refactor negative height check into its own file.

Catch overflow on devices without longint

Author: FoamyGuy

adafruit_imageload/bmp/__init__.py

@@ -50,7 +50,12 @@ def load(file, *, bitmap=None, palette=None):
     # print(bmp_header_length)
     file.seek(0x12)  # Width of the bitmap in pixels
     width = int.from_bytes(file.read(4), "little")
-    height = int.from_bytes(file.read(4), "little")
+    try:
+        height = int.from_bytes(file.read(4), "little")
+    except OverflowError:
+        raise NotImplementedError(
+            "Negative height BMP files are not supported on builds without longint"
+        )
     file.seek(0x1C)  # Number of bits per pixel
     color_depth = int.from_bytes(file.read(2), "little")
     file.seek(0x1E)  # Compression type

adafruit_imageload/bmp/indexed.py

@@ -32,6 +32,8 @@
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_ImageLoad.git"
 
+import sys
+
 
 def load(
     file,
@@ -72,8 +74,14 @@ def load(
             minimum_color_depth *= 2
 
         # convert unsigned int to signed int when height is negative
-        if height > 0x7FFFFFFF:
+        if sys.maxsize > 1073741823:
+            # pylint: disable=import-outside-toplevel
+            from .negative_height_check import negative_height_check
+
             height = height - 4294967296
+
+            # convert unsigned int to signed int when height is negative
+            height = negative_height_check(height)
         bitmap = bitmap(width, abs(height), colors)
         file.seek(data_start)
         line_size = width // (8 // color_depth)

adafruit_imageload/bmp/negative_height_check.py

@@ -0,0 +1,12 @@
+"""
+Check for negative height on the BMP.
+Seperated into it's own file to support builds
+without longint.
+"""
+
+
+def negative_height_check(height):
+    """Check the height return modified if negative."""
+    if height > 0x7FFFFFFF:
+        return height - 4294967296
+    return height