150 lines
5.2 KiB
Scheme
150 lines
5.2 KiB
Scheme
;;; An implemenation of ScshQL (or Scsh-SQL ?) with the new ODBC bindings
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;;;
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;;; Eric Knauel <knauel@informatik.uni-tuebingen.de>
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;;;
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;;; The original API was designed by Sam Thibault (and maybe Olin Shivers) and
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;;; can be found at http://web.mit.edu/samt/www/compsci/Scsh-SQL/scsh-sql.tar.gz
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(define *current-db* (make-fluid #f))
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(define (current-db) (fluid *current-db*))
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(define (with-current-db* db thunk)
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(let-fluid *current-db* db
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thunk))
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(define-syntax with-current-db
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(syntax-rules ()
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((with-current-db db body1 body2 ...)
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(with-current-db* db (lambda () body1 body2 ...)))))
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(define (with-open-db* dbname user pwd thunk)
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(let* ((conn-handle (open-db dbname user pwd)))
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(dynamic-wind
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(lambda () #t)
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(lambda ()
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(let-fluid *current-db* db thunk))
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(lambda ()
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(odbc-sql-disconnect conn-handle)))))
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(define-syntax with-open-db
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(syntax-rules ()
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((with-open-db dbname user pwd body1 body2 ...)
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(with-open-db* dbname user pwd (lambda () body1 body2 ...)))))
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(define (open-db database user password)
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(let* ((env-handle (odbc-alloc-environment-handle))
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(conn-handle (odbc-alloc-connection-handle env-handle)))
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(begin
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(db-handle (odbc-sql-connect conn-handle database user password))
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conn-handle)))
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(define (set-current-db! thing)
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(if (connection-handle? thing)
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(set-fluid! *current-db* thing)
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(error "Error: set-current-db! must be called with a db as argument."))
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thing)
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(define (close-db . maybe-db)
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(let ((conn-handle (:optional maybe-db (current-db))))
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(if (connection-handle-connected? conn-handle)
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(odbc-sql-disconnect conn-handle))
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#t))
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(define (call/db database user password proc)
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(let ((conn-handle (open-db database user password)))
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(proc conn-handle)
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(close-db conn-handle)))
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;;; what a useless function
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(define (string->sql-command sql-query)
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(if (current-db)
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(odbc-alloc-statement-handle conn-handle)
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(error "Error: You need to connect to a database first (don't ask why)")))
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(define (prepare-execute-sql-args excute-sql-optionals)
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(if (null? excute-sql-optionals)
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(values (current-db) '())
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(values (car args) (cdr args))))
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(define (maybe-make-statement-handle string-or-stmt-handle)
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(if (string? string-or-stmt-handle)
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(string->sql-command string->sql-command)
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string-or-stmt-handle))
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(define (execute-sql command . args)
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(let-values (((conn-handle params) (prepare-execute-sql-args args))
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((stmt-handle) (maybe-make-statement-handle command)))
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;;; maybe prepare stmt
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(if (string? command)
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(odbc-sql-prepare stmt-handle command))
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;;; execute stmt
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(let ((ncols (odbc-sql-num-result-cols stmt-handle)))
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(if (not (null? params))
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(bind-params stmt-handle params))
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;;; execute
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(odbc-sql-execute stmt-handle)
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;;; process answer
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(let ((rows-affected (odbc-sql-row-count stmt-handle)))
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(cond ((> rows-affected 0)
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rows-affected) ;;; must have been a DELETE, INSERT or UPDATE statement
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((zero? rows-affected) #t) ;;; is this really correct?!?!?!
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(else
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(prepare-cursor stmt-handle ncols)))))))
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;;; convert execute-sql params list to a parameter vector that is
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;;; suitable for odbc-sql-bind-parameter-exec-out
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;;; Well, acutally it's only an approximation
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(define (make-parameter-vector stmt-handle params)
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(let ((param-descriptions (get-parameter-descriptions stmt-handle)))
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(list->vector (make-parameter-value-cell-list params param-descriptions))))
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(define (make-parameter-value-cell-list params param-descriptions)
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(let ((param-descriptions-count (length param-descriptions)))
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(let loop ((params params) (index 1) (res '()))
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(if (null? params)
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(reverse res)
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(if (> index param-descriptions-count)
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(loop (cdr params) (+ index 1)
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(make-parameter-value-cell value (list-ref index param-descriptions)))
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;;; more parameters given than needed => error
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;;; don't catch error, let ODBC raise the error
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(loop (cdr params) (+ index 1)
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(cons value (cons sql-type-c-binary sql-type-unknown))))))))
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;;; takes the value for parameter and the parameter-description
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;;; (a record of type odbc-parameter) and returns a cell that is
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;;; suitable to put in a parameter vector for odbc-sql-bind-parameter-exec-out
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(define (make-parameter-value-cell value param-description)
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(let ((parameter-type (odbc-parameter-type param-description)))
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(cons value
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(cons (odbc-type-identifier->c-type-identifier parameter-type)
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parameter-type))))
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;;; returns a list of odbc-parameter records for all parameters
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;;; of stmt-handle
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(define (get-parameter-descriptions stmt-handle)
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(let ((param-count (odbc-sql-num-params stmt-handle)))
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(let loop ((param-no param-count) (res '()))
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(if (zero? param-no)
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res
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(loop (- param-no 1)
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(cons (odbc-sql-describe-param stmt-handle param-no)))))))
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(define (bind-params stmt params)
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(let ((parameter-vector (make-parameter-vector stmt-handle params)))
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(odbc-sql-bind-parameter-exec-out stmt-handle parameter-vector)))
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(define (prepare-cursor stmt ncols)
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(error "Not implemented"))
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(define fetch-row fetch)
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(define (fetch-rows cursor nrows)
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(error "Not implemented"))
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(define (fetch-all cursor)
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(error "Not implemented"))
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