add minimal shim stubs for v2 backwards compatibility

js/v2.ts

@@ -0,0 +1,43 @@
+import { Header, Cache, RangeResponse } from './v3';
+
+async function getHeaderAndRoot(a:ArrayBuffer, etag?:string): Promise<[Header, [string, number, ArrayBuffer]]> {
+	const header = {
+		specVersion: 2,
+		rootDirectoryOffset: 0,
+		rootDirectoryLength: 0,
+		jsonMetadataOffset: 0,
+		jsonMetadataLength: 0,
+		leafDirectoryOffset: 0,
+		leafDirectoryLength: undefined,
+		tileDataOffset: 512000,
+		tileDataLength: undefined,
+		numAddressedTiles: 0,
+		numTileEntries: 0,
+		numTileContents: 0,
+		clustered: false,
+		internalCompression: 0,
+		tileCompression: 0,
+		tileType: 0,
+		minZoom: 0,
+		maxZoom: 0,
+		minLon: 0,
+		minLat: 0,
+		maxLon: 0,
+		maxLat: 0,
+		centerZoom: 0,
+		centerLon: 0,
+		centerLat: 0,
+		etag: etag,
+	};	
+	return [header, ["",0,new ArrayBuffer(0)]];
+}
+
+async function getZxy(header:Header,cache:Cache): Promise<RangeResponse | undefined> {
+	return Promise.resolve(undefined);
+}
+
+export default {
+	getHeaderAndRoot: getHeaderAndRoot,
+	getZxy: getZxy
+};
+

js/v3.ts

@@ -1,4 +1,5 @@
 import { decompressSync } from "fflate";
+import v2 from "./v2";
 
 export interface BufferPosition {
 	buf: Uint8Array;
@@ -159,14 +160,15 @@ enum TileType {
 const HEADER_SIZE_BYTES = 122;
 
 export interface Header {
+	specVersion: number;
 	rootDirectoryOffset: number;
 	rootDirectoryLength: number;
 	jsonMetadataOffset: number;
 	jsonMetadataLength: number;
 	leafDirectoryOffset: number;
-	leafDirectoryLength: number;
+	leafDirectoryLength?: number;
 	tileDataOffset: number;
-	tileDataLength: number;
+	tileDataLength?: number;
 	numAddressedTiles: number;
 	numTileEntries: number;
 	numTileContents: number;
@@ -301,6 +303,7 @@ export function bytesToHeader(bytes: ArrayBuffer, etag?: string): Header {
 		throw new Error("Wrong magic number for PMTiles archive");
 	}
 	return {
+		specVersion: 3,
 		rootDirectoryOffset: Number(v.getBigUint64(3, true)),
 		rootDirectoryLength: Number(v.getBigUint64(11, true)),
 		jsonMetadataOffset: Number(v.getBigUint64(19, true)),
@@ -362,6 +365,10 @@ function deserializeIndex(buffer: ArrayBuffer): Entry[] {
 	return entries;
 }
 
+function detectVersion(a: ArrayBuffer): number {
+	return 3;
+}
+
 export class VersionMismatch extends Error {}
 
 export interface Cache {
@@ -387,9 +394,11 @@ async function getHeaderAndRoot(
 ): Promise<[Header, [string, number, Entry[] | ArrayBuffer]?]> {
 	let resp = await source.getBytes(0, 16384);
 
-	// check spec revision
-	if (false) {
-	} else {
+	// V2 COMPATIBILITY
+	if (detectVersion(resp.data) < 2) {
+		return v2.getHeaderAndRoot(resp.data, resp.etag);
+	}
+
 	const headerData = resp.data.slice(0, HEADER_SIZE_BYTES);
 	const header = bytesToHeader(headerData, resp.etag);
 
@@ -416,7 +425,6 @@ async function getHeaderAndRoot(
 	}
 
 	return [header, undefined];
-	}
 }
 
 async function getDirectory(
@@ -749,6 +757,11 @@ export class PMTiles {
 		const tile_id = zxyToTileId(z, x, y);
 		const header = await this.cache.getHeader(this.source);
 
+		// V2 COMPATIBILITY
+		if (header.specVersion < 3) {
+			return v2.getZxy(header, this.cache);
+		}
+
 		if (z < header.minZoom || z > header.maxZoom) {
 			return undefined;
 		}
@@ -809,6 +822,7 @@ export class PMTiles {
 
 	async getMetadataAttempt(): Promise<any> {
 		const header = await this.cache.getHeader(this.source);
+
 		const resp = await this.source.getBytes(
 			header.jsonMetadataOffset,
 			header.jsonMetadataLength