Adding to utils make-weak-hash-table for use in caches.

[clsql.git] / sql / utils.lisp

diff --git a/sql/utils.lisp b/sql/utils.lisp
index 7f307d63d2da32ce1c8a646df1cbd8b68ca432f9..6e4230d84d94486d8448cc9c84f9c89839bd47e4 100644 (file)
--- a/sql/utils.lisp
+++ b/sql/utils.lisp
@@ -393,4 +393,34 @@ is replaced with replacement. [FROM http://cl-cookbook.sourceforge.net/strings.h
          when pos do (write-string replacement out)
            while pos)
     (unless stream
-      (get-output-stream-string out))))
\ No newline at end of file
+      (get-output-stream-string out))))
+
+
+(defun filter-plist (plist &rest keys-to-remove)
+  "Returns a copy of the given plist with indicated key-value pairs
+removed. keys are searched with #'MEMBER"
+  (declare (dynamic-extent keys-to-remove))
+  (when plist
+    (loop for (k v . rest) = plist then rest
+          unless (member k keys-to-remove)
+            collect k and collect v
+          while rest)))
+
+(defmacro make-weak-hash-table (&rest args)
+  "Creates a weak hash table for use in a cache."
+  `(progn
+
+    ;;NB: These are generally used for caches that may not have an alternate
+    ;;clearing mechanism. If you are on an implementation that doesn't support
+    ;;weak hash tables then you're memory may accumulate.
+
+    #-(or sbcl allegro clisp lispworks)
+    (warn "UNSAFE! use of weak hash on implementation without support. (see clsql/sql/utils.lisp to add)")
+
+    (make-hash-table
+      #+allegro   :values    #+allegro :weak
+      #+clisp     :weak      #+clisp :value
+      #+lispworks :weak-kind #+lispworks :value
+      #+sbcl :weakness #+sbcl :value
+      ,@args)
+    ))