NAME
hsearch - hsearch, hcreate, hdestroy
SYNOPSIS
#define DB_DBM_HSEARCH 1
#include <db2/db.h>
typedef enum {
FIND, ENTER
} ACTION;
typedef struct entry {
char *key;
void *data;
} ENTRY;
ENTRY *
hsearch(ENTRY item, ACTION action);
int
hcreate(size_t nelem);
void
hdestroy(void);
DESCRIPTION
The hsearch interface to the DB library is intended to provide source code compatibility for historic applications. It is not recommended for any other purpose.
To compile hsearch applications, replace the application's #include of the hsearch include file (e.g., ``#include <search.h>'') with the following two lines:
#define DB_DBM_HSEARCH 1
#include <db2/db.h>
and recompile.
The hcreate function creates an in-memory database. The nelem argument is an estimation of the maximum number of key/data pairs that will be stored in the database.
The hdestroy function discards the database.
Database elements are structures of type ENTRY, which contain at least two fields: key and data. The field key is declared to be of type ``char *'' and is the key used for storage and retrieval. The field data is declared to be of type ``void *'' and is its associated data.
The hsearch function retrieves key/data pairs from, and stores key/data pairs into, the database.
The action argument must be set to one of two values:
- ENTER
-
If the key does not already appear in the database, insert the key/data pair into the database. If the key already appears in the database, return a reference to an ENTRY structure referencing the existing key and its associated data element.
- FIND
-
Retrieve the specified key/data pair from the database.
COMPATIBILITY NOTES
Historically, hsearch required applications to maintain the keys and data in the application's memory for as long as the hsearch database existed. As DB handles key and data management internally, there is no requirement that applications maintain local copies of key and data items, although the only effect of doing so should be the allocation of additional memory.
DIAGNOSTICS
The hcreate function returns 0 on failure, setting errno, and non-zero on success.
The hsearch function returns a pointer to an ENTRY structure on success, and NULL, setting errno, if the action specified was FIND and the item did not appear in the database.
ERRORS
The hcreate function may fail and return errno for any of the errors specified for the following DB and library functions: db_open(3), and memset(3).
The hsearch function may fail and return errno for any of the errors specified for the following DB and library functions: DB->get(3), DB->put(3), memset(3), and strlen(3).
In addition, the hsearch function will fail, setting errno to 0, if the action specified was FIND and the item did not appear in the database.
SEE ALSO
The DB library is a family of groups of functions that provides a modular programming interface to transactions and record-oriented file access. The library includes support for transactions, locking, logging and file page caching, as well as various indexed access methods. Many of the functional groups (e.g., the file page caching functions) are useful independent of the other DB functions, although some functional groups are explicitly based on other functional groups (e.g., transactions and logging). For a general description of the DB package, see db_intro(3).
db_archive(1), db_checkpoint(1), db_deadlock(1), db_dump(1), db_load(1), db_recover(1), db_stat(1), db_intro(3), db_appinit(3), db_cursor(3), db_dbm(3), db_internal(3), db_lock(3), db_log(3), db_mpool(3), db_open(3), db_thread(3), db_txn(3)