1# @(#)README 8.1 (Berkeley) 06/04/93 2 3This package implements a superset of the hsearch and dbm/ndbm libraries. 4 5Test Programs: 6 All test programs which need key/data pairs expect them entered 7 with key and data on separate lines 8 9 tcreat3.c 10 Takes 11 bucketsize (bsize), 12 fill factor (ffactor), and 13 initial number of elements (nelem). 14 Creates a hash table named hashtest containing the 15 keys/data pairs entered from standard in. 16 thash4.c 17 Takes 18 bucketsize (bsize), 19 fill factor (ffactor), 20 initial number of elements (nelem) 21 bytes of cache (ncached), and 22 file from which to read data (fname) 23 Creates a table from the key/data pairs on standard in and 24 then does a read of each key/data in fname 25 tdel.c 26 Takes 27 bucketsize (bsize), and 28 fill factor (ffactor). 29 file from which to read data (fname) 30 Reads each key/data pair from fname and deletes the 31 key from the hash table hashtest 32 tseq.c 33 Reads the key/data pairs in the file hashtest and writes them 34 to standard out. 35 tread2.c 36 Takes 37 butes of cache (ncached). 38 Reads key/data pairs from standard in and looks them up 39 in the file hashtest. 40 tverify.c 41 Reads key/data pairs from standard in, looks them up 42 in the file hashtest, and verifies that the data is 43 correct. 44 45NOTES: 46 47The file search.h is provided for using the hsearch compatible interface 48on BSD systems. On System V derived systems, search.h should appear in 49/usr/include. 50 51The man page ../man/db.3 explains the interface to the hashing system. 52The file hash.ps is a postscript copy of a paper explaining 53the history, implementation, and performance of the hash package. 54 55"bugs" or idiosyncracies 56 57If you have a lot of overflows, it is possible to run out of overflow 58pages. Currently, this will cause a message to be printed on stderr. 59Eventually, this will be indicated by a return error code. 60 61If you are using the ndbm interface and exit without flushing or closing the 62file, you may lose updates since the package buffers all writes. Also, 63the db interface only creates a single database file. To avoid overwriting 64the user's original file, the suffix ".db" is appended to the file name 65passed to dbm_open. Additionally, if your code "knows" about the historic 66.dir and .pag files, it will break. 67 68There is a fundamental difference between this package and the old hsearch. 69Hsearch requires the user to maintain the keys and data in the application's 70allocated memory while hash takes care of all storage management. The down 71side is that the byte strings passed in the ENTRY structure must be null 72terminated (both the keys and the data). 73