changed from open (SpiderImagePlugin) to peek (MpegImagePlugin), coverage improved to 100%

Tests/test_file_mpeg.py

@@ -6,6 +6,8 @@ import pytest
 
 from PIL import Image, MpegImagePlugin
 
+from unittest.mock import MagicMock, patch
+
 
 def test_identify() -> None:
     # Arrange
@@ -37,3 +39,15 @@ def test_load() -> None:
         # Act / Assert: cannot load
         with pytest.raises(OSError):
             im.load()
+
+
+def test_peek_with_negative_c() -> None:
+    fp = MagicMock()
+
+    return_values = [-1, 255]
+
+    with patch.object(MpegImagePlugin.BitStream, 'next', side_effect=return_values):
+        bitstream = MpegImagePlugin.BitStream(fp)
+        result = bitstream.peek(8)
+
+        assert result == 255

Tests/test_file_spider.py

@@ -173,7 +173,7 @@ def test_seek_no_frame() -> None:
         im.seek(0)
 
 
-def test_save_small_header():
+def test_save_small_header() -> None:
     width, height = 10, 10
     im = Image.new("F", (width, height))
 
@@ -183,12 +183,9 @@ def test_save_small_header():
 
     with patch("PIL.SpiderImagePlugin.makeSpiderHeader", return_value=corrupted_header):
         try:
-            # Attempt to save the image
             im.save(fp, format="SPIDER")
         except OSError as e:
-            # Check if the correct exception is raised
             assert str(e) == "Error creating Spider header"
         else:
-            # If no exception is raised, the test has failed
             assert False, "Expected an OSError due to corrupted header"
 

conftest.py

@@ -5,6 +5,7 @@ import sys
 from PIL import Image
 from PIL import PdfParser
 from PIL import SpiderImagePlugin
+from PIL import MpegImagePlugin
 
 pytest_plugins = ["Tests.helper"]
 
@@ -13,8 +14,8 @@ def calculate_coverage(test_name):
     all_branches = {
         "branches1": Image.branches,
         "branches2": PdfParser.XrefTable.branches,
-        "branches3": SpiderImagePlugin.SpiderImageFile.branches1,
-        "branches4": SpiderImagePlugin.branches2,
+        "branches3": SpiderImagePlugin.branches,
+        "branches4": MpegImagePlugin.branches,
         # Add more
     }
 

src/PIL/MpegImagePlugin.py

@@ -21,8 +21,13 @@ from ._typing import SupportsRead
 #
 # Bitstream parser
 
-
 class BitStream:
+    branches = {
+        "1": False,
+        "2": False,
+        "3": False,
+    }
+
     def __init__(self, fp: SupportsRead[bytes]) -> None:
         self.fp = fp
         self.bits = 0
@@ -33,12 +38,19 @@ class BitStream:
 
     def peek(self, bits: int) -> int:
         while self.bits < bits:
+            BitStream.branches["1"] = True
             c = self.next()
+
             if c < 0:
+                BitStream.branches["2"] = True
                 self.bits = 0
                 continue
+            else:
+                BitStream.branches["3"] = True
+
             self.bitbuffer = (self.bitbuffer << 8) + c
             self.bits += 8
+
         return self.bitbuffer >> (self.bits - bits) & (1 << bits) - 1
 
     def skip(self, bits: int) -> None:

src/PIL/SpiderImagePlugin.py

@@ -56,7 +56,7 @@ def isInt(f):
 
 iforms = [1, 3, -11, -12, -21, -22]
 
-branches2 = {
+branches = {
     "1": False,
     "2": False,
     "3": False,
@@ -106,51 +106,26 @@ class SpiderImageFile(ImageFile.ImageFile):
     format_description = "Spider 2D image"
     _close_exclusive_fp_after_loading = False
 
-    branches1 = {
-        "1": False,
-        "2": False,
-        "3": False,
-        "4": False,
-        "5": False,
-        "6": False,
-        "7": False,
-        "8": False,
-        "9": False,
-        "10": False,
-        "11": False,
-        "12": False,
-        "13": False,
-        "14": False
-    }
-
     def _open(self) -> None:
         # check header
         n = 27 * 4  # read 27 float values
         f = self.fp.read(n)
 
         try:
-            SpiderImageFile.branches1["1"] = True
             self.bigendian = 1
             t = struct.unpack(">27f", f)  # try big-endian first
             hdrlen = isSpiderHeader(t)
 
             if hdrlen == 0:
-                SpiderImageFile.branches1["2"] = True
                 self.bigendian = 0
                 t = struct.unpack("<27f", f)  # little-endian
                 hdrlen = isSpiderHeader(t)
-            else:  # ADDED FOR BRANCH MARKING
-                SpiderImageFile.branches1["3"] = True
 
             if hdrlen == 0:
-                SpiderImageFile.branches1["4"] = True
                 msg = "not a valid Spider file"
                 raise SyntaxError(msg)
-            else:  # ADDED FOR BRANCH MARKING
-                SpiderImageFile.branches1["5"] = True
 
         except struct.error as e:
-            SpiderImageFile.branches1["6"] = True
             msg = "not a valid Spider file"
             raise SyntaxError(msg) from e
 
@@ -158,23 +133,18 @@ class SpiderImageFile(ImageFile.ImageFile):
         iform = int(h[5])
 
         if iform != 1:
-            SpiderImageFile.branches1["7"] = True
             msg = "not a Spider 2D image"
             raise SyntaxError(msg)
-        else:  # ADDED FOR BRANCH MARKING
-            SpiderImageFile.branches1["8"] = True
 
         self._size = int(h[12]), int(h[2])  # size in pixels (width, height)
         self.istack = int(h[24])
         self.imgnumber = int(h[27])
 
         if self.istack == 0 and self.imgnumber == 0:
-            SpiderImageFile.branches1["9"] = True
             # stk=0, img=0: a regular 2D image
             offset = hdrlen
             self._nimages = 1
         elif self.istack > 0 and self.imgnumber == 0:
-            SpiderImageFile.branches1["10"] = True
             # stk>0, img=0: Opening the stack for the first time
             self.imgbytes = int(h[12]) * int(h[2]) * 4
             self.hdrlen = hdrlen
@@ -183,20 +153,16 @@ class SpiderImageFile(ImageFile.ImageFile):
             offset = hdrlen * 2
             self.imgnumber = 1
         elif self.istack == 0 and self.imgnumber > 0:
-            SpiderImageFile.branches1["11"] = True
             # stk=0, img>0: an image within the stack
             offset = hdrlen + self.stkoffset
             self.istack = 2  # So Image knows it's still a stack
         else:
-            SpiderImageFile.branches1["12"] = True
             msg = "inconsistent stack header values"
             raise SyntaxError(msg)
 
         if self.bigendian:
-            SpiderImageFile.branches1["13"] = True
             self.rawmode = "F;32BF"
         else:
-            SpiderImageFile.branches1["14"] = True
             self.rawmode = "F;32F"
         self._mode = "F"
 
@@ -313,18 +279,18 @@ def makeSpiderHeader(im: Image.Image) -> list[bytes]:
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
     if im.mode[0] != "F":
-        branches2["1"] = True
+        branches["1"] = True
         im = im.convert("F")
     else:
-        branches2["2"] = True
+        branches["2"] = True
 
     hdr = makeSpiderHeader(im)
     if len(hdr) < 256:
-        branches2["3"] = True
+        branches["3"] = True
         msg = "Error creating Spider header"
         raise OSError(msg)
     else:
-        branches2["4"] = True
+        branches["4"] = True
 
     # write the SPIDER header
     fp.writelines(hdr)