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Diffstat (limited to 'lib/libc/db/hash/README')
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diff --git a/lib/libc/db/hash/README b/lib/libc/db/hash/README new file mode 100644 index 0000000..80d6743 --- /dev/null +++ b/lib/libc/db/hash/README @@ -0,0 +1,69 @@ +# @(#)README 8.1 (Berkeley) 6/4/93 +# $FreeBSD$ + +This package implements a superset of the hsearch and dbm/ndbm libraries. + +Test Programs: + All test programs which need key/data pairs expect them entered + with key and data on separate lines + + tcreat3.c + Takes + bucketsize (bsize), + fill factor (ffactor), and + initial number of elements (nelem). + Creates a hash table named hashtest containing the + keys/data pairs entered from standard in. + thash4.c + Takes + bucketsize (bsize), + fill factor (ffactor), + initial number of elements (nelem) + bytes of cache (ncached), and + file from which to read data (fname) + Creates a table from the key/data pairs on standard in and + then does a read of each key/data in fname + tdel.c + Takes + bucketsize (bsize), and + fill factor (ffactor). + file from which to read data (fname) + Reads each key/data pair from fname and deletes the + key from the hash table hashtest + tseq.c + Reads the key/data pairs in the file hashtest and writes them + to standard out. + tread2.c + Takes + butes of cache (ncached). + Reads key/data pairs from standard in and looks them up + in the file hashtest. + tverify.c + Reads key/data pairs from standard in, looks them up + in the file hashtest, and verifies that the data is + correct. + +NOTES: + +The man page ../man/db.3 explains the interface to the hashing system. +The file hash.ps is a postscript copy of a paper explaining +the history, implementation, and performance of the hash package. + +"bugs" or idiosyncracies + +If you have a lot of overflows, it is possible to run out of overflow +pages. Currently, this will cause a message to be printed on stderr. +Eventually, this will be indicated by a return error code. + +If you are using the ndbm interface and exit without flushing or closing the +file, you may lose updates since the package buffers all writes. Also, +the db interface only creates a single database file. To avoid overwriting +the user's original file, the suffix ".db" is appended to the file name +passed to dbm_open. Additionally, if your code "knows" about the historic +.dir and .pag files, it will break. + +There is a fundamental difference between this package and the old hsearch. +Hsearch requires the user to maintain the keys and data in the application's +allocated memory while hash takes care of all storage management. The down +side is that the byte strings passed in the ENTRY structure must be null +terminated (both the keys and the data). |