XFA - Create Form DOM in merging template and data trees

  - Spec: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.364.2157&rep=rep1&type=pdf#page=171;
  - support for the 2 ways of merging: consumeData and matchTemplate;
  - create additional nodes in template DOM when occur node allows it;
  - support for global values in data DOM.

Author: calixteman

src/core/document.js

@@ -15,6 +15,7 @@
 
 import {
   assert,
+  bytesToString,
   FormatError,
   info,
   InvalidPDFException,
@@ -28,6 +29,7 @@ import {
   shadow,
   stringToBytes,
   stringToPDFString,
+  stringToUTF8String,
   unreachable,
   Util,
   warn,
@@ -732,6 +734,53 @@ class PDFDocument {
     });
   }
 
+  get xfaData() {
+    const acroForm = this.catalog.acroForm;
+    if (!acroForm) {
+      return shadow(this, "xfaData", null);
+    }
+
+    const xfa = acroForm.get("XFA");
+    const entries = {
+      "xdp:xdp": "",
+      template: "",
+      datasets: "",
+      config: "",
+      connectionSet: "",
+      localeSet: "",
+      stylesheet: "",
+      "/xdp:xdp": "",
+    };
+    if (isStream(xfa) && !xfa.isEmpty) {
+      entries["xdp:xdp"] = stringToUTF8String(bytesToString(xfa.getBytes()));
+      return shadow(this, "xfaData", entries);
+    }
+
+    if (Array.isArray(xfa) && xfa.length > 0) {
+      for (let i = 0, ii = xfa.length; i < ii; i += 2) {
+        let name;
+        if (i === 0) {
+          name = "xdp:xdp";
+        } else if (i === ii - 2) {
+          name = "/xdp:xdp";
+        } else {
+          name = xfa[i];
+        }
+
+        if (!entries.hasOwnProperty(name)) {
+          continue;
+        }
+        const data = this.xref.fetchIfRef(xfa[i + 1]);
+        if (!isStream(data) || data.isEmpty) {
+          continue;
+        }
+        entries[name] = stringToUTF8String(bytesToString(data.getBytes()));
+      }
+      return shadow(this, "xfaData", entries);
+    }
+    return shadow(this, "xfaData", null);
+  }
+
   get formInfo() {
     const formInfo = { hasFields: false, hasAcroForm: false, hasXfa: false };
     const acroForm = this.catalog.acroForm;