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write.go
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write.go
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package directory
import (
"crypto/sha256"
"encoding/json"
"fmt"
"os"
digest "github.com/opencontainers/go-digest"
specs "github.com/opencontainers/image-spec/specs-go"
oci "github.com/opencontainers/image-spec/specs-go/v1"
)
func (h *Handler) WriteMetadata(layers []oci.Descriptor, diffIds []digest.Digest, layerAdded bool) error {
if err := h.writeOCILayout(); err != nil {
return err
}
configDescriptor, err := h.writeConfig(diffIds)
if err != nil {
return err
}
annotations := make(map[string]string)
/* Mark that the top layer was added using hydrator */
if layerAdded {
annotations["hydrator.layerAdded"] = "true"
}
manifestDescriptor, err := h.writeManifest(layers, configDescriptor, annotations)
if err != nil {
return err
}
return h.writeIndexJson(manifestDescriptor)
}
func (h *Handler) writeOCILayout() error {
il := oci.ImageLayout{
Version: specs.Version,
}
data, err := json.Marshal(il)
if err != nil {
return err
}
return os.WriteFile(h.ociLayoutPath(), data, 0644)
}
func (h *Handler) writeConfig(diffIds []digest.Digest) (oci.Descriptor, error) {
ic := oci.Image{
Platform: oci.Platform{
Architecture: "amd64",
OS: "windows",
},
RootFS: oci.RootFS{Type: "layers", DiffIDs: diffIds},
}
d, err := h.writeBlob(ic)
if err != nil {
return oci.Descriptor{}, err
}
d.MediaType = oci.MediaTypeImageConfig
return d, nil
}
func (h *Handler) writeManifest(layers []oci.Descriptor, config oci.Descriptor, annotations map[string]string) (oci.Descriptor, error) {
im := oci.Manifest{
Versioned: specs.Versioned{SchemaVersion: 2},
Config: config,
Layers: layers,
Annotations: annotations,
}
d, err := h.writeBlob(im)
if err != nil {
return oci.Descriptor{}, err
}
d.MediaType = oci.MediaTypeImageManifest
d.Platform = &oci.Platform{OS: "windows", Architecture: "amd64"}
return d, nil
}
func (h *Handler) writeBlob(blob interface{}) (oci.Descriptor, error) {
data, err := json.Marshal(blob)
if err != nil {
return oci.Descriptor{}, err
}
if err := os.MkdirAll(h.blobsDir(), 0755); err != nil {
return oci.Descriptor{}, err
}
blobSha := fmt.Sprintf("%x", sha256.Sum256(data))
blobFile := h.blobsPath(blobSha)
if err := os.WriteFile(blobFile, data, 0644); err != nil {
return oci.Descriptor{}, err
}
return oci.Descriptor{
Size: int64(len(data)),
Digest: digest.NewDigestFromEncoded(digest.SHA256, blobSha),
}, nil
}
func (h *Handler) writeIndexJson(manifest oci.Descriptor) error {
ii := oci.Index{
Versioned: specs.Versioned{SchemaVersion: 2},
Manifests: []oci.Descriptor{manifest},
}
data, err := json.Marshal(ii)
if err != nil {
return err
}
return os.WriteFile(h.indexPath(), data, 0644)
}