ocijoin

package main

import (
	"context"
	"fmt"

	"github.com/cpuguy83/ocijoin"

	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
)

func main() {
	// Filter keeps only index descriptors matching a predicate.
	// Blob access is unaffected -- all blobs remain accessible.
	layout, _ := ocijoin.NewLocalLayout("/path/to/oci-layout")

	// Keep only non-attestation manifests.
	filtered := ocijoin.Filter(layout, func(desc ocispec.Descriptor) bool {
		return !ocijoin.IsAttestation(desc)
	})

	idx, _ := filtered.Index(context.Background())
	fmt.Println("manifests after filtering:", len(idx.Manifests))
}

Output:

package main

import (
	"context"
	"fmt"

	"github.com/cpuguy83/ocijoin"
)

func main() {
	// Join merges multiple layouts into a single view.
	// Duplicate descriptors (by JSON equality) are deduplicated.
	amd64, _ := ocijoin.NewLocalLayout("/path/to/linux-amd64")
	arm64, _ := ocijoin.NewLocalLayout("/path/to/linux-arm64")

	merged := ocijoin.Join(amd64, arm64)

	idx, _ := merged.Index(context.Background())
	for _, desc := range idx.Manifests {
		fmt.Println(desc.Digest)
	}
}

Output:

package main

import (
	"context"
	"fmt"

	"github.com/cpuguy83/ocijoin"
)

func main() {
	// Unwrap resolves a nested index. Many build tools (e.g. docker buildx)
	// produce layouts where index.json contains a single descriptor pointing
	// to an inner ImageIndex blob. Unwrap reads that blob and returns a
	// layout whose Index is the inner index.
	//
	// If the layout is not nested, it is returned unchanged.
	layout, _ := ocijoin.NewLocalLayout("/path/to/oci-layout")

	unwrapped := ocijoin.Unwrap(layout)

	idx, _ := unwrapped.Index(context.Background())
	for _, desc := range idx.Manifests {
		fmt.Println(desc.Platform.Architecture, desc.Digest)
	}
}

Output:

package main

import (
	"context"
	"fmt"

	"github.com/cpuguy83/ocijoin"
)

func main() {
	// Wrap nests a layout's index inside a new outer index with annotations.
	// This is the inverse of Unwrap and is useful for producing layouts
	// compatible with tools like oras that expect a tagged outer index.
	layout, _ := ocijoin.NewLocalLayout("/path/to/oci-layout")

	wrapped := ocijoin.Wrap(layout, map[string]string{
		"org.opencontainers.image.ref.name": "v1.0.0",
		"io.containerd.image.name":          "registry.example.com/myimage:v1.0.0",
	})

	idx, _ := wrapped.Index(context.Background())
	fmt.Println("outer descriptors:", len(idx.Manifests))
	fmt.Println("tag:", idx.Manifests[0].Annotations["org.opencontainers.image.ref.name"])
}

Output:

package main

import (
	"context"
	"fmt"

	"github.com/cpuguy83/ocijoin"
)

func main() {
	// NewLocalLayout reads an OCI layout directory from disk.
	// The index.json is parsed eagerly at construction time.
	layout, err := ocijoin.NewLocalLayout("/path/to/oci-layout")
	if err != nil {
		fmt.Println("error:", err)
		return
	}

	idx, _ := layout.Index(context.Background())
	fmt.Println("manifests:", len(idx.Manifests))
}

Output: