1 files changed, 65 insertions, 0 deletions
diff --git a/third_party/python/dlmanager/dlmanager/persist_limit.py b/third_party/python/dlmanager/dlmanager/persist_limit.py
new file mode 100644
index 0000000000..03a1829f70
--- /dev/null
+++ b/third_party/python/dlmanager/dlmanager/persist_limit.py
@@ -0,0 +1,65 @@
+import os
+import stat
+
+from collections import namedtuple
+from glob import glob
+
+from dlmanager import fs
+
+
+File = namedtuple('File', ('path', 'stat'))
+
+
+class PersistLimit(object):
+    """
+    Keep a list of files, removing the oldest ones when the size_limit
+    is reached.
+
+    The access time of a file is used to determine the oldests, e.g. the
+    last time a file was read.
+
+    :param size_limit: the size limit in bytes. A value of 0 means no limit.
+    :param file_limit: even if the size limit is reached, this force
+                       to keep at least *file_limit* files.
+    """
+    def __init__(self, size_limit, file_limit=5):
+        self.size_limit = size_limit
+        self.file_limit = file_limit
+        self.files = []
+        self._files_size = 0
+
+    def register_file(self, path):
+        """
+        register a single file.
+        """
+        try:
+            fstat = os.stat(path)
+        except OSError:
+            # file do not exists probably, just skip it
+            # note this happen when backgound files are canceled
+            return
+        if stat.S_ISREG(fstat.st_mode):
+            self.files.append(File(path=path, stat=fstat))
+            self._files_size += fstat.st_size
+
+    def register_dir_content(self, directory, pattern="*"):
+        """
+        Register every files in a directory that match *pattern*.
+        """
+        for path in glob(os.path.join(directory, pattern)):
+            self.register_file(path)
+
+    def remove_old_files(self):
+        """
+        remove oldest registered files.
+        """
+        if self.size_limit <= 0 or self.file_limit <= 0:
+            return
+        # sort by creation time, oldest first
+        files = sorted(self.files, key=lambda f: f.stat.st_atime)
+        while len(files) > self.file_limit and \
+                self._files_size >= self.size_limit:
+            f = files.pop(0)
+            fs.remove(f.path)
+            self._files_size -= f.stat.st_size
+        self.files = files