tweak render stream implementation

src/server/render-stream.js

@@ -1,6 +1,6 @@
 import stream from 'stream'
 
-const MAX_STACK_DEPTH = 500
+const MAX_STACK_DEPTH = 1000
 
 /**
  * Original RenderStream implmentation by Sasha Aickin (@aickin)
@@ -12,10 +12,42 @@ export default class RenderStream extends stream.Readable {
     super()
     this.buffer = ''
     this.render = render
+    this.expectedSize = 0
+
+    this.write = (text, next) => {
+      const n = this.expectedSize
+      this.buffer += text
+      if (this.buffer.length >= n) {
+        this.next = next
+        this.pushBySize(n)
+      } else {
+        // continue rendering until we have enough text to call this.push().
+        // sometimes do this as process.nextTick to get out of stack overflows.
+        if (this.stackDepth >= MAX_STACK_DEPTH) {
+          process.nextTick(next)
+        } else {
+          this.stackDepth++
+          next()
+          this.stackDepth--
+        }
+      }
+    }
+
+    this.end = () => {
+      // the rendering is finished; we should push out the last of the buffer.
+      this.done = true
+      this.push(this.buffer)
+    }
+  }
+
+  pushBySize (n) {
+    const bufferToPush = this.buffer.substring(0, n)
+    this.buffer = this.buffer.substring(n)
+    this.push(bufferToPush)
   }
 
   _read (n) {
-    let bufferToPush
+    this.expectedSize = n
     // it's possible that the last chunk added bumped the buffer up to > 2 * n,
     // which means we will need to go through multiple read calls to drain it
     // down to < n.
@@ -24,41 +56,13 @@ export default class RenderStream extends stream.Readable {
       return
     }
     if (this.buffer.length >= n) {
-      bufferToPush = this.buffer.substring(0, n)
-      this.buffer = this.buffer.substring(n)
-      this.push(bufferToPush)
+      this.pushBySize(n)
       return
     }
     if (!this.next) {
       this.stackDepth = 0
       // start the rendering chain.
-      this.render(
-        // write
-        (text, next) => {
-          this.buffer += text
-          if (this.buffer.length >= n) {
-            this.next = next
-            bufferToPush = this.buffer.substring(0, n)
-            this.buffer = this.buffer.substring(n)
-            this.push(bufferToPush)
-          } else {
-            // continue rendering until we have enough text to call this.push().
-            // sometimes do this as process.nextTick to get out of stack overflows.
-            if (this.stackDepth >= MAX_STACK_DEPTH) {
-              process.nextTick(next)
-            } else {
-              this.stackDepth++
-              next()
-              this.stackDepth--
-            }
-          }
-        },
-        // done
-        () => {
-          // the rendering is finished; we should push out the last of the buffer.
-          this.done = true
-          this.push(this.buffer)
-        })
+      this.render(this.write, this.end)
     } else {
       // continue with the rendering.
       this.next()