stream: improve read() performance

PR-URL: #29337 Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: David Carlier <devnexen@gmail.com>
nodejs · Aug 27, 2019 · 2efd72f28d7d7e2d3aa1fe08ce64390e1c6be947 · 2efd72f
1 parent 0c4df35
commit 2efd72f28d7d7e2d3aa1fe08ce64390e1c6be947
Unified Split

Showing with 25 additions and 29 deletions.

+25 −29 lib/internal/streams/buffer_list.js
diff --git a/lib/internal/streams/buffer_list.js b/lib/internal/streams/buffer_list.js
@@ -98,67 +98,63 @@ module.exports = class BufferList {
  // Consumes a specified amount of characters from the buffered data.
  _getString(n) {
-  
-    var p = this.head;
-  
-    var c = 1;
-  
-    var ret = p.data;
-  
-    n -= ret.length;
-  
-    while (p = p.next) {
+  
+    let ret = '';
+  
+    let p = this.head;
+  
+    let c = 0;
+  
+    do {
      const str = p.data;
-  
-      const nb = (n > str.length ? str.length : n);
-  
-      if (nb === str.length)
+  
+      if (n > str.length) {
        ret += str;
-  
-      else
-  
-        ret += str.slice(0, n);
-  
-      n -= nb;
-  
-      if (n === 0) {
-  
-        if (nb === str.length) {
+  
+        n -= str.length;
+  
+      } else {
+  
+        if (n === str.length) {
+  
+          ret += str;
          ++c;
          if (p.next)
            this.head = p.next;
          else
            this.head = this.tail = null;
        } else {
+  
+          ret += str.slice(0, n);
          this.head = p;
-  
-          p.data = str.slice(nb);
+  
+          p.data = str.slice(n);
        }
        break;
      }
      ++c;
-  
-    }
+  
+    } while (p = p.next);
    this.length -= c;
    return ret;
  }
  // Consumes a specified amount of bytes from the buffered data.
  _getBuffer(n) {
    const ret = Buffer.allocUnsafe(n);
-  
-    var p = this.head;
-  
-    var c = 1;
-  
-    p.data.copy(ret);
-  
-    n -= p.data.length;
-  
-    while (p = p.next) {
+  
+    const retLen = n;
+  
+    let p = this.head;
+  
+    let c = 0;
+  
+    do {
      const buf = p.data;
-  
-      const nb = (n > buf.length ? buf.length : n);
-  
-      if (nb === buf.length)
-  
-        ret.set(buf, ret.length - n);
-  
-      else
-  
-        ret.set(new Uint8Array(buf.buffer, buf.byteOffset, nb), ret.length - n);
-  
-      n -= nb;
-  
-      if (n === 0) {
-  
-        if (nb === buf.length) {
+  
+      if (n > buf.length) {
+  
+        ret.set(buf, retLen - n);
+  
+        n -= buf.length;
+  
+      } else {
+  
+        if (n === buf.length) {
+  
+          ret.set(buf, retLen - n);
          ++c;
          if (p.next)
            this.head = p.next;
          else
            this.head = this.tail = null;
        } else {
+  
+          ret.set(new Uint8Array(buf.buffer, buf.byteOffset, n), retLen - n);
          this.head = p;
-  
-          p.data = buf.slice(nb);
+  
+          p.data = buf.slice(n);
        }
        break;
      }
      ++c;
-  
-    }
+  
+    } while (p = p.next);
    this.length -= c;
    return ret;
  }