manifest.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  package content
    16  
    17  import (
    18  	"encoding/json"
    19  	"sort"
    20  
    21  	"github.com/opencontainers/go-digest"
    22  	specs "github.com/opencontainers/image-spec/specs-go"
    23  	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
    24  	artifact "oras.land/oras-go/pkg/artifact"
    25  )
    26  
    27  // GenerateManifest generates a manifest. The manifest will include the provided config,
    28  // and descs as layers. Raw bytes will be returned.
    29  func GenerateManifest(config *ocispec.Descriptor, annotations map[string]string, descs ...ocispec.Descriptor) ([]byte, ocispec.Descriptor, error) {
    30  	// Config - either it was set, or we have to set it
    31  	if config == nil {
    32  		_, configGen, err := GenerateConfig(nil)
    33  		if err != nil {
    34  			return nil, ocispec.Descriptor{}, err
    35  		}
    36  		config = &configGen
    37  	}
    38  	return pack(*config, annotations, descs)
    39  }
    40  
    41  // GenerateConfig generates a blank config with optional annotations.
    42  func GenerateConfig(annotations map[string]string) ([]byte, ocispec.Descriptor, error) {
    43  	configBytes := []byte("{}")
    44  	dig := digest.FromBytes(configBytes)
    45  	config := ocispec.Descriptor{
    46  		MediaType:   artifact.UnknownConfigMediaType,
    47  		Digest:      dig,
    48  		Size:        int64(len(configBytes)),
    49  		Annotations: annotations,
    50  	}
    51  	return configBytes, config, nil
    52  }
    53  
    54  // GenerateManifestAndConfig generates a config and then a manifest. Raw bytes will be returned.
    55  func GenerateManifestAndConfig(manifestAnnotations map[string]string, configAnnotations map[string]string, descs ...ocispec.Descriptor) (manifest []byte, manifestDesc ocispec.Descriptor, config []byte, configDesc ocispec.Descriptor, err error) {
    56  	config, configDesc, err = GenerateConfig(configAnnotations)
    57  	if err != nil {
    58  		return nil, ocispec.Descriptor{}, nil, ocispec.Descriptor{}, err
    59  	}
    60  	manifest, manifestDesc, err = GenerateManifest(&configDesc, manifestAnnotations, descs...)
    61  	if err != nil {
    62  		return nil, ocispec.Descriptor{}, nil, ocispec.Descriptor{}, err
    63  	}
    64  	return
    65  }
    66  
    67  // pack given a bunch of descriptors, create a manifest that references all of them
    68  func pack(config ocispec.Descriptor, annotations map[string]string, descriptors []ocispec.Descriptor) ([]byte, ocispec.Descriptor, error) {
    69  	if descriptors == nil {
    70  		descriptors = []ocispec.Descriptor{} // make it an empty array to prevent potential server-side bugs
    71  	}
    72  	// sort descriptors alphanumerically by sha hash so it always is consistent
    73  	sort.Slice(descriptors, func(i, j int) bool {
    74  		return descriptors[i].Digest < descriptors[j].Digest
    75  	})
    76  	manifest := ocispec.Manifest{
    77  		Versioned: specs.Versioned{
    78  			SchemaVersion: 2, // historical value. does not pertain to OCI or docker version
    79  		},
    80  		Config:      config,
    81  		Layers:      descriptors,
    82  		Annotations: annotations,
    83  	}
    84  	manifestBytes, err := json.Marshal(manifest)
    85  	if err != nil {
    86  		return nil, ocispec.Descriptor{}, err
    87  	}
    88  	manifestDescriptor := ocispec.Descriptor{
    89  		MediaType: ocispec.MediaTypeImageManifest,
    90  		Digest:    digest.FromBytes(manifestBytes),
    91  		Size:      int64(len(manifestBytes)),
    92  	}
    93  
    94  	return manifestBytes, manifestDescriptor, nil
    95  }
    96
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