Add experimental support for get_mapped_range (#522)

Author: almarklein

wgpu/backends/wgpu_native/_api.py

@@ -1759,7 +1759,8 @@ def callback(status_, user_data_p):
             self._internal, map_mode, offset, size, callback, ffi.NULL
         )
 
-        # Let it do some cycles
+        # Wait for the queue to process all tasks (including the mapping of the buffer).
+        # Also see WebGPU's onSubmittedWorkDone() and C's WGPUQueueWorkDoneCallback.
         self._device._poll()
 
         if status != 0:  # no-cover
@@ -1863,6 +1864,31 @@ def write_mapped(self, data, buffer_offset=None, size=None):
         # Copy data
         src_m[:] = data
 
+    def _experimental_get_mapped_range(self, buffer_offset=None, size=None):
+        """Undocumented and experimental. This API can change or be
+        removed without notice. Just here so we can benchmark this
+        approach. Returns a mapped memoryview object that can be written
+        to. Note that once the buffer unmaps, this memoryview object
+        becomes unusable, and accessing it may result in a segfault.
+        """
+        # Can we even write?
+        if self._map_state != enums.BufferMapState.mapped:
+            raise RuntimeError("Can only write to a buffer if its mapped.")
+
+        offset, size = self._check_range(buffer_offset, size)
+        if offset < self._mapped_status[0] or (offset + size) > self._mapped_status[1]:
+            raise ValueError(
+                "The range for buffer writing is not contained in the currently mapped range."
+            )
+
+        # Get mapped memoryview
+        # H: void * f(WGPUBuffer buffer, size_t offset, size_t size)
+        src_ptr = libf.wgpuBufferGetMappedRange(self._internal, offset, size)
+        src_address = int(ffi.cast("intptr_t", src_ptr))
+        src_m = get_memoryview_from_address(src_address, size)
+
+        return src_m
+
     def destroy(self):
         # NOTE: destroy means that the wgpu-core object gets into a destroyed
         # state. The wgpu-core object still exists. So destroying is quite

wgpu/resources/codegen_report.md

@@ -20,14 +20,14 @@
 * Diffs for GPUQueue: add read_buffer, add read_texture, hide copy_external_image_to_texture
 * Validated 37 classes, 114 methods, 44 properties
 ### Patching API for backends/wgpu_native/_api.py
-* Validated 37 classes, 110 methods, 0 properties
+* Validated 37 classes, 111 methods, 0 properties
 ## Validating backends/wgpu_native/_api.py
 * Enum PipelineErrorReason missing in wgpu.h
 * Enum AutoLayoutMode missing in wgpu.h
 * Enum field VertexFormat.unorm10-10-10-2 missing in wgpu.h
 * Enum CanvasAlphaMode missing in wgpu.h
 * Enum field DeviceLostReason.unknown missing in wgpu.h
 * Wrote 235 enum mappings and 47 struct-field mappings to wgpu_native/_mappings.py
-* Validated 112 C function calls
+* Validated 113 C function calls
 * Not using 91 C functions
 * Validated 76 C structs