Support raster-dem in offline mapbox#42 - use makeRequest aware of mb…

…tiles:// protocol.

src/util/ajax.js

@@ -5,6 +5,7 @@ import { extend } from './util';
 import { isMapboxHTTPURL } from './mapbox';
 import config from './config';
 import assert from 'assert';
+import pako from 'pako/lib/inflate'
 
 import type { Callback } from '../types/callback';
 import type { Cancelable } from '../types/cancelable';
@@ -90,6 +91,34 @@ export const getReferrer = isWorker() ?
         }
     };
 
+function makeDatabaseRequest(requestParameters: RequestParameters, callback: ResponseCallback<any>) {
+    const splitUrl = requestParameters.url.replace("mbtiles://", "").split("/");
+    const dbName = splitUrl[0];
+    const z = parseInt(splitUrl[1]);
+    const x = parseInt(splitUrl[2]);
+    const y = Math.pow(2, z) - parseInt(splitUrl[3]) - 1; // Tiles on database are tms (inverted y axis)
+    const params = [z, x, y];
+    const query = 'SELECT hex(tile_data) AS tile_data FROM tiles WHERE zoom_level=? AND tile_column=? AND tile_row=?';
+    const db = window.openDatabase(dbName, '1.0', dbName, 200 * 1024 * 1024);
+    db.transaction(function (txn) {
+        txn.executeSql(query, params, function (tx, res) {
+            if (res.rows.length) {
+                const tileData = res.rows.item(0).tile_data;
+                var rawData = new Uint8Array(tileData.match(/.{1,2}/g).map(byte => parseInt(byte, 16)));
+                let isGzipped = rawData[0] === 0x1f && rawData[1] === 0x8b;
+                if (isGzipped) {
+                    rawData = pako.inflate(rawData);
+                }
+                callback(null, rawData.buffer, null /*'Cache-Control'*/, null /*'Expires'*/);
+            } else {
+                callback(new Error('tile ' + params.join(',') + ' not found'));
+            }
+        });
+    }, function (error) {
+        callback(error); // Error executing SQL
+    });
+}
+
 function makeFetchRequest(requestParameters: RequestParameters, callback: ResponseCallback<any>): Cancelable {
     const controller = new window.AbortController();
     const request = new window.Request(requestParameters.url, {
@@ -169,6 +198,12 @@ export const makeRequest = function(requestParameters: RequestParameters, callba
     //   some versions (see https://bugs.webkit.org/show_bug.cgi?id=174980#c2)
     // - Requests for resources with the file:// URI scheme don't work with the Fetch API either. In
     //   this case we unconditionally use XHR on the current thread since referrers don't matter.
+    if (/^mbtiles:/.test(requestParameters.url) && isWorker() && self.worker && self.worker.actor) {
+        return self.worker.actor.send('getResource', requestParameters, callback);
+    }
+    if (/^mbtiles:/.test(requestParameters.url) && !isWorker()) {
+        return makeDatabaseRequest(requestParameters, callback);
+    }
     if (!/^file:/.test(requestParameters.url)) {
         if (window.fetch && window.Request && window.AbortController && window.Request.prototype.hasOwnProperty('signal')) {
             return makeFetchRequest(requestParameters, callback);