1 files changed, 123 insertions, 0 deletions
diff --git a/lbup/_mountinfo.py b/lbup/_mountinfo.py
new file mode 100644
index 0000000..b4d79ae
--- /dev/null
+++ b/lbup/_mountinfo.py
@@ -0,0 +1,123 @@
+import os.path
+
+from ._path import AbsPath
+
+# oct-unescape certain characters as they are in /proc/mountinfo
+# see seq_path[_root]() in linux source
+def _oct_unescape(b):
+    trans = {
+        br'\040' : b' ',  br'\011'  : b'\t',
+        br'\012' : b'\n', br'\0134' : b'\\',
+    }
+
+    for src, dst in trans.items():
+        b = b.replace(src, dst)
+
+    return b
+
+class _MountEntry:
+    "mount ID, bytes"
+    mount_id      = None
+    "parent ID, bytes"
+    parent_id     = None
+    "device number, int"
+    devnum        = None
+    "root of the mount, bytes"
+    root          = None
+    "path where the fs is mounted, bytes"
+    mount_point   = None
+    "mount options bytes"
+    mount_opts    = None
+    "optional fields, list of bytes"
+    opt_fields    = None
+    "filesystem type, bytes"
+    fstype        = None
+    "mount source, bytes or None"
+    source        = None
+    "superblock options, bytes or None"
+    super_opts    = None
+
+    "raw mountinfo line, bytes"
+    raw_entry     = None
+
+    def __init__(self, line):
+        self.raw_entry = line
+
+        items = line.split()
+        if len(items) < 6:
+            raise ValueError('Not enough items in a mountinfo line', line)
+
+        mount_id, parent_id, devnum, root, mount_point, mount_opts = items[:6]
+        self.mount_id  = mount_id
+        self.parent_id = parent_id
+
+        major, minor = map(int, devnum.split(b':'))
+        if major < 0 or major > 255 or minor < 0 or minor > 255:
+            raise ValueError('Invalid device number', devnum)
+        self.devnum = (major << 8) + minor
+
+        self.root        = AbsPath(_oct_unescape(root))
+        self.mount_point = AbsPath(_oct_unescape(mount_point))
+        self.mount_opts  = mount_opts
+
+        remainder  = items[6:]
+        opt_fields = []
+        while len(remainder) > 0 and remainder[0] != b'-':
+            opt_fields.append(remainder.pop(0))
+        self.opt_fields = opt_fields
+
+        if len(remainder) > 0:
+            sep = remainder.pop(0)
+            if sep != b'-':
+                raise ValueError('Expected separator "-", got', sep)
+        if len(remainder) > 0:
+            self.fstype = remainder.pop(0)
+        if len(remainder) > 0:
+            self.source = _oct_unescape(remainder.pop(0))
+        if len(remainder) > 0:
+            self.super_opts = remainder.pop(0)
+
+    def __str__(self):
+        return '({major}:{minor}){src}{root}->{mp}'.format(
+            major = self.devnum >> 8, minor = self.devnum & 255,
+            src = ("{%s}" % self.source) if self.source else "",
+            root = "[%s]" % self.root, mp = self.mount_point)
+
+class MountInfo:
+    """
+    A wrapper around the contents of the Linux /proc/<pid>/mountinfo file.
+    """
+
+    "a list of _MountEntry"
+    entries = None
+
+    def __init__(self, data):
+        self.entries = []
+        for line in data.splitlines():
+            self.entries.append(_MountEntry(line))
+
+    def __str__(self):
+        return '%s(%d entries)' % (self.__class__.__name__, len(self.entries))
+
+    def entries_for_mountpoint(self, mountpoint):
+        """
+        Iterate over all mountinfo entries mounted at the given mountpoint.
+        """
+        return filter(lambda entry: entry.mount_point == mountpoint, self.entries)
+
+    def mountpoint_for_path(self, path):
+        """
+        Find the longest mountpoint that is a parent of path.
+        """
+        best_match = None
+        for e in self.entries:
+            if (path in e.mount_point and
+                (best_match is None or len(best_match) < len(e.mount_point))):
+                best_match = e.mount_point
+
+        if best_match is None:
+            raise LookupError('No mountpoint for', path)
+
+        print(best_match, len(best_match))
+
+        return best_match