gecko-dev/toolkit/components/kvstore/nsIKeyValue.idl

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"
#include "nsIVariant.idl"

interface nsIKeyValueDatabaseCallback;
interface nsIKeyValueEnumeratorCallback;
interface nsIKeyValuePairCallback;
interface nsIKeyValueVariantCallback;
interface nsIKeyValueVoidCallback;

/**
 * The nsIKeyValue* interfaces provide a simple, asynchronous API to a key/value
 * storage engine.  Basic put/get/has/delete operations are supported, as is
 * enumeration of key/value pairs and the use of multiple named databases within
 * a single storage file.  Operations have ACID semantics.
 *
 * This API does not (yet) support transactions, so it will not be appropriate
 * for all use cases.  Extension of this API to support transactions is tracked
 * by bug 1499238.
 *
 * The kvstore.jsm module wraps this API in a more idiomatic, Promise-based
 * JS API that supports async/await.  In most cases, you're better off using
 * that API from JS rather than using this one directly.  Bug 1512319 tracks
 * native support for Promise in Rust-implemented XPCOM methods.
 */

/**
 * The key/value service.  Enables retrieval of handles to key/value databases.
 */
[scriptable, uuid(46c893dd-4c14-4de0-b33d-a1be18c6d062)]
interface nsIKeyValueService : nsISupports {
    /**
     * Get a handle to an existing database or a newly-created one
     * at the specified path and with the given name.
     *
     * The service supports multiple named databases at the same path
     * (i.e. within the same storage file), so you can call this method
     * multiple times with the same path and different names to retrieve
     * multiple databases stored in the same location on disk.
     */
    void getOrCreate(
        in nsIKeyValueDatabaseCallback callback,
        in AUTF8String path,
        in AUTF8String name);
};

/**
 * A key/value database.
 *
 * All methods are asynchronous and take a callback as their first argument.
 * The types of the callbacks vary, but they can all be implemented in JS
 * via an object literal with the relevant methods.
 */
[scriptable, uuid(c449398e-174c-425b-8195-da6aa0ccd9a5)]
interface nsIKeyValueDatabase : nsISupports {
    /**
     * Write the specified key/value pair to the database.
     */
    void put(
        in nsIKeyValueVoidCallback callback,
        in AUTF8String key,
        in nsIVariant value);

    /**
     * Retrieve the value of the specified key from the database.
     *
     * If the key/value pair doesn't exist in the database, and you specify
     * a default value, then the default value will be returned.  Otherwise,
     * the callback's resolve() method will be called with a variant
     * of type VTYPE_EMPTY, which translates to the JS `null` value.
     */
    void get(
        in nsIKeyValueVariantCallback callback,
        in AUTF8String key,
        [optional] in nsIVariant defaultValue);

    /**
     * Determine whether or not the key exists in the database.
     */
    void has(
        in nsIKeyValueVariantCallback callback,
        in AUTF8String key);

    /**
     * Remove the key/value pair with the given key from the database.
     *
     * If the given key doesn't exist in the database, this operation doesn't
     * fail; or rather, it fails silently, calling the resolve() method
     * of its callback rather than reject().  If you want to know whether
     * or not a key exists when deleting it, call the has() method first.
     */
    void delete(
        in nsIKeyValueVoidCallback callback,
        in AUTF8String key);

    /**
     * Enumerate key/value pairs, starting with the first key equal to
     * or greater than the "from" key (inclusive) and ending with the last key
     * less than the "to" key (exclusive) sorted lexicographically.
     *
     * If either key is omitted, the range extends to the first and/or last key
     * in the database.
     */
    void enumerate(
        in nsIKeyValueEnumeratorCallback callback,
        [optional] in AUTF8String fromKey,
        [optional] in AUTF8String toKey);
};

/**
 * A key/value pair.  Returned by nsIKeyValueEnumerator.getNext().
 */
[scriptable, uuid(bc37b06a-23b5-4b32-8281-4b8479601c7e)]
interface nsIKeyValuePair : nsISupports {
    readonly attribute AUTF8String key;
    readonly attribute nsIVariant value;
};

/**
 * An enumerator of key/value pairs.  Although its methods are similar
 * to those of nsISimpleEnumerator, this interface's getNext() method returns
 * an nsIKeyValuePair rather than an nsISupports, so consumers don't need
 * to QI it to that interface; but this interface doesn't implement the JS
 * iteration protocol (because the Rust-XPCOM bindings don't yet support it),
 * which is another reason why you should use the kvstore.jsm module from JS
 * instead of accessing this API directly.
 */
[scriptable, uuid(b9ba7116-b7ff-4717-9a28-a08e6879b199)]
interface nsIKeyValueEnumerator : nsISupports {
    bool hasMoreElements();
    nsIKeyValuePair getNext();
};

/**
 * A callback for the nsIKeyValueService.getOrCreate() method.
 *
 * The result is an nsIKeyValueDatabase.
 */
[scriptable, uuid(2becc1f8-2d80-4b63-92a8-24ee8f79ee45)]
interface nsIKeyValueDatabaseCallback : nsISupports {
    void resolve(in nsIKeyValueDatabase database);
    void reject(in AUTF8String message);
};

/**
 * A callback for the nsIKeyValueDatabase.enumerate() method.
 *
 * The result is an nsIKeyValueEnumerator.
 */
[scriptable, uuid(b7ea2183-880b-4424-ab24-5aa1555b775d)]
interface nsIKeyValueEnumeratorCallback : nsISupports {
    void resolve(in nsIKeyValueEnumerator enumerator);
    void reject(in AUTF8String message);
};

/**
 * A callback for the nsIKeyValueEnumerator.getNext() method.
 *
 * The result is the next key/value pair, expressed as separate key and value
 * parameters.
 */
[scriptable, uuid(50f65485-ec1e-4307-812b-b8a15e1f382e)]
interface nsIKeyValuePairCallback : nsISupports {
    void resolve(in nsIKeyValuePair pair);
    void reject(in AUTF8String message);
};

/**
 * A callback for the nsIKeyValueDatabase.has() and .get() methods.
 *
 * The result is an nsIVariant, which is always a boolean for the has() method
 * and can be any supported data type for the get() method.
 */
[scriptable, uuid(174ebfa1-74ea-42a7-aa90-85bbaf1da4bf)]
interface nsIKeyValueVariantCallback : nsISupports {
    void resolve(in nsIVariant result);
    void reject(in AUTF8String message);
};

/**
 * A callback for the nsIKeyValueDatabase.put() and .delete() methods.
 *
 * There is no result, but the resolve() method is still called when those
 * async operations complete, to notify consumers of completion.
 */
[scriptable, uuid(0c17497a-ccf8-451a-838d-9dfa7f846379)]
interface nsIKeyValueVoidCallback : nsISupports {
    void resolve();
    void reject(in AUTF8String message);
};