fs-fd-hash-inl.h

/* Copyright libuv project contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#ifndef UV_WIN_FS_FD_HASH_INL_H_
#define UV_WIN_FS_FD_HASH_INL_H_

#include "uv.h"
#include "internal.h"

/* Files are only inserted in uv__fd_hash when the UV_FS_O_FILEMAP flag is
 * specified. Thus, when uv__fd_hash_get returns true, the file mapping in the
 * info structure should be used for read/write operations.
 *
 * If the file is empty, the mapping field will be set to
 * INVALID_HANDLE_VALUE. This is not an issue since the file mapping needs to
 * be created anyway when the file size changes.
 *
 * Since file descriptors are sequential integers, the modulo operator is used
 * as hashing function. For each bucket, a single linked list of arrays is
 * kept to minimize allocations. A statically allocated memory buffer is kept
 * for the first array in each bucket. */


#define UV__FD_HASH_SIZE 256
#define UV__FD_HASH_GROUP_SIZE 16

struct uv__fd_info_s {
  int flags;
  BOOLEAN is_directory;
  HANDLE mapping;
  LARGE_INTEGER size;
  LARGE_INTEGER current_pos;
};

struct uv__fd_hash_entry_s {
  uv_file fd;
  struct uv__fd_info_s info;
};

struct uv__fd_hash_entry_group_s {
  struct uv__fd_hash_entry_s entries[UV__FD_HASH_GROUP_SIZE];
  struct uv__fd_hash_entry_group_s* next;
};

struct uv__fd_hash_bucket_s {
  size_t size;
  struct uv__fd_hash_entry_group_s* data;
};


static uv_mutex_t uv__fd_hash_mutex;

static struct uv__fd_hash_entry_group_s
  uv__fd_hash_entry_initial[UV__FD_HASH_SIZE * UV__FD_HASH_GROUP_SIZE];
static struct uv__fd_hash_bucket_s uv__fd_hash[UV__FD_HASH_SIZE];


INLINE static void uv__fd_hash_init(void) {
  size_t i;
  int err;

  err = uv_mutex_init(&uv__fd_hash_mutex);
  if (err) {
    uv_fatal_error(err, "uv_mutex_init");
  }

  for (i = 0; i < ARRAY_SIZE(uv__fd_hash); ++i) {
    uv__fd_hash[i].size = 0;
    uv__fd_hash[i].data =
        uv__fd_hash_entry_initial + i * UV__FD_HASH_GROUP_SIZE;
  }
}

#define FIND_COMMON_VARIABLES                                                \
  unsigned i;                                                                \
  unsigned bucket = fd % ARRAY_SIZE(uv__fd_hash);                            \
  struct uv__fd_hash_entry_s* entry_ptr = NULL;                              \
  struct uv__fd_hash_entry_group_s* group_ptr;                               \
  struct uv__fd_hash_bucket_s* bucket_ptr = &uv__fd_hash[bucket];

#define FIND_IN_GROUP_PTR(group_size)                                        \
  do {                                                                       \
    for (i = 0; i < group_size; ++i) {                                       \
      if (group_ptr->entries[i].fd == fd) {                                  \
        entry_ptr = &group_ptr->entries[i];                                  \
        break;                                                               \
      }                                                                      \
    }                                                                        \
  } while (0)

#define FIND_IN_BUCKET_PTR()                                                 \
  do {                                                                       \
    size_t first_group_size = bucket_ptr->size % UV__FD_HASH_GROUP_SIZE;     \
    if (bucket_ptr->size != 0 && first_group_size == 0)                      \
      first_group_size = UV__FD_HASH_GROUP_SIZE;                             \
    group_ptr = bucket_ptr->data;                                            \
    FIND_IN_GROUP_PTR(first_group_size);                                     \
    for (group_ptr = group_ptr->next;                                        \
         group_ptr != NULL && entry_ptr == NULL;                             \
         group_ptr = group_ptr->next)                                        \
      FIND_IN_GROUP_PTR(UV__FD_HASH_GROUP_SIZE);                             \
  } while (0)

INLINE static int uv__fd_hash_get(int fd, struct uv__fd_info_s* info) {
  FIND_COMMON_VARIABLES

  uv_mutex_lock(&uv__fd_hash_mutex);

  FIND_IN_BUCKET_PTR();

  if (entry_ptr != NULL) {
    *info = entry_ptr->info;
  }

  uv_mutex_unlock(&uv__fd_hash_mutex);
  return entry_ptr != NULL;
}

INLINE static void uv__fd_hash_add(int fd, struct uv__fd_info_s* info) {
  FIND_COMMON_VARIABLES

  uv_mutex_lock(&uv__fd_hash_mutex);

  FIND_IN_BUCKET_PTR();

  if (entry_ptr == NULL) {
    i = bucket_ptr->size % UV__FD_HASH_GROUP_SIZE;

    if (bucket_ptr->size != 0 && i == 0) {
      struct uv__fd_hash_entry_group_s* new_group_ptr =
        uv__malloc(sizeof(*new_group_ptr));
      if (new_group_ptr == NULL) {
        uv_fatal_error(ERROR_OUTOFMEMORY, "uv__malloc");
      }
      new_group_ptr->next = bucket_ptr->data;
      bucket_ptr->data = new_group_ptr;
    }

    bucket_ptr->size += 1;
    entry_ptr = &bucket_ptr->data->entries[i];
    entry_ptr->fd = fd;
  }

  entry_ptr->info = *info;

  uv_mutex_unlock(&uv__fd_hash_mutex);
}

INLINE static int uv__fd_hash_remove(int fd, struct uv__fd_info_s* info) {
  FIND_COMMON_VARIABLES

  uv_mutex_lock(&uv__fd_hash_mutex);

  FIND_IN_BUCKET_PTR();

  if (entry_ptr != NULL) {
    *info = entry_ptr->info;

    bucket_ptr->size -= 1;

    i = bucket_ptr->size % UV__FD_HASH_GROUP_SIZE;
    if (entry_ptr != &bucket_ptr->data->entries[i]) {
      *entry_ptr = bucket_ptr->data->entries[i];
    }

    if (bucket_ptr->size != 0 &&
        bucket_ptr->size % UV__FD_HASH_GROUP_SIZE == 0) {
      struct uv__fd_hash_entry_group_s* old_group_ptr = bucket_ptr->data;
      bucket_ptr->data = old_group_ptr->next;
      uv__free(old_group_ptr);
    }
  }

  uv_mutex_unlock(&uv__fd_hash_mutex);
  return entry_ptr != NULL;
}

#undef FIND_COMMON_VARIABLES
#undef FIND_IN_GROUP_PTR
#undef FIND_IN_BUCKET_PTR

#endif /* UV_WIN_FS_FD_HASH_INL_H_ */