hdestroy man page on DigitalUNIX

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hsearch(3)							    hsearch(3)

       hsearch,	 hcreate,  hdestroy, hsearch_r, hcreate_r, hdestroy_r - Manage
       hash tables

       #include <search.h>

       ENTRY *hsearch(
	       ENTRY item,
	       ACTION action ); int hcreate(
	       size_t nel ); void hdestroy(
	       void ); int hsearch_r(
	       ENTRY item,
	       ACTION action,
	       ENTRY **target,
	       struct hsearch_data *hsearch_data ); int hcreate_r(
	       size_t nel,
	       struct hsearch_data *hsearch_data ); void hdestroy_r(
	       struct hsearch_data *hsearch_data );

       Standard C Library (libc)

       Interfaces documented on this reference page conform to industry	 stan‐
       dards as follows:

       hsearch(), hcreate(), hdestroy(): XSH4.2

       Refer  to  the  standards(5)  reference page for more information about
       industry standards and associated tags.

       Identifies a structure of the type ENTRY as  defined  in	 the  search.h
       header  file.  It  contains  two pointers: Points to the comparison key
       string.	Points to any other data associated with the char *key parame‐

	      Pointers	to  types  other  than	char should be cast as char *.
	      Specifies a value for an ACTION enum type, which indicates  what
	      is  to  be  done with an item key when it cannot be found in the
	      hash table. The following two actions can be specified for  this
	      parameter:  Enter	 the  key specified by the item parameter into
	      the hash table at the appropriate place. When the table is full,
	      a	 null pointer is returned.  Do not enter the item key into the
	      table, but return a null pointer when  an	 item  key  cannot  be
	      found  in	 the hash table.  Specifies an estimate of the maximum
	      number of entries that the hash table will contain.  Under  some
	      circumstances,  the  hcreate()  function may make the hash table
	      larger than specified to obtain mathematically favorable	condi‐
	      tions  for  access to the hash table.  Points at the hash table.
	      This table is kept in the thread's address space.	 Points at the
	      size of the hash table.  Points at the log base 2 version of the
	      hash table length.  Points at the number of entries in the  hash
	      table.   Specifies  the length of the hash table.	 Specifies the
	      log base 2 version of the hash table length.  Points to the item
	      actually found.  Consists of data for the hash table.

       The  hsearch(),	hcreate(), and hdestroy() functions are used to manage
       hash table operations: The hcreate() function initializes the hash  ta‐
       ble.  You must call the hcreate() function before calling the hsearch()
       function.  The hsearch() function searches a hash table. It  returns  a
       pointer	into  a	 hash  table that indicates where a given entry can be
       found. The hsearch() function uses open addressing with	a  hash	 func‐
       tion.   The hdestroy() function deletes the hash table. This allows you
       to start a new hash table because only one table may  be	 active	 at  a
       time.  After  the  call	to  hdestroy(),	 the hash table data should no
       longer be considered accessible.

       [Tru64 UNIX]  The hsearch_r(), hcreate_r(), and hdestroy_r()  functions
       are  reentrant  versions of hsearch(), hcreate(), and hdestroy().  Upon
       successful completion, the hsearch_r() function returns 0 (zero).  Upon
       failure, it returns -1 and sets errno.

       [Tru64  UNIX]  Threads  can  share  hash tables by using the hcreate_r,
       hsearch_r, and hdestroy_r functions with a common  hsearch_data	value.
       To  prevent corruption of data when sharing a hash table, locks must be
       used around calls that use the common hsearch_data value.

       The hsearch() function returns a null pointer when the action parameter
       is  FIND	 and  the  key	pointed to by item cannot be found or when the
       specified action is ENTER and the hash table is full.

       Upon successful completion, the hcreate() function  returns  a  nonzero
       value.  Otherwise,  when sufficient space for the table cannot be allo‐
       cated, the hcreate() function returns a value of 0 (zero).

       If any of the following conditions occur, the hsearch()	function  sets
       errno to the corresponding value: The table is full.  [Tru64 UNIX]  The
       search failed.

       Functions: bsearch(3), lsearch(3), tsearch(3), qsort(3)

       Standards: standards(5)


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