# HG changeset patch
# User Bryan O'Sullivan <bryano@fb.com>
# Date 1334269314 25200
# Node ID 9fca5b056c0a2f673aefa64f7ec7488bd9188d9d
# Parent  efae1fea4bbded6ca1ae10345c0469e07c9b610c
store: speed up read and write of large fncache files

In my tests of an fncache containing 300,000 entries, this improves
read time from 567ms to 307, and write time from 1328ms to 533.

These numbers aren't so great, since the fncache file is only 17MB
in size, but they're an improvement.

diff -r efae1fea4bbd -r 9fca5b056c0a mercurial/store.py
--- a/mercurial/store.py	Thu Apr 12 15:21:52 2012 -0700
+++ b/mercurial/store.py	Thu Apr 12 15:21:54 2012 -0700
@@ -317,36 +317,36 @@
 
     def _load(self):
         '''fill the entries from the fncache file'''
-        self.entries = set()
         self._dirty = False
         try:
             fp = self.opener('fncache', mode='rb')
         except IOError:
             # skip nonexistent file
+            self.entries = set()
             return
-        for n, line in enumerate(fp):
-            if (len(line) < 2) or (line[-1] != '\n'):
-                t = _('invalid entry in fncache, line %s') % (n + 1)
-                raise util.Abort(t)
-            self.entries.add(decodedir(line[:-1]))
+        self.entries = set(map(decodedir, fp.read().splitlines()))
+        if '' in self.entries:
+            fp.seek(0)
+            for n, line in enumerate(fp):
+                if not line.rstrip('\n'):
+                    t = _('invalid entry in fncache, line %s') % (n + 1)
+                    raise util.Abort(t)
         fp.close()
 
+    def _write(self, files, atomictemp):
+        fp = self.opener('fncache', mode='wb', atomictemp=atomictemp)
+        if files:
+            fp.write('\n'.join(map(encodedir, files)) + '\n')
+        fp.close()
+        self._dirty = False
+
     def rewrite(self, files):
-        fp = self.opener('fncache', mode='wb')
-        for p in files:
-            fp.write(encodedir(p) + '\n')
-        fp.close()
+        self._write(files, False)
         self.entries = set(files)
-        self._dirty = False
 
     def write(self):
-        if not self._dirty:
-            return
-        fp = self.opener('fncache', mode='wb', atomictemp=True)
-        for p in self.entries:
-            fp.write(encodedir(p) + '\n')
-        fp.close()
-        self._dirty = False
+        if self._dirty:
+            self._write(self.entries, True)
 
     def add(self, fn):
         if self.entries is None: