From 1171705921c660f1bcee1d011d169b8ab60b58f0 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Tue, 29 May 2012 17:39:54 -0400
Subject: [PATCH] Made core.fs.File slotted to save a lot of memory usage.

---
 core/fs.py       | 44 ++++++++++++++++++++++++++------------------
 core_me/fs.py    |  9 +++++----
 core_pe/photo.py |  2 ++
 3 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/core/fs.py b/core/fs.py
index 92c22736..93aed241 100644
--- a/core/fs.py
+++ b/core/fs.py
@@ -15,7 +15,9 @@ import hashlib
 import logging
 
 from hscommon import io
-from hscommon.util import nonone, flatten, get_file_ext
+from hscommon.util import nonone, get_file_ext
+
+NOT_SET = object()
 
 class FSError(Exception):
     cls_message = "An error has occured on '{name}' in '{parent}'"
@@ -55,29 +57,35 @@ class File:
         'md5': '',
         'md5partial': '',
     }
+    # Slots for File make us save quite a bit of memory. In a memory test I've made with a lot of
+    # files, I saved 35% memory usage with "unread" files (no _read_info() call) and gains become
+    # even greater when we take into account read attributes (70%!). Yeah, it's worth it.
+    __slots__ = ('path', 'is_ref', 'words') + tuple(INITIAL_INFO.keys())
     
     def __init__(self, path):
         self.path = path
-        #This offset is where we should start reading the file to get a partial md5
-        #For audio file, it should be where audio data starts
-        self._md5partial_offset = 0x4000 #16Kb
-        self._md5partial_size   = 0x4000 #16Kb
+        for attrname in self.INITIAL_INFO:
+            setattr(self, attrname, NOT_SET)
     
     def __repr__(self):
         return "<{} {}>".format(self.__class__.__name__, str(self.path))
     
-    def __getattr__(self, attrname):
-        # Only called when attr is not there
-        if attrname in self.INITIAL_INFO:
+    def __getattribute__(self, attrname):
+        result = object.__getattribute__(self, attrname)
+        if result is NOT_SET:
             try:
                 self._read_info(attrname)
             except Exception as e:
                 logging.warning("An error '%s' was raised while decoding '%s'", e, repr(self.path))
-            try:
-                return self.__dict__[attrname]
-            except KeyError:
-                return self.INITIAL_INFO[attrname]
-        raise AttributeError()
+            result = object.__getattribute__(self, attrname)
+            if result is NOT_SET:
+                result = self.INITIAL_INFO[attrname]
+        return result
+    
+    #This offset is where we should start reading the file to get a partial md5
+    #For audio file, it should be where audio data starts
+    def _get_md5partial_offset_and_size(self):
+        return (0x4000, 0x4000) #16Kb
     
     def _read_info(self, field):
         if field in ('size', 'mtime'):
@@ -87,8 +95,7 @@ class File:
         elif field == 'md5partial':
             try:
                 fp = io.open(self.path, 'rb')
-                offset = self._md5partial_offset
-                size = self._md5partial_size
+                offset, size = self._get_md5partial_offset_and_size()
                 fp.seek(offset)
                 partialdata = fp.read(size)
                 md5 = hashlib.md5(partialdata)
@@ -116,10 +123,9 @@ class File:
         If `attrnames` is not None, caches only attrnames.
         """
         if attrnames is None:
-            attrnames = list(self.INITIAL_INFO.keys())
+            attrnames = self.INITIAL_INFO.keys()
         for attrname in attrnames:
-            if attrname not in self.__dict__:
-                self._read_info(attrname)
+            getattr(self, attrname)
     
     #--- Public
     @classmethod
@@ -159,6 +165,8 @@ class Folder(File):
     
     It has the size/md5 info of a File, but it's value are the sum of its subitems.
     """
+    __slots__ = File.__slots__ + ('_subfolders', )
+    
     def __init__(self, path):
         File.__init__(self, path)
         self._subfolders = None
diff --git a/core_me/fs.py b/core_me/fs.py
index eae01478..4733be15 100644
--- a/core_me/fs.py
+++ b/core_me/fs.py
@@ -28,6 +28,7 @@ class MusicFile(fs.File):
         'year'    : '',
         'track'   : 0,
     })
+    __slots__ = fs.File.__slots__ + tuple(INITIAL_INFO.keys())
     
     @classmethod
     def can_handle(cls, path):
@@ -35,11 +36,11 @@ class MusicFile(fs.File):
             return False
         return get_file_ext(path[-1]) in auto.EXT2CLASS
     
+    def _get_md5partial_offset_and_size(self):
+        f = auto.File(str(self.path))
+        return (f.audio_offset, f.audio_size)
+    
     def _read_info(self, field):
-        if field == 'md5partial':
-            f = auto.File(str(self.path))
-            self._md5partial_offset = f.audio_offset
-            self._md5partial_size = f.audio_size
         fs.File._read_info(self, field)
         if field in TAG_FIELDS:
             f = auto.File(str(self.path))
diff --git a/core_pe/photo.py b/core_pe/photo.py
index d87b2090..cd398a7e 100644
--- a/core_pe/photo.py
+++ b/core_pe/photo.py
@@ -16,6 +16,8 @@ class Photo(fs.File):
     INITIAL_INFO.update({
         'dimensions': (0,0),
     })
+    __slots__ = fs.File.__slots__ + tuple(INITIAL_INFO.keys())
+    
     # These extensions are supported on all platforms
     HANDLED_EXTS = {'png', 'jpg', 'jpeg', 'gif', 'bmp', 'tiff', 'tif'}