Ability to seek in command line utility

[pyderasn.git] / pyderasn.py

diff --git a/pyderasn.py b/pyderasn.py
index 717c06cce42d63a15ed38356f71eb92cce217076..3afaf60fde261bd6a985d06acd63ec4ca0e55fbd 100755 (executable)
--- a/pyderasn.py
+++ b/pyderasn.py
@@ -261,6 +261,8 @@ defined, ``value`` contains corresponding decoded value. For example
 above, ``content_info["content"].defined == (id_signedData,
 signed_data)``.
 
+.. _defines_by_path_kwarg:
+
 defines_by_path kwarg
 _____________________
 
@@ -4326,6 +4328,12 @@ def generic_decoder():  # pragma: no cover
 def main():  # pragma: no cover
     import argparse
     parser = argparse.ArgumentParser(description="PyDERASN ASN.1 DER decoder")
+    parser.add_argument(
+        "--skip",
+        type=int,
+        default=0,
+        help="Skip that number of bytes from the beginning",
+    )
     parser.add_argument(
         "--oids",
         help="Python path to dictionary with OIDs",
@@ -4334,12 +4342,17 @@ def main():  # pragma: no cover
         "--schema",
         help="Python path to schema definition to use",
     )
+    parser.add_argument(
+        "--defines-by-path",
+        help="Python path to decoder's defines_by_path",
+    )
     parser.add_argument(
         "DERFile",
         type=argparse.FileType("rb"),
         help="Path to DER file you want to decode",
     )
     args = parser.parse_args()
+    args.DERFile.seek(args.skip)
     der = memoryview(args.DERFile.read())
     args.DERFile.close()
     oids = obj_by_path(args.oids) if args.oids else {}
@@ -4349,7 +4362,13 @@ def main():  # pragma: no cover
         pprinter = partial(pprint, big_blobs=True)
     else:
         schema, pprinter = generic_decoder()
-    obj, tail = schema().decode(der)
+    obj, tail = schema().decode(
+        der,
+        defines_by_path=(
+            None if args.defines_by_path is None
+            else obj_by_path(args.defines_by_path)
+        ),
+    )
     print(pprinter(obj, oids=oids))
     if tail != b"":
         print("\nTrailing data: %s" % hexenc(tail))