391 lines
13 KiB
Scheme
391 lines
13 KiB
Scheme
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;;; DBM processing code
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;;; Copyright (c) 1995 by David Albertz (dalbertz@clark.lcs.mit.edu).
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;;; This code is freely available for use by anyone for any purpose,
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;;; so long as you don't charge money for it, remove this notice, or
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;;; hold us liable for any results of its use. --enjoy.
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;;; Usage: (dbm-open name flags mode . access_method access_info)
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;;; name := name of database file (no extension)
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;;; flags := file access flags (open/create etc.)
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;;; mode := file access modes (privileges)
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;;; access_method := *if* you have Berkeley dbm, then
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;;; you can specify btree, hash, or
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;;; recno access methods (0, 1, or 2)
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;;; access_info := *if* you have Berkeley dbm, then
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;;; you can specify an access information
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;;; record, which must correspond to the
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;;; correct access method.
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;;; *Note*: If you do *not* have Berkeley dbm, then specifying
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;;; access_method and/or access_info will generate an
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;;; error. If access_method is omitted and you *do*
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;;; have Berkeley dbm, the default is btree.
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;;; Return: dbm-record which contains the Alien value pointer
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;;; to the open DBM structure and an open
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;;; status flag set to #t.
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;;; Usage: (dbm-close db)
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;;; db := The dbm-record returned by dbm-open
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;;; Return: Return value is undefined
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;;; Usage: (dbm-fetch db key)
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;;; db := The dbm-record returnd by dbm-open
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;;; key := The key value of data to be retrieved
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;;; Return: String containing data associated with key
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;;; Usage: (dbm-insert db key data)
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;;; db := The dbm-record returned by dbm-open
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;;; key := The key value to be associated with data
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;;; data := The data to be stored with the key
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;;; Note: Insert will return an error if you try to
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;;; insert a duplicate key into the database
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;;; Return: Return value is undefined
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;;; Usage: (dbm-replace db key data)
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;;; db := The dbm-record returned by dbm-open
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;;; key := The key value whose data is to be changed
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;;; data := The data to be stored with the key
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;;; Note: If you try to replace the data for a non-existent
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;;; key, dbm-replace will act like dbm-insert
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;;; Return: Return value is undefined
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;;; Usage: (dbm-delete db key)
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;;; db := The dbm-record returned by dbm-open
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;;; key := The key value of data to be deleted
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;;; Return: Integer returned by UNIX dbm_delete routine
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;;; Usage: (dbm-firstkey db)
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;;; db := The dbm-record returned by dbm-open
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;;; Return: First key value stored in database hash table.
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;;; Usage: (dbm-nextkey db)
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;;; db := The dbm-record returned by dbm-open
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;;; Return: Next key value stored in database hash table.
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;;; Returns the null string when there are no more keys.
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;;; If a database error is detected during any read or write operation,
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;;; the error number returned by the UNIX dbm_error routine is passed
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;;; back as an error condition.
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;;; ***NOTE: All key and data elements must be strings
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;;; Scheme48 implementation.
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(foreign-source
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"#include <sys/types.h>"
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"#include <limits.h>"
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"#include <ndbm.h>"
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"#include <db.h>"
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""
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"extern int errno;"
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""
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"#define errno_or_false(x) (((x) == -1) ? ENTER_FIXNUM(errno) : SCHFALSE)"
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"" "")
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;;; This record will hold the pointer the the dbm structure plus
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;;; a boolean flag with open status information
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(define-record dbm-record
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open?
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dbm)
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;;; Use this record to pass btree access method specific data to dbm-open
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(define-record btree-info
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flags
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cachesize
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maxkeypage
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minkeypage
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psize
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lorder)
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;;; Use this record to pass hash access method specific data to dbm-open
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(define-record hash-info
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bsize
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ffactor
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nelem
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cachesize
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lorder)
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;;; Use this record to pass recno access method specific data to dbm-open
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(define-record recno-info
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flags
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cachesize
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psize
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lorder
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reclen
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bval
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bfname)
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;;; Internal routine returns true if Berkeley dbm code is available
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(define-foreign %db-check (db_check)
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bool)
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;;; If you don't specifiy an access method, this is the default
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;;; internal routine that will be called. The only one you can
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;;; use if you don't have Berkely dbm.
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(define-foreign %dbm-open (db_open_default (string file)
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(integer flags)
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(integer mode))
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(to-scheme integer errno_or_false) ; error flag
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(C DB**)) ; DB structure
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;;; Internal routine to open btree database
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(define-foreign %dbm-open-btree (db_open_btree (string file)
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(integer flags)
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(integer mode)
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(integer pass-info?)
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(integer access-flags)
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(integer cachesize)
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(integer maxkeypage)
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(integer minkeypage)
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(integer psize)
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(integer lorder))
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(to-scheme integer errno_or_false) ; error flag
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(C DB**)) ; DB structure
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;;; Internal routine to open hash database
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(define-foreign %dbm-open-hash (db_open_hash (string file)
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(integer flags)
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(integer mode)
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(integer pass-info?)
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(integer bsize)
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(integer ffactor)
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(integer nelem)
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(integer cachesize)
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(integer lorder))
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(to-scheme integer errno_or_false) ; error flag
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(C DB**)) ; DB structure
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;;; Internal routine to open recno database
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(define-foreign %dbm-open-recno (db_open_recno (string file)
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(integer flags)
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(integer mode)
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(integer pass-info?)
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(integer access-flags)
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(integer cachesize)
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(integer psize)
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(integer lorder)
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(integer reclen)
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(char bval)
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(string bfname))
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(to-scheme integer errno_or_false) ; error flag
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(C DB**)) ; DB structure
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;;; Convenient names for the access methods - these are exported
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(define btree/method 0)
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(define hash/method 1)
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(define recno/method 2)
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;;; Several utility routines to help parse optional parameters
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(define (maybe-car lst)
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(if (pair? lst)
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(car lst)
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#f))
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(define (maybe-cdr lst)
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(if (pair? lst)
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(cdr lst)
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#f))
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(define (maybe-cadr lst)
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(maybe-car (maybe-cdr lst)))
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;;; This routine returns to correct internal %dbm-open-foo routine
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;;; based on the specified access method. If Berkeley dbm is not
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;;; present on the system it will return an error condition if
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;;; any access method is specified.
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(define (get-access-method access-parms)
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(let ((Berkeley? (%db-check))
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(access-method (maybe-car access-parms)))
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(if (and (not Berkeley?) access-method)
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(error "You need the Berkeley dbm library - it's free!")
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(cond ((equal? access-method btree/method) %dbm-open-btree)
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((equal? access-method hash/method) %dbm-open-hash)
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((equal? access-method recno/method) %dbm-open-recno)
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((not access-method) %dbm-open)
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(else (error "Invalid access method specified"))))))
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;;; This routine checks for an optional access method specific information
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;;; record (btree-info, hash-info, or recno-info). It returns an error
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;;; condition of the record type does not match the access method.
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;;; Case 1: no access method or access info record provided
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;;; Return the empty list
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;;; Case 2: Access method provided but not the info record
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;;; Return a list with 0 as the first element
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;;; and the correct number of remaining
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;;; elements for the specified access method.
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;;; The values in these elements are arbitrary.
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;;; Case 3: Both access method and access info record provided
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;;; Return a list with 1 as the first element and
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;;; the individual fields within the info record as
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;;; the remaining elements in the list.
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;;;
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;;; The resulting list will be used for application of the %dbm-open-foo
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(define (get-access-data access-parms)
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(let ((access-method (maybe-car access-parms))
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(access-info (maybe-cadr access-parms)))
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(cond ((btree-info? access-info)
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(if (eqv? access-method btree/method)
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(list 1
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(btree-info:flags access-info)
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(btree-info:cachesize access-info)
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(btree-info:maxkeypage access-info)
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(btree-info:minkeypage access-info)
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(btree-info:psize access-info)
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(btree-info:lorder access-info))
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(error "Invalid access method for btree information")))
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((hash-info? access-info)
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(if (eqv? access-method hash/method)
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(list 1
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(hash-info:bsize access-info)
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(hash-info:ffactor access-info)
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(hash-info:nelem access-info)
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(hash-info:cachesize access-info)
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(hash-info:lorder access-info))
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(error "Invalid access method for hash information")))
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((recno-info? access-info)
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(if (eqv? access-method recno/method)
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(list 1
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(recno-info:flags access-info)
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(recno-info:cachesize access-info)
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(recno-info:psize access-info)
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(recno-info:lorder access-info)
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(recno-info:reclen access-info)
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(recno-info:bval access-info)
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(recno-info:bfname access-info))
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(error "Invalid access method for recno information")))
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((not access-info)
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(cond ((eqv? access-method btree/method)
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(list 0 0 0 0 0 0 0))
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((equal? access-method hash/method)
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(list 0 0 0 0 0 0))
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((eqv? access-method recno/method)
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(list 0 0 0 0 0 0 #\0 ""))
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((not access-method)
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'())
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(else (error "Invalid access method specified"))))
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(else (error "Invalid access information specified")))))
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;;; The visible version of the dbm-open routine
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;;; Returns error or a cons cell with the tag "dbm" in car
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;;; and the alien value from %dbm-open-foo in cdr
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(define (dbm-open file flags mode . maybe-access)
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(let ((access-method (get-access-method maybe-access))
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(access-data (append (list file flags mode)
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(get-access-data maybe-access))))
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(receive (err dbm) (apply access-method access-data)
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(if err
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(errno-error err dbm-open)
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(make-dbm-record #t dbm)))))
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;;; Common utility routine that makes sure dbm is an open database
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(define (check-dbm dbm)
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(check-arg dbm-record? dbm "Not a database")
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(check-arg dbm-record:open? dbm "Database not open"))
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;;; Common utility routine to check for database errors
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;;; result should be the result of applying the routine that might cause
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;;; the error, e.g. (dbm-error dbm (%dbm-delete dbm key)) would
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;;; give back the result of the delete, or an error if it occurred
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(define (dbm-error dbm result)
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(let ((err (%dbm-error (dbm-record:dbm dbm))))
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(if (= err 0)
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result
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(begin
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(%dbm-clearerr (dbm-record:dbm dbm))
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(error "Database error" err)))))
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;;; Close routines. Note that the cdr of a dbm cons cell is set to #f
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;;; to prevent someone from issuing subsequent calls to that database
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;;; without re-opening it.
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(define-foreign %dbm-close (dbm_close ((C DBM*) dbm))
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integer);
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(define (dbm-close dbm)
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(%dbm-close (dbm-record:dbm (check-dbm dbm)))
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(set-dbm-record:open? dbm #f))
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;;; Database error return. Straight forward implementation of UNIX call
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;;; If this returns zero, you can be confident that the previous call
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;;; to the database worked correctly.
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(define-foreign %dbm-error (dbm_error ((C DBM*) dbm))
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integer)
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;;; Clear database errors. Straight forward implementation of UNIX call
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;;; Resets database so dbm-error returns zero again.
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(define-foreign %dbm-clearerr (dbm_clearerr ((C DBM*) dbm))
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integer)
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;;; Delete key from database if it exists
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(define-foreign %dbm-delete (database_delete ((C DBM*) dbm)
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(string-desc key))
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integer)
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(define (dbm-delete dbm key)
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(dbm-error dbm (%dbm-delete (dbm-record:dbm (check-dbm dbm)) key)))
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;;; Return the data associated with key if it exists, otherwise
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;;; it returns a null string
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(define-foreign %dbm-fetch (database_fetch ((C DBM*) dbm)
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(string-desc key))
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string)
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(define (dbm-fetch dbm key)
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(dbm-error dbm (%dbm-fetch (dbm-record:dbm (check-dbm dbm)) key)))
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;;; Store a new occurance of the associated <key,data> pair in the database
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;;; if flags is zero, otherwise replace old data for key with new data
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(define-foreign %dbm-store (database_store ((C DBM*) dbm)
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(string-desc key)
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(string-desc data)
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(integer flags))
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integer)
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;;; Insert a new occurance of <key,data> into database
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(define (dbm-insert dbm key data)
|
||
|
|
(let ((insret (dbm-error dbm
|
||
|
|
(%dbm-store (dbm-record:dbm (check-dbm dbm))
|
||
|
|
key
|
||
|
|
data
|
||
|
|
0))))
|
||
|
|
(if (not (= insret 0))
|
||
|
|
(error "Attempt to insert duplicate key")
|
||
|
|
insret)))
|
||
|
|
|
||
|
|
;;; Replace old data for key with new data
|
||
|
|
(define (dbm-replace dbm key data)
|
||
|
|
(dbm-error dbm (%dbm-store (dbm-record:dbm (check-dbm dbm)) key data 1)))
|
||
|
|
|
||
|
|
|
||
|
|
;;; Returns a string containing the key of first record in database
|
||
|
|
(define-foreign %dbm-firstkey (database_first ((C DBM*) dbm))
|
||
|
|
string)
|
||
|
|
|
||
|
|
(define (dbm-firstkey dbm)
|
||
|
|
(dbm-error dbm (%dbm-firstkey (dbm-record:dbm (check-dbm dbm)))))
|
||
|
|
|
||
|
|
;;; Returns a string containing the key of the next sequential
|
||
|
|
;;; record on the database since the last firstkey or nextkey
|
||
|
|
;;; operation. Records are returned in some arbitrary sequence.
|
||
|
|
(define-foreign %dbm-nextkey (database_next ((C DBM*) dbm))
|
||
|
|
string)
|
||
|
|
|
||
|
|
(define (dbm-nextkey dbm)
|
||
|
|
(dbm-error dbm (%dbm-nextkey (dbm-record:dbm (check-dbm dbm)))))
|