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elpa/skewer-mode-20180706.1807/cache-table.el

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+;;; cache-table.el --- a hash table with expiring entries -*- lexical-binding: t; -*-
+
+;; This is free and unencumbered software released into the public domain.
+
+;; Author: Christopher Wellons <mosquitopsu@gmail.com>
+;; Version: 1.0
+
+;;; Commentary:
+
+;; See the docstring of `cache-table-create'. There is no
+;; `cache-table-put': use `setf' on `cache-table-get' instead.
+
+;;; Code:
+
+(require 'cl-lib)
+
+(cl-defstruct (cache-table (:constructor cache-table--create))
+  "A cache table with expiring entries."
+  expire-time table)
+
+(defun cache-table-create (expire-time &rest keyword-args)
+  "Create a new cache-table with entries automatically removed
+from the table after EXPIRE-TIME seconds. This function accepts
+the same keyword arguments as `make-hash-table'. Entries are not
+actually removed from the cache-table until an access is made to
+the cache-table.
+
+Use `cache-table-get' to get and put (via setf) entries."
+  (cache-table--create :expire-time expire-time
+                       :table (apply #'make-hash-table keyword-args)))
+
+(defun cache-table-clear-expired (cache-table)
+  "Remove all expired entries from CACHE-TABLE."
+  (cl-loop with expire-time = (cache-table-expire-time cache-table)
+           with table = (cache-table-table cache-table)
+           with dead-time = (- (float-time) expire-time)
+           for key being the hash-keys of table using (hash-value entry)
+           for (time . value) = entry
+           when (< time dead-time) do (remhash key table)))
+
+(defun cache-table-get (key cache-table &optional default)
+  "Access the value for KEY in CACHE-TABLE if it has not yet
+expired. Behaves just like `gethash'."
+  (cache-table-clear-expired cache-table)
+  (cdr (gethash key (cache-table-table cache-table) (cons 0 default))))
+
+(gv-define-setter cache-table-get (value key cache-table)
+  "Put an entry in the hash table, like (setf (gethash key table) value)."
+  `(progn
+     (cache-table-clear-expired ,cache-table)
+     (puthash ,key (cons (float-time) ,value)
+              (cache-table-table ,cache-table))))
+
+(defun cache-table-map (f cache-table)
+  "Like `maphash', call F for all non-expired entries in CACHE-TABLE."
+  (cache-table-clear-expired cache-table)
+  (maphash (lambda (k v) (funcall f k (cdr v)))
+           (cache-table-table cache-table)))
+
+(defun cache-table-count (cache-table)
+  "Like `hash-table-count', count the number of non-expired entries."
+  (hash-table-count (cache-table-table cache-table)))
+
+(provide 'cache-table)
+
+;;; cache-table.el ends here