source/blender/gpu/GPU_index_buffer.h

@@ -89,13 +89,11 @@ void GPU_indexbuf_create_subrange_in_place(GPUIndexBuf *elem,
                                            uint length);
 
 /**
- * (Download and) return a pointer containing the data of an index buffer.
+ * (Download and) fill data with the contents of the index buffer.
  *
- * Note that the returned pointer is still owned by the driver. To get an
- * local copy, use `GPU_indexbuf_unmap` after calling `GPU_indexbuf_read`.
+ * NOTE: caller is responsible to reserve enough memory.
  */
-const uint32_t *GPU_indexbuf_read(GPUIndexBuf *elem);
-uint32_t *GPU_indexbuf_unmap(const GPUIndexBuf *elem, const uint32_t *mapped_buffer);
+void GPU_indexbuf_read(GPUIndexBuf *elem, uint32_t *data);
 
 void GPU_indexbuf_discard(GPUIndexBuf *elem);
 

source/blender/gpu/GPU_vertex_buffer.h

@@ -64,13 +64,10 @@ GPUVertBuf *GPU_vertbuf_create_with_format_ex(const GPUVertFormat *, GPUUsageTyp
   GPU_vertbuf_create_with_format_ex(format, GPU_USAGE_STATIC)
 
 /**
- * (Download and) return a pointer containing the data of a vertex buffer.
- *
- * Note that the returned pointer is still owned by the driver. To get an
- * local copy, use `GPU_vertbuf_unmap` after calling `GPU_vertbuf_read`.
+ * (Download and) fill data with the data from the vertex buffer.
+ * NOTE: caller is responsible to reserve enough memory of the data parameter.
  */
-const void *GPU_vertbuf_read(GPUVertBuf *verts);
-void *GPU_vertbuf_unmap(const GPUVertBuf *verts, const void *mapped_data);
+void GPU_vertbuf_read(GPUVertBuf *verts, void *data);
 /** Same as discard but does not free. */
 void GPU_vertbuf_clear(GPUVertBuf *verts);
 void GPU_vertbuf_discard(GPUVertBuf *);

source/blender/gpu/intern/gpu_index_buffer.cc

@@ -399,14 +399,6 @@ void IndexBuf::squeeze_indices_short(uint min_idx,
   }
 }
 
-uint32_t *IndexBuf::unmap(const uint32_t *mapped_memory) const
-{
-  size_t size = size_get();
-  uint32_t *result = static_cast<uint32_t *>(MEM_mallocN(size, __func__));
-  memcpy(result, mapped_memory, size);
-  return result;
-}
-
 }  // namespace blender::gpu
 
 /** \} */
@@ -456,14 +448,9 @@ void GPU_indexbuf_create_subrange_in_place(GPUIndexBuf *elem,
   unwrap(elem)->init_subrange(unwrap(elem_src), start, length);
 }
 
-const uint32_t *GPU_indexbuf_read(GPUIndexBuf *elem)
+void GPU_indexbuf_read(GPUIndexBuf *elem, uint32_t *data)
 {
-  return unwrap(elem)->read();
-}
-
-uint32_t *GPU_indexbuf_unmap(const GPUIndexBuf *elem, const uint32_t *mapped_buffer)
-{
-  return unwrap(elem)->unmap(mapped_buffer);
+  return unwrap(elem)->read(data);
 }
 
 void GPU_indexbuf_discard(GPUIndexBuf *elem)

source/blender/gpu/intern/gpu_index_buffer_private.hh

@@ -98,8 +98,7 @@ class IndexBuf {
 
   virtual void bind_as_ssbo(uint binding) = 0;
 
-  virtual const uint32_t *read() const = 0;
-  uint32_t *unmap(const uint32_t *mapped_memory) const;
+  virtual void read(uint32_t *data) const = 0;
 
   virtual void update_sub(uint start, uint len, const void *data) = 0;
 

source/blender/gpu/intern/gpu_vertex_buffer.cc

@@ -153,14 +153,9 @@ GPUVertBuf *GPU_vertbuf_duplicate(GPUVertBuf *verts_)
   return wrap(unwrap(verts_)->duplicate());
 }
 
-const void *GPU_vertbuf_read(GPUVertBuf *verts)
+void GPU_vertbuf_read(GPUVertBuf *verts, void *data)
 {
-  return unwrap(verts)->read();
-}
-
-void *GPU_vertbuf_unmap(const GPUVertBuf *verts, const void *mapped_data)
-{
-  return unwrap(verts)->unmap(mapped_data);
+  unwrap(verts)->read(data);
 }
 
 void GPU_vertbuf_clear(GPUVertBuf *verts)

source/blender/gpu/intern/gpu_vertex_buffer_private.hh

@@ -94,8 +94,7 @@ class VertBuf {
   }
 
   virtual void update_sub(uint start, uint len, const void *data) = 0;
-  virtual const void *read() const = 0;
-  virtual void *unmap(const void *mapped_data) const = 0;
+  virtual void read(void *data) const = 0;
 
  protected:
   virtual void acquire_data() = 0;

source/blender/gpu/metal/mtl_index_buffer.hh

@@ -48,7 +48,7 @@ class MTLIndexBuf : public IndexBuf {
   ~MTLIndexBuf();
 
   void bind_as_ssbo(uint32_t binding) override;
-  const uint32_t *read() const override;
+  void read(uint32_t *data) const override;
 
   void upload_data() override;
   void update_sub(uint32_t start, uint32_t len, const void *data) override;

source/blender/gpu/metal/mtl_index_buffer.mm

@@ -46,16 +46,13 @@ void MTLIndexBuf::bind_as_ssbo(uint32_t binding)
   MTL_LOG_WARNING("MTLIndexBuf::bind_as_ssbo not yet implemented!\n");
 }
 
-const uint32_t *MTLIndexBuf::read() const
+void MTLIndexBuf::read(uint32_t *data) const
 {
   if (ibo_ != nullptr) {
-
-    /* Return host pointer. */
-    void *data = ibo_->get_host_ptr();
-    return static_cast<uint32_t *>(data);
+    void *host_ptr = ibo_->get_host_ptr();
+    memcpy(data, host_ptr, size_get());
   }
   BLI_assert(false && "Index buffer not ready to be read.");
-  return nullptr;
 }
 
 void MTLIndexBuf::upload_data()

source/blender/gpu/metal/mtl_vertex_buffer.hh

@@ -56,8 +56,7 @@ class MTLVertBuf : public VertBuf {
 
   void update_sub(uint start, uint len, const void *data) override;
 
-  const void *read() const override;
-  void *unmap(const void *mapped_data) const override;
+  void read(void *data) const override;
 
   void wrap_handle(uint64_t handle) override;
 

source/blender/gpu/metal/mtl_vertex_buffer.mm

@@ -328,21 +328,12 @@ void MTLVertBuf::bind_as_texture(uint binding)
   GPU_texture_bind(buffer_texture_, binding);
 }
 
-const void *MTLVertBuf::read() const
+void MTLVertBuf::read(void *data) const
 {
   BLI_assert(vbo_ != nullptr);
   BLI_assert(usage_ != GPU_USAGE_DEVICE_ONLY);
-  void *return_ptr = vbo_->get_host_ptr();
-  BLI_assert(return_ptr != nullptr);
-
-  return return_ptr;
-}
-
-void *MTLVertBuf::unmap(const void *mapped_data) const
-{
-  void *result = MEM_mallocN(alloc_size_, __func__);
-  memcpy(result, mapped_data, alloc_size_);
-  return result;
+  void *host_ptr = vbo_->get_host_ptr();
+  memcpy(data, host_ptr, alloc_size_);
 }
 
 void MTLVertBuf::wrap_handle(uint64_t handle)

source/blender/gpu/opengl/gl_index_buffer.cc

@@ -46,12 +46,12 @@ void GLIndexBuf::bind_as_ssbo(uint binding)
   glBindBufferBase(GL_SHADER_STORAGE_BUFFER, binding, ibo_id_);
 }
 
-const uint32_t *GLIndexBuf::read() const
+void GLIndexBuf::read(uint32_t *data) const
 {
   BLI_assert(is_active());
-  void *data = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_READ_ONLY);
-  uint32_t *result = static_cast<uint32_t *>(data);
-  return result;
+  void *buffer = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_READ_ONLY);
+  memcpy(data, buffer, size_get());
+  glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
 }
 
 bool GLIndexBuf::is_active() const

source/blender/gpu/opengl/gl_index_buffer.hh

@@ -29,7 +29,7 @@ class GLIndexBuf : public IndexBuf {
   void bind();
   void bind_as_ssbo(uint binding) override;
 
-  const uint32_t *read() const override;
+  void read(uint32_t *data) const override;
 
   void *offset_ptr(uint additional_vertex_offset) const
   {

source/blender/gpu/opengl/gl_vertex_buffer.cc

@@ -125,18 +125,12 @@ void GLVertBuf::bind_as_texture(uint binding)
   GPU_texture_bind(buffer_texture_, binding);
 }
 
-const void *GLVertBuf::read() const
+void GLVertBuf::read(void *data) const
 {
   BLI_assert(is_active());
   void *result = glMapBuffer(GL_ARRAY_BUFFER, GL_READ_ONLY);
-  return result;
-}
-
-void *GLVertBuf::unmap(const void *mapped_data) const
-{
-  void *result = MEM_mallocN(vbo_size_, __func__);
-  memcpy(result, mapped_data, vbo_size_);
-  return result;
+  memcpy(data, result, size_used_get());
+  glUnmapBuffer(GL_ARRAY_BUFFER);
 }
 
 void GLVertBuf::wrap_handle(uint64_t handle)

source/blender/gpu/opengl/gl_vertex_buffer.hh

@@ -37,8 +37,7 @@ class GLVertBuf : public VertBuf {
 
   void update_sub(uint start, uint len, const void *data) override;
 
-  const void *read() const override;
-  void *unmap(const void *mapped_data) const override;
+  void read(void *data) const override;
 
   void wrap_handle(uint64_t handle) override;
 

source/blender/gpu/tests/gpu_shader_test.cc

@@ -151,8 +151,8 @@ static void test_gpu_shader_compute_vbo()
   GPU_memory_barrier(GPU_BARRIER_SHADER_STORAGE);
 
   /* Download the vertex buffer. */
-  const float *data = static_cast<const float *>(GPU_vertbuf_read(vbo));
-  ASSERT_NE(data, nullptr);
+  float data[SIZE * 4];
+  GPU_vertbuf_read(vbo, data);
   for (int index = 0; index < SIZE; index++) {
     float expected_value = index;
     EXPECT_FLOAT_EQ(data[index * 4 + 0], expected_value);
@@ -195,8 +195,8 @@ static void test_gpu_shader_compute_ibo()
   GPU_memory_barrier(GPU_BARRIER_SHADER_STORAGE);
 
   /* Download the index buffer. */
-  const uint32_t *data = GPU_indexbuf_read(ibo);
-  ASSERT_NE(data, nullptr);
+  uint32_t data[SIZE];
+  GPU_indexbuf_read(ibo, data);
   for (int index = 0; index < SIZE; index++) {
     uint32_t expected = index;
     EXPECT_EQ(data[index], expected);

source/blender/gpu/vulkan/vk_index_buffer.cc

@@ -17,9 +17,8 @@ void VKIndexBuffer::bind_as_ssbo(uint /*binding*/)
 {
 }
 
-const uint32_t *VKIndexBuffer::read() const
+void VKIndexBuffer::read(uint32_t * /*data*/) const
 {
-  return 0;
 }
 
 void VKIndexBuffer::update_sub(uint /*start*/, uint /*len*/, const void * /*data*/)

source/blender/gpu/vulkan/vk_index_buffer.hh

@@ -17,7 +17,7 @@ class VKIndexBuffer : public IndexBuf {
 
   void bind_as_ssbo(uint binding) override;
 
-  const uint32_t *read() const override;
+  void read(uint32_t *data) const override;
 
   void update_sub(uint start, uint len, const void *data) override;
 

source/blender/gpu/vulkan/vk_vertex_buffer.cc

@@ -32,14 +32,8 @@ void VKVertexBuffer::update_sub(uint /*start*/, uint /*len*/, const void * /*dat
 {
 }
 
-const void *VKVertexBuffer::read() const
+void VKVertexBuffer::read(void * /*data*/) const
 {
-  return nullptr;
-}
-
-void *VKVertexBuffer::unmap(const void * /*mapped_data*/) const
-{
-  return nullptr;
 }
 
 void VKVertexBuffer::acquire_data()

source/blender/gpu/vulkan/vk_vertex_buffer.hh

@@ -20,8 +20,7 @@ class VKVertexBuffer : public VertBuf {
   void wrap_handle(uint64_t handle) override;
 
   void update_sub(uint start, uint len, const void *data) override;
-  const void *read() const override;
-  void *unmap(const void *mapped_data) const override;
+  void read(void *data) const override;
 
  protected:
   void acquire_data() override;