github.com/m3db/m3@v1.5.0/src/dbnode/digest/fd_digest.go (about)

     1  // Copyright (c) 2016 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package digest
    22  
    23  import (
    24  	"hash"
    25  	"hash/adler32"
    26  	"os"
    27  
    28  	xresource "github.com/m3db/m3/src/x/resource"
    29  )
    30  
    31  // FdWithDigest is a container for a file descriptor and the digest for the file contents.
    32  type FdWithDigest interface {
    33  	xresource.Closer
    34  
    35  	// Fd returns the file descriptor.
    36  	Fd() *os.File
    37  
    38  	// Digest returns the digest.
    39  	Digest() hash.Hash32
    40  
    41  	// Reset resets the file descriptor and the digest.
    42  	Reset(fd *os.File)
    43  }
    44  
    45  type fdWithDigest struct {
    46  	fd     *os.File
    47  	digest hash.Hash32
    48  }
    49  
    50  func newFdWithDigest() FdWithDigest {
    51  	return &fdWithDigest{
    52  		digest: adler32.New(),
    53  	}
    54  }
    55  
    56  func (fwd *fdWithDigest) Fd() *os.File {
    57  	return fwd.fd
    58  }
    59  
    60  func (fwd *fdWithDigest) Digest() hash.Hash32 {
    61  	return fwd.digest
    62  }
    63  
    64  func (fwd *fdWithDigest) Reset(fd *os.File) {
    65  	fwd.fd = fd
    66  	fwd.digest.Reset()
    67  }
    68  
    69  // Close closes the file descriptor.
    70  func (fwd *fdWithDigest) Close() error {
    71  	if fwd.fd == nil {
    72  		return nil
    73  	}
    74  	err := fwd.fd.Close()
    75  	fwd.fd = nil
    76  	return err
    77  }