untar.go

Documentation: oras.land/oras-go/pkg/content

     1  /*
     2  Copyright The ORAS Authors.
     3  Licensed under the Apache License, Version 2.0 (the "License");
     4  you may not use this file except in compliance with the License.
     5  You may obtain a copy of the License at
     6  
     7  http://www.apache.org/licenses/LICENSE-2.0
     8  
     9  Unless required by applicable law or agreed to in writing, software
    10  distributed under the License is distributed on an "AS IS" BASIS,
    11  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  See the License for the specific language governing permissions and
    13  limitations under the License.
    14  */
    15  
    16  package content
    17  
    18  import (
    19  	"archive/tar"
    20  	"fmt"
    21  	"io"
    22  
    23  	"github.com/containerd/containerd/content"
    24  )
    25  
    26  // NewUntarWriter wrap a writer with an untar, so that the stream is untarred
    27  //
    28  // By default, it calculates the hash when writing. If the option `skipHash` is true,
    29  // it will skip doing the hash. Skipping the hash is intended to be used only
    30  // if you are confident about the validity of the data being passed to the writer,
    31  // and wish to save on the hashing time.
    32  func NewUntarWriter(writer content.Writer, opts ...WriterOpt) content.Writer {
    33  	// process opts for default
    34  	wOpts := DefaultWriterOpts()
    35  	for _, opt := range opts {
    36  		if err := opt(&wOpts); err != nil {
    37  			return nil
    38  		}
    39  	}
    40  
    41  	return NewPassthroughWriter(writer, func(r io.Reader, w io.Writer, done chan<- error) {
    42  		tr := tar.NewReader(r)
    43  		var err error
    44  		for {
    45  			_, err := tr.Next()
    46  			if err == io.EOF {
    47  				// clear the error, since we do not pass an io.EOF
    48  				err = nil
    49  				break // End of archive
    50  			}
    51  			if err != nil {
    52  				// pass the error on
    53  				err = fmt.Errorf("UntarWriter tar file header read error: %v", err)
    54  				break
    55  			}
    56  			// write out the untarred data
    57  			// we can handle io.EOF, just go to the next file
    58  			// any other errors should stop and get reported
    59  			b := make([]byte, wOpts.Blocksize, wOpts.Blocksize)
    60  			for {
    61  				var n int
    62  				n, err = tr.Read(b)
    63  				if err != nil && err != io.EOF {
    64  					err = fmt.Errorf("UntarWriter file data read error: %v\n", err)
    65  					break
    66  				}
    67  				l := n
    68  				if n > len(b) {
    69  					l = len(b)
    70  				}
    71  				if _, err2 := w.Write(b[:l]); err2 != nil {
    72  					err = fmt.Errorf("UntarWriter error writing to underlying writer: %v", err2)
    73  					break
    74  				}
    75  				if err == io.EOF {
    76  					// go to the next file
    77  					break
    78  				}
    79  			}
    80  			// did we break with a non-nil and non-EOF error?
    81  			if err != nil && err != io.EOF {
    82  				break
    83  			}
    84  		}
    85  		done <- err
    86  	}, opts...)
    87  }
    88  
    89  // NewUntarWriterByName wrap multiple writers with an untar, so that the stream is untarred and passed
    90  // to the appropriate writer, based on the filename. If a filename is not found, it is up to the called func
    91  // to determine how to process it.
    92  func NewUntarWriterByName(writers func(string) (content.Writer, error), opts ...WriterOpt) content.Writer {
    93  	// process opts for default
    94  	wOpts := DefaultWriterOpts()
    95  	for _, opt := range opts {
    96  		if err := opt(&wOpts); err != nil {
    97  			return nil
    98  		}
    99  	}
   100  
   101  	// need a PassthroughMultiWriter here
   102  	return NewPassthroughMultiWriter(writers, func(r io.Reader, getwriter func(name string) io.Writer, done chan<- error) {
   103  		tr := tar.NewReader(r)
   104  		var err error
   105  		for {
   106  			header, err := tr.Next()
   107  			if err == io.EOF {
   108  				// clear the error, since we do not pass an io.EOF
   109  				err = nil
   110  				break // End of archive
   111  			}
   112  			if err != nil {
   113  				// pass the error on
   114  				err = fmt.Errorf("UntarWriter tar file header read error: %v", err)
   115  				break
   116  			}
   117  			// get the filename
   118  			filename := header.Name
   119  
   120  			// get the writer for this filename
   121  			w := getwriter(filename)
   122  			if w == nil {
   123  				continue
   124  			}
   125  
   126  			// write out the untarred data
   127  			// we can handle io.EOF, just go to the next file
   128  			// any other errors should stop and get reported
   129  			b := make([]byte, wOpts.Blocksize, wOpts.Blocksize)
   130  			for {
   131  				var n int
   132  				n, err = tr.Read(b)
   133  				if err != nil && err != io.EOF {
   134  					err = fmt.Errorf("UntarWriter file data read error: %v\n", err)
   135  					break
   136  				}
   137  				l := n
   138  				if n > len(b) {
   139  					l = len(b)
   140  				}
   141  				if _, err2 := w.Write(b[:l]); err2 != nil {
   142  					err = fmt.Errorf("UntarWriter error writing to underlying writer at for name '%s': %v", filename, err2)
   143  					break
   144  				}
   145  				if err == io.EOF {
   146  					// go to the next file
   147  					break
   148  				}
   149  			}
   150  			// did we break with a non-nil and non-EOF error?
   151  			if err != nil && err != io.EOF {
   152  				break
   153  			}
   154  		}
   155  		done <- err
   156  	}, opts...)
   157  }
   158
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