debugging stat on generated files

fs.py

@@ -2,28 +2,62 @@
 
 import os, sys, shutil, pathlib
 from fuse import FUSE, FuseOSError, Operations
+from collections import namedtuple
+
+Translator = namedtuple('Translator', ['mode', 'output_filename', 'command'])
 
 class FilterFS(Operations):
     def __init__(self, source, cache):
         self.source = source
         self.cache = cache
-    def _original(self, path):
-        print(path)
+    
+    def _mkparents(self, f):
+        pathlib.Path(os.path.dirname(f)).mkdir(parents = True, exist_ok = True)
+    def _parse(self, s):
+        if not s.startswith('/!/'):
+            return None
+        s = s[3:]
+        components = s.split('/')
+        return Translator(
+            mode = int(components[0], base=8),
+            output_filename = components[1], # TODO: forbid ../ attacks
+            command = '/'.join(components[2:])
+        )
+    def _peek(self, why, path):
+        print('peek', path)
         p = os.path.join(self.source, path.lstrip('/'))
         if os.path.islink(p):
             rl = os.readlink(p)
             if rl.startswith('/!/'):
-                cached_output = os.path.join(self.cache, path.lstrip('/'))
+                get = os.path.join(self.cache, 'get', path.lstrip('/'))
+                peek = os.path.join(self.cache, 'peek', path.lstrip('/'))
+                if os.path.exists(get):
+                    p = get
+                else:
+                    translator = self._parse(rl)
+                    p = peek
+                    self._mkparents(p)
+                    pathlib.Path(p).touch()
+                    os.chmod(p, translator.mode)
+        return p
+
+    def _get(self, why, path):
+        print('get', why, path)
+        p = os.path.join(self.source, path.lstrip('/'))
+        if os.path.islink(p):
+            rl = os.readlink(p)
+            if rl.startswith('/!/'):
+                cached_output = os.path.join(self.cache, 'get', path.lstrip('/'))
                 if not os.path.exists(cached_output):
-                    rl = rl[3:]
+                    translator = self._parse(rl)
                     d = os.path.dirname(p)
                     # begin hack
                     old_cwd = os.getcwd()
                     os.chdir(d)
-                    os.system(rl)
+                    os.system(translator.command)
                     os.chdir(old_cwd)
-                    pathlib.Path(os.path.dirname(cached_output)).mkdir(parents = True, exist_ok = True)
-                    shutil.move(os.path.join(d, 'out'), cached_output)
+                    self._mkparents(cached_output)
+                    shutil.move(os.path.join(d, translator.output_filename), cached_output)
                     # end hack
                 p = cached_output
         return p
@@ -32,13 +66,14 @@ class FilterFS(Operations):
     def readdir(self, path, fh):
         yield '.'
         yield '..'
-        if os.path.isdir(self._original(path)):
-            for d in os.listdir(self._original(path)):
+        orig = self._get("readdir", path)
+        if os.path.isdir(orig):
+            for d in os.listdir(orig):
                 yield d
 
     # directory, file etc.
     def getattr(self, path, file_handle = None):
-        st = os.lstat(self._original(path))
+        st = os.lstat(self._peek("getattr", path))
         return {
             'st_mode': st.st_mode, # 0o100775 file, 0o40775 dir
             #'st_ino': 42,
@@ -46,7 +81,7 @@ class FilterFS(Operations):
             'st_nlink': st.st_nlink,
             'st_uid': st.st_uid,
             'st_gid': st.st_gid,
-            'st_size': st.st_size,
+            'st_size': 999999999999999, #st.st_size, # TODO: max file size
             'st_atime': st.st_atime,
             'st_mtime': st.st_mtime,
             'st_ctime': st.st_ctime,
@@ -54,7 +89,7 @@ class FilterFS(Operations):
     
     # file
     def open(self, path, flags):
-        return os.open(self._original(path), flags)
+        return os.open(self._get("open", path), flags)
     def read(self, path, length, offset, file_handle):
         os.lseek(file_handle, offset, os.SEEK_SET)
         return os.read(file_handle, length)

source/foo.mp3

@@ -1 +1 @@
-/!/lame -vbr -b 240 foo.ogg output.mp3; mv output.mp3 out
+/!/100644/out.mp3/ffmpeg -i foo.ogg -acodec libmp3lame -map_metadata 0:s:0 out.mp3

source/some_dir/bbb

@@ -1 +1 @@
-/!/tr '[:lower:]' '[:upper:'] < aaa > out
+/!/10644/out/tr '[:lower:]' '[:upper:'] < aaa > out