Fix #6

.github/workflows/build.yaml

@@ -22,12 +22,16 @@ jobs:
           for i in {1..100};do
             echo "hello world" >> test/test.txt
           done
-          dd if=/dev/zero of=test.ext4 count=1024 bs=1024
-          mkfs.ext4 test.ext4 -d test
+          dd if=/dev/zero of=test.ext4.tmp count=1024 bs=1024
+          mkfs.ext4 test.ext4.tmp -d test
+          echo -n F > test.ext4
+          cat test.ext4.tmp >> test.ext4
       - uses: actions/upload-artifact@v4
         with:
           name: test.ext4
-          path: test.ext4
+          path: |
+            test.ext4
+            test.ext4.tmp
           if-no-files-found: error
   test:
     name: Test on ${{ matrix.os }} python ${{ matrix.python }}

ext4/struct.py

@@ -41,8 +41,8 @@ def field_type(cls, name):
         return None
 
     def read_from_volume(self):
-        self.volume.stream.seek(self.offset)
-        data = self.volume.stream.read(sizeof(self))
+        self.volume.seek(self.offset)
+        data = self.volume.read(sizeof(self))
         memmove(addressof(self), data, sizeof(self))
 
     @property

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ext4"
-version = "1.1.0"
+version = "1.1.1"
 authors = [
   { name="Eeems", email="eeems@eeems.email" },
 ]

test.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 import sys
 import ext4
 
@@ -43,9 +44,26 @@ def _assert(source: str):
 test_path_tuple("/test/test", (b"test", b"test"))
 test_path_tuple(b"/test/test", (b"test", b"test"))
 
+offset = os.path.getsize("test.ext4") - os.path.getsize("test.ext4.tmp")
+_assert("offset > 0")
 with open("test.ext4", "rb") as f:
+    try:
+        print("check MagicError: ", end="")
+        _ = ext4.Volume(f, offset=0)
+        FAILED = True
+        print("fail")
+        print("  MagicError not raised")
+    except ext4.struct.MagicError:
+        print("pass")
+
+    except Exception as e:
+        FAILED = True
+        print("fail")
+        print("  ", end="")
+        print(e)
+
     # Extract specific file
-    volume = ext4.Volume(f, offset=0)
+    volume = ext4.Volume(f, offset=offset)
     inode = cast(ext4.File, volume.inode_at("/test.txt"))
     _assert("isinstance(inode, ext4.File)")
     b = inode.open()

test.sh

@@ -20,8 +20,10 @@ if ! [ -f test.ext4 ];then
   for i in {1..100};do
     echo "hello world" >> "$tmp_dir"/test.txt
   done
-  dd if=/dev/zero of=test.ext4 count=1024 bs=1024
-  trap "rm test.ext4" EXIT
-  mkfs.ext4 test.ext4 -d "$tmp_dir"
+  trap "rm -f test.ext4{,.tmp}" EXIT
+  dd if=/dev/zero of=test.ext4.tmp count=1024 bs=1024
+  mkfs.ext4 test.ext4.tmp -d "$tmp_dir"
+  echo -n F > test.ext4
+  cat test.ext4.tmp >> test.ext4
 fi
 python test.py