zhashx man page

zhashx — extended generic hash container

Synopsis

//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
//  This class has draft methods, which may change over time. They are not
//  in stable releases, by default. Use --enable-drafts to enable.
// Destroy an item
typedef void (zhashx_destructor_fn) (
    void **item);

// Duplicate an item
typedef void * (zhashx_duplicator_fn) (
    const void *item);

// Compare two items, for sorting
typedef int (zhashx_comparator_fn) (
    const void *item1, const void *item2);

// compare two items, for sorting
typedef void (zhashx_free_fn) (
    void *data);

// compare two items, for sorting
typedef size_t (zhashx_hash_fn) (
    const void *key);

// Serializes an item to a longstr.
// The caller takes ownership of the newly created object.
typedef char * (zhashx_serializer_fn) (
    const void *item);

// Deserializes a longstr into an item.
// The caller takes ownership of the newly created object.
typedef void * (zhashx_deserializer_fn) (
    const char *item_str);

//  Create a new, empty hash container
CZMQ_EXPORT zhashx_t *
    zhashx_new (void);

//  Unpack binary frame into a new hash table. Packed data must follow format
//  defined by zhashx_pack. Hash table is set to autofree. An empty frame
//  unpacks to an empty hash table.
CZMQ_EXPORT zhashx_t *
    zhashx_unpack (zframe_t *frame);

//  Destroy a hash container and all items in it
CZMQ_EXPORT void
    zhashx_destroy (zhashx_t **self_p);

//  Insert item into hash table with specified key and item.
//  If key is already present returns -1 and leaves existing item unchanged
//  Returns 0 on success.
CZMQ_EXPORT int
    zhashx_insert (zhashx_t *self, const void *key, void *item);

//  Update or insert item into hash table with specified key and item. If the
//  key is already present, destroys old item and inserts new one. If you set
//  a container item destructor, this is called on the old value. If the key
//  was not already present, inserts a new item. Sets the hash cursor to the
//  new item.
CZMQ_EXPORT void
    zhashx_update (zhashx_t *self, const void *key, void *item);

//  Remove an item specified by key from the hash table. If there was no such
//  item, this function does nothing.
CZMQ_EXPORT void
    zhashx_delete (zhashx_t *self, const void *key);

//  Delete all items from the hash table. If the key destructor is
//  set, calls it on every key. If the item destructor is set, calls
//  it on every item.
CZMQ_EXPORT void
    zhashx_purge (zhashx_t *self);

//  Return the item at the specified key, or null
CZMQ_EXPORT void *
    zhashx_lookup (zhashx_t *self, const void *key);

//  Reindexes an item from an old key to a new key. If there was no such
//  item, does nothing. Returns 0 if successful, else -1.
CZMQ_EXPORT int
    zhashx_rename (zhashx_t *self, const void *old_key, const void *new_key);

//  Set a free function for the specified hash table item. When the item is
//  destroyed, the free function, if any, is called on that item.
//  Use this when hash items are dynamically allocated, to ensure that
//  you don't have memory leaks. You can pass 'free' or NULL as a free_fn.
//  Returns the item, or NULL if there is no such item.
CZMQ_EXPORT void *
    zhashx_freefn (zhashx_t *self, const void *key, zhashx_free_fn free_fn);

//  Return the number of keys/items in the hash table
CZMQ_EXPORT size_t
    zhashx_size (zhashx_t *self);

//  Return a zlistx_t containing the keys for the items in the
//  table. Uses the key_duplicator to duplicate all keys and sets the
//  key_destructor as destructor for the list.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlistx_t *
    zhashx_keys (zhashx_t *self);

//  Return a zlistx_t containing the values for the items in the
//  table. Uses the duplicator to duplicate all items and sets the
//  destructor as destructor for the list.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlistx_t *
    zhashx_values (zhashx_t *self);

//  Simple iterator; returns first item in hash table, in no given order,
//  or NULL if the table is empty. This method is simpler to use than the
//  foreach() method, which is deprecated. To access the key for this item
//  use zhashx_cursor(). NOTE: do NOT modify the table while iterating.
CZMQ_EXPORT void *
    zhashx_first (zhashx_t *self);

//  Simple iterator; returns next item in hash table, in no given order,
//  or NULL if the last item was already returned. Use this together with
//  zhashx_first() to process all items in a hash table. If you need the
//  items in sorted order, use zhashx_keys() and then zlistx_sort(). To
//  access the key for this item use zhashx_cursor(). NOTE: do NOT modify
//  the table while iterating.
CZMQ_EXPORT void *
    zhashx_next (zhashx_t *self);

//  After a successful first/next method, returns the key for the item that
//  was returned. This is a constant string that you may not modify or
//  deallocate, and which lasts as long as the item in the hash. After an
//  unsuccessful first/next, returns NULL.
CZMQ_EXPORT const void *
    zhashx_cursor (zhashx_t *self);

//  Add a comment to hash table before saving to disk. You can add as many
//  comment lines as you like. These comment lines are discarded when loading
//  the file. If you use a null format, all comments are deleted.
CZMQ_EXPORT void
    zhashx_comment (zhashx_t *self, const char *format, ...) CHECK_PRINTF (2);

//  Save hash table to a text file in name=value format. Hash values must be
//  printable strings; keys may not contain '=' character. Returns 0 if OK,
//  else -1 if a file error occurred.
CZMQ_EXPORT int
    zhashx_save (zhashx_t *self, const char *filename);

//  Load hash table from a text file in name=value format; hash table must
//  already exist. Hash values must printable strings; keys may not contain
//  '=' character. Returns 0 if OK, else -1 if a file was not readable.
CZMQ_EXPORT int
    zhashx_load (zhashx_t *self, const char *filename);

//  When a hash table was loaded from a file by zhashx_load, this method will
//  reload the file if it has been modified since, and is "stable", i.e. not
//  still changing. Returns 0 if OK, -1 if there was an error reloading the
//  file.
CZMQ_EXPORT int
    zhashx_refresh (zhashx_t *self);

//  Serialize hash table to a binary frame that can be sent in a message.
//  The packed format is compatible with the 'dictionary' type defined in
//  http://rfc.zeromq.org/spec:35/FILEMQ, and implemented by zproto:
//
//     ; A list of name/value pairs
//     dictionary      = dict-count *( dict-name dict-value )
//     dict-count      = number-4
//     dict-value      = longstr
//     dict-name       = string
//
//     ; Strings are always length + text contents
//     longstr         = number-4 *VCHAR
//     string          = number-1 *VCHAR
//
//     ; Numbers are unsigned integers in network byte order
//     number-1        = 1OCTET
//     number-4        = 4OCTET
//
//  Comments are not included in the packed data. Item values MUST be
//  strings.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zframe_t *
    zhashx_pack (zhashx_t *self);

//  Make a copy of the list; items are duplicated if you set a duplicator
//  for the list, otherwise not. Copying a null reference returns a null
//  reference. Note that this method's behavior changed slightly for CZMQ
//  v3.x, as it does not set nor respect autofree. It does however let you
//  duplicate any hash table safely. The old behavior is in zhashx_dup_v2.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zhashx_t *
    zhashx_dup (zhashx_t *self);

//  Set a user-defined deallocator for hash items; by default items are not
//  freed when the hash is destroyed.
CZMQ_EXPORT void
    zhashx_set_destructor (zhashx_t *self, zhashx_destructor_fn destructor);

//  Set a user-defined duplicator for hash items; by default items are not
//  copied when the hash is duplicated.
CZMQ_EXPORT void
    zhashx_set_duplicator (zhashx_t *self, zhashx_duplicator_fn duplicator);

//  Set a user-defined deallocator for keys; by default keys are freed
//  when the hash is destroyed using free().
CZMQ_EXPORT void
    zhashx_set_key_destructor (zhashx_t *self, zhashx_destructor_fn destructor);

//  Set a user-defined duplicator for keys; by default keys are duplicated
//  using strdup.
CZMQ_EXPORT void
    zhashx_set_key_duplicator (zhashx_t *self, zhashx_duplicator_fn duplicator);

//  Set a user-defined comparator for keys; by default keys are
//  compared using strcmp.
CZMQ_EXPORT void
    zhashx_set_key_comparator (zhashx_t *self, zhashx_comparator_fn comparator);

//  Set a user-defined comparator for keys; by default keys are
//  compared using strcmp.
CZMQ_EXPORT void
    zhashx_set_key_hasher (zhashx_t *self, zhashx_hash_fn hasher);

//  Make copy of hash table; if supplied table is null, returns null.
//  Does not copy items themselves. Rebuilds new table so may be slow on
//  very large tables. NOTE: only works with item values that are strings
//  since there's no other way to know how to duplicate the item value.
CZMQ_EXPORT zhashx_t *
    zhashx_dup_v2 (zhashx_t *self);

//  Self test of this class.
CZMQ_EXPORT void
    zhashx_test (bool verbose);

#ifdef CZMQ_BUILD_DRAFT_API
//  *** Draft method, for development use, may change without warning ***
//  Same as unpack but uses a user-defined deserializer function to convert
//  a longstr back into item format.
CZMQ_EXPORT zhashx_t *
    zhashx_unpack_own (zframe_t *frame, zhashx_deserializer_fn deserializer);

//  *** Draft method, for development use, may change without warning ***
//  Same as pack but uses a user-defined serializer function to convert items
//  into longstr.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zframe_t *
    zhashx_pack_own (zhashx_t *self, zhashx_serializer_fn serializer);

#endif // CZMQ_BUILD_DRAFT_API

Description

zhashx is an extended hash table container with more functionality than zhash, its simpler cousin.

The hash table always has a size that is prime and roughly doubles its size when 75% full. In case of hash collisions items are chained in a linked list. The hash table size is increased slightly (up to 5 times before roughly doubling the size) when an overly long chain (between 1 and 63 items depending on table size) is detected.

Example

From zhashx_test method.

zhashx_t *hash = zhashx_new ();
assert (hash);
assert (zhashx_size (hash) == 0);
assert (zhashx_first (hash) == NULL);
assert (zhashx_cursor (hash) == NULL);

//  Insert some items
int rc;
rc = zhashx_insert (hash, "DEADBEEF", "dead beef");
char *item = (char *) zhashx_first (hash);
assert (streq ((char *) zhashx_cursor (hash), "DEADBEEF"));
assert (streq (item, "dead beef"));
assert (rc == 0);
rc = zhashx_insert (hash, "ABADCAFE", "a bad cafe");
assert (rc == 0);
rc = zhashx_insert (hash, "C0DEDBAD", "coded bad");
assert (rc == 0);
rc = zhashx_insert (hash, "DEADF00D", "dead food");
assert (rc == 0);
assert (zhashx_size (hash) == 4);

//  Look for existing items
item = (char *) zhashx_lookup (hash, "DEADBEEF");
assert (streq (item, "dead beef"));
item = (char *) zhashx_lookup (hash, "ABADCAFE");
assert (streq (item, "a bad cafe"));
item = (char *) zhashx_lookup (hash, "C0DEDBAD");
assert (streq (item, "coded bad"));
item = (char *) zhashx_lookup (hash, "DEADF00D");
assert (streq (item, "dead food"));

//  Look for non-existent items
item = (char *) zhashx_lookup (hash, "foo");
assert (item == NULL);

//  Try to insert duplicate items
rc = zhashx_insert (hash, "DEADBEEF", "foo");
assert (rc == -1);
item = (char *) zhashx_lookup (hash, "DEADBEEF");
assert (streq (item, "dead beef"));

//  Some rename tests

//  Valid rename, key is now LIVEBEEF
rc = zhashx_rename (hash, "DEADBEEF", "LIVEBEEF");
assert (rc == 0);
item = (char *) zhashx_lookup (hash, "LIVEBEEF");
assert (streq (item, "dead beef"));

//  Trying to rename an unknown item to a non-existent key
rc = zhashx_rename (hash, "WHATBEEF", "NONESUCH");
assert (rc == -1);

//  Trying to rename an unknown item to an existing key
rc = zhashx_rename (hash, "WHATBEEF", "LIVEBEEF");
assert (rc == -1);
item = (char *) zhashx_lookup (hash, "LIVEBEEF");
assert (streq (item, "dead beef"));

//  Trying to rename an existing item to another existing item
rc = zhashx_rename (hash, "LIVEBEEF", "ABADCAFE");
assert (rc == -1);
item = (char *) zhashx_lookup (hash, "LIVEBEEF");
assert (streq (item, "dead beef"));
item = (char *) zhashx_lookup (hash, "ABADCAFE");
assert (streq (item, "a bad cafe"));

//  Test keys method
zlistx_t *keys = zhashx_keys (hash);
assert (zlistx_size (keys) == 4);
zlistx_destroy (&keys);

zlistx_t *values = zhashx_values(hash);
assert (zlistx_size (values) == 4);
zlistx_destroy (&values);

//  Test dup method
zhashx_t *copy = zhashx_dup (hash);
assert (zhashx_size (copy) == 4);
item = (char *) zhashx_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhashx_destroy (&copy);

//  Test pack/unpack methods
zframe_t *frame = zhashx_pack (hash);
copy = zhashx_unpack (frame);
zframe_destroy (&frame);
assert (zhashx_size (copy) == 4);
item = (char *) zhashx_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhashx_destroy (&copy);

#ifdef CZMQ_BUILD_DRAFT_API
//  Test own pack/unpack methods
zhashx_t *own_hash = zhashx_new ();
zhashx_set_destructor (own_hash, s_test_destroy_int);
assert (own_hash);
int *val1 = (int *) zmalloc (sizeof (int));
int *val2 = (int *) zmalloc (sizeof (int));
*val1 = 25;
*val2 = 100;
zhashx_insert (own_hash, "val1", val1);
zhashx_insert (own_hash, "val2", val2);
frame = zhashx_pack_own (own_hash, s_test_serialize_int);
copy = zhashx_unpack_own (frame, s_test_deserialze_int);
zhashx_set_destructor (copy, s_test_destroy_int);
zframe_destroy (&frame);
assert (zhashx_size (copy) == 2);
assert (*((int *) zhashx_lookup (copy, "val1")) == 25);
assert (*((int *) zhashx_lookup (copy, "val2")) == 100);
zhashx_destroy (&copy);
zhashx_destroy (&own_hash);
#endif // CZMQ_BUILD_DRAFT_API

//  Test save and load
zhashx_comment (hash, "This is a test file");
zhashx_comment (hash, "Created by %s", "czmq_selftest");
zhashx_save (hash, ".cache");
copy = zhashx_new ();
assert (copy);
zhashx_load (copy, ".cache");
item = (char *) zhashx_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhashx_destroy (&copy);
zsys_file_delete (".cache");

//  Delete a item
zhashx_delete (hash, "LIVEBEEF");
item = (char *) zhashx_lookup (hash, "LIVEBEEF");
assert (item == NULL);
assert (zhashx_size (hash) == 3);

//  Check that the queue is robust against random usage
struct {
    char name [100];
    bool exists;
} testset [200];
memset (testset, 0, sizeof (testset));
int testmax = 200, testnbr, iteration;

srandom ((unsigned) time (NULL));
for (iteration = 0; iteration < 25000; iteration++) {
    testnbr = randof (testmax);
    if (testset [testnbr].exists) {
        item = (char *) zhashx_lookup (hash, testset [testnbr].name);
        assert (item);
        zhashx_delete (hash, testset [testnbr].name);
        testset [testnbr].exists = false;
    }
    else {
        sprintf (testset [testnbr].name, "%x-%x", rand (), rand ());
        if (zhashx_insert (hash, testset [testnbr].name, "") == 0)
            testset [testnbr].exists = true;
    }
}
//  Test 10K lookups
for (iteration = 0; iteration < 10000; iteration++)
    item = (char *) zhashx_lookup (hash, "DEADBEEFABADCAFE");

//  Destructor should be safe to call twice
zhashx_destroy (&hash);
zhashx_destroy (&hash);
assert (hash == NULL);

//  Test destructor; automatically copies and frees string values
hash = zhashx_new ();
assert (hash);
zhashx_set_destructor (hash, (zhashx_destructor_fn *) zstr_free);
zhashx_set_duplicator (hash, (zhashx_duplicator_fn *) strdup);
char value [255];
strcpy (value, "This is a string");
rc = zhashx_insert (hash, "key1", value);
assert (rc == 0);
strcpy (value, "Ring a ding ding");
rc = zhashx_insert (hash, "key2", value);
assert (rc == 0);
assert (streq ((char *) zhashx_lookup (hash, "key1"), "This is a string"));
assert (streq ((char *) zhashx_lookup (hash, "key2"), "Ring a ding ding"));
zhashx_destroy (&hash);

Authors

The czmq manual was written by the authors in the Authors file.

Resources

Main web site:

Report bugs to the email <zeromq-dev@lists.zeromq.org[1]>

Notes

1.

zeromq-dev@lists.zeromq.org

mailto:zeromq-dev@lists.zeromq.org

Referenced By

czmq(7).

11/11/2016 CZMQ 4.0.1 CZMQ Manual