TTTTCCCCLLLL____OOOONNNNEEEE____WWWWOOOORRRRDDDD____KKKKEEEEYYYYSSSS Keys are single-word values; they are passed to
hashing routines and stored in hash table
entries as ``char *'' values. The pointer value
is the key; it need not (and usually doesn't)
actually point to a string.
_o_t_h_e_r If _k_e_y_T_y_p_e is not TCL_STRING_KEYS or
TCL_ONE_WORD_KEYS, then it must be an integer
value greater than 1. In this case the keys
will be arrays of ``int'' values, where _k_e_y_T_y_p_e
gives the number of ints in each key. This
allows structures to be used as keys. All keys
must have the same size. Array keys are passed
into hashing functions using the address of the
first int in the array.
TTTTccccllll____DDDDeeeelllleeeetttteeeeHHHHaaaasssshhhhTTTTaaaabbbblllleeee deletes all of the entries in a hash table and frees
up the memory associated with the table's bucket array and entries. It
does not free the actual table structure (pointed to by _t_a_b_l_e_P_t_r), since
that memory is assumed to be managed by the client. TTTTccccllll____DDDDeeeelllleeeetttteeeeHHHHaaaasssshhhhTTTTaaaabbbblllleeee
also does not free or otherwise manipulate the values of the hash table
entries. If the entry values point to dynamically-allocated memory, then
it is the client's responsibility to free these structures before
deleting the table.
TTTTccccllll____CCCCrrrreeeeaaaatttteeeeHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy locates the entry corresponding to a particular key,
creating a new entry in the table if there wasn't already one with the
given key. If an entry already existed with the given key then *_n_e_w_P_t_r
is set to zero. If a new entry was created, then *_n_e_w_P_t_r is set to a
non-zero value and the value of the new entry will be set to zero. The
return value from TTTTccccllll____CCCCrrrreeeeaaaatttteeeeHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy is a pointer to the entry, which
may be used to retrieve and modify the entry's value or to delete the
entry from the table.
TTTTccccllll____DDDDeeeelllleeeetttteeeeHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy will remove an existing entry from a table. The
memory associated with the entry itself will be freed, but the client is
responsible for any cleanup associated with the entry's value, such as
freeing a structure that it points to.
TTTTccccllll____FFFFiiiinnnnddddHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy is similar to TTTTccccllll____CCCCrrrreeeeaaaatttteeeeHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy except that it
doesn't create a new entry if the key doesn't exist; instead, it returns
NULL as result.
TTTTccccllll____GGGGeeeettttHHHHaaaasssshhhhVVVVaaaalllluuuueeee and TTTTccccllll____SSSSeeeettttHHHHaaaasssshhhhVVVVaaaalllluuuueeee are used to read and write an
entry's value, respectively. Values are stored and retrieved as type
``ClientData'', which is large enough to hold a pointer value. On almost
all machines this is large enough to hold an integer value too.
TTTTccccllll____GGGGeeeettttHHHHaaaasssshhhhKKKKeeeeyyyy returns the key for a given hash table entry, either as a
pointer to a string, a one-word (``char *'') key, or as a pointer to the
first word of an array of integers, depending on the _k_e_y_T_y_p_e used to
create a hash table. In all cases TTTTccccllll____GGGGeeeettttHHHHaaaasssshhhhKKKKeeeeyyyy returns a result with
type ``char *''. When the key is a string or array, the result of
TTTTccccllll____GGGGeeeettttHHHHaaaasssshhhhKKKKeeeeyyyy points to information in the table entry; this
information will remain valid until the entry is deleted or its table is
deleted.
TTTTccccllll____FFFFiiiirrrrssssttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy and TTTTccccllll____NNNNeeeexxxxttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy may be used to scan all of the
entries in a hash table. A structure of type ``Tcl_HashSearch'',
provided by the client, is used to keep track of progress through the
table. TTTTccccllll____FFFFiiiirrrrssssttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy initializes the search record and returns the
first entry in the table (or NULL if the table is empty). Each
subsequent call to TTTTccccllll____NNNNeeeexxxxttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy returns the next entry in the table
or NULL if the end of the table has been reached. A call to
TTTTccccllll____FFFFiiiirrrrssssttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy followed by calls to TTTTccccllll____NNNNeeeexxxxttttHHHHaaaasssshhhhEEEEnnnnttttrrrryyyy will return
each of the entries in the table exactly once, in an arbitrary order. It
is unadvisable to modify the structure of the table, e.g. by creating or
deleting entries, while the search is in progress.
TTTTccccllll____HHHHaaaasssshhhhSSSSttttaaaattttssss returns a dynamically-allocated string with overall
information about a hash table, such as the number of entries it
contains, the number of buckets in its hash array, and the utilization of
the buckets. It is the caller's responsibility to free the result string
by passing it to ffffrrrreeeeeeee.
The header file ttttccccllll....hhhh defines the actual data structures used to
implement hash tables. This is necessary so that clients can allocate
Tcl_HashTable structures and so that macros can be used to read and write
the values of entries. However, users of the hashing routines should
never refer directly to any of the fields of any of the hash-related data
structures; use the procedures and macros defined here.
