https://github.com/iraikov/chicken-lmdb
Chicken Scheme bindings for the LMDB key value database
https://github.com/iraikov/chicken-lmdb
chicken-scheme chicken-scheme-eggs database key-value key-value-database key-value-store lmdb scheme-language
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Chicken Scheme bindings for the LMDB key value database
- Host: GitHub
- URL: https://github.com/iraikov/chicken-lmdb
- Owner: iraikov
- License: other
- Created: 2016-01-22T19:05:08.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2020-07-14T02:06:01.000Z (over 5 years ago)
- Last Synced: 2025-01-30T16:28:01.728Z (9 months ago)
- Topics: chicken-scheme, chicken-scheme-eggs, database, key-value, key-value-database, key-value-store, lmdb, scheme-language
- Language: Scheme
- Size: 74.2 KB
- Stars: 7
- Watchers: 3
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# chicken-lmdb
Chicken Scheme bindings for the Lightning Memory-Mapped Database
Manager (LMDB) (http://symas.com/mdb/doc/index.html) database
management library.
## Library procedures
`(db-open filename [key: enckey] [mapsize: size])`
Opens or creates LMDB database with optional encryption key and map size.
`(db-close db)`
Closes LMDB database handle.
`(db-begin db [dbname: dbname] [flags: 0])`
Begins LMDB transaction with optional database name and flags returned by `db-flags`.
Commits and ends LMDB transaction.
`(db-flags flag-name ...)`
Returns a bit mask that represents LMDB environment flags. The flag name is one of the following keywords:
- `#:fixed-map` : mmap at a fixed address
- `#:no-subdirectory` : no environment directory
- `#:read-only` : read only
- `#:write-map` : use writable mmap
- `#:no-meta-sync` : don't fsync metapage after commit
- `#:no-sync` : don't fsync after commit
- `#:map-async` : use asynchronous sync with `#:write-map` is used
- `#:no-lock` : don't do locking
- `#:no-read-ahead` : don't do readahead
`(db-abort db)`
Aborts LMDB transaction.
`(db-delete db key)`
Removes a key from the database.
`(db-delete-database dbname)`
Deletes LMDB database.
`(db-ref db key)`
Looks up key in database.
`(db-set! db key value)`
Sets a key-value pair in the database.
`(db-count db)`
Returns number of key-value pairs in database.
`(db-keys db)`
Returns a list of database keys.
`(db-values db)`
Returns a list of database values.
`(db-key-len m)`
Returns the length of the current key.
`(db-value-len m)`
Returns the length of the current value.
`(db-key m buf)`
Copies the current key to the specified blob.
`(db-value m buf)`
Copies the current value to the specified blob.
`(db-fold f init db)`
Fold over the keys and values in the database.
`(db-for-each f db)`
Iterate over the keys and values in the database.
`(hash-table->db t dbfile [enckey])`
Saves SRFI-69 hash table to database.
`(db->hash-table dbfile [enckey])`
Load database into SRFI-69 hash table.
## Examples
```scheme
;; lmdb encrypted key-value creation and lookup
(let* ((fname (make-pathname "." "mydb.mdb"))
(keys (list "k1" 'k2 '(k3)))
(values (list 'one 2 "three"))
(cryptokey (string->blob "1234"))
(mm (db-open fname key: cryptokey)))
(db-begin mm)
(let loop ((ks keys) (vs values))
(if (> (length ks) 0)
(begin
(db-set! mm (string->blob (->string (car ks))) (string->blob (->string (car vs))))
(loop (cdr ks) (cdr vs)))))
(db-end mm)
(db-begin mm)
(let ((res (let loop ((ks keys) (vs values))
(if (= (length ks) 0) #t
(let ((v (db-ref mm (string->blob (->string (car ks))))))
(if (not (equal? (string->blob (->string (car vs))) v)) #f
(loop (cdr ks) (cdr vs)))))))
)
(db-end mm)
(db-close mm)
res)
)
```
```scheme
;; lmdb readonly test
(let* ((fname (make-pathname "." "unittest.mdb")))
(db-delete-database fname)
(let ((mm (db-open fname maxdbs: 2)))
(db-begin mm)
;; set foo
(db-set! mm (string->blob "foo") (string->blob "one"))
(db-end mm)
;; reopen as readonly
(db-begin mm flags: (db-flags #:read-only))
;; foo is still set
(test (string->blob "one")
(db-ref mm (string->blob "foo")))
;; cannot set bar
(test 'unknown
(condition-case (db-set! mm (string->blob "bar") (string->blob "two"))
((exn lmdb unknown) 'unknown)))
(db-close mm)))
```