'\" t
.\"     Title: zhash
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 03/02/2024
.\"    Manual: CZMQ Manual
.\"    Source: CZMQ 4.2.1
.\"  Language: English
.\"
.TH "ZHASH" "3" "03/02/2024" "CZMQ 4\&.2\&.1" "CZMQ Manual"
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.\" * MAIN CONTENT STARTS HERE *
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.SH "NAME"
zhash \- Class for simple generic hash container
.SH "SYNOPSIS"
.sp
.nf
//  This is a stable class, and may not change except for emergencies\&. It
//  is provided in stable builds\&.
// Callback function for zhash_freefn method
typedef void (zhash_free_fn) (
    void *data);

//  Create a new, empty hash container
CZMQ_EXPORT zhash_t *
    zhash_new (void);

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

//  Destroy a hash container and all items in it
CZMQ_EXPORT void
    zhash_destroy (zhash_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
    zhash_insert (zhash_t *self, const char *key, void *item);

//  Update item into hash table with specified key and item\&.
//  If key is already present, destroys old item and inserts new one\&.
//  Use free_fn method to ensure deallocator is properly called on item\&.
CZMQ_EXPORT void
    zhash_update (zhash_t *self, const char *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
    zhash_delete (zhash_t *self, const char *key);

//  Return the item at the specified key, or null
CZMQ_EXPORT void *
    zhash_lookup (zhash_t *self, const char *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
    zhash_rename (zhash_t *self, const char *old_key, const char *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\*(Aqt have memory leaks\&. You can pass \*(Aqfree\*(Aq or NULL as a free_fn\&.
//  Returns the item, or NULL if there is no such item\&.
CZMQ_EXPORT void *
    zhash_freefn (zhash_t *self, const char *key, zhash_free_fn free_fn);

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

//  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\*(Aqs no other way to know how to duplicate the item value\&.
//  Caller owns return value and must destroy it when done\&.
CZMQ_EXPORT zhash_t *
    zhash_dup (zhash_t *self);

//  Return keys for items in table
//  Caller owns return value and must destroy it when done\&.
CZMQ_EXPORT zlist_t *
    zhash_keys (zhash_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 zhash_cursor()\&. NOTE: do NOT modify the table while iterating\&.
CZMQ_EXPORT void *
    zhash_first (zhash_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
//  zhash_first() to process all items in a hash table\&. If you need the
//  items in sorted order, use zhash_keys() and then zlist_sort()\&. To
//  access the key for this item use zhash_cursor()\&. NOTE: do NOT modify
//  the table while iterating\&.
CZMQ_EXPORT void *
    zhash_next (zhash_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 char *
    zhash_cursor (zhash_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
    zhash_comment (zhash_t *self, const char *format, \&.\&.\&.) CHECK_PRINTF (2);

//  Serialize hash table to a binary frame that can be sent in a message\&.
//  The packed format is compatible with the \*(Aqdictionary\*(Aq 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 *
    zhash_pack (zhash_t *self);

//  Save hash table to a text file in name=value format\&. Hash values must be
//  printable strings; keys may not contain \*(Aq=\*(Aq character\&. Returns 0 if OK,
//  else \-1 if a file error occurred\&.
CZMQ_EXPORT int
    zhash_save (zhash_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
//  \*(Aq=\*(Aq character\&. Returns 0 if OK, else \-1 if a file was not readable\&.
CZMQ_EXPORT int
    zhash_load (zhash_t *self, const char *filename);

//  When a hash table was loaded from a file by zhash_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
    zhash_refresh (zhash_t *self);

//  Set hash for automatic value destruction\&. Note that this assumes that
//  values are NULL\-terminated strings\&. Do not use with different types\&.
CZMQ_EXPORT void
    zhash_autofree (zhash_t *self);

//  Self test of this class\&.
CZMQ_EXPORT void
    zhash_test (bool verbose);

Please add \*(Aq@interface\*(Aq section in \*(Aq\&./\&.\&./src/zhash\&.c\*(Aq\&.
.fi
.SH "DESCRIPTION"
.sp
zhash is an expandable hash table container\&. This is a simple container\&. For heavy\-duty applications we recommend using zhashx\&.
.sp
Note that it\(cqs relatively slow (50K insertions/deletes per second), so don\(cqt do inserts/updates on the critical path for message I/O\&. It can do 2\&.5M lookups per second for 16\-char keys\&. Timed on a 1\&.6GHz CPU\&.
.SH "EXAMPLE"
.PP
\fBFrom zhash_test method\fR. 
.sp
.if n \{\
.RS 4
.\}
.nf
zhash_t *hash = zhash_new ();
assert (hash);
assert (zhash_size (hash) == 0);
assert (zhash_first (hash) == NULL);
assert (zhash_cursor (hash) == NULL);

//  Insert some items
int rc;
rc = zhash_insert (hash, "DEADBEEF", "dead beef");
char *item = (char *) zhash_first (hash);
assert (streq (zhash_cursor (hash), "DEADBEEF"));
assert (streq (item, "dead beef"));
assert (rc == 0);
rc = zhash_insert (hash, "ABADCAFE", "a bad cafe");
assert (rc == 0);
rc = zhash_insert (hash, "C0DEDBAD", "coded bad");
assert (rc == 0);
rc = zhash_insert (hash, "DEADF00D", "dead food");
assert (rc == 0);
assert (zhash_size (hash) == 4);

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

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

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

//  Some rename tests

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

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

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

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

//  Test keys method
zlist_t *keys = zhash_keys (hash);
assert (zlist_size (keys) == 4);
zlist_destroy (&keys);

//  Test dup method
zhash_t *copy = zhash_dup (hash);
assert (zhash_size (copy) == 4);
item = (char *) zhash_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhash_destroy (&copy);

//  Test pack/unpack methods
zframe_t *frame = zhash_pack (hash);
copy = zhash_unpack (frame);
zframe_destroy (&frame);
assert (zhash_size (copy) == 4);
item = (char *) zhash_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhash_destroy (&copy);

//  Test save and load
zhash_comment (hash, "This is a test file");
zhash_comment (hash, "Created by %s", "czmq_selftest");
zhash_save (hash, "\&.cache");
copy = zhash_new ();
assert (copy);
zhash_load (copy, "\&.cache");
item = (char *) zhash_lookup (copy, "LIVEBEEF");
assert (item);
assert (streq (item, "dead beef"));
zhash_destroy (&copy);
zsys_file_delete ("\&.cache");

//  Delete a item
zhash_delete (hash, "LIVEBEEF");
item = (char *) zhash_lookup (hash, "LIVEBEEF");
assert (item == NULL);
assert (zhash_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 *) zhash_lookup (hash, testset [testnbr]\&.name);
        assert (item);
        zhash_delete (hash, testset [testnbr]\&.name);
        testset [testnbr]\&.exists = false;
    }
    else {
        sprintf (testset [testnbr]\&.name, "%x\-%x", rand (), rand ());
        if (zhash_insert (hash, testset [testnbr]\&.name, "") == 0)
            testset [testnbr]\&.exists = true;
    }
}
//  Test 10K lookups
for (iteration = 0; iteration < 10000; iteration++)
    item = (char *) zhash_lookup (hash, "DEADBEEFABADCAFE");

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

// Test autofree; automatically copies and frees string values
hash = zhash_new ();
assert (hash);
zhash_autofree (hash);
char value [255];
strcpy (value, "This is a string");
rc = zhash_insert (hash, "key1", value);
assert (rc == 0);
strcpy (value, "Inserting with the same key will fail");
rc = zhash_insert (hash, "key1", value);
assert (rc == \-1);
strcpy (value, "Ring a ding ding");
rc = zhash_insert (hash, "key2", value);
assert (rc == 0);
assert (streq ((char *) zhash_lookup (hash, "key1"), "This is a string"));
assert (streq ((char *) zhash_lookup (hash, "key2"), "Ring a ding ding"));
zhash_destroy (&hash);

#if defined (__WINDOWS__)
zsys_shutdown();
#endif
.fi
.if n \{\
.RE
.\}
.sp
.SH "AUTHORS"
.sp
The czmq manual was written by the authors in the AUTHORS file\&.
.SH "RESOURCES"
.sp
Main web site: \m[blue]\fB\%\fR\m[]
.sp
Report bugs to the email <\m[blue]\fBzeromq\-dev@lists\&.zeromq\&.org\fR\m[]\&\s-2\u[1]\d\s+2>
.SH "COPYRIGHT"
.sp
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\&.
.SH "NOTES"
.IP " 1." 4
zeromq-dev@lists.zeromq.org
.RS 4
\%mailto:zeromq-dev@lists.zeromq.org
.RE