1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
18#define LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
19
20#include "common/core/types.h"
21
22namespace le_fx {
23
24namespace sigmod {
25
26// Interpolation base-class that provides the interface, while it is the derived
27// class that provides the specific interpolation algorithm. The following list
28// of interpolation algorithms are currently present:
29//
30// InterpolationSine<T>: weighted interpolation between y_data[n] and
31//                       y_data[n+1] using a sin(.) weighting factor from
32//                       0 to pi/4.
33// InterpolationLinear<T>: linear interpolation
34// InterpolationSplines<T>: spline-based interpolation
35//
36// Example (using derived spline-based interpolation class):
37//  InterpolatorSplines<float> interp(x_data, y_data, data_length);
38//  for (int n = 0; n < data_length; n++) Y[n] = interp.Interpolate(X[n]);
39//
40template <typename T, class Algorithm>
41class InterpolatorBase {
42 public:
43  InterpolatorBase();
44  ~InterpolatorBase();
45
46  // Generic random-access interpolation with arbitrary spaced x-axis samples.
47  // Below X[0], the interpolator returns Y[0]. Above X[data_length-1], it
48  // returns Y[data_length-1].
49  T Interpolate(T x);
50
51  bool get_status() const {
52    return status_;
53  }
54
55  // Initializes internal buffers.
56  //  x_data: [(data_length)x1] x-axis coordinates (searching axis)
57  //  y_data: [(data_length)x1] y-axis coordinates (interpolation axis)
58  //  data_length: number of points
59  // returns `true` if everything is ok, `false`, otherwise
60  bool Initialize(const T *x_data, const T *y_data, int data_length);
61
62  // Initializes internal buffers.
63  //  x_data: x-axis coordinates (searching axis)
64  //  y_data: y-axis coordinates (interpolating axis)
65  // returns `true` if everything is ok, `false`, otherwise
66  bool Initialize(const vector<T> &x_data, const vector<T> &y_data);
67
68  // Initialization for regularly sampled sequences, where:
69  //  x_data[i] = x_start_offset + i * x_sampling_interval
70  bool Initialize(double x_start_offset,
71                  double x_sampling_interval,
72                  const vector<T> &y_data);
73
74  // Initialization for regularly sampled sequences, where:
75  //  x_data[i] = x_start_offset + i * x_sampling_interval
76  bool Initialize(double x_start_offset,
77                  double x_sampling_interval,
78                  const T *y_data,
79                  int data_length);
80
81 protected:
82  // Is set to false if something goes wrong, and to true if everything is ok.
83  bool status_;
84
85  // The start-index of the previously searched interval
86  int cached_index_;
87
88  // Data points
89  const T *x_data_;  // Externally or internally owned, depending on own_x_data_
90  const T *y_data_;  // Externally owned (always)
91  int data_length_;
92  // Index of the last element `data_length_ - 1` kept here for optimization
93  int last_element_index_;
94  bool own_x_data_;
95  // For regularly-samples sequences, keep only the boundaries and the intervals
96  T x_start_offset_;
97  float x_inverse_sampling_interval_;
98
99  // Algorithm state (internally owned)
100  double *state_;
101
102 private:
103  LE_FX_DISALLOW_COPY_AND_ASSIGN(InterpolatorBase);
104};
105
106}  // namespace sigmod
107
108}  // namespace le_fx
109
110#include "dsp/core/interpolator_base-inl.h"
111
112#endif  // LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
113