performance improvement of reading DOCTYPE

Author: amitguptagwl

src/xmlparser/DocTypeReader.js

@@ -100,11 +100,12 @@ export default class DocTypeReader {
         i = skipWhitespace(xmlData, i);
 
         // Read entity name
-        let entityName = "";
+        const startIndex = i;
         while (i < xmlData.length && !/\s/.test(xmlData[i]) && xmlData[i] !== '"' && xmlData[i] !== "'") {
-            entityName += xmlData[i];
             i++;
         }
+        let entityName = xmlData.substring(startIndex, i);
+
         validateEntityName(entityName);
 
         // Skip whitespace after entity name
@@ -141,11 +142,13 @@ export default class DocTypeReader {
         i = skipWhitespace(xmlData, i);
 
         // Read notation name
-        let notationName = "";
+
+        const startIndex = i;
         while (i < xmlData.length && !/\s/.test(xmlData[i])) {
-            notationName += xmlData[i];
             i++;
         }
+        let notationName = xmlData.substring(startIndex, i);
+
         !this.suppressValidationErr && validateEntityName(notationName);
 
         // Skip whitespace after notation name
@@ -219,11 +222,11 @@ export default class DocTypeReader {
         i = skipWhitespace(xmlData, i);
 
         // Read element name
-        let elementName = "";
+        const startIndex = i;
         while (i < xmlData.length && !/\s/.test(xmlData[i])) {
-            elementName += xmlData[i];
             i++;
         }
+        let elementName = xmlData.substring(startIndex, i);
 
         // Validate element name
         if (!this.suppressValidationErr && !isName(elementName)) {
@@ -240,10 +243,12 @@ export default class DocTypeReader {
             i++; // Move past '('
 
             // Read content model
+            const startIndex = i;
             while (i < xmlData.length && xmlData[i] !== ")") {
-                contentModel += xmlData[i];
                 i++;
             }
+            contentModel = xmlData.substring(startIndex, i);
+
             if (xmlData[i] !== ")") {
                 throw new Error("Unterminated content model");
             }
@@ -264,11 +269,11 @@ export default class DocTypeReader {
         i = skipWhitespace(xmlData, i);
 
         // Read element name
-        let elementName = "";
+        let startIndex = i;
         while (i < xmlData.length && !/\s/.test(xmlData[i])) {
-            elementName += xmlData[i];
             i++;
         }
+        let elementName = xmlData.substring(startIndex, i);
 
         // Validate element name
         validateEntityName(elementName)
@@ -277,11 +282,11 @@ export default class DocTypeReader {
         i = skipWhitespace(xmlData, i);
 
         // Read attribute name
-        let attributeName = "";
+        startIndex = i;
         while (i < xmlData.length && !/\s/.test(xmlData[i])) {
-            attributeName += xmlData[i];
             i++;
         }
+        let attributeName = xmlData.substring(startIndex, i);
 
         // Validate attribute name
         if (!validateEntityName(attributeName)) {
@@ -309,11 +314,13 @@ export default class DocTypeReader {
             // Read the list of allowed notations
             let allowedNotations = [];
             while (i < xmlData.length && xmlData[i] !== ")") {
-                let notation = "";
+
+
+                const startIndex = i;
                 while (i < xmlData.length && xmlData[i] !== "|" && xmlData[i] !== ")") {
-                    notation += xmlData[i];
                     i++;
                 }
+                let notation = xmlData.substring(startIndex, i);
 
                 // Validate notation name
                 notation = notation.trim();
@@ -339,10 +346,11 @@ export default class DocTypeReader {
             attributeType += " (" + allowedNotations.join("|") + ")";
         } else {
             // Handle simple types (e.g., CDATA, ID, IDREF, etc.)
+            const startIndex = i;
             while (i < xmlData.length && !/\s/.test(xmlData[i])) {
-                attributeType += xmlData[i];
                 i++;
             }
+            attributeType += xmlData.substring(startIndex, i);
 
             // Validate simple attribute type
             const validTypes = ["CDATA", "ID", "IDREF", "IDREFS", "ENTITY", "ENTITIES", "NMTOKEN", "NMTOKENS"];