fs-fd-hash-inl.h

Go to the documentation of this file.

#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) {
  int i, 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_ */