refactor: Split up code for readability and add docs

types.go

@@ -0,0 +1,79 @@
+package main
+
+import "time"
+
+// This type represents the rootfs-key of the Docker image config.
+// It specifies the digest (i.e. usually SHA256 hash) of the tar'ed, but NOT
+// compressed image layers.
+type RootFs struct {
+	// The digests of the non-compressed FS layers.
+	DiffIds []string `json:"diff_ids"`
+
+	// Type should always be set to "layers"
+	Type string `json:"type"`
+}
+
+// This type represents an entry in the Docker image config's history key.
+// Every history element "belongs" to a filesystem layer.
+type History struct {
+	Created   time.Time `json:"created"`
+	CreatedBy string    `json:"created_by"`
+}
+
+// This type represents runtime-configuration for the Docker image.
+// A lot of possible keys are omitted here, see:
+// https://github.com/docker/docker/blob/master/image/spec/v1.2.md#image-json-description
+type ImageConfig struct {
+	Cmd []string
+	Env []string
+}
+
+// This type represents the Docker image configuration
+type Config struct {
+	Created time.Time `json:"created"`
+	Author  string    `json:"author"`
+
+	// Architecture should be "amd64"
+	Architecture string `json:"architecture"`
+
+	// OS should be "linux"
+	Os string `json:"os"`
+
+	// Configuration can be set to 'nil', in which case all options have to be
+	// supplied at container launch time.
+	Config *ImageConfig `json:"config"`
+
+	// Filesystem layers and history elements have to be in the same order.
+	RootFs  RootFs    `json:"rootfs"`
+	History []History `json:"history"`
+}
+
+// This type represents any manifest
+type Element struct {
+	MediaType string `json:"mediaType"`
+	Size      int    `json:"size"`
+	Digest    string `json:"digest"`
+}
+
+// This type represents a Docker image manifest as used by the registry
+// protocol V2.
+type Manifest struct {
+	SchemaVersion int       `json:"schemaVersion"` // Must be 2
+	MediaType     string    `json:"mediaType"`     // Use ManifestMediaType const
+	Config        Element   `json:"config"`
+	Layers        []Element `json:"layers"`
+}
+
+// A really "dumb" representation of an image, with its data blob and related
+// metadata.
+// Note: This is not a registry API type.
+type Image struct {
+	Layer       []byte
+	LayerDigest string
+
+	Manifest       []byte
+	ManifestDigest string
+
+	Config       []byte
+	ConfigDigest string
+}