/*
   * Copyright (C) 2014 Hamburg University of Applied Sciences (HAW)
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup pthread
   * @{
   * @file
   * @brief       RIOT POSIX thread local storage
   * @author      Martin Landsmann <martin.landsmann@haw-hamburg.de>
   * @author      René Kijewski <rene.kijewski@fu-berlin.de>
   * @}
   */
  
  #include <malloc.h>
  
  #include "pthread.h"
  
  #define ENABLE_DEBUG (0)
  #include "debug.h"
  
  typedef struct __pthread_tls_datum {
      pthread_key_t key;
      struct __pthread_tls_datum *next;
      void *value;
  } tls_data_t;
  
  struct __pthread_tls_key {
      void (*destructor)(void *);
  };
  
  /**
   * @brief   Used while manipulating the TLS of a pthread.
   */
  static mutex_t tls_mutex;
  
  /**
   * @brief        Find a thread-specific datum.
   * @param[in]    tls    Pointer to the list of the thread-specific datums.
   * @param[in]    key    The key to look up.
   * @param[out]   prev   The datum before the result. `NULL` if the result is the first key. Spurious if the key was not found.
   * @returns      The datum or `NULL`.
   */
  static tls_data_t *find_specific(tls_data_t **tls, pthread_key_t key, tls_data_t **prev)
  {
      tls_data_t *specific = *tls;
      *prev = NULL;
  
      while (specific) {
          if (specific->key == key) {
              return specific;
          }
  
          *prev = specific;
          specific = specific->next;
      }
  
      return 0;
  }
  
  /**
   * @brief       Find or allocate a thread specific datum.
   * @details     The `key` must be initialized.
   *              The result will be the head of the thread-specific datums afterwards.
   * @param[in]   key   The key to lookup.
   * @returns     The datum. `NULL` on ENOMEM or if the caller is not a pthread.
   */
  static tls_data_t *get_specific(pthread_key_t key)
  {
      pthread_t self_id = pthread_self();
      if (self_id == 0) {
          DEBUG("ERROR called pthread_self() returned 0 in \"%s\"!\n", __func__);
          return NULL;
      }
  
      tls_data_t **tls = __pthread_get_tls_head(self_id);
      tls_data_t *prev, *specific = find_specific(tls, key, &prev);
  
      /* Did the datum already exist? */
      if (specific) {
          if (prev) {
              /* Move the datum to the front for a faster next lookup. */
              /* Let's pretend that we have a totally degenerated splay tree. ;-) */
              prev->next = specific->next;
              specific->next = *tls;
              *tls = specific;
          }
          return specific;
      }
  
      /* Allocate new datum. */
      specific = malloc(sizeof (*specific));
      if (specific) {
          specific->key = key;
          specific->next = *tls;
          specific->value = NULL;
          *tls = specific;
      }
      else {
          DEBUG("ERROR out of memory in %s!\n", __func__);
      }
      return specific;
  }
  
  int pthread_key_create(pthread_key_t *key, void (*destructor)(void *))
  {
      *key = malloc(sizeof (**key));
      if (!*key) {
          return ENOMEM;
      }
  
      (*key)->destructor = destructor;
      return 0;
  }
  
  int pthread_key_delete(pthread_key_t key)
  {
      if (!key) {
          return EINVAL;
      }
  
      mutex_lock(&tls_mutex);
      for (unsigned i = 1; i <= MAXTHREADS; ++i) {
          tls_data_t **tls = __pthread_get_tls_head(i);
          if (!tls) {
              continue;
          }
  
          tls_data_t *prev, *specific = find_specific(tls, key, &prev);
          if (specific) {
              if (prev) {
                  prev->next = specific->next;
              }
              else {
                  *tls = specific->next;
              }
              free(specific);
          }
      }
      mutex_unlock(&tls_mutex);
  
      return 0;
  }
  
  void *pthread_getspecific(pthread_key_t key)
  {
      if (!key) {
          return NULL;
      }
  
      mutex_lock(&tls_mutex);
      tls_data_t *specific = get_specific(key);
      void *result = specific ? specific->value : NULL;
      mutex_unlock(&tls_mutex);
  
      return result;
  }
  
  int pthread_setspecific(pthread_key_t key, const void *value)
  {
      if (!key) {
          return EINVAL;
      }
  
      mutex_lock(&tls_mutex);
      tls_data_t *specific = get_specific(key);
      if (specific) {
          specific->value = (void *) value;
      }
      mutex_unlock(&tls_mutex);
  
      return specific ? 0 : ENOMEM;
  }
  
  void __pthread_keys_exit(int self_id)
  {
      tls_data_t **tls = __pthread_get_tls_head(self_id);
  
      /* Calling the dtor could cause another pthread_exit(), so we dehead and free defore calling it. */
      mutex_lock(&tls_mutex);
      for (tls_data_t *specific; (specific = *tls); ) {
          *tls = specific->next;
          void *value = specific->value;
          void (*destructor)(void *) = specific->key->destructor;
          free(specific);
  
          if (value && destructor) {
              mutex_unlock(&tls_mutex);
              destructor(value);
              mutex_lock(&tls_mutex);
          }
      }
      mutex_unlock(&tls_mutex);
  }