Feature: ChainIds computing was not pure + Max docker layers was 1000\nSolution: Use function rather than class method depending on self + use iteration rather than recursion

Author: AmozPay

src/aleph_client/commands/container/image.py

@@ -8,6 +8,30 @@
 Command = NewType('Command', Dict[str, str])
 ConfigValue = NewType('ConfigValue', Union[str, bool, None, Command])
 
+
+def compute_chain_ids(diff_ids: List[str], layers_ids: List[str]) -> List[str]:
+    # diff_ids are stored sequentially, from parent to child.
+    # If the file has been tempered, this method cannot work.
+    # ChainID(A) = DiffID(A)
+    # ChainID(A|B) = Digest(ChainID(A) + " " + DiffID(B))
+    # ChainID(A|B|C) = Digest(ChainID(A|B) + " " + DiffID(C))
+    # https://github.com/opencontainers/image-spec/blob/main/config.md
+    index = 0
+    chain_ids = []
+    diff_id = diff_ids[index]
+    chain_ids.append(diff_id)
+    index += 1
+    while index < len(layers_ids):
+        chain_id = "sha256:" + sha256(
+            chain_ids[index - 1].encode()
+            + " ".encode()
+            + diff_ids[index].encode()
+        ).hexdigest()
+        chain_ids.append(chain_id)
+        index += 1
+    return chain_ids
+
+
 class Image:
     config: Dict[str, ConfigValue]
     image_digest: str
@@ -42,55 +66,11 @@ def __init__(self, path: str):
             manifest = self.__load_metadata(tar, "manifest.json")
             self.repositories = self.__load_metadata(tar, "repositories")
             self.image_digest = manifest[0]["Config"].split(".")[0]
-            self.config = self.__load_metadata(tar, f"{self.image_digest}.json")
+            self.config = self.__load_metadata(
+                tar, f"{self.image_digest}.json")
         self.layers_ids = list(map(
             lambda name: name.split('/')[0],
             manifest[0]["Layers"]
-        )) # Only keep the Layer id, not the file path
+        ))  # Only keep the Layer id, not the file path
         self.diff_ids = self.config["rootfs"]["diff_ids"]
-        self.chain_ids = self.__compute_chain_ids()
-
-    def __compute_chain_ids(self) -> List[str]:
-        chain_ids = []
-        # diff_ids are stored sequentially, from parent to child.
-        # If the file has been tempered, this method cannot work.
-
-        # I used recursion because it was simpler to execute, not because it's better
-        # cause it's not. TODO: use iteration
-        def recursive_compute_chain_id(index: int) -> str:
-            # ChainID(A) = DiffID(A)
-            # ChainID(A|B) = Digest(ChainID(A) + " " + DiffID(B))
-            # ChainID(A|B|C) = Digest(ChainID(A|B) + " " + DiffID(C))
-            # https://github.com/opencontainers/image-spec/blob/main/config.md
-            if index == 0:
-                diff_id = self.diff_ids[index]
-                chain_ids.append(diff_id)
-                return diff_id
-            chain_id = "sha256:" + sha256(
-                recursive_compute_chain_id(index - 1).encode()
-                + " ".encode()
-                + self.diff_ids[index].encode()
-            ).hexdigest()
-            chain_ids.append(chain_id)
-            return chain_id
-
-
-
-        # TODO: test this iterative version
-        iterative_chain_ids = []
-        def iterative_compute_chain_id(index: int) -> str:
-            diff_id = self.diff_ids[0]
-            iterative_chain_ids.append(diff_id)
-            i = 1
-            while i < index:
-                chain_id = "sha256:" + sha256(
-                iterative_chain_ids[i - 1].encode()
-                + " ".encode()
-                + self.diff_ids[i].encode()
-            ).hexdigest()
-            iterative_chain_ids.append(chain_id)
-            return
-
-        recursive_compute_chain_id(len(self.layers_ids) - 1)
-
-        return chain_ids
+        self.chain_ids = compute_chain_ids(self.diff_ids, self.layers_ids)