ZHASHX(3)

NAME
zhashx - Class for 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);
// Destroy an item.
typedef void (zhashx_free_fn) (
    void *data);
// Hash function for keys.
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.
//  The callback function should return zero (0) on matching
//  items.
CZMQ_EXPORT void
    zhashx_set_key_comparator (zhashx_t *self, zhashx_comparator_fn comparator);
//  Set a user-defined hash function for keys; by default keys are
//  hashed by a modified Bernstein hashing function.
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
Please add '@interface' section in '/home/builder/.termux-build/libczmq/src/doc/../src/zhashx.c'.

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);
        assert (testnbr != testmax);
        assert (testnbr < 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 randof() limits - should be within (0..testmax)
    //  and randomness distribution - should not have (many) zero-counts
    //  If there are - maybe the ZSYS_RANDOF_MAX is too big for this platform
    //  Note: This test can take a while on systems with weak floating point HW
    testmax = 999;
    size_t rndcnt[999];
    assert ((sizeof (rndcnt)/sizeof(rndcnt[0])) == testmax);
    memset (rndcnt, 0, sizeof (rndcnt));
    for (iteration = 0; iteration < 10000000; iteration++) {
        testnbr = randof (testmax);
        assert (testnbr != testmax);
        assert (testnbr < testmax);
        assert (testnbr >= 0);
        rndcnt[testnbr]++;
    }
    int rndmisses = 0;
    for (iteration = 0; iteration < testmax; iteration++) {
        if (rndcnt[iteration] == 0) {
            zsys_warning("zhashx_test() : random distribution fault : got 0 hits for %d/%d",
                iteration, testmax);
            rndmisses++;
        }
    }
    //  Too many misses are suspicious... we can lose half the entries
    //  for each bit not used in the assumed ZSYS_RANDOF_MAX...
    assert ( (rndmisses < (testmax / 3 )) );
    //  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);
    //  Test purger and shrinker: no data should end up unreferenced in valgrind
    hash = zhashx_new ();
    assert (hash);
    zhashx_set_destructor (hash, (zhashx_destructor_fn *) zstr_free);
    zhashx_set_duplicator (hash, (zhashx_duplicator_fn *) strdup);
    char valuep [255];
    strcpy (valuep, "This is a string");
    rc = zhashx_insert (hash, "key1", valuep);
    assert (rc == 0);
    strcpy (valuep, "Ring a ding ding");
    rc = zhashx_insert (hash, "key2", valuep);
    assert (rc == 0);
    strcpy (valuep, "Cartahena delenda est");
    rc = zhashx_insert (hash, "key3", valuep);
    assert (rc == 0);
    strcpy (valuep, "So say we all!");
    rc = zhashx_insert (hash, "key4", valuep);
    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"));
    assert (streq ((char *) zhashx_lookup (hash, "key3"), "Cartahena delenda est"));
    assert (streq ((char *) zhashx_lookup (hash, "key4"), "So say we all!"));
    zhashx_purge (hash);
    zhashx_destroy (&hash);
    #if defined (__WINDOWS__)
    zsys_shutdown();
    #endif

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]>

COPYRIGHT

Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: http://czmq.zeromq.org. This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution.

NOTES

1.  zeromq-dev@lists.zeromq.org
    mailto:zeromq-dev@lists.zeromq.org