Merge pull request #295 from fsantovito/context-manager

I solved the issue with Python 3.9. However, I do not like the way old versions of Python are current installed because DeadSnakes removes old versions from time to time and it breaks frequently the builds. I will review this (and also add Python 3.14). So I merge this PR as it is currently, and will do the modifications in later commits.

Author: andrivet

AUTHORS.rst

@@ -6,4 +6,5 @@ The following people have contributed to Python-ASN1. Collectively they own the
 
 * Geert Jansen <geert@boskant.nl>
 * Sebastien Andrivet <sebastien@andrivet.com>
+* Filippo Santovito <filippo.santovito@gmail.com>
 

CHANGELOG.rst

@@ -1,6 +1,14 @@
 Changelog
 =========
 
+3.1.1 (2026-31-01)
+------------------
+
+* Support for using Encoder via context manager
+* Support for encoding sequences via context manager
+* Support for encoding sets via context manager
+* Support for using Decoder via context manager
+
 3.1.0 (2025-05-16)
 ------------------
 

Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:20.04
+FROM ubuntu:22.04
 LABEL authors="Sebastien Andrivet"
 
 ARG DEBIAN_FRONTEND=noninteractive
@@ -12,10 +12,10 @@ RUN apt-get update && \
       python2.7 \
       python3.4 \
       python3.5 \
-      python3.6 python3.6-distutils \
+      # python3.6 python3.6-distutils \
       python3.7 python3.7-distutils \
       python3.8 python3.8-distutils \
-      python3.9 \
+      # python3.9 \
       python3.10 \
       python3.11 \
       python3.12 \

docs/credits.rst

@@ -7,5 +7,5 @@ The following projects have provided inspiration for Python-ASN1:
 * `Samba`_ In particular **libads** for the stack based approach for
   building constructed types.
 
-.. _pyasn1: https://pyasn1.sourceforge.net/
+.. _pyasn1: https://web.archive.org/web/20191231214902/http://snmplabs.com/pyasn1/index.html
 .. _Samba: https://github.com/samba-team/samba/tree/master/source3/libads

docs/usage.rst

@@ -93,6 +93,16 @@ If you want to encode data and retrieve its DER-encoded representation, use code
   encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
   encoded_bytes = encoder.output()
 
+or using the new context manager api:
+
+.. code-block:: python
+
+  import asn1
+
+  with asn1.Encoder() as encoder:
+      encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
+      encoded_bytes = encoder.output()
+
 It is also possible to encode data directly to a file or any stream:
 
 .. code-block:: python
@@ -104,6 +114,16 @@ It is also possible to encode data directly to a file or any stream:
     encoder.start(f)
     encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
 
+or using the new context manager api:
+
+.. code-block:: python
+
+  import asn1
+
+  with open('output.der', 'wb') as f:
+    with asn1.Encoder(stream=f) as encoder:
+        encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
+
 You can encode complex data structures such as sequences and sets:
 
 .. code-block:: python
@@ -139,6 +159,22 @@ If you want to precisely specify the ASN.1 type, you have to use the `Encoder.en
         encoder.leave()
         encoder.leave()
 
+or using the new context manager api:
+
+.. code-block:: python
+
+  import asn1
+
+  with open('output.der', 'wb') as f:
+        with asn1.Encoder(stream=f) as encoder:
+            with encoder.sequence():
+                encoder.write('test1', asn1.Numbers.PrintableString)
+                encoder.write('test2', asn1.Numbers.PrintableString)
+                with encoder.sequence():
+                    encoder.write(1, asn1.Numbers.Integer)
+                    encoder.write(0.125, asn1.Numbers.Real)
+                    encoder.write(b'\x01\x02\x03', asn1.Numbers.OctetString)
+
 This also allows to encode data progressively, without having to keep everything in memory.
 
 DER and CER
@@ -196,6 +232,15 @@ If you want to decode ASN.1 from BER (DER, CER, ...) encoded bytes, use code suc
   decoder.start(encoded_bytes)
   tag, value = decoder.read()
 
+or using the new context manager api:
+
+.. code-block:: python
+
+  import asn1
+
+  with asn1.Decoder(stream=encoded_bytes) as decoder:
+      tag, value = decoder.read()
+
 It is also possible to decode data directly from a file or any stream:
 
 .. code-block:: python

examples/examples-cm-decoder.py

@@ -0,0 +1,133 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of Python-ASN1. Python-ASN1 is free software that is
+# made available under the MIT license. Consult the file "LICENSE" that
+# is distributed together with this file for the exact licensing terms.
+#
+# Python-ASN1 is copyright (c) 2007-2016 by the Python-ASN1 authors. See
+# the file "AUTHORS" for a complete overview.
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from builtins import open
+import asn1
+import pprint
+
+
+def example1():
+    """Decoding from a file."""
+    print("Example 1")
+    with open("example3.der", "rb") as f:
+        with asn1.Decoder(stream=f) as decoder:
+            tag, value = decoder.read()
+            print(tag)
+            print(value)
+    print()
+
+
+def example2():
+    """Decoding of a bit string with unused bits."""
+    print("Example 2")
+    encoded = b"\x23\x0c\x03\x02\x00\x0b\x03\x02\x00\x0b\x03\x02\x04\x0f"
+    with asn1.Decoder(stream=encoded) as decoder:
+        tag, (val, unused) = decoder.read(asn1.ReadFlags.WithUnused)
+        print("Tag:", tag)
+        print("Value:", val)
+        print("Unused bits:", unused)
+    print()
+
+
+def example3():
+    """Decoding of sequences."""
+    print("Example 3")
+    encoded = b"\x30\x80\x13\x05\x74\x65\x73\x74\x31\x13\x05\x74\x65\x73\x74\x32\x30\x80\x02\x01\x01\x09\x03\x80\xfd\x01\x04\x03\x01\x02\x03\x00\x00\x00\x00"
+    with asn1.Decoder(stream=encoded) as decoder:
+        tag, value = decoder.read()
+        print(tag)
+        pprint.pprint(value)
+    print()
+
+
+def example4():
+    """Decoding of a complex data."""
+    print("Example 4")
+    encoded = (
+        b"\x30\x82\x04\x0e\x30\x82\x03\x77\xa0\x03\x02\x01\x02\x02\x02\x15"
+        b"\x30\x30\x0d\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x01\x05\x05\x00"
+        b"\x30\x81\xbb\x31\x0b\x30\x09\x06\x03\x55\x04\x06\x13\x02\x2d\x2d"
+        b"\x31\x12\x30\x10\x06\x03\x55\x04\x08\x13\x09\x53\x6f\x6d\x65\x53"
+        b"\x74\x61\x74\x65\x31\x11\x30\x0f\x06\x03\x55\x04\x07\x13\x08\x53"
+        b"\x6f\x6d\x65\x43\x69\x74\x79\x31\x19\x30\x17\x06\x03\x55\x04\x0a"
+        b"\x13\x10\x53\x6f\x6d\x65\x4f\x72\x67\x61\x6e\x69\x7a\x61\x74\x69"
+        b"\x6f\x6e\x31\x1f\x30\x1d\x06\x03\x55\x04\x0b\x13\x16\x53\x6f\x6d"
+        b"\x65\x4f\x72\x67\x61\x6e\x69\x7a\x61\x74\x69\x6f\x6e\x61\x6c\x55"
+        b"\x6e\x69\x74\x31\x1e\x30\x1c\x06\x03\x55\x04\x03\x13\x15\x6c\x6f"
+        b"\x63\x61\x6c\x68\x6f\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d"
+        b"\x61\x69\x6e\x31\x29\x30\x27\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01"
+        b"\x09\x01\x16\x1a\x72\x6f\x6f\x74\x40\x6c\x6f\x63\x61\x6c\x68\x6f"
+        b"\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69\x6e\x30\x1e"
+        b"\x17\x0d\x30\x38\x30\x32\x30\x35\x30\x39\x32\x33\x33\x31\x5a\x17"
+        b"\x0d\x30\x39\x30\x32\x30\x34\x30\x39\x32\x33\x33\x31\x5a\x30\x81"
+        b"\xbb\x31\x0b\x30\x09\x06\x03\x55\x04\x06\x13\x02\x2d\x2d\x31\x12"
+        b"\x30\x10\x06\x03\x55\x04\x08\x13\x09\x53\x6f\x6d\x65\x53\x74\x61"
+        b"\x74\x65\x31\x11\x30\x0f\x06\x03\x55\x04\x07\x13\x08\x53\x6f\x6d"
+        b"\x65\x43\x69\x74\x79\x31\x19\x30\x17\x06\x03\x55\x04\x0a\x13\x10"
+        b"\x53\x6f\x6d\x65\x4f\x72\x67\x61\x6e\x69\x7a\x61\x74\x69\x6f\x6e"
+        b"\x31\x1f\x30\x1d\x06\x03\x55\x04\x0b\x13\x16\x53\x6f\x6d\x65\x4f"
+        b"\x72\x67\x61\x6e\x69\x7a\x61\x74\x69\x6f\x6e\x61\x6c\x55\x6e\x69"
+        b"\x74\x31\x1e\x30\x1c\x06\x03\x55\x04\x03\x13\x15\x6c\x6f\x63\x61"
+        b"\x6c\x68\x6f\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69"
+        b"\x6e\x31\x29\x30\x27\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x09\x01"
+        b"\x16\x1a\x72\x6f\x6f\x74\x40\x6c\x6f\x63\x61\x6c\x68\x6f\x73\x74"
+        b"\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69\x6e\x30\x81\x9f\x30"
+        b"\x0d\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x01\x01\x05\x00\x03\x81"
+        b"\x8d\x00\x30\x81\x89\x02\x81\x81\x00\xd5\x18\xcd\x40\x91\x90\x27"
+        b"\x5a\x77\x37\x22\xca\xba\x05\xdf\x13\x31\xe8\x74\x43\x4f\x7e\x08"
+        b"\xa3\xa5\x76\xcd\x7b\xdd\x37\xd0\x7f\x12\x9e\x81\x73\x87\x55\x66"
+        b"\x0d\xda\x68\xee\x38\xeb\x34\xe2\xf4\xeb\x95\xd5\xe0\xde\xef\x08"
+        b"\x57\xf9\x03\x14\x69\xa8\x6f\x7c\xa4\xfa\x64\x51\x39\x36\xd5\x09"
+        b"\x37\x61\x83\x13\x8c\x41\x25\xba\x60\x91\x20\x86\x5b\x60\xb5\xe2"
+        b"\x83\x65\x66\xad\x06\xb3\x45\x71\x83\x67\xd2\xe5\x5f\x40\x42\x4b"
+        b"\x37\xf8\x87\xd0\x09\x49\xb8\xad\x34\x76\xa3\x1b\xbf\xc1\x0f\xb7"
+        b"\xfb\x43\xbe\x62\x33\x02\x02\x10\x61\x02\x03\x01\x00\x01\xa3\x82"
+        b"\x01\x1d\x30\x82\x01\x19\x30\x1d\x06\x03\x55\x1d\x0e\x04\x16\x04"
+        b"\x14\x0a\x4b\xfa\x87\x54\x17\x7e\x30\xb4\x21\x71\x56\x51\x0f\xd2"
+        b"\x91\xc3\x30\x02\x36\x30\x81\xe9\x06\x03\x55\x1d\x23\x04\x81\xe1"
+        b"\x30\x81\xde\x80\x14\x0a\x4b\xfa\x87\x54\x17\x7e\x30\xb4\x21\x71"
+        b"\x56\x51\x0f\xd2\x91\xc3\x30\x02\x36\xa1\x81\xc1\xa4\x81\xbe\x30"
+        b"\x81\xbb\x31\x0b\x30\x09\x06\x03\x55\x04\x06\x13\x02\x2d\x2d\x31"
+        b"\x12\x30\x10\x06\x03\x55\x04\x08\x13\x09\x53\x6f\x6d\x65\x53\x74"
+        b"\x61\x74\x65\x31\x11\x30\x0f\x06\x03\x55\x04\x07\x13\x08\x53\x6f"
+        b"\x6d\x65\x43\x69\x74\x79\x31\x19\x30\x17\x06\x03\x55\x04\x0a\x13"
+        b"\x10\x53\x6f\x6d\x65\x4f\x72\x67\x61\x6e\x69\x7a\x61\x74\x69\x6f"
+        b"\x6e\x31\x1f\x30\x1d\x06\x03\x55\x04\x0b\x13\x16\x53\x6f\x6d\x65"
+        b"\x4f\x72\x67\x61\x6e\x69\x7a\x61\x74\x69\x6f\x6e\x61\x6c\x55\x6e"
+        b"\x69\x74\x31\x1e\x30\x1c\x06\x03\x55\x04\x03\x13\x15\x6c\x6f\x63"
+        b"\x61\x6c\x68\x6f\x73\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61"
+        b"\x69\x6e\x31\x29\x30\x27\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x09"
+        b"\x01\x16\x1a\x72\x6f\x6f\x74\x40\x6c\x6f\x63\x61\x6c\x68\x6f\x73"
+        b"\x74\x2e\x6c\x6f\x63\x61\x6c\x64\x6f\x6d\x61\x69\x6e\x82\x02\x15"
+        b"\x30\x30\x0c\x06\x03\x55\x1d\x13\x04\x05\x30\x03\x01\x01\xff\x30"
+        b"\x0d\x06\x09\x2a\x86\x48\x86\xf7\x0d\x01\x01\x05\x05\x00\x03\x81"
+        b"\x81\x00\x4e\x12\x46\x58\xa3\x57\xc5\x9a\xab\xfa\x32\xf5\xde\x87"
+        b"\xfb\x77\xa8\x79\x38\x1d\x4f\xd3\x7c\x3a\x16\x60\x82\x7d\x92\xa1"
+        b"\x58\xd2\x53\x7b\x11\x90\xec\x6d\xb0\xb0\x58\xee\x33\xb4\x7b\x1d"
+        b"\xb8\x95\xd8\x98\xc3\x10\x81\x83\x08\x46\xe8\x9a\xb9\x6c\xbf\x8f"
+        b"\x9e\x73\xf7\x61\x89\xc4\x6a\x1b\xc1\x98\xc6\xab\xfc\x91\xb6\x59"
+        b"\xb8\xa5\x05\x91\x2a\xbb\xc4\x30\x16\x53\xbf\x1a\xfe\x2f\x01\x25"
+        b"\xae\xef\xc7\xb9\xfa\xa5\x53\xf8\xd9\xf5\x8f\xae\x91\xea\x57\x28"
+        b"\xfa\xdf\x34\x03\x29\xe8\x97\xee\x2e\x9e\x8a\x62\x45\xc7\xfc\x58"
+        b"\xb4\x5a"
+    )
+
+    with asn1.Decoder(stream=encoded) as decoder:
+        tag, value = decoder.read()
+        print(tag)
+        pprint.pprint(value)
+    print()
+
+
+example1()
+example2()
+example3()
+example4()

examples/examples-cm-encoder.py

@@ -0,0 +1,84 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of Python-ASN1. Python-ASN1 is free software that is
+# made available under the MIT license. Consult the file "LICENSE" that
+# is distributed together with this file for the exact licensing terms.
+#
+# Python-ASN1 is copyright (c) 2007-2016 by the Python-ASN1 authors. See
+# the file "AUTHORS" for a complete overview.
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from builtins import open, str
+import asn1
+import binascii
+import pprint
+
+
+def example1():
+    """Encoding an object identifier."""
+    print("Example 1")
+    with asn1.Encoder() as encoder:
+        encoder.write("1.2.3", asn1.Numbers.ObjectIdentifier)
+        print(str(binascii.hexlify(encoder.output(), " ", 1).upper(), encoding="ascii"))
+    print()
+
+
+def example2():
+    """Encoding an object identifier directly to a file."""
+    print("Example 2")
+    with open("example2.der", "wb") as f:
+        with asn1.Encoder(
+            stream=f, encoding=asn1.Encoding.DER
+        ) as encoder:  # CER is the default when using a stream
+            encoder.write("1.2.3", asn1.Numbers.ObjectIdentifier)
+
+
+def example3():
+    """Encoding of complex data."""
+    print("Example 3")
+    with open("example3.der", "wb") as f:
+        with asn1.Encoder(
+            stream=f, encoding=asn1.Encoding.DER
+        ) as encoder:  # CER is the default when using a stream
+            encoder.write(["test1", "test2", [1, 0.125, b"\x01\x02\x03"]])
+    print()
+
+
+def example4():
+    """Encoding of sequences."""
+    print("Example 4")
+    with asn1.Encoder() as encoder:
+        with encoder.sequence():
+            encoder.write("test1", asn1.Numbers.PrintableString)
+            encoder.write("test2", asn1.Numbers.PrintableString)
+            with encoder.sequence():
+                encoder.write(1, asn1.Numbers.Integer)
+                encoder.write(0.125, asn1.Numbers.Real)
+                encoder.write(b"\x01\x02\x03", asn1.Numbers.OctetString)
+        print(str(binascii.hexlify(encoder.output(), " ", 1).upper(), encoding="ascii"))
+    print()
+
+
+def example5():
+    """Using CER encoding with a stream (file)."""
+    print("Example 5")
+    with open("example6.cer", "wb") as f:
+        with asn1.Encoder(stream=f) as encoder:
+            encoder.write("1.2.3", asn1.Numbers.ObjectIdentifier)
+
+
+def example6():
+    """Using DER encoding with a stream (file)."""
+    print("Example 6")
+    with open("example7.der", "wb") as f:
+        with asn1.Encoder(stream=f, encoding=asn1.Encoding.DER) as encoder:
+            encoder.write("1.2.3", asn1.Numbers.ObjectIdentifier)
+
+
+example1()
+example2()
+example3()
+example4()
+example5()
+example6()

setup.py

@@ -29,7 +29,7 @@ def read(*names, **kwargs):
 
 setup(
     name='asn1',
-    version='3.1.0',
+    version='3.1.1',
     license='BSD',
     description='Python-ASN1 is a simple ASN.1 encoder and decoder for Python 2.7+ and 3.5+.',
     long_description='%s\n%s' % (