Add methods to prevent numbers, vectors and strings from getting too big

This should prevent numbers from getting too big or small, as well as prevent strings and vectors from getting too long.

All the code was written by @mcgirjau and can be found here:
b75e000a38

src/propeller/push/utils/globals.cljc

@@ -9,3 +9,22 @@
 ;; We might want to extend this to limit all the different that things may be
 ;; placed on a stack.
 (def max-stack-items 100)
+
+
+
+;; =============================================================================
+;; Values used by the Push instructions to keep computed values within
+;; reasonable size limits.
+;; =============================================================================
+
+;; Used by keep-number-reasonable as the maximum magnitude of any integer/float
+(def max-number-magnitude 1.0E12)
+
+;; Used by keep-number-reasonable as the minimum magnitude of any float
+(def min-number-magnitude 1.0E-10)
+
+;; Used by reasonable-string-length? to ensure that strings don't get too large
+(def max-string-length 1000)
+
+;; Used by keep-vector-reasonable to ensure that vectors don't get too large
+(def max-vector-length 1000)

src/propeller/push/utils/helpers.cljc

@@ -2,9 +2,40 @@
   (:require [clojure.set]
             [propeller.push.core :as push]
             [propeller.push.state :as state]
+            [propeller.push.utils.globals :as globals]
             #?(:cljs [goog.string :as gstring])
             #?(:cljs [goog.string.format])))
 
+;; Returns a version of the number n that is within reasonable size bounds
+(defn keep-number-reasonable
+  [n]
+  (cond
+    (integer? n)
+    (cond
+      (> n globals/max-number-magnitude) (long globals/max-number-magnitude)
+      (< n (- globals/max-number-magnitude)) (long (- globals/max-number-magnitude))
+      :else n)
+    :else
+    (cond
+      (Double/isNaN n) 0.0
+      (or (= n Double/POSITIVE_INFINITY)
+          (> n globals/max-number-magnitude)) globals/max-number-magnitude
+      (or (= n Double/NEGATIVE_INFINITY)
+          (< n (- globals/max-number-magnitude))) (- globals/max-number-magnitude)
+      (< (- globals/min-number-magnitude) n globals/min-number-magnitude) 0.0
+      :else n)))
+
+;; Returns true if the string is of a reasonable size
+(defn reasonable-string-length?
+  [string]
+  (let [length (count string)]
+    (<= length globals/max-string-length)))
+
+;; Returns true if the vector is of a reasonable size
+(defn reasonable-vector-length?
+  [vector]
+  (let [length (count vector)]
+    (<= length globals/max-vector-length)))
 
 ;; Takes a state and a collection of stacks to take args from. If there are
 ;; enough args on each of the desired stacks, returns a map with keys
@@ -40,8 +71,22 @@
       state
       (let [result (apply function (:args popped-args))
             new-state (:state popped-args)]
-        (if (= result :ignore-instruction)
+        (cond
+          (number? result)
+          (state/push-to-stack new-state return-stack (keep-number-reasonable result))
+          ;;
+          (and (string? result)
+               (not (reasonable-string-length? result)))
           state
+          ;;
+          (and (vector? result)
+               (not (reasonable-vector-length? result)))
+          state
+          ;;
+          (= result :ignore-instruction)
+          state
+          ;;
+          :else
           (state/push-to-stack new-state return-stack result))))))
 
 ;; Given a set of stacks, returns all instructions that operate on those stacks