/* Copyright 2017 The OpenXLA Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef XLA_SERVICE_GPU_BUFFER_ALLOCATIONS_H_
#define XLA_SERVICE_GPU_BUFFER_ALLOCATIONS_H_

#include <cstddef>
#include <optional>
#include <set>
#include <string>
#include <vector>

#include "absl/status/status.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"
#include "absl/types/span.h"
#include "xla/service/buffer_assignment.h"
#include "xla/stream_executor/device_address.h"
#include "xla/stream_executor/device_address_allocator.h"

namespace xla {
namespace gpu {

// A thread-compatible class that encapsulates the base addresses of the
// allocated device buffers.
class BufferAllocations {
 public:
  BufferAllocations(absl::Span<se::DeviceAddressBase const> buffers,
                    int device_ordinal,
                    se::DeviceAddressAllocator* memory_allocator)
      : buffers_(buffers.begin(), buffers.end()),
        device_ordinal_(device_ordinal),
        memory_allocator_(memory_allocator) {}

  BufferAllocations(BufferAllocations&& other) = default;
  BufferAllocations& operator=(BufferAllocations&& other) = default;
  BufferAllocations(const BufferAllocations&) = delete;
  BufferAllocations& operator=(const BufferAllocations&) = delete;

  se::DeviceAddressAllocator* memory_allocator() const {
    return memory_allocator_;
  }
  int device_ordinal() const { return device_ordinal_; }

  // Returns the device address of buffer `buffer_index`. `buffer_index` must be
  // a valid index, i.e., in [0, buffer_count). This function returns null if
  // `buffer_index` is not assigned to a buffer address.
  se::DeviceAddressBase GetDeviceAddress(
      BufferAllocation::Index buffer_index) const;

  // Returns a mutable value for the allocation at a given `buffer_index`.
  se::DeviceAddressBase& GetMutableDeviceAddress(
      BufferAllocation::Index buffer_index);

  // Same as above, but also adjusts the returned address for the offset and
  // size contained in the given slice.
  se::DeviceAddressBase GetDeviceAddress(
      const BufferAllocation::Slice& buffer_slice) const;

  // Returns a buffer allocation index for the given device address if it
  // belongs to one of the buffer allocations. Returns nullptr otherwise.
  std::optional<BufferAllocation::Index> FindAllocationIndex(
      const se::DeviceAddressBase& addr) const;

  // Tears down all buffers allocated by this object that are not in
  // `live_addresses`.
  absl::Status TearDown(const std::set<se::DeviceAddressBase>& live_addresses,
                        absl::Span<const BufferAllocation* const> allocations);

  std::string ToString() const {
    std::string out;
    for (BufferAllocation::Index i = 0; i < buffers_.size(); ++i) {
      const auto& buf = buffers_[i];
      if (i > 0) {
        absl::StrAppend(&out, "; ");
      }
      absl::StrAppendFormat(&out, "Buffer %d -> %p (%d B)", i, buf.opaque(),
                            buf.size());
    }
    return out;
  }

  absl::Span<const se::DeviceAddressBase> buffers() const { return buffers_; }

  size_t size() const { return buffers_.size(); }

 private:
  // An array of device pointers that stores the address of each buffer
  // indexed by Index. Each element can point to a temporary buffer, an
  // input buffer, or nullptr if no buffer is needed for that Index.
  std::vector<se::DeviceAddressBase> buffers_;
  int device_ordinal_;
  se::DeviceAddressAllocator* memory_allocator_;
};

}  // namespace gpu
}  // namespace xla

#endif  // XLA_SERVICE_GPU_BUFFER_ALLOCATIONS_H_