[Refactor] IsResizableBuffer -> IsFixedLengthArrayBuffer, per spec

.eslintrc

@@ -13,7 +13,7 @@
 				"DetachArrayBuffer",
 				"GetIntrinsic",
 				"IsDetachedBuffer",
-				"IsResizableArrayBuffer",
+				"IsFixedLengthArrayBuffer",
 				"ToIndex",
 			],
 		}],

aos/ArrayBufferCopyAndDetach.js

@@ -9,45 +9,49 @@ var $Uint8Array = GetIntrinsic('%Uint8Array%', true);
 
 var callBound = require('call-bind/callBound');
 
+var byteLength = require('array-buffer-byte-length');
 var $maxByteLength = callBound('%ArrayBuffer.prototype.maxByteLength%', true);
-
-var copyInto = function copyAB(dest, src, start, end) {
-	var that = new $Uint8Array(src);
+var copy = function copyAB(src, start, end) {
+	/* globals Uint8Array: false */
+	var that = new Uint8Array(src);
 	if (typeof end === 'undefined') {
 		end = that.length; // eslint-disable-line no-param-reassign
 	}
-	var resultArray = new $Uint8Array(dest);
+	var result = new ArrayBuffer(end - start);
+	var resultArray = new Uint8Array(result);
 	for (var i = 0; i < resultArray.length; i++) {
 		resultArray[i] = that[i + start];
 	}
-	return dest;
+	return result;
 };
-
-var arrayBufferByteLength = require('array-buffer-byte-length');
-var arrayBufferSlice = require('arraybuffer.prototype.slice');
-var isArrayBuffer = require('is-array-buffer');
-var isSharedArrayBuffer = require('is-shared-array-buffer');
+var $abSlice = callBound('%ArrayBuffer.prototype.slice%', true)
+	|| function slice(ab, a, b) { // in node < 0.11, slice is an own nonconfigurable property
+		return ab.slice ? ab.slice(a, b) : copy(ab, a, b); // node 0.8 lacks `slice`
+	};
 
 var DetachArrayBuffer = require('es-abstract/2023/DetachArrayBuffer');
 var IsDetachedBuffer = require('es-abstract/2023/IsDetachedBuffer');
 var ToIndex = require('es-abstract/2023/ToIndex');
 
-var IsResizableArrayBuffer = require('./IsResizableArrayBuffer');
+var IsFixedLengthArrayBuffer = require('./IsFixedLengthArrayBuffer');
+
+var isArrayBuffer = require('is-array-buffer');
+var isSharedArrayBuffer = require('is-shared-array-buffer');
 
 module.exports = function ArrayBufferCopyAndDetach(arrayBuffer, newLength, preserveResizability) {
-	if (preserveResizability !== 'preserve-resizability' && preserveResizability !== 'fixed-length') {
-		throw new $TypeError('`preserveResizability` must be "preserve-resizability" or "fixed-length"');
+	if (preserveResizability !== 'PRESERVE-RESIZABILITY' && preserveResizability !== 'FIXED-LENGTH') {
+		throw new $TypeError('`preserveResizability` must be ~PRESERVE-RESIZABILITY~ or ~FIXED-LENGTH~');
 	}
 
 	if (!isArrayBuffer(arrayBuffer) || isSharedArrayBuffer(arrayBuffer)) {
-		throw new $TypeError('`arrayBuffer` must be an ArrayBuffer'); // step 1
+		throw new $TypeError('`arrayBuffer` must be an ArrayBuffer'); // steps 1 - 2
 	}
 
 	var abByteLength;
 
 	var newByteLength;
 	if (typeof newLength === 'undefined') { // step 3
-		newByteLength = arrayBufferByteLength(arrayBuffer); // step 3.a
+		newByteLength = byteLength(arrayBuffer); // step 3.a
 		abByteLength = newByteLength;
 	} else { // step 4
 		newByteLength = ToIndex(newLength); // step 4.a
@@ -58,26 +62,31 @@ module.exports = function ArrayBufferCopyAndDetach(arrayBuffer, newLength, prese
 	}
 
 	var newMaxByteLength;
-	if (preserveResizability === 'preserve-resizability' && IsResizableArrayBuffer(arrayBuffer)) { // step 6
+	if (preserveResizability === 'PRESERVE-RESIZABILITY' && !IsFixedLengthArrayBuffer(arrayBuffer)) { // step 6
 		newMaxByteLength = $maxByteLength(arrayBuffer); // step 6.a
 	} else { // step 7
-		newMaxByteLength = 'empty'; // step 7.a
+		newMaxByteLength = 'EMPTY'; // step 7.a
 	}
 
 	// commented out since there's no way to set or access this key
 
 	// 8. If arrayBuffer.[[ArrayBufferDetachKey]] is not undefined, throw a TypeError exception.
 
 	// 9. Let newBuffer be ? AllocateArrayBuffer(%ArrayBuffer%, newByteLength, newMaxByteLength).
-	var newBuffer = newMaxByteLength === 'empty' ? new $ArrayBuffer(newByteLength) : new $ArrayBuffer(newByteLength, { maxByteLength: newMaxByteLength });
+	var newBuffer = newMaxByteLength === 'EMPTY' ? new $ArrayBuffer(newByteLength) : new $ArrayBuffer(newByteLength, { maxByteLength: newMaxByteLength });
+
 	if (typeof abByteLength !== 'number') {
-		abByteLength = arrayBufferByteLength(arrayBuffer);
+		abByteLength = byteLength(arrayBuffer);
 	}
 	var copyLength = min(newByteLength, abByteLength); // step 10
-	if (newByteLength === copyLength) {
-		newBuffer = arrayBufferSlice(arrayBuffer, 0, copyLength); // ??
+	if (newByteLength > copyLength) {
+		var taNew = new $Uint8Array(newBuffer);
+		var taOld = new $Uint8Array(arrayBuffer);
+		for (var i = 0; i < copyLength; i++) {
+			taNew[i] = taOld[i];
+		}
 	} else {
-		copyInto(newBuffer, arrayBuffer, 0, copyLength);
+		newBuffer = $abSlice(arrayBuffer, 0, copyLength); // ? optimization for when the new buffer will not be larger than the old one
 	}
 	/*
 	11. Let fromBlock be arrayBuffer.[[ArrayBufferData]].

aos/IsResizableArrayBuffer.js → aos/IsFixedLengthArrayBuffer.js

@@ -10,29 +10,20 @@ var $sharedArrayGrowable = callBound('%SharedArrayBuffer.prototype.growable%', t
 var isArrayBuffer = require('is-array-buffer');
 var isSharedArrayBuffer = require('is-shared-array-buffer');
 
-module.exports = function IsResizableArrayBuffer(arrayBuffer) {
+// https://262.ecma-international.org/15.0/#sec-isfixedlengtharraybuffer
+
+module.exports = function IsFixedLengthArrayBuffer(arrayBuffer) {
 	var isAB = isArrayBuffer(arrayBuffer);
 	var isSAB = isSharedArrayBuffer(arrayBuffer);
 	if (!isAB && !isSAB) {
 		throw new $TypeError('Assertion failed: `arrayBuffer` must be an ArrayBuffer or SharedArrayBuffer');
 	}
-	// 1. If arrayBuffer has an [[ArrayBufferMaxByteLength]] internal slot, return true.
-
-	// 2. Return false.
 
-	if (isAB) {
-		try {
-			return !!$arrayBufferResizable && $arrayBufferResizable(arrayBuffer); // step 1
-		} catch (e) {
-			return false; // step 2
-		}
+	if (isAB && $arrayBufferResizable) {
+		return !$arrayBufferResizable(arrayBuffer); // step 1
 	}
-	if (isSAB) {
-		try {
-			return !!$sharedArrayGrowable && $sharedArrayGrowable(arrayBuffer); // step 1
-		} catch (e) {
-			return false; // step 2
-		}
+	if (isSAB && $sharedArrayGrowable) {
+		return !$sharedArrayGrowable(arrayBuffer); // step 1
 	}
-	return false; // step 2
+	return true; // step 2
 };

implementation.js

@@ -5,5 +5,5 @@ var ArrayBufferCopyAndDetach = require('./aos/ArrayBufferCopyAndDetach');
 module.exports = function transferToFixedLength() {
 	var newLength = arguments.length > 0 ? arguments[0] : void undefined;
 	var O = this; // step 1
-	return ArrayBufferCopyAndDetach(O, newLength, 'fixed-length'); // step 2
+	return ArrayBufferCopyAndDetach(O, newLength, 'FIXED-LENGTH'); // step 2
 };

test/tests.js

@@ -50,7 +50,7 @@ module.exports = function runTests(transferToFixedLength, t) {
 		st.equal(IsDetachedBuffer(nbLen), false, 'new ArrayBuffer is not detached');
 
 		st.equal(byteLength(ab2), 0, 'detached original ArrayBuffer has length 0');
-		st.equal(byteLength(nbLen), 4, 'newly transferToFixedLengthred ArrayBuffer has length 4');
+		st.equal(byteLength(nbLen), 4, 'newly transferred ArrayBuffer has length 4');
 
 		st.test('test262: test/built-ins/ArrayBuffer/prototype/transferToFixedLength/from-fixed-to-larger.js', function (s2t) {
 			var source = new ArrayBuffer(4);