michael@0: // Serves a file with a given mime type and size at an optionally given rate.
michael@0: 
michael@0: function getQuery(request) {
michael@0:   var query = {};
michael@0:   request.queryString.split('&').forEach(function (val) {
michael@0:     var [name, value] = val.split('=');
michael@0:     query[name] = unescape(value);
michael@0:   });
michael@0:   return query;
michael@0: }
michael@0: 
michael@0: function handleResponse() {
michael@0:   // Is this a rate limited response?
michael@0:   if (this.state.rate > 0) {
michael@0:     // Calculate how many bytes we have left to send.
michael@0:     var bytesToWrite = this.state.totalBytes - this.state.sentBytes;
michael@0: 
michael@0:     // Do we have any bytes left to send? If not we'll just fall thru and
michael@0:     // cancel our repeating timer and finalize the response.
michael@0:     if (bytesToWrite > 0) {
michael@0:       // Figure out how many bytes to send, based on the rate limit.
michael@0:       bytesToWrite =
michael@0:         (bytesToWrite > this.state.rate) ? this.state.rate : bytesToWrite;
michael@0: 
michael@0:       for (let i = 0; i < bytesToWrite; i++) {
michael@0:         try {
michael@0:           this.response.bodyOutputStream.write("0", 1);
michael@0:         } catch (e) {
michael@0:           // Connection was closed by client.
michael@0:           if (e == Components.results.NS_ERROR_NOT_AVAILABLE) {
michael@0:             // There's no harm in calling this multiple times.
michael@0:             this.response.finish();
michael@0: 
michael@0:             // It's possible that our timer wasn't cancelled in time
michael@0:             // and we'll be called again.
michael@0:             if (this.timer) {
michael@0:               this.timer.cancel();
michael@0:               this.timer = null;
michael@0:             }
michael@0: 
michael@0:             return;
michael@0:           }
michael@0:         }
michael@0:       }
michael@0: 
michael@0:       // Update the number of bytes we've sent to the client.
michael@0:       this.state.sentBytes += bytesToWrite;
michael@0: 
michael@0:       // Wait until the next call to do anything else.
michael@0:       return;
michael@0:     }
michael@0:   }
michael@0:   else {
michael@0:     // Not rate limited, write it all out.
michael@0:     for (let i = 0; i < this.state.totalBytes; i++) {
michael@0:       this.response.write("0");
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   // Finalize the response.
michael@0:   this.response.finish();
michael@0: 
michael@0:   // All done sending, go ahead and cancel our repeating timer.
michael@0:   this.timer.cancel();
michael@0: 
michael@0:   // Clear the timer.
michael@0:   this.timer = null;
michael@0: }
michael@0: 
michael@0: function handleRequest(request, response) {
michael@0:   var query = getQuery(request);
michael@0: 
michael@0:   // sending at a specific rate requires our response to be asynchronous so
michael@0:   // we handle all requests asynchronously. See handleResponse().
michael@0:   response.processAsync();
michael@0: 
michael@0:   // Default status when responding.
michael@0:   var version = "1.1";
michael@0:   var statusCode = 200;
michael@0:   var description = "OK";
michael@0: 
michael@0:   // Default values for content type, size and rate.
michael@0:   var contentType = "text/plain";
michael@0:   var contentRange = null;
michael@0:   var size = 1024;
michael@0:   var rate = 0;
michael@0: 
michael@0:   // optional content type to be used by our response.
michael@0:   if ("contentType" in query) {
michael@0:     contentType = query["contentType"];
michael@0:   }
michael@0: 
michael@0:   // optional size (in bytes) for generated file.
michael@0:   if ("size" in query) {
michael@0:     size = parseInt(query["size"]);
michael@0:   }
michael@0: 
michael@0:   // optional range request check.
michael@0:   if (request.hasHeader("range")) {
michael@0:     version = "1.1";
michael@0:     statusCode = 206;
michael@0:     description = "Partial Content";
michael@0: 
michael@0:     // We'll only support simple range byte style requests.
michael@0:     var [offset, total] = request.getHeader("range").slice("bytes=".length).split("-");
michael@0:     // Enforce valid Number values.
michael@0:     offset = parseInt(offset);
michael@0:     offset = isNaN(offset) ? 0 : offset;
michael@0:     // Same.
michael@0:     total = parseInt(total);
michael@0:     total = isNaN(total) ? 0 : total;
michael@0: 
michael@0:     // We'll need to original total size as part of the Content-Range header
michael@0:     // value in our response.
michael@0:     var originalSize = size;
michael@0: 
michael@0:     // If we have a total size requested, we must make sure to send that number
michael@0:     // of bytes only (minus the start offset).
michael@0:     if (total && total < size) {
michael@0:       size = total - offset;
michael@0:     } else if (offset) {
michael@0:       // Looks like we just have a byte offset to deal with.
michael@0:       size = size - offset;
michael@0:     }
michael@0: 
michael@0:     // We specifically need to add a Content-Range header to all responses for
michael@0:     // requests that include a range request header.
michael@0:     contentRange = "bytes " + offset + "-" + (size - 1) + "/" + originalSize;
michael@0:   }
michael@0: 
michael@0:   // optional rate (in bytes/s) at which to send the file.
michael@0:   if ("rate" in query) {
michael@0:     rate = parseInt(query["rate"]);
michael@0:   }
michael@0: 
michael@0:   // The context for the responseHandler.
michael@0:   var context = {
michael@0:     response: response,
michael@0:     state: {
michael@0:       contentType: contentType,
michael@0:       totalBytes: size,
michael@0:       sentBytes: 0,
michael@0:       rate: rate
michael@0:     },
michael@0:     timer: null
michael@0:   };
michael@0: 
michael@0:   // The notify implementation for the timer.
michael@0:   context.notify = handleResponse.bind(context);
michael@0: 
michael@0:   context.timer =
michael@0:     Components.classes["@mozilla.org/timer;1"]
michael@0:               .createInstance(Components.interfaces.nsITimer);
michael@0: 
michael@0:   // generate the content.
michael@0:   response.setStatusLine(version, statusCode, description);
michael@0:   response.setHeader("Content-Type", contentType, false);
michael@0:   if (contentRange) {
michael@0:     response.setHeader("Content-Range", contentRange, false);
michael@0:   }
michael@0:   response.setHeader("Content-Length", size.toString(), false);
michael@0: 
michael@0:   // initialize the timer and start writing out the response.
michael@0:   context.timer.initWithCallback(
michael@0:     context,
michael@0:     1000,
michael@0:     Components.interfaces.nsITimer.TYPE_REPEATING_SLACK
michael@0:   );
michael@0: 
michael@0: }