don't do "bigint" conversion for nanosecond mtime

2**63 nanoseconds are 292 years, so this change is good until 2262.
See also https://en.wikipedia.org/wiki/Time_formatting_and_storage_bugs#Year_2262

I expect that we will have plenty of time to revert this commit in time
for 2262.

timespec := time_t + long, so it's probably only 64 bits on some platforms
anyway.

src/borg/cache.py

@@ -15,7 +15,7 @@ from .hashindex import ChunkIndex, ChunkIndexEntry
 from .helpers import Location
 from .helpers import Error
 from .helpers import get_cache_dir, get_security_dir
-from .helpers import decode_dict, int_to_bigint, bigint_to_int, bin_to_hex
+from .helpers import bin_to_hex
 from .helpers import format_file_size
 from .helpers import yes
 from .helpers import remove_surrogates
@@ -350,7 +350,7 @@ Chunk index:    {0.total_unique_chunks:20d} {0.total_chunks:20d}"""
                     # this is to avoid issues with filesystem snapshots and mtime granularity.
                     # Also keep files from older backups that have not reached BORG_FILES_CACHE_TTL yet.
                     entry = FileCacheEntry(*msgpack.unpackb(item))
-                    if entry.age == 0 and bigint_to_int(entry.mtime) < self._newest_mtime or \
+                    if entry.age == 0 and entry.mtime < self._newest_mtime or \
                        entry.age > 0 and entry.age < ttl:
                         msgpack.pack((path_hash, entry), fd)
         pi.output('Saving cache config')
@@ -567,7 +567,7 @@ Chunk index:    {0.total_unique_chunks:20d} {0.total_chunks:20d}"""
         if not entry:
             return None
         entry = FileCacheEntry(*msgpack.unpackb(entry))
-        if (entry.size == st.st_size and bigint_to_int(entry.mtime) == st.st_mtime_ns and
+        if (entry.size == st.st_size and entry.mtime == st.st_mtime_ns and
                 (ignore_inode or entry.inode == st.st_ino)):
             self.files[path_hash] = msgpack.packb(entry._replace(age=0))
             return entry.chunk_ids
@@ -577,6 +577,6 @@ Chunk index:    {0.total_unique_chunks:20d} {0.total_chunks:20d}"""
     def memorize_file(self, path_hash, st, ids):
         if not (self.do_files and stat.S_ISREG(st.st_mode)):
             return
-        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, mtime=int_to_bigint(st.st_mtime_ns), chunk_ids=ids)
+        entry = FileCacheEntry(age=0, inode=st.st_ino, size=st.st_size, mtime=st.st_mtime_ns, chunk_ids=ids)
         self.files[path_hash] = msgpack.packb(entry)
         self._newest_mtime = max(self._newest_mtime or 0, st.st_mtime_ns)

src/borg/item.pyx

@@ -1,6 +1,5 @@
 from .constants import ITEM_KEYS
 from .helpers import safe_encode, safe_decode
-from .helpers import bigint_to_int, int_to_bigint
 from .helpers import StableDict
 
 API_VERSION = 1
@@ -153,9 +152,9 @@ class Item(PropDict):
     rdev = PropDict._make_property('rdev', int)
     bsdflags = PropDict._make_property('bsdflags', int)
 
-    atime = PropDict._make_property('atime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
-    ctime = PropDict._make_property('ctime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
-    mtime = PropDict._make_property('mtime', int, 'bigint', encode=int_to_bigint, decode=bigint_to_int)
+    atime = PropDict._make_property('atime', int)
+    ctime = PropDict._make_property('ctime', int)
+    mtime = PropDict._make_property('mtime', int)
 
     hardlink_master = PropDict._make_property('hardlink_master', bool)
 

src/borg/testsuite/item.py

@@ -77,17 +77,6 @@ def test_item_int_property():
         item.mode = "invalid"
 
 
-def test_item_bigint_property():
-    item = Item()
-    small, big = 42, 2 ** 65
-    item.atime = small
-    assert item.atime == small
-    assert item.as_dict() == {'atime': small}
-    item.atime = big
-    assert item.atime == big
-    assert item.as_dict() == {'atime': b'\0' * 8 + b'\x02'}
-
-
 def test_item_user_group_none():
     item = Item()
     item.user = None