DataView support (#143)

* fix: rename test file so uvu picks it up

* chore: add simple benchmarks

Based on Svelte's benchmark scaffolding.

* feat: simplify TypedArray slices

* feat: use native alternatives to encode/decode base64

* feat: whitelist `Float16Array`

* fix: guarantee flatten return type

* chore: add prettier configuration

Add a `.prettierrc` file matching Svelte's.

* chore: add missing (boxed) primitives tests

* fix: support boxed bigints and boxed sentinel values

* fix: reject `Symbol`s instead of producing invalid output

* fix: correct typed array construction in `uneval`'s reference path

* chore: add more repetition tests

* fix: handle missing types in `uneval`'s reference path

* feat: add `DataView` support

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

Author: mrkishi

.changeset/common-cases-shake.md

@@ -0,0 +1,5 @@
+---
+'devalue': minor
+---
+
+feat: add `DataView` support

src/parse.js

@@ -156,7 +156,8 @@ export function unflatten(parsed, revivers) {
 					case 'Float32Array':
 					case 'Float64Array':
 					case 'BigInt64Array':
-					case 'BigUint64Array': {
+					case 'BigUint64Array':
+					case 'DataView': {
 						if (values[value[1]][0] !== 'ArrayBuffer') {
 							// without this, if we receive malformed input we could
 							// end up trying to hydrate in a circle or allocate

src/stringify.js

@@ -223,7 +223,8 @@ export function stringify(value, reducers) {
 				case 'Float32Array':
 				case 'Float64Array':
 				case 'BigInt64Array':
-				case 'BigUint64Array': {
+				case 'BigUint64Array':
+				case 'DataView': {
 					/** @type {import("./types.js").TypedArray} */
 					const typedArray = thing;
 					str = '["' + type + '",' + flatten(typedArray.buffer);

src/uneval.js

@@ -96,6 +96,7 @@ export function uneval(value, replacer) {
 				case 'Float64Array':
 				case 'BigInt64Array':
 				case 'BigUint64Array':
+				case 'DataView':
 					walk(thing.buffer);
 					return;
 
@@ -303,6 +304,23 @@ export function uneval(value, replacer) {
 				return str;
 			}
 
+			case 'DataView': {
+				let str = `new DataView`;
+
+				if (!names.has(thing.buffer)) {
+					str += `(new Uint8Array([${new Uint8Array(thing.buffer)}]).buffer`;
+				} else {
+					str += `(${stringify(thing.buffer)}`;
+				}
+
+				// handle subviews
+				if (thing.byteLength !== thing.buffer.byteLength) {
+					str += `,${thing.startOffset},${thing.byteLength}`;
+				}
+
+				return str + ')';
+			}
+
 			case 'ArrayBuffer': {
 				const ui8 = new Uint8Array(thing);
 				return `new Uint8Array([${ui8.toString()}]).buffer`;
@@ -439,6 +457,27 @@ export function uneval(value, replacer) {
 					break;
 				}
 
+				case 'DataView': {
+					let str = `new DataView`;
+
+					if (!names.has(thing.buffer)) {
+						str += `(new Uint8Array([${new Uint8Array(thing.buffer)}]).buffer`;
+					} else {
+						str += `(${stringify(thing.buffer)}`;
+					}
+
+					// handle subviews
+					if (thing.byteLength !== thing.buffer.byteLength) {
+						str += `,${thing.byteOffset},${thing.byteLength}`;
+					}
+
+					str += ')';
+
+					values.push(`{}`);
+					statements.push(`${name}=${str}`);
+					break;
+				}
+
 				case 'ArrayBuffer':
 					values.push(`new Uint8Array([${new Uint8Array(thing)}]).buffer`);
 					break;

test/index.test.js

@@ -305,6 +305,12 @@ const fixtures = {
 			js: 'new Uint8Array([1,2,3]).buffer',
 			json: '[["ArrayBuffer","AQID"]]'
 		},
+		{
+			name: 'DataView',
+			value: new DataView(new Uint8Array([1, 2, 3]).buffer),
+			js: 'new DataView(new Uint8Array([1,2,3]).buffer)',
+			json: '[["DataView",1],["ArrayBuffer","AQID"]]'
+		},
 		{
 			name: 'URL',
 			value: new URL('https://user:password@example.com/<script>/path?foo=bar#hash'),
@@ -670,6 +676,28 @@ const fixtures = {
 			})(),
 			js: '(function(a,b){a=new Uint8Array(b);return [a,a,new Uint16Array(b)]}({},new Uint8Array([0,1,2,3,4,5,6,7,8,9]).buffer))',
 			json: '[[1,1,3],["Uint8Array",2],["ArrayBuffer","AAECAwQFBgcICQ=="],["Uint16Array",2]]'
+		},
+
+		{
+			name: 'DataView (repetition)',
+			value: (() => {
+				const uint8 = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+				const dv = new DataView(uint8.buffer);
+				return [dv, dv];
+			})(),
+			js: '(function(a){a=new DataView(new Uint8Array([0,1,2,3,4,5,6,7,8,9]).buffer);return [a,a]}({}))',
+			json: '[[1,1],["DataView",2],["ArrayBuffer","AAECAwQFBgcICQ=="]]'
+		},
+
+		{
+			name: 'Array Buffer and DataView (repetition)',
+			value: (() => {
+				const uint8 = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+				const dv = new DataView(uint8.buffer);
+				return [dv, dv, uint8.buffer];
+			})(),
+			js: '(function(a,b){a=new DataView(b);return [a,a,b]}({},new Uint8Array([0,1,2,3,4,5,6,7,8,9]).buffer))',
+			json: '[[1,1,2],["DataView",2],["ArrayBuffer","AAECAwQFBgcICQ=="]]'
 		}
 	],