/* Copyright 2015 Google Inc. All Rights Reserved.

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 TENSORFLOW_CORE_FRAMEWORK_TENSOR_SHAPE_H_
#define TENSORFLOW_CORE_FRAMEWORK_TENSOR_SHAPE_H_

#include <string>

#include "third_party/eigen3/unsupported/Eigen/CXX11/Tensor"
#include "tensorflow/core/framework/tensor_shape.pb.h"
#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/lib/core/stringpiece.h"
#include "tensorflow/core/lib/gtl/array_slice.h"
#include "tensorflow/core/lib/gtl/inlined_vector.h"
#include "tensorflow/core/lib/strings/strcat.h"
#include "tensorflow/core/platform/logging.h"

namespace tensorflow {

class TensorShapeIter;  // Declared below

class TensorShape {
 public:
  /// \brief Construct a `TensorShape` from the provided sizes.
  /// REQUIRES: `dim_sizes[i] >= 0`
  explicit TensorShape(gtl::ArraySlice<int64> dim_sizes);
  TensorShape(std::initializer_list<int64> dim_sizes)
      : TensorShape(gtl::ArraySlice<int64>(dim_sizes)) {}

  /// REQUIRES: `IsValid(proto)`
  explicit TensorShape(const TensorShapeProto& proto);

  /// Create a tensor shape with no dimensions and one element, which you can
  /// then call `AddDim()` on.
  TensorShape();

  ~TensorShape();

  /// Copy the specified shape
  TensorShape(const TensorShape& b);
  void operator=(const TensorShape& b);

  /// Returns `true` iff `proto` is a valid tensor shape.
  static bool IsValid(const TensorShapeProto& proto);

  /// Returns `OK` iff `proto` is a valid tensor shape, and a descriptive error
  /// status otherwise.
  static Status IsValidShape(const TensorShapeProto& proto);

  /// Clear a tensor shape
  void Clear();

  /// \brief Add a dimension to the end ("inner-most").
  /// REQUIRES: `size >= 0`
  void AddDim(int64 size);

  /// Appends all the dimensions from `shape`.
  void AppendShape(const TensorShape& shape);

  // Maximum number of dimensions in a tensor.
  static constexpr int MaxDimensions() { return 255; }

  /// \brief Insert a dimension somewhere in the `TensorShape`.
  /// REQUIRES: `0 <= d <= dims()`
  /// REQUIRES: `size >= 0`
  void InsertDim(int d, int64 size);

  /// \brief Modifies the size of the dimension `d` to be `size`
  /// REQUIRES: `0 <= d < dims()`
  /// REQUIRES: `size >= 0`
  void set_dim(int d, int64 size);

  /// \brief Removes dimension `d` from the `TensorShape`.
  /// REQUIRES: `0 <= d < dims()`
  void RemoveDim(int d);

  /// Return the number of dimensions in the tensor.
  int dims() const {
    DCHECK(tag() != REP_OUT_OF_LINE || (*as64()->dims_).size() == ndims_byte());
    return ndims_byte();
  }

  /// \brief Returns the number of elements in dimension `d`.
  /// REQUIRES: `0 <= d < dims()`
  // TODO(touts): Rename to `dimension()` to match
  // `Eigen::Tensor::dimension()`?
  int64 dim_size(int d) const;

  /// Returns sizes of all dimensions.
  gtl::InlinedVector<int64, 4> dim_sizes() const;

  /// \brief Returns the number of elements in the tensor.
  ///
  /// We use `int64` and not `size_t` to be compatible with `Eigen::Tensor`
  /// which uses `ptrdiff_t`.
  int64 num_elements() const { return num_elements_; }

  /// Returns true if `*this` and `b` have the same sizes. Ignores
  /// dimension names.
  bool IsSameSize(const TensorShape& b) const;
  bool operator==(const TensorShape& b) const { return IsSameSize(b); }
  bool operator!=(const TensorShape& b) const { return !IsSameSize(b); }

  /// Fill `*proto` from `*this`.
  void AsProto(TensorShapeProto* proto) const;

  /// Fill `*dsizes` from `*this`.
  template <int NDIMS>
  Eigen::DSizes<Eigen::DenseIndex, NDIMS> AsEigenDSizes() const;

  /// Same as `AsEigenDSizes()` but allows for `NDIMS > dims()` -- in
  /// which case we pad the rest of the sizes with 1.
  template <int NDIMS>
  Eigen::DSizes<Eigen::DenseIndex, NDIMS> AsEigenDSizesWithPadding() const;

  /// For iterating through the dimensions.
  TensorShapeIter begin() const;
  TensorShapeIter end() const;

  /// For error messages.
  string DebugString() const;

  /// Same as `TensorShape(proto).DebugString()` but doesn't crash for
  /// invalid protos.
  static string DebugString(const TensorShapeProto& proto);

  void DumpRep() const;  // XXX
 private:
  void DestructorOutOfLine();
  void ClearAllButDataType();
  void SlowCopyFrom(const TensorShape& b);

  void RecomputeNumElements();

  void CheckDimsEqual(int NDIMS) const;
  void CheckDimsAtLeast(int NDIMS) const;

  // We use 16 bytes to represent a TensorShape.  Because we need to
  // be able to support full 64-bit dimension sizes and an arbitrary
  // number of dimensions for a Tensor, but most tensor dimensions are
  // significantly smaller than 64 bits and most tensors are 1, 2, or 3
  // dimensions, we have several representations.
  // Rep16: Supports up to 6 dimensions where each dimension is < 2^16
  // Rep32: Supports up to 3 dimensions where each dimension is < 2^32
  // Rep64: Supports arbitrary dimensionality, 64-bit dimensions using
  //        an out of line vector.
  struct Rep16 {
    int16 dims_[6];
  };
  struct Rep32 {
    int32 dims_[3];
  };
  struct Rep64 {
    gtl::InlinedVector<int64, 4>* dims_;
  };

  static const int64 kMaxRep16 = 32768;
  static const int64 kMaxRep32 = (1ull << 31) - 1;

  uint8* buf() { return &u_.buf[0]; }
  const uint8* buf() const { return &u_.buf[0]; }

  Rep16* as16() { return reinterpret_cast<Rep16*>(buf()); }
  Rep32* as32() { return reinterpret_cast<Rep32*>(buf()); }
  Rep64* as64() { return reinterpret_cast<Rep64*>(buf()); }

  const Rep16* as16() const { return reinterpret_cast<const Rep16*>(buf()); }
  const Rep32* as32() const { return reinterpret_cast<const Rep32*>(buf()); }
  const Rep64* as64() const { return reinterpret_cast<const Rep64*>(buf()); }

  enum RepTag { REP16 = 0, REP32 = 1, REP_OUT_OF_LINE = 2 };

  // Since we have a convenient extra byte available, we allow the
  // Tensor class to store an 8-bit value in this extra storage.  This
  // allows it to store the Tensor's datatype enum value here and avoid
  // an extra word of storage.
  friend class Tensor;
  friend class TensorShapeTestHelper;
  friend class BitcastOp;
  DataType data_type() const { return static_cast<DataType>(buf()[13]); }
  void set_data_type(DataType dt) {
    // We only have 8 bits available to store DataType, so make sure it fits
    DCHECK_LT(static_cast<uint32>(dt), 256);
    buf()[13] = static_cast<uint8>(dt);
  }

  // We store the number of dimensions in byte 14, and the RepTag in byte 15.
  // Bytes [0..13] vary depending on the representation
  uint8 ndims_byte() const { return buf()[14]; }
  void set_ndims_byte(uint8 nd) { buf()[14] = nd; }

  RepTag tag() const { return static_cast<RepTag>(buf()[15]); }
  void set_tag(RepTag tag) { buf()[15] = static_cast<uint8>(tag); }

  union {
    uint8 buf[16];
    // Force data to be aligned enough for a pointer.
    Rep64* unused_aligner;
  } u_;
  int64 num_elements_;
};

struct TensorShapeDim {
  explicit TensorShapeDim(int64 s) : size(s) {}
  int64 size;
};

class TensorShapeIter {
 public:
  TensorShapeIter(const TensorShape* shape, int d) : shape_(shape), d_(d) {}
  bool operator==(const TensorShapeIter& rhs) {
    DCHECK(shape_ == rhs.shape_);
    return d_ == rhs.d_;
  }
  bool operator!=(const TensorShapeIter& rhs) {
    DCHECK(shape_ == rhs.shape_);
    return d_ != rhs.d_;
  }
  void operator++() { ++d_; }
  TensorShapeDim operator*() { return TensorShapeDim(shape_->dim_size(d_)); }

 private:
  const TensorShape* shape_;
  int d_;
};

/// \brief Static helper routines for `TensorShape`. Includes a few common
/// predicates on a tensor shape.
class TensorShapeUtils {
 public:
  static bool IsScalar(const TensorShape& shape) { return shape.dims() == 0; }

  static bool IsVector(const TensorShape& shape) { return shape.dims() == 1; }

  static bool IsVectorOrHigher(const TensorShape& shape) {
    return shape.dims() >= 1;
  }

  static bool IsMatrix(const TensorShape& shape) { return shape.dims() == 2; }

  static bool IsMatrixOrHigher(const TensorShape& shape) {
    return shape.dims() >= 2;
  }

  /// \brief Returns a `TensorShape` whose dimensions are
  /// `dims[0]`, `dims[1]`, ..., `dims[n-1]`.
  static Status MakeShape(const int32* dims, int n, TensorShape* out);
  static Status MakeShape(const int64* dims, int n, TensorShape* out);

  static string ShapeListString(const gtl::ArraySlice<TensorShape>& shapes);

  static bool StartsWith(const TensorShape& shape0, const TensorShape& shape1);
};

// ----------------------------------------------------------------------------
// Template method implementation details below
// ----------------------------------------------------------------------------

template <int NDIMS>
Eigen::DSizes<Eigen::DenseIndex, NDIMS> TensorShape::AsEigenDSizes() const {
  CheckDimsEqual(NDIMS);
  return AsEigenDSizesWithPadding<NDIMS>();
}

template <int NDIMS>
Eigen::DSizes<Eigen::DenseIndex, NDIMS> TensorShape::AsEigenDSizesWithPadding()
    const {
  CheckDimsAtLeast(NDIMS);
  static_assert(NDIMS <= TensorShape::MaxDimensions(), "Too many dimensions");
  Eigen::DSizes<Eigen::DenseIndex, NDIMS> dsizes;
  for (int d = 0; d < dims(); d++) {
    dsizes[d] = dim_size(d);
  }
  for (int d = dims(); d < NDIMS; d++) {
    dsizes[d] = 1;
  }
  return dsizes;
}

// ----------------------------------------------------------------------------
// Inlining of some performance critical routines
// ----------------------------------------------------------------------------

inline TensorShape::TensorShape(const TensorShape& b) {
  num_elements_ = b.num_elements_;
  if (b.tag() != REP_OUT_OF_LINE) {
    memcpy(buf(), b.buf(), sizeof(u_.buf));
    // memcpy above Implicitly does:
    //   set_ndims_byte(b.ndims_byte());
    //   set_tag(b.tag());
  } else {
    set_tag(REP16);  // So that SlowCopyFrom does not try to deallocate
    SlowCopyFrom(b);
  }
}

inline TensorShape::~TensorShape() {
  if (tag() == REP_OUT_OF_LINE) {
    DestructorOutOfLine();
  }
}

inline void TensorShape::operator=(const TensorShape& b) {
  num_elements_ = b.num_elements_;
  if (tag() != REP_OUT_OF_LINE && b.tag() != REP_OUT_OF_LINE) {
    memcpy(buf(), b.buf(), sizeof(u_.buf));
    // memcpy above implicitly also does:
    //   set_tag(b.tag());
    //   set_ndims_byte(b.ndims_byte());
  } else {
    SlowCopyFrom(b);
  }
}

}  // namespace tensorflow

#endif  // TENSORFLOW_CORE_FRAMEWORK_TENSOR_SHAPE_H_
