index.go

Documentation: github.com/google/go-containerregistry/pkg/v1/layout

     1  // Copyright 2018 Google LLC All Rights Reserved.
     2  //
     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  package layout
    16  
    17  import (
    18  	"encoding/json"
    19  	"errors"
    20  	"fmt"
    21  	"io"
    22  	"os"
    23  
    24  	v1 "github.com/google/go-containerregistry/pkg/v1"
    25  	"github.com/google/go-containerregistry/pkg/v1/partial"
    26  	"github.com/google/go-containerregistry/pkg/v1/types"
    27  )
    28  
    29  var _ v1.ImageIndex = (*layoutIndex)(nil)
    30  
    31  type layoutIndex struct {
    32  	mediaType types.MediaType
    33  	path      Path
    34  	rawIndex  []byte
    35  }
    36  
    37  // ImageIndexFromPath is a convenience function which constructs a Path and returns its v1.ImageIndex.
    38  func ImageIndexFromPath(path string) (v1.ImageIndex, error) {
    39  	lp, err := FromPath(path)
    40  	if err != nil {
    41  		return nil, err
    42  	}
    43  	return lp.ImageIndex()
    44  }
    45  
    46  // ImageIndex returns a v1.ImageIndex for the Path.
    47  func (l Path) ImageIndex() (v1.ImageIndex, error) {
    48  	rawIndex, err := os.ReadFile(l.path("index.json"))
    49  	if err != nil {
    50  		return nil, err
    51  	}
    52  
    53  	idx := &layoutIndex{
    54  		mediaType: types.OCIImageIndex,
    55  		path:      l,
    56  		rawIndex:  rawIndex,
    57  	}
    58  
    59  	return idx, nil
    60  }
    61  
    62  func (i *layoutIndex) MediaType() (types.MediaType, error) {
    63  	return i.mediaType, nil
    64  }
    65  
    66  func (i *layoutIndex) Digest() (v1.Hash, error) {
    67  	return partial.Digest(i)
    68  }
    69  
    70  func (i *layoutIndex) Size() (int64, error) {
    71  	return partial.Size(i)
    72  }
    73  
    74  func (i *layoutIndex) IndexManifest() (*v1.IndexManifest, error) {
    75  	var index v1.IndexManifest
    76  	err := json.Unmarshal(i.rawIndex, &index)
    77  	return &index, err
    78  }
    79  
    80  func (i *layoutIndex) RawManifest() ([]byte, error) {
    81  	return i.rawIndex, nil
    82  }
    83  
    84  func (i *layoutIndex) Image(h v1.Hash) (v1.Image, error) {
    85  	// Look up the digest in our manifest first to return a better error.
    86  	desc, err := i.findDescriptor(h)
    87  	if err != nil {
    88  		return nil, err
    89  	}
    90  
    91  	if !isExpectedMediaType(desc.MediaType, types.OCIManifestSchema1, types.DockerManifestSchema2) {
    92  		return nil, fmt.Errorf("unexpected media type for %v: %s", h, desc.MediaType)
    93  	}
    94  
    95  	img := &layoutImage{
    96  		path: i.path,
    97  		desc: *desc,
    98  	}
    99  	return partial.CompressedToImage(img)
   100  }
   101  
   102  func (i *layoutIndex) ImageIndex(h v1.Hash) (v1.ImageIndex, error) {
   103  	// Look up the digest in our manifest first to return a better error.
   104  	desc, err := i.findDescriptor(h)
   105  	if err != nil {
   106  		return nil, err
   107  	}
   108  
   109  	if !isExpectedMediaType(desc.MediaType, types.OCIImageIndex, types.DockerManifestList) {
   110  		return nil, fmt.Errorf("unexpected media type for %v: %s", h, desc.MediaType)
   111  	}
   112  
   113  	rawIndex, err := i.path.Bytes(h)
   114  	if err != nil {
   115  		return nil, err
   116  	}
   117  
   118  	return &layoutIndex{
   119  		mediaType: desc.MediaType,
   120  		path:      i.path,
   121  		rawIndex:  rawIndex,
   122  	}, nil
   123  }
   124  
   125  func (i *layoutIndex) Blob(h v1.Hash) (io.ReadCloser, error) {
   126  	return i.path.Blob(h)
   127  }
   128  
   129  func (i *layoutIndex) findDescriptor(h v1.Hash) (*v1.Descriptor, error) {
   130  	im, err := i.IndexManifest()
   131  	if err != nil {
   132  		return nil, err
   133  	}
   134  
   135  	if h == (v1.Hash{}) {
   136  		if len(im.Manifests) != 1 {
   137  			return nil, errors.New("oci layout must contain only a single image to be used with layout.Image")
   138  		}
   139  		return &(im.Manifests)[0], nil
   140  	}
   141  
   142  	for _, desc := range im.Manifests {
   143  		if desc.Digest == h {
   144  			return &desc, nil
   145  		}
   146  	}
   147  
   148  	return nil, fmt.Errorf("could not find descriptor in index: %s", h)
   149  }
   150  
   151  // TODO: Pull this out into methods on types.MediaType? e.g. instead, have:
   152  // * mt.IsIndex()
   153  // * mt.IsImage()
   154  func isExpectedMediaType(mt types.MediaType, expected ...types.MediaType) bool {
   155  	for _, allowed := range expected {
   156  		if mt == allowed {
   157  			return true
   158  		}
   159  	}
   160  	return false
   161  }
   162
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