/*

 * Copyright (c) 2021, Alliance for Open Media. All rights reserved

 *

 * This source code is subject to the terms of the BSD 3-Clause Clear License

 * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear

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

 * can obtain it at aomedia.org/license/software-license/bsd-3-c-c/.  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

 * aomedia.org/license/patent-license/.

 */

//

// Multi-threaded worker

//

// Original source:

//  https://chromium.googlesource.com/webm/libwebp

// Enable GNU extensions in glibc so that we can call pthread_setname_np().

// This must be before any #include statements.

#ifndef _GNU_SOURCE

#define _GNU_SOURCE

#endif

#include <assert.h>

#include <string.h>  // for memset()

#include "avm_mem/avm_mem.h"

#include "avm_util/avm_thread.h"

#if CONFIG_MULTITHREAD

struct AVxWorkerImpl {

  pthread_mutex_t mutex_;

  pthread_cond_t condition_;

  pthread_t thread_;

};

//------------------------------------------------------------------------------

static void execute(AVxWorker *const worker);  // Forward declaration.

static THREADFN thread_loop(void *ptr) {

  AVxWorker *const worker = (AVxWorker *)ptr;

#ifdef __APPLE__

  if (worker->thread_name != NULL) {

    // Apple's version of pthread_setname_np takes one argument and operates on

    // the current thread only. The maximum size of the thread_name buffer was

    // noted in the Chromium source code and was confirmed by experiments. If

    // thread_name is too long, pthread_setname_np returns -1 with errno

    // ENAMETOOLONG (63).

    char thread_name[64];

    strncpy(thread_name, worker->thread_name, sizeof(thread_name) - 1);

    thread_name[sizeof(thread_name) - 1] = '\0';

    pthread_setname_np(thread_name);

  }

#elif defined(__GLIBC__) || defined(__BIONIC__)

  if (worker->thread_name != NULL) {

    // Linux and Android require names (with nul) fit in 16 chars, otherwise

    // pthread_setname_np() returns ERANGE (34).

    char thread_name[16];

    strncpy(thread_name, worker->thread_name, sizeof(thread_name) - 1);

    thread_name[sizeof(thread_name) - 1] = '\0';

    pthread_setname_np(pthread_self(), thread_name);

  }

#endif

  int done = 0;

  while (!done) {

    pthread_mutex_lock(&worker->impl_->mutex_);

    while (worker->status_ == OK) {  // wait in idling mode

      pthread_cond_wait(&worker->impl_->condition_, &worker->impl_->mutex_);

    }

    if (worker->status_ == WORK) {

      execute(worker);

      worker->status_ = OK;

    } else if (worker->status_ == NOT_OK) {  // finish the worker

      done = 1;

    }

    // signal to the main thread that we're done (for sync())

    pthread_cond_signal(&worker->impl_->condition_);

    pthread_mutex_unlock(&worker->impl_->mutex_);

  }

  return THREAD_RETURN(NULL);  // Thread is finished

}

// main thread state control

static void change_state(AVxWorker *const worker, AVxWorkerStatus new_status) {

  // No-op when attempting to change state on a thread that didn't come up.

  // Checking status_ without acquiring the lock first would result in a data

  // race.

  if (worker->impl_ == NULL) return;

  pthread_mutex_lock(&worker->impl_->mutex_);

  if (worker->status_ >= OK) {

    // wait for the worker to finish

    while (worker->status_ != OK) {

      pthread_cond_wait(&worker->impl_->condition_, &worker->impl_->mutex_);

    }

    // assign new status and release the working thread if needed

    if (new_status != OK) {

      worker->status_ = new_status;

      pthread_cond_signal(&worker->impl_->condition_);

    }

  }

  pthread_mutex_unlock(&worker->impl_->mutex_);

}

#endif  // CONFIG_MULTITHREAD

//------------------------------------------------------------------------------

static void init(AVxWorker *const worker) {

  memset(worker, 0, sizeof(*worker));

  worker->status_ = NOT_OK;

}

static int sync(AVxWorker *const worker) {

#if CONFIG_MULTITHREAD

  change_state(worker, OK);

#endif

  assert(worker->status_ <= OK);

  return !worker->had_error;

}

static int reset(AVxWorker *const worker) {

  int ok = 1;

  worker->had_error = 0;

  if (worker->status_ < OK) {

#if CONFIG_MULTITHREAD

    worker->impl_ = (AVxWorkerImpl *)avm_calloc(1, sizeof(*worker->impl_));

    if (worker->impl_ == NULL) {

      return 0;

    }

    if (pthread_mutex_init(&worker->impl_->mutex_, NULL)) {

      goto Error;

    }

    if (pthread_cond_init(&worker->impl_->condition_, NULL)) {

      pthread_mutex_destroy(&worker->impl_->mutex_);

      goto Error;

    }

    pthread_attr_t attr;

    if (pthread_attr_init(&attr)) goto Error2;

#if defined(__APPLE__)

    size_t stacksize;

    if (!pthread_attr_getstacksize(&attr, &stacksize)) {

      const size_t kMinStackSize = MIN_THREAD_STACK_SIZE;

      if (stacksize < kMinStackSize &&

          pthread_attr_setstacksize(&attr, kMinStackSize)) {

        pthread_attr_destroy(&attr);

        goto Error2;

      }

    }

#endif  // __APPLE__

    pthread_mutex_lock(&worker->impl_->mutex_);

    ok = !pthread_create(&worker->impl_->thread_, &attr, thread_loop, worker);

    if (ok) worker->status_ = OK;

    pthread_mutex_unlock(&worker->impl_->mutex_);

    pthread_attr_destroy(&attr);

    if (!ok) {

    Error2:

      pthread_mutex_destroy(&worker->impl_->mutex_);

      pthread_cond_destroy(&worker->impl_->condition_);

    Error:

      avm_free(worker->impl_);

      worker->impl_ = NULL;

      return 0;

    }

#else

    worker->status_ = OK;

#endif

  } else if (worker->status_ > OK) {

    ok = sync(worker);

  }

  assert(!ok || (worker->status_ == OK));

  return ok;

}

static void execute(AVxWorker *const worker) {

  if (worker->hook != NULL) {

    worker->had_error |= !worker->hook(worker->data1, worker->data2);

  }

}

static void launch(AVxWorker *const worker) {

#if CONFIG_MULTITHREAD

  change_state(worker, WORK);

#else

  execute(worker);

#endif

}

static void end(AVxWorker *const worker) {

#if CONFIG_MULTITHREAD

  if (worker->impl_ != NULL) {

    change_state(worker, NOT_OK);

    pthread_join(worker->impl_->thread_, NULL);

    pthread_mutex_destroy(&worker->impl_->mutex_);

    pthread_cond_destroy(&worker->impl_->condition_);

    avm_free(worker->impl_);

    worker->impl_ = NULL;

  }

#else

  worker->status_ = NOT_OK;

  assert(worker->impl_ == NULL);

#endif

  assert(worker->status_ == NOT_OK);

}

//------------------------------------------------------------------------------

static AVxWorkerInterface g_worker_interface = { init,   reset,   sync,

                                                 launch, execute, end };

int avm_set_worker_interface(const AVxWorkerInterface *const winterface) {

  if (winterface == NULL || winterface->init == NULL ||

      winterface->reset == NULL || winterface->sync == NULL ||

      winterface->launch == NULL || winterface->execute == NULL ||

      winterface->end == NULL) {

    return 0;

  }

  g_worker_interface = *winterface;

  return 1;

}

const AVxWorkerInterface *avm_get_worker_interface(void) {

  return &g_worker_interface;

}

//------------------------------------------------------------------------------