[EP API] header-only adapter for EP API

Author: fs-eire

include/onnxruntime/ep/README.md

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+## EP adapter
+
+This folder contains a set of C++ header files. They are used specifically for allowing ONNX Runtime internal kernel-based EPs to use the plugin-style EP API while keep minimal changes to existing code.
+
+### Usage
+
+Make sure to include "ep/_pch.h" for all source code in the implementation. Using PCH is recommended.

include/onnxruntime/ep/_pch.h

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#include "api.h"
+#include "common.h"
+
+// This header is only used when building WebGPU/CUDA EP as a shared library.
+//
+// This header file is used as a precompiled header so it is always included first.
+
+#pragma push_macro("ORT_EP_API_ADAPTER_HEADER_INCLUDED")
+#define ORT_EP_API_ADAPTER_HEADER_INCLUDED
+
+#include "adapter/allocator.h"
+#include "adapter/logging.h"
+#include "adapter/ep.h"
+#include "adapter/kernel_registry.h"
+
+#pragma pop_macro("ORT_EP_API_ADAPTER_HEADER_INCLUDED")
+
+//
+// EP specific using declarations
+//
+
+#define EP_SPECIFIC_USING_DECLARATIONS                                              \
+  using FuncManager = onnxruntime::ep::adapter::FuncManager;                        \
+  using KernelCreatePtrFn = onnxruntime::ep::adapter::KernelCreatePtrFn;            \
+  using KernelDefBuilder = onnxruntime::ep::adapter::KernelDefBuilder;              \
+  using KernelRegistry = onnxruntime::ep::adapter::KernelRegistry;                  \
+  using KernelCreateInfo = onnxruntime::ep::adapter::KernelCreateInfo;              \
+  using BuildKernelCreateInfoFn = onnxruntime::ep::adapter::KernelCreateInfo (*)(); \
+  using OpKernelInfo = onnxruntime::ep::adapter::OpKernelInfo;                      \
+  using OpKernelContext = onnxruntime::ep::adapter::OpKernelContext;                \
+  using OpKernel = onnxruntime::ep::adapter::OpKernel;                              \
+  using DataTransferManager = onnxruntime::ep::adapter::DataTransferManager;        \
+  namespace logging {                                                               \
+  using Logger = onnxruntime::ep::adapter::Logger;                                  \
+  }
+
+namespace onnxruntime {
+namespace webgpu {
+EP_SPECIFIC_USING_DECLARATIONS
+}  // namespace webgpu
+namespace cuda {
+EP_SPECIFIC_USING_DECLARATIONS
+}  // namespace cuda
+
+#ifndef DISABLE_CONTRIB_OPS
+namespace contrib {
+namespace webgpu {
+EP_SPECIFIC_USING_DECLARATIONS
+}  // namespace webgpu
+namespace cuda {
+EP_SPECIFIC_USING_DECLARATIONS
+}  // namespace cuda
+}  // namespace contrib
+#endif
+
+}  // namespace onnxruntime

include/onnxruntime/ep/adapter/allocator.h

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#include "core/framework/allocator.h"
+
+namespace onnxruntime {
+namespace ep {
+namespace adapter {
+
+/// <summary>
+/// A bridge class between the EP API OrtAllocator and an IAllocator implementation.
+/// </summary>
+class Allocator : public OrtAllocator {
+ public:
+  explicit Allocator(const OrtMemoryInfo* memory_info, AllocatorPtr impl)
+      : OrtAllocator{}, memory_info_(memory_info), impl_(impl) {
+    version = ORT_API_VERSION;
+    Alloc = AllocImpl;
+    Free = FreeImpl;
+    Info = InfoImpl;
+  }
+
+ private:
+  static void* ORT_API_CALL AllocImpl(OrtAllocator* this_ptr, size_t size) noexcept {
+    auto* allocator = static_cast<Allocator*>(this_ptr);
+    return allocator->impl_->Alloc(size);
+  }
+
+  static void ORT_API_CALL FreeImpl(OrtAllocator* this_ptr, void* p) noexcept {
+    auto* allocator = static_cast<Allocator*>(this_ptr);
+    allocator->impl_->Free(p);
+  }
+
+  static const OrtMemoryInfo* ORT_API_CALL InfoImpl(const OrtAllocator* this_ptr) noexcept {
+    auto* allocator = static_cast<const Allocator*>(this_ptr);
+    return allocator->memory_info_;
+  }
+
+  const OrtMemoryInfo* memory_info_;
+  AllocatorPtr impl_;
+};
+
+}  // namespace adapter
+}  // namespace ep
+}  // namespace onnxruntime

include/onnxruntime/ep/adapter/data_transfer_manager.h

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#if !defined(ORT_EP_API_ADAPTER_HEADER_INCLUDED)
+#error "This header should not be included directly. Include ep/_pch.h instead."
+#endif
+
+#include "core/common/status.h"
+#include "core/common/common.h"
+#include "core/framework/data_transfer.h"
+#include "core/framework/tensor.h"
+
+namespace onnxruntime {
+namespace ep {
+namespace adapter {
+
+/// <summary>
+/// An adapter class partially implementing the facade of `onnxruntime::DataTransferManager`.
+/// </summary>
+struct DataTransferManager {
+  explicit DataTransferManager(std::unique_ptr<IDataTransfer> impl) : impl_{std::move(impl)} {}
+
+  common::Status CopyTensor(const Tensor& src, Tensor& dst) const {
+    if (src.Shape().Size() != dst.Shape().Size()) {
+      return ORT_MAKE_STATUS(ONNXRUNTIME,
+                             FAIL,
+                             "Tensor size mismatch: source tensor size is ",
+                             src.Shape().Size(),
+                             ", destination tensor size is ",
+                             dst.Shape().Size());
+    }
+
+    if (impl_->CanCopy(src.Location().device, dst.Location().device)) {
+      return impl_->CopyTensor(src, dst);
+    }
+
+    return ORT_MAKE_STATUS(ONNXRUNTIME,
+                           FAIL,
+                           "There's no data transfer registered for copying tensors from ",
+                           src.Location().device.ToString(),
+                           " to ",
+                           dst.Location().device.ToString());
+  }
+
+ private:
+  ORT_DISALLOW_COPY_ASSIGNMENT_AND_MOVE(DataTransferManager);
+  std::unique_ptr<IDataTransfer> impl_;
+};
+
+}  // namespace adapter
+}  // namespace ep
+}  // namespace onnxruntime

include/onnxruntime/ep/adapter/ep.h

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#if !defined(ORT_EP_API_ADAPTER_HEADER_INCLUDED)
+#error "This header should not be included directly. Include ep/_pch.h instead."
+#endif
+
+#include "data_transfer_manager.h"
+
+#include "core/framework/execution_provider.h"
+
+namespace onnxruntime {
+namespace ep {
+namespace adapter {
+
+/// <summary>
+/// Wrapper around IExecutionProvider to expose via OrtEp.
+/// </summary>
+class Ep : public OrtEp {
+ protected:
+  explicit Ep(IExecutionProvider* impl, AllocatorPtr temp_space_cpu_allocator, AllocatorPtr temp_space_allocator)
+      : OrtEp{},
+        impl_(impl),
+        data_transfer_manager_{impl->GetDataTransfer()},
+        profiler_{impl->GetProfiler()},
+        temp_space_cpu_allocator_{temp_space_cpu_allocator},
+        temp_space_allocator_{temp_space_allocator} {
+  }
+
+ public:
+  inline IExecutionProvider* EpImpl() const noexcept {
+    return impl_.get();
+  }
+  inline const DataTransferManager& GetDataTransferManager() const noexcept {
+    return data_transfer_manager_;
+  }
+  [[nodiscard]] Status GetTempSpaceCPUAllocator(AllocatorPtr* output) const {
+    *output = temp_space_cpu_allocator_;
+    return Status::OK();
+  }
+  [[nodiscard]] Status GetTempSpaceAllocator(AllocatorPtr* output) const {
+    *output = temp_space_allocator_;
+    return Status::OK();
+  }
+
+ private:
+  std::unique_ptr<IExecutionProvider> impl_;
+  DataTransferManager data_transfer_manager_;
+  std::unique_ptr<profiling::EpProfiler> profiler_;
+  AllocatorPtr temp_space_cpu_allocator_;
+  AllocatorPtr temp_space_allocator_;
+};
+
+}  // namespace adapter
+}  // namespace ep
+}  // namespace onnxruntime

include/onnxruntime/ep/adapter/kernel_def.h

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+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#if !defined(ORT_EP_API_ADAPTER_HEADER_INCLUDED)
+#error "This header should not be included directly. Include ep/_pch.h instead."
+#endif
+
+#include <memory>
+
+namespace onnxruntime {
+namespace ep {
+namespace adapter {
+
+/// <summary>
+/// An adapter class partially implementing the facade of `onnxruntime::KernelDef`.
+/// </summary>
+class KernelDef {
+ public:
+  explicit KernelDef(const OrtKernelInfo* kernel_info) : kernel_info_{kernel_info} {}
+
+  const std::string OpName() const {
+    return kernel_info_.GetNodeName();
+  }
+
+  const std::string Domain() const {
+    return kernel_info_.GetOperatorDomain();
+  }
+
+ private:
+  const Ort::ConstKernelInfo kernel_info_;
+};
+
+}  // namespace adapter
+}  // namespace ep
+}  // namespace onnxruntime