[pbs-devel] [RFC v2 proxmox-backup 09/42] s3 client: add dedicated type for s3 object keys

[Christian Ebner]

S3 objects are uniquely identified within a bucket by their object
key [0].

Implements conversion and utility traits to easily convert and encode
a string or a chunk digest as corresponding object key for the S3
storage backend. Adds type checking for s3 client operations requiring
an object key.

[0] https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-keys.html

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
 pbs-s3-client/src/lib.rs        |  2 ++
 pbs-s3-client/src/object_key.rs | 64 +++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 pbs-s3-client/src/object_key.rs

diff --git a/pbs-s3-client/src/lib.rs b/pbs-s3-client/src/lib.rs
index 5a60b92ec..a4081df15 100644
--- a/pbs-s3-client/src/lib.rs
+++ b/pbs-s3-client/src/lib.rs
@@ -1,3 +1,5 @@
 mod aws_sign_v4;
 mod client;
 pub use client::{S3Client, S3ClientOptions};
+mod object_key;
+pub use object_key::{S3ObjectKey, S3_CONTENT_PREFIX};
diff --git a/pbs-s3-client/src/object_key.rs b/pbs-s3-client/src/object_key.rs
new file mode 100644
index 000000000..362c0cd55
--- /dev/null
+++ b/pbs-s3-client/src/object_key.rs
@@ -0,0 +1,64 @@
+use crate::aws_sign_v4::aws_sign_v4_uri_encode;
+
+pub const S3_CONTENT_PREFIX: &str = ".content";
+
+#[derive(Clone)]
+pub struct S3ObjectKey {
+    object_key: String,
+}
+
+// All regular keys (non-digests) get prefixed by a `/.contents`, so that
+// content listing without all the chunks can be done by that prefix.
+impl core::convert::From<&str> for S3ObjectKey {
+    fn from(object_key: &str) -> Self {
+        let object_key = object_key.strip_prefix("/").unwrap_or(object_key);
+        let object_key = format!(
+            "/{S3_CONTENT_PREFIX}/{object_key}",
+            object_key = aws_sign_v4_uri_encode(object_key, true)
+        );
+
+        Self { object_key }
+    }
+}
+
+impl core::convert::From<&[u8; 32]> for S3ObjectKey {
+    fn from(digest: &[u8; 32]) -> Self {
+        // Use the same layout as on regular PBS datastores, including the 4 hex digit prefix
+        let object_key = hex::encode(digest);
+        let prefix = &object_key[..4];
+        Self {
+            object_key: format!("/.chunks/{prefix}/{object_key}"),
+        }
+    }
+}
+
+impl core::convert::From<[u8; 32]> for S3ObjectKey {
+    fn from(digest: [u8; 32]) -> Self {
+        Self::from(&digest)
+    }
+}
+
+impl std::ops::Deref for S3ObjectKey {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        &self.object_key
+    }
+}
+
+impl std::fmt::Display for S3ObjectKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.object_key)
+    }
+}
+
+impl S3ObjectKey {
+    /// Generate source key for copy object operations given the source bucket.
+    pub fn to_copy_source_key(&self, source_bucket: &str) -> Self {
+        Self {
+            // object key already contains the required separator slash in-between source bucket
+            // and source object key.
+            object_key: format!("{source_bucket}{}", self.object_key),
+        }
+    }
+}
-- 
2.39.5