1 files changed, 74 insertions, 0 deletions
diff --git a/src/py/libcamera/utils/MappedFrameBuffer.py b/src/py/libcamera/utils/MappedFrameBuffer.py
new file mode 100644
index 00000000..e7dd16ec
--- /dev/null
+++ b/src/py/libcamera/utils/MappedFrameBuffer.py
@@ -0,0 +1,74 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+# Copyright (C) 2022, Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
+
+class MappedFrameBuffer:
+    def __init__(self, fb):
+        self.__fb = fb
+
+    def __enter__(self):
+        import os
+        import mmap
+
+        fb = self.__fb
+
+        # Collect information about the buffers
+
+        bufinfos = {}
+
+        for i in range(fb.num_planes):
+            fd = fb.fd(i)
+
+            if fd not in bufinfos:
+                buflen = os.lseek(fd, 0, os.SEEK_END)
+                bufinfos[fd] = {'maplen': 0, 'buflen': buflen}
+            else:
+                buflen = bufinfos[fd]['buflen']
+
+            if fb.offset(i) > buflen or fb.offset(i) + fb.length(i) > buflen:
+                raise RuntimeError(f'plane is out of buffer: buffer length={buflen}, ' +
+                                   f'plane offset={fb.offset(i)}, plane length={fb.length(i)}')
+
+            bufinfos[fd]['maplen'] = max(bufinfos[fd]['maplen'], fb.offset(i) + fb.length(i))
+
+        # mmap the buffers
+
+        maps = []
+
+        for fd, info in bufinfos.items():
+            map = mmap.mmap(fd, info['maplen'], mmap.MAP_SHARED, mmap.PROT_READ | mmap.PROT_WRITE)
+            info['map'] = map
+            maps.append(map)
+
+        self.__maps = tuple(maps)
+
+        # Create memoryviews for the planes
+
+        planes = []
+
+        for i in range(fb.num_planes):
+            fd = fb.fd(i)
+            info = bufinfos[fd]
+
+            mv = memoryview(info['map'])
+
+            start = fb.offset(i)
+            end = fb.offset(i) + fb.length(i)
+
+            mv = mv[start:end]
+
+            planes.append(mv)
+
+        self.__planes = tuple(planes)
+
+        return self
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        for p in self.__planes:
+            p.release()
+
+        for mm in self.__maps:
+            mm.close()
+
+    @property
+    def planes(self):
+        return self.__planes