snapshot of https://github.com/tldraw/tldraw.git (main, 2026-09-23; blobs > 131072B omitted)

apps/dotcom/sync-worker/src/utils/base64.ts

@@ -0,0 +1,41 @@
+// Chunked base64 helpers. String.fromCharCode(...bytes) overflows the engine's argument limit on
+// large buffers (a PNG screenshot is megabytes), so encoding walks the bytes in 32k chunks.
+
+export function arrayBufferToBase64(buffer: ArrayBuffer): string {
+	const bytes = new Uint8Array(buffer)
+	// workerd (V8 14+) has the native encoder, which skips the intermediate binary string that
+	// matters when the .tldr download inlines multi-MB assets inside a memory-capped DO. Node < 25
+	// under vitest does not have it.
+	if (typeof bytes.toBase64 === 'function') return bytes.toBase64()
+	return btoa(bytesToBinaryString(bytes))
+}
+
+export function base64ToArrayBuffer(base64: string): ArrayBuffer {
+	return binaryStringToBytes(atob(base64)).buffer
+}
+
+// Base64url (RFC 4648 §5): the URL-safe alphabet with padding stripped, used for the signed
+// render tokens that ride in the render page's query string.
+export function base64UrlEncode(bytes: Uint8Array): string {
+	return btoa(bytesToBinaryString(bytes)).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '')
+}
+
+export function base64UrlDecode(value: string): Uint8Array<ArrayBuffer> {
+	return binaryStringToBytes(atob(value.replace(/-/g, '+').replace(/_/g, '/')))
+}
+
+function bytesToBinaryString(bytes: Uint8Array): string {
+	let binary = ''
+	for (let i = 0; i < bytes.length; i += 0x8000) {
+		binary += String.fromCharCode(...bytes.subarray(i, i + 0x8000))
+	}
+	return binary
+}
+
+function binaryStringToBytes(binary: string): Uint8Array<ArrayBuffer> {
+	const bytes = new Uint8Array(new ArrayBuffer(binary.length))
+	for (let i = 0; i < binary.length; i++) {
+		bytes[i] = binary.charCodeAt(i)
+	}
+	return bytes
+}