73 lines
2.6 KiB
Plaintext
73 lines
2.6 KiB
Plaintext
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# @(#)README 8.1 (Berkeley) 6/4/93
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This package implements a superset of the hsearch and dbm/ndbm libraries.
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Test Programs:
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All test programs which need key/data pairs expect them entered
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with key and data on separate lines
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tcreat3.c
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Takes
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bucketsize (bsize),
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fill factor (ffactor), and
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initial number of elements (nelem).
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Creates a hash table named hashtest containing the
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keys/data pairs entered from standard in.
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thash4.c
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Takes
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bucketsize (bsize),
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fill factor (ffactor),
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initial number of elements (nelem)
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bytes of cache (ncached), and
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file from which to read data (fname)
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Creates a table from the key/data pairs on standard in and
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then does a read of each key/data in fname
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tdel.c
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Takes
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bucketsize (bsize), and
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fill factor (ffactor).
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file from which to read data (fname)
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Reads each key/data pair from fname and deletes the
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key from the hash table hashtest
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tseq.c
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Reads the key/data pairs in the file hashtest and writes them
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to standard out.
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tread2.c
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Takes
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butes of cache (ncached).
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Reads key/data pairs from standard in and looks them up
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in the file hashtest.
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tverify.c
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Reads key/data pairs from standard in, looks them up
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in the file hashtest, and verifies that the data is
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correct.
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NOTES:
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The file search.h is provided for using the hsearch compatible interface
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on BSD systems. On System V derived systems, search.h should appear in
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/usr/include.
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The man page ../man/db.3 explains the interface to the hashing system.
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The file hash.ps is a postscript copy of a paper explaining
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the history, implementation, and performance of the hash package.
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"bugs" or idiosyncracies
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If you have a lot of overflows, it is possible to run out of overflow
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pages. Currently, this will cause a message to be printed on stderr.
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Eventually, this will be indicated by a return error code.
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If you are using the ndbm interface and exit without flushing or closing the
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file, you may lose updates since the package buffers all writes. Also,
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the db interface only creates a single database file. To avoid overwriting
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the user's original file, the suffix ".db" is appended to the file name
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passed to dbm_open. Additionally, if your code "knows" about the historic
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.dir and .pag files, it will break.
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There is a fundamental difference between this package and the old hsearch.
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Hsearch requires the user to maintain the keys and data in the application's
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allocated memory while hash takes care of all storage management. The down
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side is that the byte strings passed in the ENTRY structure must be null
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terminated (both the keys and the data).
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