perf: use specialized code for sAttribValueQuoted

lib/saxes.js

@@ -1554,20 +1554,40 @@ class SaxesParser {
 
   /** @private */
   sAttribValueQuoted() {
+    // We deliberately do not use captureTo here. The specialized code we use
+    // here is faster than using captureTo.
     const { q } = this;
-    const c = this.captureTo([q, AMP, LESS], "text");
-    if (c === q) {
-      this.pushAttrib(this.name, this.text);
-      this.name = this.text = "";
-      this.q = null;
-      this.state = S_ATTRIB_VALUE_CLOSED;
-    }
-    else if (c === AMP) {
-      this.state = S_ENTITY;
-      this.entityReturnState = S_ATTRIB_VALUE_QUOTED;
-    }
-    else if (c === LESS) {
-      this.fail("disallowed character.");
+    const { chunk, limit, i: start } = this;
+    // eslint-disable-next-line no-constant-condition
+    while (true) {
+      if (this.i >= limit) {
+        // This is faster than adding codepoints one by one.
+        this.text += chunk.substring(start);
+        return;
+      }
+      const code = this.getCode();
+      if (code === q || code === AMP || code === LESS) {
+        // This is faster than adding codepoints one by one.
+        const slice = chunk.substring(start,
+                                      this.i - (code <= 0xFFFF ? 1 : 2));
+        switch (code) {
+        case q:
+          this.pushAttrib(this.name, this.text + slice);
+          this.name = this.text = "";
+          this.q = null;
+          this.state = S_ATTRIB_VALUE_CLOSED;
+          return;
+        case AMP:
+          this.text += slice;
+          this.state = S_ENTITY;
+          this.entityReturnState = S_ATTRIB_VALUE_QUOTED;
+          return;
+        default:
+          this.text += slice;
+          this.fail("disallowed character.");
+          return;
+        }
+      }
     }
   }