From b801e4a061f1804a7d02e2f1eac6489e8d2ae12a Mon Sep 17 00:00:00 2001
From: RishabhSaini <rsaini@redhat.com>
Date: Fri, 21 Oct 2022 16:06:04 -0400
Subject: [PATCH] Add get_layer_info

This API exposes the "GetLayerInfosForCopy" API in containers/image,
which can be used to create a mapping between blob and diff IDs,
allowing pulling via diffID.

Signed-off-by: RishabhSaini <rsaini@redhat.com>
---
 src/imageproxy.rs | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/src/imageproxy.rs b/src/imageproxy.rs
index 5e94ead..56cc9bf 100644
--- a/src/imageproxy.rs
+++ b/src/imageproxy.rs
@@ -32,6 +32,8 @@ const MAX_MSG_SIZE: usize = 32 * 1024;
 // Introduced in https://github.com/containers/skopeo/pull/1523
 static BASE_PROTO_VERSION: Lazy<semver::VersionReq> =
     Lazy::new(|| semver::VersionReq::parse("0.2.3").unwrap());
+static LAYER_INFO_PROTO_VERSION: Lazy<semver::VersionReq> =
+    Lazy::new(|| semver::VersionReq::parse("0.2.5").unwrap());
 
 #[derive(Serialize)]
 struct Request {
@@ -192,6 +194,20 @@ impl TryFrom<ImageProxyConfig> for Command {
     }
 }
 
+/// BlobInfo collects known information about a blob
+#[derive(Debug, serde::Deserialize)]
+pub struct ConvertedLayerInfo {
+    /// Uncompressed digest of a layer; for more information, see
+    /// https://github.com/opencontainers/image-spec/blob/main/config.md#layer-diffid
+    pub digest: String,
+
+    /// Size of blob
+    pub size: i64,
+
+    /// Mediatype of blob
+    pub media_type: oci_spec::image::MediaType,
+}
+
 impl ImageProxy {
     /// Create an image proxy that fetches the target image, using default configuration.
     pub async fn new() -> Result<Self> {
@@ -430,6 +446,18 @@ impl ImageProxy {
         Ok((fd, finish))
     }
 
+    ///Returns data that can be used to find the "diffid" corresponding to a particular layer.
+    #[instrument]
+    pub async fn get_layer_info(&self, img: &OpenedImage) -> Result<Option<Vec<ConvertedLayerInfo>>> {
+        tracing::debug!("Getting layer info");
+        if !LAYER_INFO_PROTO_VERSION.matches(&self.protover) {
+            return Ok(None);
+        }
+        let reply = self.impl_request("GetLayerInfo", [img.0]).await?;
+        let layers: Vec<ConvertedLayerInfo> = reply.0;
+        Ok(Some(layers))
+    }
+
     /// Close the connection and wait for the child process to exit successfully.
     #[instrument]
     pub async fn finalize(self) -> Result<()> {