lmdb

  1. lmdb
  2. Usage
  3. Documentation
    1. Library procedures
  4. Examples
  5. About this egg
    1. Author
    2. Version history
    3. License

Usage

(require-extension lmdb)

Documentation

The lmdb library provides bindings for the Lightning Memory-Mapped Database Manager (LMDB) database management library.

Library procedures

[procedure] (lmdb-open dbname [key: enckey] [mapsize: size])

Opens or creates LMDB database with optional encryption key and map size, and returns database environment handle.

[procedure] (lmdb-close db)

Closes database handle.

[procedure] (lmdb-begin db [dbname: dbname])

Begins LMDB transaction with optional database name. This is required for all operations.

[procedure] (lmdb-end db)

Commits and ends transaction.

[procedure] (lmdb-delete dbname)

Deletes LMDB database.

[procedure] (lmdb-ref db key)

Looks up key in database.

[procedure] (lmdb-set! db key value)

Sets a key-value pair in the database.

[procedure] (lmdb-count db)

Returns number of key-value pairs in database.

[procedure] (lmdb-keys db)

Returns a list of database keys.

[procedure] (lmdb-values db)

Returns a list of database values.

[procedure] (lmdb-fold f init db)

Folds over the keys and values in the database.

[procedure] (lmdb-for-each f db)

Iterates over the keys and values in the database.

[procedure] (hash-table->lmdb t dbfile [enckey])

Saves SRFI-69 hash table to database.

[procedure] (lmdb->table dbfile [enckey])

Loads database into SRFI-69 hash table.

Examples

;; 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 (lmdb-open fname key: cryptokey)))
  (lmdb-begin mm)
  (let loop ((ks keys) (vs values))
    (if (> (length ks) 0) 
        (begin
          (lmdb-set! mm (string->blob (->string (car ks))) (string->blob (->string (car vs))))
          (loop (cdr ks) (cdr vs)))))
  (lmdb-end mm)
  (lmdb-begin mm)
  (let ((res (let loop ((ks keys) (vs values))
               (if (= (length ks) 0) #t
                   (let ((v (lmdb-ref mm (string->blob (->string (car ks))))))
                     (if (not (equal? (string->blob (->string (car vs))) v))  #f
                         (loop (cdr ks) (cdr vs)))))))
        )
    (lmdb-end mm)
    (lmdb-close mm)
    res)
  )

About this egg

Author

Based on the lmdb library from LambdaNative - a cross-platform Scheme framework. Copyright (c) 2009-2015, University of British Columbia All rights reserved.

Packaged for Chicken by Ivan Raikov and Caolan McMahon.

Version history

2.3
Using (exn lmdb ...) style composite conditions to signal lmdb exceptions [thanks to Caolan McMahon].
2.0
Added lmdb-begin/end procedures for explicit transaction control.
1.0
Initial release

License


Redistribution and use in source and binary forms, with or without
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  Neither the name of the author nor the names of its contributors may
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without specific prior written permission.

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