UPD: use single temporary directory for dynamic libraries

ADD: automatically clean up temporary files on exit
ADD: module cache for tempimporter

paker/_tempimporter.py

@@ -1,10 +1,17 @@
 import os
 import sys
+import atexit
 import ctypes
+import shutil
+import logging
 import tempfile
 import importlib.util
 import importlib.machinery
 
+module_cache = {}
+logger = logging.getLogger("tempimporter")
+paker_tempdir = os.path.join(tempfile.gettempdir(), "paker")
+
 
 def load_dynamic(name, path, file=None):
     """Replaces deprecated imp.load_dynamic."""
@@ -16,18 +23,26 @@ def load_dynamic(name, path, file=None):
 
 
 def import_module(data, initfuncname, fullname, filename):
-    """Import module from temporary directory. Used when _memimporter is not available."""
+    """Import module from temporary file. Used when _memimporter is not available."""
     return load_library(data, fullname, filename, dlopen=False, initfuncname=initfuncname)
 
 
 def load_library(data, fullname, filename, dlopen=True, initfuncname=None):
-    """Create temporary directory and import module. Used for '.pyd', '.dll' and '.so' files."""
-    tempdir = tempfile.TemporaryDirectory()
-    tempdir_path = tempdir.name
-    filename = os.path.join(tempdir_path, filename)
+    """Create temporary file on disk and import module. Used for '.pyd', '.dll' and '.so' files."""
+    logger.info("importing {} from temporary file".format(fullname))
+    if fullname in module_cache:
+        return module_cache[fullname][1]
+
+    if os.path.isfile(paker_tempdir):
+        os.remove(paker_tempdir)
+    if not os.path.isdir(paker_tempdir):
+        os.makedirs(paker_tempdir, exist_ok=True)
+
+    filename = os.path.join(paker_tempdir, filename)
     try:
         with open(filename, "wb+") as f:
             f.write(data)
+        logger.debug("created temporary file {} for module {}".format(filename, fullname))
 
         if dlopen:
             result = ctypes.CDLL(filename)
@@ -38,4 +53,22 @@ def load_library(data, fullname, filename, dlopen=True, initfuncname=None):
                 result = load_dynamic(fullname, filename)
     except Exception as e:
         raise e
+
+    if len(module_cache) == 0:
+        logger.debug("registering cleanup atexit function")
+        atexit.register(_cleanup)
+    module_cache[fullname] = (filename, result)
     return result
+
+
+def _cleanup():
+    """Python does not support unloading dynamic libraries in runtime, so
+    cleanup is ran once at exit."""
+    for module in module_cache.values():
+        info = "module '{}' from '{}'".format(module[1].__name__, module[0])
+        try:
+            logger.debug("removing {}".format(info))
+            os.remove(module[0])
+        except Exception as e:
+            logger.error("failed to remove {}: {}".format(info, e))
+    shutil.rmtree(paker_tempdir, ignore_errors=True)