WIP Allow new-style buffer interfaces to be read/write

src/PIL/Image.py

@@ -3182,7 +3182,7 @@ def frombuffer(
                 from . import ImagePalette
 
                 im.palette = ImagePalette.ImagePalette("RGB", im.im.getpalette("RGB"))
-            im.readonly = 1
+            im.readonly = im.im.readonly
             return im
 
     return frombytes(mode, size, data, decoder_name, args)

src/PIL/ImageFile.py

@@ -229,7 +229,7 @@ def load(self):
                     self.im = Image.core.map_buffer(
                         self.map, self.size, decoder_name, offset, args
                     )
-                    readonly = 1
+                    readonly = self.im.readonly
                     # After trashing self.im,
                     # we might need to reload the palette data.
                     if self.palette:

src/_imaging.c

@@ -3791,13 +3791,19 @@ _getattr_unsafe_ptrs(ImagingObject *self, void *closure) {
     );
 }
 
+static PyObject *
+_getattr_readonly(ImagingObject *self, void *closure) {
+    return PyLong_FromLong(self->image->readonly);
+}
+
 static struct PyGetSetDef getsetters[] = {
     {"mode", (getter)_getattr_mode},
     {"size", (getter)_getattr_size},
     {"bands", (getter)_getattr_bands},
     {"id", (getter)_getattr_id},
     {"ptr", (getter)_getattr_ptr},
     {"unsafe_ptrs", (getter)_getattr_unsafe_ptrs},
+    {"readonly", (getter)_getattr_readonly},
     {NULL}
 };
 

src/libImaging/Imaging.h

@@ -86,6 +86,7 @@ struct ImagingMemoryInstance {
     int bands;                      /* Number of bands (1, 2, 3, or 4) */
     int xsize;                      /* Image dimension. */
     int ysize;
+    int readonly;
 
     /* Colour palette (for "P" images only) */
     ImagingPalette palette;

src/libImaging/Storage.c

@@ -59,6 +59,7 @@ ImagingNewPrologueSubtype(const char *mode, int xsize, int ysize, int size) {
     im->xsize = xsize;
     im->ysize = ysize;
 
+    im->readonly = 0;
     im->type = IMAGING_TYPE_UINT8;
 
     if (strcmp(mode, "1") == 0) {

src/map.c

@@ -126,6 +126,7 @@ PyImaging_MapBuffer(PyObject *self, PyObject *args) {
         return NULL;
     }
 
+    im->readonly = view.readonly;
     /* setup file pointers */
     if (ystep > 0) {
         for (y = 0; y < ysize; y++) {