[Python-bugs-list] dircache not kept consistent (PR#188)

[tage@acm.org]

Full_Name: Tage Stabell-Kulø
Version: 1.5.2
OS: FreeBSD
Submission from: (NULL) (129.242.16.231)


The documentation for the dircache module states:
"Return a directory listing of path, as gotten from 
os.listdir(). Note that unless path changes, further call 
to listdir() will not re-read the directory structure. "

The following program demonstrates that this is misleading (at best):
#! /usr/bin/env python

import whrandom
import os
import dircache
import string

generator = whrandom.whrandom()

while 1:
    dirlist = dircache.listdir(".")
    files = []
    while 1:
        file = ""
        for i in range(10):
            file = file + string.hexdigits[generator.randint(0,15)]
        files.append(file);
        fd = open(file, "w")
        fd.close()
        if file in dircache.listdir("."):
            break
    print "Created %d files" % len(files)
    for i in files:
        os.unlink(i)

The output (on my FreeBSD machine) is
Created 28 files
Created 69 files
Created 48 files
Created 58 files
Created 53 files

In my view, this is an outright bug.  I suggest that either the documentation
is changed to say:
	The cache is updated only once a second.

The reason is, of cource, that the st_mtime field is a time_t and holds 
seconds.

Or, better, change posixmodule.c with this patch (more text after the patch)
======
--- posixmodule.c.org   Mon Jan 24 17:08:06 2000
+++ posixmodule.c       Mon Jan 24 17:31:39 2000
@@ -559,7 +559,7 @@
                             (long)st.st_mtime,
                             (long)st.st_ctime);
 #else
-       return Py_BuildValue("(lLllllLlll)",
+       return Py_BuildValue("(lLllllLllll)",
                             (long)st.st_mode,
                             (LONG_LONG)st.st_ino,
                             (long)st.st_dev,
@@ -569,7 +569,8 @@
                             (LONG_LONG)st.st_size,
                             (long)st.st_atime,
                             (long)st.st_mtime,
-                            (long)st.st_ctime);
+                            (long)st.st_ctime,
+                            (long)st.st_mtimespec.tv_nsec);
 #endif
 }
 
@@ -2637,7 +2638,7 @@
                             (long)st.st_mtime,
                             (long)st.st_ctime);
 #else
-       return Py_BuildValue("(lLllllLlll)",
+       return Py_BuildValue("(lLllllLllll)",
                             (long)st.st_mode,
                             (LONG_LONG)st.st_ino,
                             (long)st.st_dev,
@@ -2647,7 +2648,8 @@
                             (LONG_LONG)st.st_size,
                             (long)st.st_atime,
                             (long)st.st_mtime,
-                            (long)st.st_ctime);
+                            (long)st.st_ctime,
+                            (long)st.st_mtimespec.tv_nsec);
 #endif
 }


======

and apply the following patch to the dircache module:

 +++ dircache.py Mon Jan 24 17:48:53 2000
@@ -15,7 +15,11 @@
        except KeyError:
                cached_mtime, list = -1, []
        try:
-               mtime = os.stat(path)[8]
+               st = os.stat(path)
+               if len(st) == 11:
+                       mtime = st[10]
+               else:
+                       mtime = st[8]
        except os.error:
                return []
        if mtime <> cached_mtime:


I appreciate your effort to maintain Python; I hope you find my small
contribution useful.

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