1 files changed, 62 insertions, 0 deletions
diff --git a/testing/xpcshell/node-ws/lib/subprotocol.js b/testing/xpcshell/node-ws/lib/subprotocol.js
new file mode 100644
index 0000000000..d4381e8864
--- /dev/null
+++ b/testing/xpcshell/node-ws/lib/subprotocol.js
@@ -0,0 +1,62 @@
+'use strict';
+
+const { tokenChars } = require('./validation');
+
+/**
+ * Parses the `Sec-WebSocket-Protocol` header into a set of subprotocol names.
+ *
+ * @param {String} header The field value of the header
+ * @return {Set} The subprotocol names
+ * @public
+ */
+function parse(header) {
+  const protocols = new Set();
+  let start = -1;
+  let end = -1;
+  let i = 0;
+
+  for (i; i < header.length; i++) {
+    const code = header.charCodeAt(i);
+
+    if (end === -1 && tokenChars[code] === 1) {
+      if (start === -1) start = i;
+    } else if (
+      i !== 0 &&
+      (code === 0x20 /* ' ' */ || code === 0x09) /* '\t' */
+    ) {
+      if (end === -1 && start !== -1) end = i;
+    } else if (code === 0x2c /* ',' */) {
+      if (start === -1) {
+        throw new SyntaxError(`Unexpected character at index ${i}`);
+      }
+
+      if (end === -1) end = i;
+
+      const protocol = header.slice(start, end);
+
+      if (protocols.has(protocol)) {
+        throw new SyntaxError(`The "${protocol}" subprotocol is duplicated`);
+      }
+
+      protocols.add(protocol);
+      start = end = -1;
+    } else {
+      throw new SyntaxError(`Unexpected character at index ${i}`);
+    }
+  }
+
+  if (start === -1 || end !== -1) {
+    throw new SyntaxError('Unexpected end of input');
+  }
+
+  const protocol = header.slice(start, i);
+
+  if (protocols.has(protocol)) {
+    throw new SyntaxError(`The "${protocol}" subprotocol is duplicated`);
+  }
+
+  protocols.add(protocol);
+  return protocols;
+}
+
+module.exports = { parse };