From 13652e081e13baf62f968f5dfc89a3aff28ddfd6 Mon Sep 17 00:00:00 2001
From: Brian Goff <cpuguy83@gmail.com>
Date: Fri, 10 Feb 2023 00:27:11 +0000
Subject: [PATCH] fetch: Use data from descriptor when available.

OCI added support for a `data` field in a descriptor.
This field is expected to contain the content being pointed to by the
descriptor.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
---
 content/helpers.go  | 4 ++++
 remotes/handlers.go | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/content/helpers.go b/content/helpers.go
index 13af9d7d5..f74d72a93 100644
--- a/content/helpers.go
+++ b/content/helpers.go
@@ -59,6 +59,10 @@ func NewReader(ra ReaderAt) io.Reader {
 //
 // Avoid using this for large blobs, such as layers.
 func ReadBlob(ctx context.Context, provider Provider, desc ocispec.Descriptor) ([]byte, error) {
+	if int64(len(desc.Data)) == desc.Size && digest.FromBytes(desc.Data) == desc.Digest {
+		return desc.Data, nil
+	}
+
 	ra, err := provider.ReaderAt(ctx, desc)
 	if err != nil {
 		return nil, err
diff --git a/remotes/handlers.go b/remotes/handlers.go
index b0d8880f6..16279caf7 100644
--- a/remotes/handlers.go
+++ b/remotes/handlers.go
@@ -17,6 +17,7 @@
 package remotes
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -139,6 +140,10 @@ func Fetch(ctx context.Context, ingester content.Ingester, fetcher Fetcher, desc
 		return err
 	}
 
+	if desc.Size == int64(len(desc.Data)) {
+		return content.Copy(ctx, cw, bytes.NewReader(desc.Data), desc.Size, desc.Digest)
+	}
+
 	rc, err := fetcher.Fetch(ctx, desc)
 	if err != nil {
 		return err