builder.go

Documentation: github.com/docker/distribution/manifest/ocischema

     1  package ocischema
     2  
     3  import (
     4  	"context"
     5  	"errors"
     6  
     7  	"github.com/docker/distribution"
     8  	"github.com/docker/distribution/manifest"
     9  	"github.com/opencontainers/go-digest"
    10  	v1 "github.com/opencontainers/image-spec/specs-go/v1"
    11  )
    12  
    13  // Builder is a type for constructing manifests.
    14  type Builder struct {
    15  	// bs is a BlobService used to publish the configuration blob.
    16  	bs distribution.BlobService
    17  
    18  	// configJSON references
    19  	configJSON []byte
    20  
    21  	// layers is a list of layer descriptors that gets built by successive
    22  	// calls to AppendReference.
    23  	layers []distribution.Descriptor
    24  
    25  	// Annotations contains arbitrary metadata relating to the targeted content.
    26  	annotations map[string]string
    27  
    28  	// For testing purposes
    29  	mediaType string
    30  }
    31  
    32  // NewManifestBuilder is used to build new manifests for the current schema
    33  // version. It takes a BlobService so it can publish the configuration blob
    34  // as part of the Build process, and annotations.
    35  func NewManifestBuilder(bs distribution.BlobService, configJSON []byte, annotations map[string]string) distribution.ManifestBuilder {
    36  	mb := &Builder{
    37  		bs:          bs,
    38  		configJSON:  make([]byte, len(configJSON)),
    39  		annotations: annotations,
    40  		mediaType:   v1.MediaTypeImageManifest,
    41  	}
    42  	copy(mb.configJSON, configJSON)
    43  
    44  	return mb
    45  }
    46  
    47  // SetMediaType assigns the passed mediatype or error if the mediatype is not a
    48  // valid media type for oci image manifests currently: "" or "application/vnd.oci.image.manifest.v1+json"
    49  func (mb *Builder) SetMediaType(mediaType string) error {
    50  	if mediaType != "" && mediaType != v1.MediaTypeImageManifest {
    51  		return errors.New("invalid media type for OCI image manifest")
    52  	}
    53  
    54  	mb.mediaType = mediaType
    55  	return nil
    56  }
    57  
    58  // Build produces a final manifest from the given references.
    59  func (mb *Builder) Build(ctx context.Context) (distribution.Manifest, error) {
    60  	m := Manifest{
    61  		Versioned: manifest.Versioned{
    62  			SchemaVersion: 2,
    63  			MediaType:     mb.mediaType,
    64  		},
    65  		Layers:      make([]distribution.Descriptor, len(mb.layers)),
    66  		Annotations: mb.annotations,
    67  	}
    68  	copy(m.Layers, mb.layers)
    69  
    70  	configDigest := digest.FromBytes(mb.configJSON)
    71  
    72  	var err error
    73  	m.Config, err = mb.bs.Stat(ctx, configDigest)
    74  	switch err {
    75  	case nil:
    76  		// Override MediaType, since Put always replaces the specified media
    77  		// type with application/octet-stream in the descriptor it returns.
    78  		m.Config.MediaType = v1.MediaTypeImageConfig
    79  		return FromStruct(m)
    80  	case distribution.ErrBlobUnknown:
    81  		// nop
    82  	default:
    83  		return nil, err
    84  	}
    85  
    86  	// Add config to the blob store
    87  	m.Config, err = mb.bs.Put(ctx, v1.MediaTypeImageConfig, mb.configJSON)
    88  	// Override MediaType, since Put always replaces the specified media
    89  	// type with application/octet-stream in the descriptor it returns.
    90  	m.Config.MediaType = v1.MediaTypeImageConfig
    91  	if err != nil {
    92  		return nil, err
    93  	}
    94  
    95  	return FromStruct(m)
    96  }
    97  
    98  // AppendReference adds a reference to the current ManifestBuilder.
    99  func (mb *Builder) AppendReference(d distribution.Describable) error {
   100  	mb.layers = append(mb.layers, d.Descriptor())
   101  	return nil
   102  }
   103  
   104  // References returns the current references added to this builder.
   105  func (mb *Builder) References() []distribution.Descriptor {
   106  	return mb.layers
   107  }
   108
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