[Impeller] remove Buffer type and associated abstractions. (#49702)

Now that the HostBuffer isn't implementing Buffer, there is really no reason to have a Buffer/DeviceBuffer split. make BufferViews use a DeviceBuffer, and remove the data ptr from buffer views (as we can always reach into the device buffer).

Makes some other cleanups too, since we always use a std::shared_ptr<DeviceBuffer>, then we can eliminated the shared_from_this call for AsBufferView by making this a static method.

Author: Jonah Williams

ci/licenses_golden/licenses_flutter

@@ -5050,8 +5050,6 @@ ORIGIN: ../../../flutter/impeller/compiler/utilities.cc + ../../../flutter/LICEN
 ORIGIN: ../../../flutter/impeller/compiler/utilities.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/core/allocator.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/core/allocator.h + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/impeller/core/buffer.cc + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/impeller/core/buffer.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/core/buffer_view.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/core/buffer_view.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/core/capture.cc + ../../../flutter/LICENSE
@@ -7877,8 +7875,6 @@ FILE: ../../../flutter/impeller/compiler/utilities.cc
 FILE: ../../../flutter/impeller/compiler/utilities.h
 FILE: ../../../flutter/impeller/core/allocator.cc
 FILE: ../../../flutter/impeller/core/allocator.h
-FILE: ../../../flutter/impeller/core/buffer.cc
-FILE: ../../../flutter/impeller/core/buffer.h
 FILE: ../../../flutter/impeller/core/buffer_view.cc
 FILE: ../../../flutter/impeller/core/buffer_view.h
 FILE: ../../../flutter/impeller/core/capture.cc

impeller/base/backend_cast.h

@@ -5,8 +5,6 @@
 #ifndef FLUTTER_IMPELLER_BASE_BACKEND_CAST_H_
 #define FLUTTER_IMPELLER_BASE_BACKEND_CAST_H_
 
-#include "flutter/fml/macros.h"
-
 namespace impeller {
 
 template <class Sub, class Base>

impeller/core/BUILD.gn

@@ -8,8 +8,6 @@ impeller_component("core") {
   sources = [
     "allocator.cc",
     "allocator.h",
-    "buffer.cc",
-    "buffer.h",
     "buffer_view.cc",
     "buffer_view.h",
     "capture.cc",

impeller/core/buffer.cc

@@ -5,14 +5,15 @@
 #ifndef FLUTTER_IMPELLER_CORE_BUFFER_VIEW_H_
 #define FLUTTER_IMPELLER_CORE_BUFFER_VIEW_H_
 
-#include "impeller/core/buffer.h"
+#include <memory>
 #include "impeller/core/range.h"
 
 namespace impeller {
 
+class DeviceBuffer;
+
 struct BufferView {
-  std::shared_ptr<const Buffer> buffer;
-  uint8_t* contents;
+  std::shared_ptr<const DeviceBuffer> buffer;
   Range range;
 
   constexpr explicit operator bool() const { return static_cast<bool>(buffer); }

impeller/core/buffer.h

@@ -10,18 +10,13 @@ DeviceBuffer::DeviceBuffer(DeviceBufferDescriptor desc) : desc_(desc) {}
 
 DeviceBuffer::~DeviceBuffer() = default;
 
-// |Buffer|
-std::shared_ptr<const DeviceBuffer> DeviceBuffer::GetDeviceBuffer() const {
-  return shared_from_this();
-}
-
 void DeviceBuffer::Flush(std::optional<Range> range) const {}
 
-BufferView DeviceBuffer::AsBufferView() const {
+// static
+BufferView DeviceBuffer::AsBufferView(std::shared_ptr<DeviceBuffer> buffer) {
   BufferView view;
-  view.buffer = shared_from_this();
-  view.contents = OnGetContents();
-  view.range = {0u, desc_.size};
+  view.buffer = std::move(buffer);
+  view.range = {0u, view.buffer->desc_.size};
   return view;
 }
 

impeller/core/buffer_view.h

@@ -9,16 +9,14 @@
 #include <string>
 
 #include "impeller/core/allocator.h"
-#include "impeller/core/buffer.h"
 #include "impeller/core/buffer_view.h"
 #include "impeller/core/device_buffer_descriptor.h"
 #include "impeller/core/range.h"
 #include "impeller/core/texture.h"
 
 namespace impeller {
 
-class DeviceBuffer : public Buffer,
-                     public std::enable_shared_from_this<DeviceBuffer> {
+class DeviceBuffer {
  public:
   virtual ~DeviceBuffer();
 
@@ -30,16 +28,14 @@ class DeviceBuffer : public Buffer,
 
   virtual bool SetLabel(const std::string& label, Range range) = 0;
 
-  BufferView AsBufferView() const;
+  /// @brief Create a buffer view of this entire buffer.
+  static BufferView AsBufferView(std::shared_ptr<DeviceBuffer> buffer);
 
   virtual std::shared_ptr<Texture> AsTexture(
       Allocator& allocator,
       const TextureDescriptor& descriptor,
       uint16_t row_bytes) const;
 
-  // |Buffer|
-  std::shared_ptr<const DeviceBuffer> GetDeviceBuffer() const;
-
   const DeviceBufferDescriptor& GetDeviceBufferDescriptor() const;
 
   virtual uint8_t* OnGetContents() const = 0;

impeller/core/device_buffer.cc

@@ -41,29 +41,29 @@ void HostBuffer::SetLabel(std::string label) {
 BufferView HostBuffer::Emplace(const void* buffer,
                                size_t length,
                                size_t align) {
-  auto [data, range, device_buffer] = EmplaceInternal(buffer, length, align);
+  auto [range, device_buffer] = EmplaceInternal(buffer, length, align);
   if (!device_buffer) {
     return {};
   }
-  return BufferView{std::move(device_buffer), data, range};
+  return BufferView{std::move(device_buffer), range};
 }
 
 BufferView HostBuffer::Emplace(const void* buffer, size_t length) {
-  auto [data, range, device_buffer] = EmplaceInternal(buffer, length);
+  auto [range, device_buffer] = EmplaceInternal(buffer, length);
   if (!device_buffer) {
     return {};
   }
-  return BufferView{std::move(device_buffer), data, range};
+  return BufferView{std::move(device_buffer), range};
 }
 
 BufferView HostBuffer::Emplace(size_t length,
                                size_t align,
                                const EmplaceProc& cb) {
-  auto [data, range, device_buffer] = EmplaceInternal(length, align, cb);
+  auto [range, device_buffer] = EmplaceInternal(length, align, cb);
   if (!device_buffer) {
     return {};
   }
-  return BufferView{std::move(device_buffer), data, range};
+  return BufferView{std::move(device_buffer), range};
 }
 
 HostBuffer::TestStateQuery HostBuffer::GetStateForTest() {
@@ -74,10 +74,9 @@ HostBuffer::TestStateQuery HostBuffer::GetStateForTest() {
   };
 }
 
-void HostBuffer::MaybeCreateNewBuffer(size_t required_size) {
+void HostBuffer::MaybeCreateNewBuffer() {
   current_buffer_++;
   if (current_buffer_ >= device_buffers_[frame_index_].size()) {
-    FML_DCHECK(required_size <= kAllocatorBlockSize);
     DeviceBufferDescriptor desc;
     desc.size = kAllocatorBlockSize;
     desc.storage_mode = StorageMode::kHostVisible;
@@ -86,10 +85,10 @@ void HostBuffer::MaybeCreateNewBuffer(size_t required_size) {
   offset_ = 0;
 }
 
-std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
-HostBuffer::EmplaceInternal(size_t length,
-                            size_t align,
-                            const EmplaceProc& cb) {
+std::tuple<Range, std::shared_ptr<DeviceBuffer>> HostBuffer::EmplaceInternal(
+    size_t length,
+    size_t align,
+    const EmplaceProc& cb) {
   if (!cb) {
     return {};
   }
@@ -108,28 +107,27 @@ HostBuffer::EmplaceInternal(size_t length,
       cb(device_buffer->OnGetContents());
       device_buffer->Flush(Range{0, length});
     }
-    return std::make_tuple(device_buffer->OnGetContents(), Range{0, length},
-                           device_buffer);
+    return std::make_tuple(Range{0, length}, device_buffer);
   }
 
   auto old_length = GetLength();
   if (old_length + length > kAllocatorBlockSize) {
-    MaybeCreateNewBuffer(length);
+    MaybeCreateNewBuffer();
   }
   old_length = GetLength();
 
   auto current_buffer = GetCurrentBuffer();
-  cb(current_buffer->OnGetContents() + old_length);
+  auto contents = current_buffer->OnGetContents();
+  cb(contents + old_length);
   current_buffer->Flush(Range{old_length, length});
 
   offset_ += length;
-  auto contents = current_buffer->OnGetContents();
-  return std::make_tuple(contents, Range{old_length, length},
-                         std::move(current_buffer));
+  return std::make_tuple(Range{old_length, length}, std::move(current_buffer));
 }
 
-std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
-HostBuffer::EmplaceInternal(const void* buffer, size_t length) {
+std::tuple<Range, std::shared_ptr<DeviceBuffer>> HostBuffer::EmplaceInternal(
+    const void* buffer,
+    size_t length) {
   // If the requested allocation is bigger than the block size, create a one-off
   // device buffer and write to that.
   if (length > kAllocatorBlockSize) {
@@ -146,38 +144,37 @@ HostBuffer::EmplaceInternal(const void* buffer, size_t length) {
         return {};
       }
     }
-    return std::make_tuple(device_buffer->OnGetContents(), Range{0, length},
-                           device_buffer);
+    return std::make_tuple(Range{0, length}, device_buffer);
   }
 
   auto old_length = GetLength();
   if (old_length + length > kAllocatorBlockSize) {
-    MaybeCreateNewBuffer(length);
+    MaybeCreateNewBuffer();
   }
   old_length = GetLength();
 
   auto current_buffer = GetCurrentBuffer();
+  auto contents = current_buffer->OnGetContents();
   if (buffer) {
-    ::memmove(current_buffer->OnGetContents() + old_length, buffer, length);
+    ::memmove(contents + old_length, buffer, length);
     current_buffer->Flush(Range{old_length, length});
   }
   offset_ += length;
-  auto contents = current_buffer->OnGetContents();
-  return std::make_tuple(contents, Range{old_length, length},
-                         std::move(current_buffer));
+  return std::make_tuple(Range{old_length, length}, std::move(current_buffer));
 }
 
-std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
+std::tuple<Range, std::shared_ptr<DeviceBuffer>>
 HostBuffer::EmplaceInternal(const void* buffer, size_t length, size_t align) {
   if (align == 0 || (GetLength() % align) == 0) {
     return EmplaceInternal(buffer, length);
   }
 
   {
-    auto [buffer, range, device_buffer] =
-        EmplaceInternal(nullptr, align - (GetLength() % align));
-    if (!buffer) {
-      return {};
+    auto padding = align - (GetLength() % align);
+    if (offset_ + padding < kAllocatorBlockSize) {
+      offset_ += padding;
+    } else {
+      MaybeCreateNewBuffer();
     }
   }
 

impeller/core/device_buffer.h

@@ -12,7 +12,7 @@
 #include <string>
 #include <type_traits>
 
-#include "impeller/core/buffer.h"
+#include "impeller/core/allocator.h"
 #include "impeller/core/buffer_view.h"
 #include "impeller/core/platform.h"
 
@@ -134,18 +134,18 @@ class HostBuffer {
   TestStateQuery GetStateForTest();
 
  private:
-  [[nodiscard]] std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
+  [[nodiscard]] std::tuple<Range, std::shared_ptr<DeviceBuffer>>
   EmplaceInternal(const void* buffer, size_t length);
 
-  std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
+  std::tuple<Range, std::shared_ptr<DeviceBuffer>>
   EmplaceInternal(size_t length, size_t align, const EmplaceProc& cb);
 
-  std::tuple<uint8_t*, Range, std::shared_ptr<DeviceBuffer>>
+  std::tuple<Range, std::shared_ptr<DeviceBuffer>>
   EmplaceInternal(const void* buffer, size_t length, size_t align);
 
   size_t GetLength() const { return offset_; }
 
-  void MaybeCreateNewBuffer(size_t required_size);
+  void MaybeCreateNewBuffer();
 
   std::shared_ptr<DeviceBuffer>& GetCurrentBuffer() {
     return device_buffers_[frame_index_][current_buffer_];