Use file mode if mmap is not available

Author: oschwald

maxminddb/file.py

@@ -0,0 +1,36 @@
+"""This is intended for internal use only"""
+
+import os
+
+
+class FileBuffer(object):
+
+    """A slice-able file reader"""
+
+    def __init__(self, database):
+        self._handle = open(database, 'rb')
+        self._size = os.fstat(self._handle.fileno()).st_size
+
+    def __getitem__(self, key):
+        if isinstance(key, slice):
+            self._handle.seek(key.start)
+            return self._handle.read(key.stop - key.start)
+        elif isinstance(key, int):
+            self._handle.seek(key)
+            return self._handle.read(1)
+        else:
+            raise TypeError("Invalid argument type.")
+
+    def rfind(self, needle, beg):
+        start = max(0, beg)
+        self._handle.seek(start)
+        pos = self._handle.read(self._size - start - 1).rfind(needle)
+        if pos == -1:
+            return pos
+        return start + pos
+
+    def size(self):
+        return self._size
+
+    def close(self):
+        self._handle.close()

maxminddb/reader.py

@@ -7,12 +7,17 @@
 """
 from __future__ import unicode_literals
 
-import mmap
+try:
+    import mmap
+except:
+    mmap = None
+
 import struct
 
 from maxminddb.compat import byte_from_int, int_from_byte, ipaddress
 from maxminddb.decoder import Decoder
 from maxminddb.errors import InvalidDatabaseError
+from maxminddb.file import FileBuffer
 
 
 class Reader(object):
@@ -34,9 +39,12 @@ def __init__(self, database):
         database -- A path to a valid MaxMind DB file such as a GeoIP2
                     database file.
         """
-        with open(database, 'rb') as db_file:
-            self._buffer = mmap.mmap(
-                db_file.fileno(), 0, access=mmap.ACCESS_READ)
+        if mmap:
+            with open(database, 'rb') as db_file:
+                self._buffer = mmap.mmap(
+                    db_file.fileno(), 0, access=mmap.ACCESS_READ)
+        else:
+            self._buffer = FileBuffer(database)
 
         metadata_start = self._buffer.rfind(self._METADATA_START_MARKER,
                                             self._buffer.size() - 128 * 1024)

tests/reader_test.py

@@ -163,7 +163,7 @@ def test_closed_get(self):
         reader.close()
         self.assertRaisesRegex(ValueError,
                                'Attempt to read from a closed MaxMind DB.'
-                               '|closed or invalid',
+                               '|closed',
                                reader.get, ('1.1.1.1'))
 
     # XXX - Figure out whether we want to have the same behavior on both the