A module version of this application, with express.js

1 files changed, 121 insertions, 0 deletions

diff --git a/mjpeg-proxy.js b/mjpeg-proxy.js
new file mode 100644
index 0000000..6009e7d
--- /dev/null
+++ b/mjpeg-proxy.js
@@ -0,0 +1,121 @@
+var url = require('url');
+var http = require('http');
+
+require('buffertools');
+
+function extractBoundary(contentType) {
+  var startIndex = contentType.indexOf('boundary=');
+  var endIndex = contentType.indexOf(';', startIndex);
+  if (endIndex == -1) { //boundary is the last option
+    // some servers, like mjpeg-streamer puts a '\r' character at the end of each line.
+    if ((endIndex = contentType.indexOf('\r', startIndex)) == -1) {
+      endIndex = contentType.length;
+    }
+  }
+  return contentType.substring(startIndex + 9, endIndex);
+}
+
+var MjpegProxy = exports.MjpegProxy = function(mjpegUrl) {
+  var self = this;
+
+  if (!mjpegUrl) throw new Error('Please provide a source MJPEG URL');
+
+  self.mjpegOptions = url.parse(mjpegUrl);
+
+  self.audienceResponses = [];
+  self.newAudienceResponses = [];
+
+  self.boundary = null;
+  self.globalMjpegResponse = null;
+
+  self.proxyRequest = function(req, res) {
+
+    // There is already another client consuming the MJPEG response
+    if (self.audienceResponses.length > 0) {
+      self._newClient(req, res);
+    } else {
+      // Send source MJPEG request
+      var mjpegRequest = http.request(self.mjpegOptions, function(mjpegResponse) {
+        self.globalMjpegResponse = mjpegResponse;
+        self.boundary = extractBoundary(mjpegResponse.headers['content-type']);
+
+        self._newClient(req, res);
+
+        var lastByte1 = null;
+        var lastByte2 = null;
+
+        mjpegResponse.on('data', function(chunk) {
+          // Fix CRLF issue on iOS 6+: boundary should be preceded by CRLF.
+          if (lastByte1 != null && lastByte2 != null) {
+            var oldheader = '--' + self.boundary;
+            var p = chunk.indexOf(oldheader); // indexOf provided by buffertools
+
+            if (p == 0 && !(lastByte2 == 0x0d && lastByte1 == 0x0a) || p > 1 && !(chunk[p - 2] == 0x0d && chunk[p - 1] == 0x0a)) {
+              var b1 = chunk.slice(0, p);
+              var b2 = new Buffer('\r\n--' + self.boundary);
+              var b3 = chunk.slice(p + oldheader.length);
+              chunk = Buffer.concat([b1, b2, b3]);
+            }
+          }
+
+          lastByte1 = chunk[chunk.length - 1];
+          lastByte2 = chunk[chunk.length - 2];
+
+          for (var i = self.audienceResponses.length; i--;) {
+            var res = self.audienceResponses[i];
+
+            // First time we push data... lets start at a boundary
+            if (self.newAudienceResponses.indexOf(res) >= 0) {
+              var p = chunk.indexOf('--' + self.boundary); // indexOf provided by buffertools
+              res.write(chunk.slice(p));
+
+              self.newAudienceResponses.splice(self.newAudienceResponses.indexOf(res), 1); // remove from new
+            } else {
+              res.write(chunk);
+            }
+          }
+        });
+        mjpegResponse.on('end', function () {
+          // console.log("...end");
+          for (var i = self.audienceResponses.length; i--;) {
+            var res = self.audienceResponses[i];
+            res.end();
+          }
+        });
+        mjpegResponse.on('close', function () {
+          // console.log("...close");
+        });
+      });
+
+      mjpegRequest.on('error', function(e) {
+        console.log('problem with request: ', e);
+      });
+      mjpegRequest.end();
+    }
+  }
+
+  self._newClient = function(req, res) {
+    res.writeHead(200, {
+      'Expires': 'Mon, 01 Jul 1980 00:00:00 GMT',
+      'Cache-Control': 'no-cache, no-store, must-revalidate',
+      'Pragma': 'no-cache',
+      'Content-Type': 'multipart/x-mixed-replace;boundary=' + self.boundary
+    });
+
+    self.audienceResponses.push(res);
+    self.newAudienceResponses.push(res);
+
+    res.socket.on('close', function () {
+      // console.log('exiting client!');
+
+      self.audienceResponses.splice(self.audienceResponses.indexOf(res), 1);
+      if (self.newAudienceResponses.indexOf(res) >= 0) {
+        self.newAudienceResponses.splice(self.newAudienceResponses.indexOf(res), 1); // remove from new
+      }
+
+      if (self.audienceResponses.length == 0) {
+        self.globalMjpegResponse.destroy();
+      }
+    });
+  }
+}
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