[elbe-devel] [PATCH v3 2/8] Add 'realpath' method to 'Filesystem'

[dion at linutronix.de]

From: Olivier Dion <dion at linutronix.de>

Signed-off-by: Olivier Dion <dion at linutronix.de>
---
 elbepack/filesystem.py | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/elbepack/filesystem.py b/elbepack/filesystem.py
index d9f3e50e..cd5e8133 100644
--- a/elbepack/filesystem.py
+++ b/elbepack/filesystem.py
@@ -84,6 +84,48 @@ class Filesystem(object):
     def mkdir(self, path):
         os.makedirs(self.fname(path))
 
+    # Taken from 'posixpath.py'
+    def _joinrealpath(self, path, rest, seen):
+        if os.path.isabs(rest):
+            rest = rest[1:]
+            path = self.path
+
+        while rest:
+            name, _, rest = rest.partition(os.sep)
+            if not name or name == os.curdir:
+                continue
+            if name == os.pardir:
+                if path:
+                    # Block going outside of RFS
+                    if path == self.path:
+                        continue
+                    path, name = os.path.split(path)
+                    if name == os.pardir:
+                        path = os.path.join(path, os.pardir, os.pardir)
+                else:
+                    path = os.pardir
+                continue
+            newpath = os.path.join(path, name)
+            if not os.path.islink(newpath):
+                path = newpath
+                continue
+            if newpath in seen:
+                path = seen[newpath]
+                if path is not None:
+                    continue
+                return os.path.join(newpath, rest), False
+            seen[newpath] = None
+            path, ok = self._joinrealpath(path, os.readlink(newpath), seen)
+            if not ok:
+                return os.path.join(path, rest), False
+            seen[newpath] = path
+
+        return path, True
+
+    def realpath(self, path):
+        path, ok = self._joinrealpath(self.path, path, {})
+        return os.path.abspath(path)
+
     def symlink(self, src, path, allow_exists=False):
         try:
             os.symlink(src, self.fname(path))
-- 
2.11.0