Use the position of the previous xref stream if any when saving a pdf (bug 1823296)

src/core/worker.js

@@ -660,6 +660,7 @@ class WorkerMessageHandler {
               });
             }
 
+            const lastXRefStreamPos = xref.lastXRefStreamPos;
             newXrefInfo = {
               rootRef: xref.trailer.getRaw("Root") || null,
               encryptRef: xref.trailer.getRaw("Encrypt") || null,
@@ -667,7 +668,8 @@ class WorkerMessageHandler {
               infoRef: xref.trailer.getRaw("Info") || null,
               info: infoObj,
               fileIds: xref.trailer.get("ID") || null,
-              startXRef,
+              startXRef:
+                lastXRefStreamPos === null ? startXRef : lastXRefStreamPos,
               filename,
             };
           }
@@ -836,6 +838,11 @@ class WorkerMessageHandler {
       handler.on("GetXFADatasets", function (data) {
         return pdfManager.ensureDoc("xfaDatasets");
       });
+      handler.on("GetXRefPrevValue", function (data) {
+        return pdfManager
+          .ensureXRef("trailer")
+          .then(trailer => trailer.get("Prev"));
+      });
     }
 
     return workerHandlerName;

src/core/xref.js

@@ -756,6 +756,11 @@ class XRef {
     throw new XRefParseException();
   }
 
+  get lastXRefStreamPos() {
+    const pos = Object.keys(this.xrefstms);
+    return pos.length === 0 ? null : Math.max(...pos);
+  }
+
   getEntry(i) {
     const xrefEntry = this.entries[i];
     if (xrefEntry && !xrefEntry.free && xrefEntry.offset) {

src/display/api.js

@@ -777,6 +777,11 @@ class PDFDocumentProxy {
           return this._transport.getXFADatasets();
         },
       });
+      Object.defineProperty(this, "getXRefPrevValue", {
+        value: () => {
+          return this._transport.getXRefPrevValue();
+        },
+      });
     }
   }
 
@@ -2397,6 +2402,11 @@ class WorkerTransport {
           return this.messageHandler.sendWithPromise("GetXFADatasets", null);
         },
       });
+      Object.defineProperty(this, "getXRefPrevValue", {
+        value: () => {
+          return this.messageHandler.sendWithPromise("GetXRefPrevValue", null);
+        },
+      });
     }
   }
 

test/pdfs/bug1823296.pdf.link

@@ -0,0 +1,2 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=9324226
+

test/test_manifest.json

@@ -7496,5 +7496,12 @@
       "md5": "d95a83a868671a03cbf322f16b2e2b9d",
       "link": true,
       "type": "other"
+   },
+   {
+      "id": "bug1823296",
+      "file": "pdfs/bug1823296.pdf",
+      "md5": "f71e89ebe3d6e75e0c83ce41cd72df1f",
+      "link": true,
+      "type": "other"
    }
 ]

test/unit/api_spec.js

@@ -14,6 +14,7 @@
  */
 
 import {
+  AnnotationEditorType,
   AnnotationMode,
   AnnotationType,
   createPromiseCapability,
@@ -1980,6 +1981,35 @@ describe("api", function () {
       await loadingTask.destroy();
     });
 
+    it("write a a new annotation, save the pdf and check that the prev entry in xref stream is correct", async function () {
+      if (isNodeJS) {
+        pending("Linked test-cases are not supported in Node.js.");
+      }
+
+      let loadingTask = getDocument(buildGetDocumentParams("bug1823296.pdf"));
+      let pdfDoc = await loadingTask.promise;
+      pdfDoc.annotationStorage.setValue("pdfjs_internal_editor_0", {
+        annotationType: AnnotationEditorType.FREETEXT,
+        rect: [12, 34, 56, 78],
+        rotation: 0,
+        fontSize: 10,
+        color: [0, 0, 0],
+        value: "Hello PDF.js World!",
+        pageIndex: 0,
+      });
+
+      const data = await pdfDoc.saveDocument();
+      await loadingTask.destroy();
+
+      loadingTask = getDocument(data);
+      pdfDoc = await loadingTask.promise;
+      const xrefPrev = await pdfDoc.getXRefPrevValue();
+
+      expect(xrefPrev).toEqual(143954);
+
+      await loadingTask.destroy();
+    });
+
     describe("Cross-origin", function () {
       let loadingTask;
       function _checkCanLoad(expectSuccess, filename, options) {