// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SINC_RESAMPLER_H_
#define SINC_RESAMPLER_H_

#include <functional>
#include <memory>

#include "mem.h"

namespace base {

// SincResampler is a high-quality single-channel sample-rate converter.
class SincResampler {
 public:
  enum {
    // The kernel size can be adjusted for quality (higher is better) at the
    // expense of performance.  Must be a multiple of 32.
    // TODO(dalecurtis): Test performance to see if we can jack this up to 64+.
    kKernelSize = 32,

    // Default request size.  Affects how often and for how much SincResampler
    // calls back for input.  Must be greater than kKernelSize.
    kDefaultRequestSize = 512,

    // The kernel offset count is used for interpolation and is the number of
    // sub-sample kernel shifts.  Can be adjusted for quality (higher is better)
    // at the expense of allocating more memory.
    kKernelOffsetCount = 32,
    kKernelStorageSize = kKernelSize * (kKernelOffsetCount + 1),
  };

  // Callback type for providing more data into the resampler.  Expects |frames|
  // of data to be rendered into |destination|; zero padded if not enough frames
  // are available to satisfy the request.
  typedef std::function<void(int frames, float* destination)> ReadCB;

  // Constructs a SincResampler.  |io_sample_rate_ratio| is the ratio
  // of input / output sample rates.  |request_frames| controls the size in
  // frames of the buffer requested by each |read_cb| call.  The value must be
  // greater than kKernelSize.  Specify kDefaultRequestSize if there are no
  // request size constraints.
  SincResampler(double io_sample_rate_ratio, int request_frames);
  ~SincResampler();

  // Resample |frames| of data from |read_cb| into |destination|.
  void Resample(int frames, float* destination, ReadCB read_cb);

  // The maximum size in frames that guarantees Resample() will only make a
  // single call to |read_cb_| for more data.  Note: If PrimeWithSilence() is
  // not called, chunk size will grow after the first two Resample() calls by
  // kKernelSize / (2 * io_sample_rate_ratio).  See the .cc file for details.
  int ChunkSize() const { return chunk_size_; }

  // Returns the max number of frames that could be requested (via multiple
  // calls to |read_cb_|) during one Resample(|output_frames_requested|) call.
  int GetMaxInputFramesRequested(int output_frames_requested) const;

  // Guarantees that ChunkSize() will not change between calls by initializing
  // the input buffer with silence.  Note, this will cause the first few samples
  // of output to be biased towards silence. Must be called again after Flush().
  void PrimeWithSilence();

  // Flush all buffered data and reset internal indices.  Not thread safe, do
  // not call while Resample() is in progress.  Note, if PrimeWithSilence() was
  // previously called it must be called again after the Flush().
  void Flush();

  // Update |io_sample_rate_ratio_|.  SetRatio() will cause a reconstruction of
  // the kernels used for resampling.  Not thread safe, do not call while
  // Resample() is in progress.
  void SetRatio(double io_sample_rate_ratio);

  float* get_kernel_for_testing() { return kernel_storage_.get(); }

  // Return number of input frames consumed by a callback but not yet processed.
  // Since input/output ratio can be fractional, so can this value.
  // Zero before first call to Resample().
  double BufferedFrames() const;

 private:
  void InitializeKernel();
  void UpdateRegions(bool second_load);

  // Compute convolution of |k1| and |k2| over |input_ptr|, resultant sums are
  // linearly interpolated using |kernel_interpolation_factor|.  On x86, the
  // underlying implementation is chosen at run time based on SSE support.  On
  // ARM, NEON support is chosen at compile time based on compilation flags.
  static float Convolve_C(const float* input_ptr,
                          const float* k1,
                          const float* k2,
                          double kernel_interpolation_factor);
#if defined(_M_X64) || defined(__x86_64__) || defined(__i386__)
  static float Convolve_SSE(const float* input_ptr,
                            const float* k1,
                            const float* k2,
                            double kernel_interpolation_factor);
#elif defined(_M_ARM64) || defined(__aarch64__)
  static float Convolve_NEON(const float* input_ptr,
                             const float* k1,
                             const float* k2,
                             double kernel_interpolation_factor);
#endif

  // The ratio of input / output sample rates.
  double io_sample_rate_ratio_;

  // An index on the source input buffer with sub-sample precision.  It must be
  // double precision to avoid drift.
  double virtual_source_idx_;

  // The buffer is primed once at the very beginning of processing.
  bool buffer_primed_;

  // The size (in samples) to request from each |read_cb_| execution.
  const int request_frames_;

  // The number of source frames processed per pass.
  int block_size_;

  // Cached value used for ChunkSize().  The maximum size in frames that
  // guarantees Resample() will only ask for input at most once.
  int chunk_size_;

  // The size (in samples) of the internal buffer used by the resampler.
  const int input_buffer_size_;

  // Contains kKernelOffsetCount kernels back-to-back, each of size kKernelSize.
  // The kernel offsets are sub-sample shifts of a windowed sinc shifted from
  // 0.0 to 1.0 sample.
  base::AlignedMemPtr<float[]> kernel_storage_;
  base::AlignedMemPtr<float[]> kernel_pre_sinc_storage_;
  base::AlignedMemPtr<float[]> kernel_window_storage_;

  // Data from the source is copied into this buffer for each processing pass.
  base::AlignedMemPtr<float[]> input_buffer_;

  // Pointers to the various regions inside |input_buffer_|.  See the diagram at
  // the top of the .cc file for more information.
  float* r0_;
  float* const r1_;
  float* const r2_;
  float* r3_;
  float* r4_;

  SincResampler(SincResampler const&) = delete;
  SincResampler& operator=(SincResampler const&) = delete;
};

}  // namespace base

#endif  // SINC_RESAMPLER_H_
