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/*

 * Copyright (c) 2016, Alliance for Open Media. All rights reserved.

 * This source code is subject to the terms of the BSD 2 Clause License and

 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License

 * was not distributed with this source code in the LICENSE file, you can

 * obtain it at www.aomedia.org/license/software. If the Alliance for Open

 * Media Patent License 1.0 was not distributed with this source code in the

 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.

*/

#ifndef AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_

#define AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_

#include <stdio.h>

#include <stdlib.h>

#include <stdbool.h>

#include <memory.h>

#include "aom_dsp/pyramid.h"

#include "aom_util/aom_pthread.h"

#ifdef __cplusplus

extern "C" {

#endif

#define MAX_CORNERS 4096

typedef struct corner_list {

#if CONFIG_MULTITHREAD

  // Mutex which is used to prevent the corner list from being computed twice

  // at the same time

//

  // Semantics:

  // * This mutex must be held whenever reading or writing the `valid` flag

//

  // * This mutex must also be held while computing the image pyramid,

  //   to ensure that only one thread may do so at a time.

//

  // * However, once you have read the valid flag and seen a true value,

  //   it is safe to drop the mutex and read from the remaining fields.

  //   This is because, once the image pyramid is computed, its contents

  //   will not be changed until the parent frame buffer is recycled,

  //   which will not happen until there are no more outstanding references

  //   to the frame buffer.

  pthread_mutex_t mutex;

#endif  // CONFIG_MULTITHREAD

  // Flag indicating whether the corner list contains valid data

  bool valid;

  // Number of corners found

  int num_corners;

  // (x, y) coordinates of each corner

  int corners[2 * MAX_CORNERS];

} CornerList;

size_t av1_get_corner_list_size(void);

CornerList *av1_alloc_corner_list(void);

bool av1_compute_corner_list(const YV12_BUFFER_CONFIG *frame, int bit_depth,

                             int downsample_level, CornerList *corners);

#ifndef NDEBUG

// Check if a corner list has already been computed.

// This is mostly a debug helper - as it is necessary to hold corners->mutex

// while reading the valid flag, we cannot just write:

//   assert(corners->valid);

// This function allows the check to be correctly written as:

//   assert(aom_is_corner_list_valid(corners));

bool aom_is_corner_list_valid(CornerList *corners);

#endif

void av1_invalidate_corner_list(CornerList *corners);

void av1_free_corner_list(CornerList *corners);

#ifdef __cplusplus

#endif

#endif  // AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_