Switch from Base64 to Z85

src/parse.js

@@ -1,4 +1,4 @@
-import { decode64 } from './base64.js';
+import { decode85 } from './z85.js';
 import {
 	HOLE,
 	NAN,
@@ -125,8 +125,7 @@ export function unflatten(parsed, revivers) {
 					}
 
 					case 'ArrayBuffer': {
-						const base64 = value[1];
-						const arraybuffer = decode64(base64);
+						const arraybuffer = decode85(value[1]);
 						hydrated[index] = arraybuffer;
 						break;
 					}

src/stringify.js

@@ -15,7 +15,7 @@ import {
 	POSITIVE_INFINITY,
 	UNDEFINED
 } from './constants.js';
-import { encode64 } from './base64.js';
+import { encode85 } from './z85.js';
 
 /**
  * Turn a value into a JSON string that can be parsed with `devalue.parse`
@@ -177,11 +177,7 @@ export function stringify(value, reducers) {
 				}
 
 				case 'ArrayBuffer': {
-					/** @type {ArrayBuffer} */
-					const arraybuffer = thing;
-					const base64 = encode64(arraybuffer);
-
-					str = `["ArrayBuffer","${base64}"]`;
+					str = `["ArrayBuffer","${encode85(thing)}"]`;
 					break;
 				}
 

src/z85.js

@@ -0,0 +1,62 @@
+const ENCODE = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#";
+const DECODE = [-1, 68, -1, 84, 83, 82, 72, -1, 75, 76, 70, 65, -1, 63, 62, 69, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 64, -1, 73, 66, 74, 71, 81, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 77, -1, 78, 67, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 79, -1, 80, -1, -1];
+const POW_85 = [1, 85, 7225, 614125, 52200625];
+const POW_256 = [1, 256, 65536, 16777216];
+
+/**
+ * Encodes binary data into a Z85 string.
+ * @param {ArrayBuffer} data - The binary data to encode
+ * @returns {string} The Z85 encoded string
+ */
+export function encode85(data) {
+  const u8a = new Uint8Array(data);
+  const length = u8a.length;
+  const padding = (4 - (length % 4)) % 4;
+
+  let result = '', value = 0;
+  for (let i = 0; i < length + padding; ++i) {
+    const isPadding = i >= length;
+    value = value * 256 + (isPadding ? 0 : u8a[i]);
+    if ((i + 1) % 4 !== 0) continue;
+
+    if (!isPadding) {
+      result += ENCODE[Math.floor(value / POW_85[4]) % 85];
+      result += ENCODE[Math.floor(value / POW_85[3]) % 85];
+      result += ENCODE[Math.floor(value / POW_85[2]) % 85];
+      result += ENCODE[Math.floor(value / POW_85[1]) % 85];
+      result += ENCODE[value % 85];
+    } else {
+      for (let j = 5; j > padding; --j) {
+        result += ENCODE[Math.floor(value / POW_85[j - 1]) % 85];
+      }
+    }
+    value = 0;
+  }
+
+  return result;
+};
+
+/**
+ * Decodes a Z85 string into binary data.
+ * @param {string} string - The Z85 encoded string
+ * @returns {ArrayBuffer} The decoded binary data
+ */
+export function decode85(string) {
+  const remainder = string.length % 5;
+  const padding = 5 - (remainder === 0 ? 5 : remainder);
+  string = string.padEnd(string.length + padding, ENCODE[ENCODE.length - 1]);
+  const length = string.length;
+
+  let buffer = new Uint8Array((length * 4 / 5) - padding);
+  let value = 0, char = 0, byte = 0;
+  for (let i = 0; i < length; ++i) {
+    value = value * 85 + DECODE[string.charCodeAt(char++) - 32];
+    if (char % 5 !== 0) continue;
+
+    for (let j = 3; j >= 0; --j)
+      buffer[byte++] = Math.floor(value / POW_256[j]) % 256;
+    value = 0;
+  }
+
+  return buffer.buffer;
+}

test/test.js

@@ -172,13 +172,13 @@ const fixtures = {
 			name: 'Uint8Array',
 			value: new Uint8Array([1, 2, 3]),
 			js: 'new Uint8Array([1,2,3])',
-			json: '[["Uint8Array",1],["ArrayBuffer","AQID"]]'
+			json: '[["Uint8Array",1],["ArrayBuffer","0rJu"]]'
 		},
 		{
 			name: 'ArrayBuffer',
 			value: new Uint8Array([1, 2, 3]).buffer,
 			js: 'new Uint8Array([1,2,3]).buffer',
-			json: '[["ArrayBuffer","AQID"]]'
+			json: '[["ArrayBuffer","0rJu"]]'
 		},
 		{
 			name: 'URL',
@@ -198,7 +198,7 @@ const fixtures = {
 			name: 'Sliced typed array',
 			value: new Uint16Array([10, 20, 30, 40]).subarray(1, 3),
 			js: 'new Uint16Array([10,20,30,40]).subarray(1,3)',
-			json: '[["Uint16Array",1,1,3],["ArrayBuffer","CgAUAB4AKAA="]]'
+			json: '[["Uint16Array",1,1,3],["ArrayBuffer","3ig+u9SNO*"]]'
 		},
 		{
 			name: 'Temporal.Duration',
@@ -478,7 +478,7 @@ const fixtures = {
 				return [uint8, uint16];
 			})(),
 			js: '(function(a){return [new Uint8Array([a]),new Uint16Array([a])]}(new Uint8Array([0,1,2,3,4,5,6,7,8,9]).buffer))',
-			json: '[[1,3],["Uint8Array",2],["ArrayBuffer","AAECAwQFBgcICQ=="],["Uint16Array",2]]',
+			json: '[[1,3],["Uint8Array",2],["ArrayBuffer","009c61o!#m2NH"],["Uint16Array",2]]',
 			validate: ([uint8, uint16]) => {
 				return uint8.buffer === uint16.buffer;
 			}