Editorial: Introduce ResolveBounds

Author: gibson042

spec.emu

@@ -11,6 +11,36 @@ shortname: <a href="https://github.com/tc39/proposal-immutable-arraybuffer"&g
 contributors: Mark S. Miller, Richard Gibson
 </pre>
 
+<emu-clause id="sec-operations-on-objects" number="7">
+  <h1>Operations on Objects</h1>
+
+  <ins class="block">
+
+    <emu-clause id="sec-resolvebounds" type="abstract operation">
+      <h1>
+        ResolveBounds (
+          _len_: an integer,
+          _start_: an ECMAScript language value,
+          _end_: an ECMAScript language value,
+        ): either a normal completion containing a Record with fields [[From]] (a non-negative integer) and [[To]] (a non-negative integer) or a throw completion
+      </h1>
+      <dl class="header">
+      </dl>
+      <emu-alg>
+        1. Let _relativeStart_ be ? ToIntegerOrInfinity(_start_).
+        1. If _relativeStart_ = -∞, let _from_ be 0.
+        1. Else if _relativeStart_ &lt; 0, let _from_ be max(_len_ + _relativeStart_, 0).
+        1. Else, let _from_ be min(_relativeStart_, _len_).
+        1. If _end_ is *undefined*, let _relativeEnd_ be _len_; else let _relativeEnd_ be ? ToIntegerOrInfinity(_end_).
+        1. If _relativeEnd_ = -∞, let _to_ be 0.
+        1. Else if _relativeEnd_ &lt; 0, let _to_ be max(_len_ + _relativeEnd_, 0).
+        1. Else, let _to_ be min(_relativeEnd_, _len_).
+        1. Return the Record { [[From]]: _from_, [[To]]: _to_ }.
+      </emu-alg>
+    </emu-clause>
+  </ins>
+</emu-clause>
+
 <emu-clause id="sec-ordinary-and-exotic-objects-behaviours" number="10">
   <h1>Ordinary and Exotic Objects Behaviours</h1>
 
@@ -633,14 +663,9 @@ contributors: Mark S. Miller, Richard Gibson
           1. If IsSharedArrayBuffer(_O_) is *true*, throw a *TypeError* exception.
           1. If IsDetachedBuffer(_O_) is *true*, throw a *TypeError* exception.
           1. Let _len_ be _O_.[[ArrayBufferByteLength]].
-          1. Let _relativeStart_ be ? ToIntegerOrInfinity(_start_).
-          1. If _relativeStart_ = -∞, let _first_ be 0.
-          1. Else if _relativeStart_ &lt; 0, let _first_ be max(_len_ + _relativeStart_, 0).
-          1. Else, let _first_ be min(_relativeStart_, _len_).
-          1. If _end_ is *undefined*, let _relativeEnd_ be _len_; else let _relativeEnd_ be ? ToIntegerOrInfinity(_end_).
-          1. If _relativeEnd_ = -∞, let _final_ be 0.
-          1. Else if _relativeEnd_ &lt; 0, let _final_ be max(_len_ + _relativeEnd_, 0).
-          1. Else, let _final_ be min(_relativeEnd_, _len_).
+          1. Let _bounds_ be ? ResolveBounds(_len_, _start_, _end_).
+          1. Let _first_ be _bounds_.[[From]].
+          1. Let _final_ be _bounds_.[[To]].
           1. Let _newLen_ be max(_final_ - _first_, 0).
           1. Let _ctor_ be ? SpeciesConstructor(_O_, %ArrayBuffer%).
           1. Let _new_ be ? Construct(_ctor_, « 𝔽(_newLen_) »).