--- /dev/null
+;;; registry.el --- Track and remember data items by various fields
+
+;; Copyright (C) 2011-2016 Free Software Foundation, Inc.
+
+;; Author: Teodor Zlatanov <tzz@lifelogs.com>
+;; Keywords: data
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This library provides a general-purpose EIEIO-based registry
+;; database with persistence, initialized with these fields:
+
+;; version: a float
+
+;; max-size: an integer, default most-positive-fixnum
+
+;; prune-factor: a float between 0 and 1, default 0.1
+
+;; precious: a list of symbols
+
+;; tracked: a list of symbols
+
+;; tracker: a hashtable tuned for 100 symbols to track (you should
+;; only access this with the :lookup2-function and the
+;; :lookup2+-function)
+
+;; data: a hashtable with default size 10K and resize threshold 2.0
+;; (this reflects the expected usage so override it if you know better)
+
+;; ...plus methods to do all the work: `registry-search',
+;; `registry-lookup', `registry-lookup-secondary',
+;; `registry-lookup-secondary-value', `registry-insert',
+;; `registry-delete', `registry-prune', `registry-size' which see
+
+;; and with the following properties:
+
+;; Every piece of data has a unique ID and some general-purpose fields
+;; (F1=D1, F2=D2, F3=(a b c)...) expressed as an alist, e.g.
+
+;; ((F1 D1) (F2 D2) (F3 a b c))
+
+;; Note that whether a field has one or many pieces of data, the data
+;; is always a list of values.
+
+;; The user decides which fields are "precious", F2 for example. When
+;; the registry is pruned, any entries without the F2 field will be
+;; removed until the size is :max-size * :prune-factor _less_ than the
+;; maximum database size. No entries with the F2 field will be removed
+;; at PRUNE TIME, which means it may not be possible to prune back all
+;; the way to the target size.
+
+;; When an entry is inserted, the registry will reject new entries if
+;; they bring it over the :max-size limit, even if they have the F2
+;; field.
+
+;; The user decides which fields are "tracked", F1 for example. Any
+;; new entry is then indexed by all the tracked fields so it can be
+;; quickly looked up that way. The data is always a list (see example
+;; above) and each list element is indexed.
+
+;; Precious and tracked field names must be symbols. All other
+;; fields can be any other Emacs Lisp types.
+
+;;; Code:
+
+(eval-when-compile (require 'cl))
+
+(eval-and-compile
+ (or (ignore-errors (progn
+ (require 'eieio)
+ (require 'eieio-base)))
+ ;; gnus-fallback-lib/ from gnus/lisp/gnus-fallback-lib
+ (ignore-errors
+ (let ((load-path (cons (expand-file-name
+ "gnus-fallback-lib/eieio"
+ (file-name-directory (locate-library "gnus")))
+ load-path)))
+ (require 'eieio)
+ (require 'eieio-base)))
+ (error
+ "eieio not found in `load-path' or gnus-fallback-lib/ directory.")))
+
+(eval-when-compile
+ (unless (fboundp 'cl-remf)
+ (defalias 'cl-remf 'remf)
+ (defalias 'cl-loop 'loop)
+ (defalias 'cl-subseq 'subseq)))
+
+;; The version number needs to be kept outside of the class definition
+;; itself. The persistent-save process does *not* write to file any
+;; slot values that are equal to the default :initform value. If a
+;; database object is at the most recent version, therefore, its
+;; version number will not be written to file. That makes it
+;; difficult to know when a database needs to be upgraded.
+(defvar registry-db-version 0.2
+ "The current version of the registry format.")
+
+(eval `
+(defclass registry-db (eieio-persistent)
+ ((version :initarg :version
+ :initform nil
+ :type (or null float)
+ :documentation "The registry version.")
+ (max-size :initarg :max-size
+ ;; EIEIO's :initform is not 100% compatible with CLOS in
+ ;; that if the form is an atom, it assumes it's constant
+ ;; value rather than an expression, so in order to get the value
+ ;; of `most-positive-fixnum', we need to use an
+ ;; expression that's not just a symbol.
+ :initform ,(symbol-value 'most-positive-fixnum)
+ :type integer
+ :custom integer
+ :documentation "The maximum number of registry entries.")
+ (prune-factor
+ :initarg :prune-factor
+ :initform 0.1
+ :type float
+ :custom float
+ :documentation "Prune to (:max-size * :prune-factor) less
+ than the :max-size limit. Should be a float between 0 and 1.")
+ (tracked :initarg :tracked
+ :initform nil
+ :type t
+ :documentation "The tracked (indexed) fields, a list of symbols.")
+ (precious :initarg :precious
+ :initform nil
+ :type t
+ :documentation "The precious fields, a list of symbols.")
+ (tracker :initarg :tracker
+ :type hash-table
+ :documentation "The field tracking hashtable.")
+ (data :initarg :data
+ :type hash-table
+ :documentation "The data hashtable.")))
+)
+
+(defmethod initialize-instance :BEFORE ((this registry-db) slots)
+ "Check whether a registry object needs to be upgraded."
+ ;; Hardcoded upgrade routines. Version 0.1 to 0.2 requires the
+ ;; :max-soft slot to disappear, and the :max-hard slot to be renamed
+ ;; :max-size.
+ (let ((current-version
+ (and (plist-member slots :version)
+ (plist-get slots :version))))
+ (when (or (null current-version)
+ (eql current-version 0.1))
+ (setq slots
+ (plist-put slots :max-size (plist-get slots :max-hard)))
+ (setq slots
+ (plist-put slots :version registry-db-version))
+ (cl-remf slots :max-hard)
+ (cl-remf slots :max-soft))))
+
+(defmethod initialize-instance :AFTER ((this registry-db) slots)
+ "Set value of data slot of THIS after initialization."
+ (with-slots (data tracker) this
+ (unless (member :data slots)
+ (setq data
+ (make-hash-table :size 10000 :rehash-size 2.0 :test 'equal)))
+ (unless (member :tracker slots)
+ (setq tracker (make-hash-table :size 100 :rehash-size 2.0)))))
+
+(defmethod registry-lookup ((db registry-db) keys)
+ "Search for KEYS in the registry-db THIS.
+Returns an alist of the key followed by the entry in a list, not a cons cell."
+ (let ((data (oref db data)))
+ (delq nil
+ (mapcar
+ (lambda (k)
+ (when (gethash k data)
+ (list k (gethash k data))))
+ keys))))
+
+(defmethod registry-lookup-breaks-before-lexbind ((db registry-db) keys)
+ "Search for KEYS in the registry-db THIS.
+Returns an alist of the key followed by the entry in a list, not a cons cell."
+ (let ((data (oref db data)))
+ (delq nil
+ (loop for key in keys
+ when (gethash key data)
+ collect (list key (gethash key data))))))
+
+(defmethod registry-lookup-secondary ((db registry-db) tracksym
+ &optional create)
+ "Search for TRACKSYM in the registry-db THIS.
+When CREATE is not nil, create the secondary index hashtable if needed."
+ (let ((h (gethash tracksym (oref db :tracker))))
+ (if h
+ h
+ (when create
+ (puthash tracksym
+ (make-hash-table :size 800 :rehash-size 2.0 :test 'equal)
+ (oref db tracker))
+ (gethash tracksym (oref db tracker))))))
+
+(defmethod registry-lookup-secondary-value ((db registry-db) tracksym val
+ &optional set)
+ "Search for TRACKSYM with value VAL in the registry-db THIS.
+When SET is not nil, set it for VAL (use t for an empty list)."
+ ;; either we're asked for creation or there should be an existing index
+ (when (or set (registry-lookup-secondary db tracksym))
+ ;; set the entry if requested,
+ (when set
+ (puthash val (if (eq t set) '() set)
+ (registry-lookup-secondary db tracksym t)))
+ (gethash val (registry-lookup-secondary db tracksym))))
+
+(defun registry--match (mode entry check-list)
+ ;; for all members
+ (when check-list
+ (let ((key (nth 0 (nth 0 check-list)))
+ (vals (cdr-safe (nth 0 check-list)))
+ found)
+ (while (and key vals (not found))
+ (setq found (case mode
+ (:member
+ (member (car-safe vals) (cdr-safe (assoc key entry))))
+ (:regex
+ (string-match (car vals)
+ (mapconcat
+ 'prin1-to-string
+ (cdr-safe (assoc key entry))
+ "\0"))))
+ vals (cdr-safe vals)))
+ (or found
+ (registry--match mode entry (cdr-safe check-list))))))
+
+(defmethod registry-search ((db registry-db) &rest spec)
+ "Search for SPEC across the registry-db THIS.
+For example calling with `:member \\='(a 1 2)' will match entry \((a 3 1)).
+Calling with `:all t' (any non-nil value) will match all.
+Calling with `:regex \\='(a \"h.llo\")' will match entry \(a \"hullo\" \"bye\").
+The test order is to check :all first, then :member, then :regex."
+ (when db
+ (let ((all (plist-get spec :all))
+ (member (plist-get spec :member))
+ (regex (plist-get spec :regex)))
+ (loop for k being the hash-keys of (oref db data)
+ using (hash-values v)
+ when (or
+ ;; :all non-nil returns all
+ all
+ ;; member matching
+ (and member (registry--match :member v member))
+ ;; regex matching
+ (and regex (registry--match :regex v regex)))
+ collect k))))
+
+(defmethod registry-delete ((db registry-db) keys assert &rest spec)
+ "Delete KEYS from the registry-db THIS.
+If KEYS is nil, use SPEC to do a search.
+Updates the secondary ('tracked') indices as well.
+With assert non-nil, errors out if the key does not exist already."
+ (let* ((data (oref db data))
+ (keys (or keys
+ (apply 'registry-search db spec)))
+ (tracked (oref db tracked)))
+
+ (dolist (key keys)
+ (let ((entry (gethash key data)))
+ (when assert
+ (assert entry nil
+ "Key %s does not exist in database" key))
+ ;; clean entry from the secondary indices
+ (dolist (tr tracked)
+ ;; is this tracked symbol indexed?
+ (when (registry-lookup-secondary db tr)
+ ;; for every value in the entry under that key...
+ (dolist (val (cdr-safe (assq tr entry)))
+ (let* ((value-keys (registry-lookup-secondary-value
+ db tr val)))
+ (when (member key value-keys)
+ ;; override the previous value
+ (registry-lookup-secondary-value
+ db tr val
+ ;; with the indexed keys MINUS the current key
+ ;; (we pass t when the list is empty)
+ (or (delete key value-keys) t)))))))
+ (remhash key data)))
+ keys))
+
+(defmethod registry-size ((db registry-db))
+ "Returns the size of the registry-db object THIS.
+This is the key count of the `data' slot."
+ (hash-table-count (oref db data)))
+
+(defmethod registry-full ((db registry-db))
+ "Checks if registry-db THIS is full."
+ (>= (registry-size db)
+ (oref db max-size)))
+
+(defmethod registry-insert ((db registry-db) key entry)
+ "Insert ENTRY under KEY into the registry-db THIS.
+Updates the secondary ('tracked') indices as well.
+Errors out if the key exists already."
+
+ (assert (not (gethash key (oref db data))) nil
+ "Key already exists in database")
+
+ (assert (not (registry-full db))
+ nil
+ "registry max-size limit reached")
+
+ ;; store the entry
+ (puthash key entry (oref db data))
+
+ ;; store the secondary indices
+ (dolist (tr (oref db tracked))
+ ;; for every value in the entry under that key...
+ (dolist (val (cdr-safe (assq tr entry)))
+ (let* ((value-keys (registry-lookup-secondary-value db tr val)))
+ (pushnew key value-keys :test 'equal)
+ (registry-lookup-secondary-value db tr val value-keys))))
+ entry)
+
+(defmethod registry-reindex ((db registry-db))
+ "Rebuild the secondary indices of registry-db THIS."
+ (let ((count 0)
+ (expected (* (length (oref db tracked)) (registry-size db))))
+ (dolist (tr (oref db tracked))
+ (let (values)
+ (maphash
+ (lambda (key v)
+ (incf count)
+ (when (and (< 0 expected)
+ (= 0 (mod count 1000)))
+ (message "reindexing: %d of %d (%.2f%%)"
+ count expected (/ (* 100.0 count) expected)))
+ (dolist (val (cdr-safe (assq tr v)))
+ (let* ((value-keys (registry-lookup-secondary-value db tr val)))
+ (push key value-keys)
+ (registry-lookup-secondary-value db tr val value-keys))))
+ (oref db data))))))
+
+(defmethod registry-prune ((db registry-db) &optional sortfunc)
+ "Prunes the registry-db object DB.
+
+Attempts to prune the number of entries down to \(*
+:max-size :prune-factor) less than the max-size limit, so
+pruning doesn't need to happen on every save. Removes only
+entries without the :precious keys, so it may not be possible to
+reach the target limit.
+
+Entries to be pruned are first sorted using SORTFUNC. Entries
+from the front of the list are deleted first.
+
+Returns the number of deleted entries."
+ (let ((size (registry-size db))
+ (target-size
+ (floor (- (oref db max-size)
+ (* (oref db max-size)
+ (oref db prune-factor)))))
+ candidates)
+ (if (registry-full db)
+ (progn
+ (setq candidates
+ (registry-collect-prune-candidates
+ db (- size target-size) sortfunc))
+ (length (registry-delete db candidates nil)))
+ 0)))
+
+(defmethod registry-collect-prune-candidates ((db registry-db) limit sortfunc)
+ "Collects pruning candidates from the registry-db object DB.
+
+Proposes only entries without the :precious keys, and attempts to
+return LIMIT such candidates. If SORTFUNC is provided, sort
+entries first and return candidates from beginning of list."
+ (let* ((precious (oref db precious))
+ (precious-p (lambda (entry-key)
+ (cdr (memq (car entry-key) precious))))
+ (data (oref db data))
+ (candidates (cl-loop for k being the hash-keys of data
+ using (hash-values v)
+ when (notany precious-p v)
+ collect (cons k v))))
+ ;; We want the full entries for sorting, but should only return a
+ ;; list of entry keys.
+ (when sortfunc
+ (setq candidates (sort candidates sortfunc)))
+ (cl-subseq (mapcar #'car candidates) 0 (min limit (length candidates)))))
+
+(provide 'registry)
+;;; registry.el ends here
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