Support streamed response from HttpNodeInstance

samples/misc/NodeServicesExamples/Controllers/ResizeImage.cs

@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc;
@@ -36,10 +37,10 @@ namespace NodeServicesExamples.Controllers
                 return NotFound();
             }
 
-            // Invoke Node and convert the base64 result back to bytes
+            // Invoke Node and pipe the result to the response
             var mimeType = GetContentType(imagePath);
-            var resizedImage = await _nodeServices.Invoke<ResizeImageResult>("./Node/resizeImage", fileInfo.PhysicalPath, mimeType, maxWidth, maxHeight);
-            return File(Convert.FromBase64String(resizedImage.Base64), mimeType);
+            var imageStream = await _nodeServices.Invoke<Stream>("./Node/resizeImage", fileInfo.PhysicalPath, mimeType, maxWidth, maxHeight);
+            return File(imageStream, mimeType);
         }
 
         private string GetContentType(string path)

samples/misc/NodeServicesExamples/Node/resizeImage.js

@@ -1,9 +1,7 @@
 var sharp = require('sharp');
 
-module.exports = function(cb, physicalPath, mimeType, maxWidth, maxHeight) {
+module.exports = function(result, physicalPath, mimeType, maxWidth, maxHeight) {
     sharp(physicalPath)
         .resize(maxWidth > 0 ? maxWidth : null, maxHeight > 0 ? maxHeight : null)
-        .toBuffer(function (err, buffer) {
-            cb(err, { base64: buffer && buffer.toString('base64') });
-        });
+        .pipe(result.stream);
 }

src/Microsoft.AspNetCore.NodeServices/Content/Node/entrypoint-http.js

@@ -42,6 +42,19 @@ var server = http.createServer(function(req, res) {
             }
         };
 
+        // Support streamed responses
+        Object.defineProperty(callback, 'stream', {
+            enumerable: true,
+            get: function() {
+                if (!hasSentResult) {
+                    hasSentResult = true;
+                    res.setHeader('Content-Type', 'application/octet-stream');
+                }
+
+                return res;
+            }
+        });
+
         try {
             func.apply(null, [callback].concat(bodyJson.args));
         } catch (synchronousException) {

src/Microsoft.AspNetCore.NodeServices/HostingModels/HttpNodeInstance.cs

@@ -1,4 +1,5 @@
 using System;
+using System.IO;
 using System.Net.Http;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -52,27 +53,46 @@ namespace Microsoft.AspNetCore.NodeServices
             var payloadJson = JsonConvert.SerializeObject(invocationInfo, JsonSerializerSettings);
             var payload = new StringContent(payloadJson, Encoding.UTF8, "application/json");
             var response = await _client.PostAsync("http://localhost:" + _portNumber, payload);
-            var responseString = await response.Content.ReadAsStringAsync();
 
             if (!response.IsSuccessStatusCode)
             {
-                throw new Exception("Call to Node module failed with error: " + responseString);
+                var responseErrorString = await response.Content.ReadAsStringAsync();
+                throw new Exception("Call to Node module failed with error: " + responseErrorString);
             }
 
-            var responseIsJson = response.Content.Headers.ContentType.MediaType == "application/json";
-            if (responseIsJson)
+            var responseContentType = response.Content.Headers.ContentType;
+            switch (responseContentType.MediaType)
             {
-                return JsonConvert.DeserializeObject<T>(responseString);
-            }
+                case "text/plain":
+                    // String responses can skip JSON encoding/decoding
+                    if (typeof(T) != typeof(string))
+                    {
+                        throw new ArgumentException(
+                            "Node module responded with non-JSON string. This cannot be converted to the requested generic type: " +
+                            typeof(T).FullName);
+                    }
 
-            if (typeof(T) != typeof(string))
-            {
-                throw new ArgumentException(
-                    "Node module responded with non-JSON string. This cannot be converted to the requested generic type: " +
-                    typeof(T).FullName);
-            }
+                    var responseString = await response.Content.ReadAsStringAsync();
+                    return (T)(object)responseString;
 
-            return (T)(object)responseString;
+                case "application/json":
+                    var responseJson = await response.Content.ReadAsStringAsync();
+                    return JsonConvert.DeserializeObject<T>(responseJson);
+
+                case "application/octet-stream":
+                    // Streamed responses have to be received as System.IO.Stream instances
+                    if (typeof(T) != typeof(Stream))
+                    {
+                        throw new ArgumentException(
+                            "Node module responded with binary stream. This cannot be converted to the requested generic type: " +
+                            typeof(T).FullName + ". Instead you must use the generic type System.IO.Stream.");
+                    }
+
+                    return (T)(object)(await response.Content.ReadAsStreamAsync());
+
+                default:
+                    throw new InvalidOperationException("Unexpected response content type: " + responseContentType.MediaType);
+            }
         }
 
         protected override void OnOutputDataReceived(string outputData)