// Copyright (c) the JPEG XL Project 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 LIB_JXL_PROGRESSIVE_SPLIT_H_

#define LIB_JXL_PROGRESSIVE_SPLIT_H_

#include <cstddef>

#include <cstdint>

#include <limits>

#include "lib/jxl/base/compiler_specific.h"

#include "lib/jxl/base/status.h"

#include "lib/jxl/common.h"  // kMaxNumPasses

#include "lib/jxl/frame_header.h"

// Functions to split DCT coefficients in multiple passes. All the passes of a

// single frame are added together.

namespace jxl {

class AcStrategy;

constexpr size_t kNoDownsamplingFactor = std::numeric_limits<size_t>::max();

struct PassDefinition {

  // Side of the square of the coefficients that should be kept in each 8x8

  // block. Must be greater than 1, and at most 8. Should be in non-decreasing

  // order.

  size_t num_coefficients;

  // How much to shift the encoded values by, with rounding.

  size_t shift;

  // If specified, this indicates that if the requested downsampling factor is

  // sufficiently high, then it is fine to stop decoding after this pass.

  // By default, passes are not marked as being suitable for any downsampling.

  size_t suitable_for_downsampling_of_at_least;

};

struct ProgressiveMode {

  size_t num_passes = 1;

  PassDefinition passes[kMaxNumPasses] = {

      PassDefinition{/*num_coefficients=*/8, /*shift=*/0,

                     /*suitable_for_downsampling_of_at_least=*/1}};

  ProgressiveMode() = default;

  template <size_t nump>

  explicit ProgressiveMode(const PassDefinition (&p)[nump]) {

    static_assert(nump <= kMaxNumPasses, "Too many passes");

    num_passes = nump;

    PassDefinition previous_pass{

        /*num_coefficients=*/1, /*shift=*/0,

        /*suitable_for_downsampling_of_at_least=*/kNoDownsamplingFactor};

    size_t last_downsampling_factor = kNoDownsamplingFactor;

    for (size_t i = 0; i < nump; i++) {

      JXL_DASSERT(p[i].num_coefficients > previous_pass.num_coefficients ||

                  (p[i].num_coefficients == previous_pass.num_coefficients &&

                   p[i].shift < previous_pass.shift));

      JXL_DASSERT(p[i].suitable_for_downsampling_of_at_least ==

                      kNoDownsamplingFactor ||

                  p[i].suitable_for_downsampling_of_at_least <=

                      last_downsampling_factor);

      // Only used inside assert.

      (void)last_downsampling_factor;

      if (p[i].suitable_for_downsampling_of_at_least != kNoDownsamplingFactor) {

        last_downsampling_factor = p[i].suitable_for_downsampling_of_at_least;

      }

      previous_pass = passes[i] = p[i];

    }

  }

Unexecuted instantiation: jxl::ProgressiveMode::ProgressiveMode<2ul>(jxl::PassDefinition const (&) [2ul])

Unexecuted instantiation: jxl::ProgressiveMode::ProgressiveMode<3ul>(jxl::PassDefinition const (&) [3ul])

};

class ProgressiveSplitter {

 public:

  void SetProgressiveMode(ProgressiveMode mode) { mode_ = mode; }

  size_t GetNumPasses() const { return mode_.num_passes; }

  Status InitPasses(Passes* JXL_RESTRICT passes) const {

    passes->num_passes = static_cast<uint32_t>(GetNumPasses());

    passes->num_downsample = 0;

    JXL_ENSURE(passes->num_passes != 0);

    passes->shift[passes->num_passes - 1] = 0;

    if (passes->num_passes == 1) return true;  // Done, arrays are empty

    for (uint32_t i = 0; i < mode_.num_passes - 1; ++i) {

      const size_t min_downsampling_factor =

          mode_.passes[i].suitable_for_downsampling_of_at_least;

      passes->shift[i] = mode_.passes[i].shift;

      if (1 < min_downsampling_factor &&

          min_downsampling_factor != kNoDownsamplingFactor) {

        passes->downsample[passes->num_downsample] = min_downsampling_factor;

        passes->last_pass[passes->num_downsample] = i;

        if (mode_.passes[i + 1].suitable_for_downsampling_of_at_least <

            min_downsampling_factor) {

          passes->num_downsample += 1;

        }

      }

    }

    return true;

  }

  template <typename T>

  void SplitACCoefficients(const T* JXL_RESTRICT block, const AcStrategy& acs,

                           size_t bx, size_t by,

                           T* JXL_RESTRICT output[kMaxNumPasses]);

 private:

  ProgressiveMode mode_;

};

extern template void ProgressiveSplitter::SplitACCoefficients<int32_t>(

    const int32_t* JXL_RESTRICT, const AcStrategy&, size_t, size_t,

    int32_t* JXL_RESTRICT[kMaxNumPasses]);

extern template void ProgressiveSplitter::SplitACCoefficients<int16_t>(

    const int16_t* JXL_RESTRICT, const AcStrategy&, size_t, size_t,

    int16_t* JXL_RESTRICT[kMaxNumPasses]);

}  // namespace jxl

#endif  // LIB_JXL_PROGRESSIVE_SPLIT_H_