Python ledger tweaks (#2677)

doc/audit/python_library.rst

@@ -88,7 +88,7 @@ Alternatively, ``read_ledger.py`` can parse the content of a snapshot file:
 
 .. note::
 
-    The output of the ``read_ledger.py`` utility can be filtered by key-value store :ref:`table <build_apps/kv/kv_how_to/Creating a Map>` using the ``--tables <regex>`` arguments, e.g.:
+    The output of the ``read_ledger.py`` utility can be filtered by :ref:`key-value store table <build_apps/kv/kv_how_to:Creating a Map>` using the ``--tables <regex>`` arguments, e.g.:
 
     .. code-block:: bash
 
@@ -129,4 +129,4 @@ API
     :members:
 
 .. automodule:: ccf.receipt
-    :members:
+    :members:

python/ccf/ledger.py

@@ -221,11 +221,11 @@ class PublicDomain:
 
 
 def _byte_read_safe(file, num_of_bytes):
+    offset = file.tell()
     ret = file.read(num_of_bytes)
     if len(ret) != num_of_bytes:
         raise ValueError(
-            "Failed to read precise number of bytes: %u, actual = %u"
-            % (num_of_bytes, len(ret))
+            f"Failed to read precise number of bytes in {file.name} at offset {offset}: {len(ret)}/{num_of_bytes}"
         )
     return ret
 
@@ -702,25 +702,16 @@ class Ledger:
     def __iter__(self):
         return self
 
-    def signature_count(self):
-        return self._ledger_validator.signature_count
-
-    def last_verified_txid(self):
-        return TxID(
-            self._ledger_validator.last_verified_view,
-            self._ledger_validator.last_verified_seqno,
-        )
-
     def get_transaction(self, seqno: int) -> Transaction:
         """
-        Return the :py:class:`ccf.Ledger.Transaction` recorded in the ledger at the given sequence number.
+        Return the :py:class:`ccf.ledger.Transaction` recorded in the ledger at the given sequence number.
 
         Note that the transaction returned may not yet be verified by a
         signature transaction nor committed by the service.
 
         :param int seqno: Sequence number of the transaction to fetch.
 
-        :return: :py:class:`ccf.Ledger.Transaction`
+        :return: :py:class:`ccf.ledger.Transaction`
         """
         if seqno < 1:
             raise ValueError("Ledger first seqno is 1")
@@ -775,6 +766,29 @@ class Ledger:
 
         return public_tables, latest_seqno
 
+    def signature_count(self) -> int:
+        """
+        Return the number of verified signature transactions in the *parsed* ledger.
+
+        Note: The ledger should first be parsed before calling this function.
+
+        :return int: Number of verified signature transactions.
+        """
+        return self._ledger_validator.signature_count
+
+    def last_verified_txid(self) -> TxID:
+        """
+        Return the :py:class:`ccf.tx_id.TxID` of the last verified signature transaction in the *parsed* ledger.
+
+        Note: The ledger should first be parsed before calling this function.
+
+        :return: :py:class:`ccf.tx_id.TxID`
+        """
+        return TxID(
+            self._ledger_validator.last_verified_view,
+            self._ledger_validator.last_verified_seqno,
+        )
+
 
 class InvalidRootException(Exception):
     """MerkleTree root doesn't match with the root reported in the signature's table"""

python/ccf/read_ledger.py

@@ -118,13 +118,18 @@ if __name__ == "__main__":
         LOG.info(f"Reading ledger from {ledger_dirs}")
         LOG.info(f"Contains {counted_string(ledger, 'chunk')}")
 
-        for chunk in ledger:
+        try:
+            for chunk in ledger:
+                LOG.info(
+                    f"chunk {chunk.filename()} ({'' if chunk.is_committed() else 'un'}committed)"
+                )
+                for transaction in chunk:
+                    dump_entry(transaction, table_filter)
+        except Exception as e:
+            LOG.exception(f"Error parsing ledger: {e}")
+        else:
+            LOG.success("Ledger verification complete")
+        finally:
             LOG.info(
-                f"chunk {chunk.filename()} ({'' if chunk.is_committed() else 'un'}committed)"
+                f"Found {ledger.signature_count()} signatures, and verified until {ledger.last_verified_txid()}"
             )
-            for transaction in chunk:
-                dump_entry(transaction, table_filter)
-
-        LOG.success(
-            f"Ledger verification complete. Found {ledger.signature_count()} signatures, and verified until {ledger.last_verified_txid()}"
-        )