers[0]); err != nil {
    49  			return nil, err
    50  		}
    51  	} else {
    52  		if r, err = zstd.NewReader(readers[0]); err != nil {
    53  			return nil, err
    54  		}
    55  
    56  		runtime.SetFinalizer(r, (*zstd.Decoder).Close)
    57  	}
    58  
    59  	return &readCloser{
    60  		c: readers[0],
    61  		r: r,
    62  	}, nil
    63  }