Implement file reading

background.js

@@ -112,6 +112,54 @@ function getMetadata(options, successCallback, errorCallback) {
 	}
 }
 
+let openFiles = {};
+
+function openFile(options, successCallback, errorCallback) {
+	//TODO: Check if file exists (through getMetadata, or by sending HEAD for the file)
+
+	openFiles[options.requestId] = options.fileSystemId + options.filePath;
+	successCallback();
+}
+
+function closeFile(options, successCallback, errorCallback) {
+	if(options.openRequestId in openFiles) {
+		delete openFiles[options.openRequestId];
+		successCallback();
+	} else {
+		errorCallback("FAILED");
+	}
+}
+
+function readFile(options, successCallback, errorCallback) {
+	let url = openFiles[options.openRequestId];
+	let start = options.offset;
+	let end = start + options.length - 1;
+
+	let request = new XMLHttpRequest();
+	request.open("GET", url);
+	request.setRequestHeader("Range", "bytes=" + start + "-" + end);
+	request.responseType = "arraybuffer";
+	request.onreadystatechange = function() {
+		if(request.readyState != XMLHttpRequest.DONE) return;
+
+		successCallback(request.response, false);
+	}
+	try {
+		request.send();
+	} catch(exception) {
+		if(request.status == 404) {
+			errorCallback("NOT_FOUND");
+		} else {
+			console.log("readFile failed");
+			console.log(exception);
+			errorCallback("FAILED");
+		}
+	}
+}
+
 chrome.fileSystemProvider.onMountRequested.addListener(onMountRequested);
 chrome.fileSystemProvider.onReadDirectoryRequested.addListener(readDirectory);
 chrome.fileSystemProvider.onGetMetadataRequested.addListener(getMetadata);
+chrome.fileSystemProvider.onOpenFileRequested.addListener(openFile);
+chrome.fileSystemProvider.onCloseFileRequested.addListener(closeFile);
+chrome.fileSystemProvider.onReadFileRequested.addListener(readFile);