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/*
* Copyright (C) 2013 The Android Open Source Project
*
* 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 LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
#define LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
#include "common/core/types.h"
namespace le_fx {
namespace sigmod {
// Interpolation base-class that provides the interface, while it is the derived
// class that provides the specific interpolation algorithm. The following list
// of interpolation algorithms are currently present:
//
// InterpolationSine<T>: weighted interpolation between y_data[n] and
// y_data[n+1] using a sin(.) weighting factor from
// 0 to pi/4.
// InterpolationLinear<T>: linear interpolation
// InterpolationSplines<T>: spline-based interpolation
//
// Example (using derived spline-based interpolation class):
// InterpolatorSplines<float> interp(x_data, y_data, data_length);
// for (int n = 0; n < data_length; n++) Y[n] = interp.Interpolate(X[n]);
//
template <typename T, class Algorithm>
class InterpolatorBase {
public:
InterpolatorBase();
~InterpolatorBase();
// Generic random-access interpolation with arbitrary spaced x-axis samples.
// Below X[0], the interpolator returns Y[0]. Above X[data_length-1], it
// returns Y[data_length-1].
T Interpolate(T x);
bool get_status() const {
return status_;
}
// Initializes internal buffers.
// x_data: [(data_length)x1] x-axis coordinates (searching axis)
// y_data: [(data_length)x1] y-axis coordinates (interpolation axis)
// data_length: number of points
// returns `true` if everything is ok, `false`, otherwise
bool Initialize(const T *x_data, const T *y_data, int data_length);
// Initializes internal buffers.
// x_data: x-axis coordinates (searching axis)
// y_data: y-axis coordinates (interpolating axis)
// returns `true` if everything is ok, `false`, otherwise
bool Initialize(const vector<T> &x_data, const vector<T> &y_data);
// Initialization for regularly sampled sequences, where:
// x_data[i] = x_start_offset + i * x_sampling_interval
bool Initialize(double x_start_offset,
double x_sampling_interval,
const vector<T> &y_data);
// Initialization for regularly sampled sequences, where:
// x_data[i] = x_start_offset + i * x_sampling_interval
bool Initialize(double x_start_offset,
double x_sampling_interval,
const T *y_data,
int data_length);
protected:
// Is set to false if something goes wrong, and to true if everything is ok.
bool status_;
// The start-index of the previously searched interval
int cached_index_;
// Data points
const T *x_data_; // Externally or internally owned, depending on own_x_data_
const T *y_data_; // Externally owned (always)
int data_length_;
// Index of the last element `data_length_ - 1` kept here for optimization
int last_element_index_;
bool own_x_data_;
// For regularly-samples sequences, keep only the boundaries and the intervals
T x_start_offset_;
float x_inverse_sampling_interval_;
// Algorithm state (internally owned)
double *state_;
private:
LE_FX_DISALLOW_COPY_AND_ASSIGN(InterpolatorBase);
};
} // namespace sigmod
} // namespace le_fx
#include "dsp/core/interpolator_base-inl.h"
#endif // LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_BASE_H_
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