Compress the data when saving annotions

CompressionStream API has been added in Firefox 113
(see https://bugzilla.mozilla.org/show_bug.cgi?id=1823619)
hence we can use it to compress the streams with added/modified
annotations.

src/core/annotation.js

@@ -273,7 +273,7 @@ class AnnotationFactory {
             baseFont.set("Encoding", Name.get("WinAnsiEncoding"));
             const buffer = [];
             baseFontRef = xref.getNewTemporaryRef();
-            writeObject(baseFontRef, baseFont, buffer, null);
+            await writeObject(baseFontRef, baseFont, buffer, null);
             dependencies.push({ ref: baseFontRef, data: buffer.join("") });
           }
           promises.push(
@@ -1479,7 +1479,7 @@ class MarkupAnnotation extends Annotation {
       const transform = xref.encrypt
         ? xref.encrypt.createCipherTransform(apRef.num, apRef.gen)
         : null;
-      writeObject(apRef, ap, buffer, transform);
+      await writeObject(apRef, ap, buffer, transform);
       dependencies.push({ ref: apRef, data: buffer.join("") });
     } else {
       annotationDict = this.createNewDict(annotation, xref, {});
@@ -1489,7 +1489,7 @@ class MarkupAnnotation extends Annotation {
     const transform = xref.encrypt
       ? xref.encrypt.createCipherTransform(annotationRef.num, annotationRef.gen)
       : null;
-    writeObject(annotationRef, annotationDict, buffer, transform);
+    await writeObject(annotationRef, annotationDict, buffer, transform);
 
     return { ref: annotationRef, data: buffer.join("") };
   }
@@ -1922,7 +1922,7 @@ class WidgetAnnotation extends Annotation {
         appearanceDict.set("Matrix", rotationMatrix);
       }
 
-      writeObject(newRef, appearanceStream, buffer, newTransform);
+      await writeObject(newRef, appearanceStream, buffer, newTransform);
 
       changes.push(
         // data for the new AP
@@ -1937,7 +1937,7 @@ class WidgetAnnotation extends Annotation {
     }
 
     dict.set("M", `D:${getModificationDate()}`);
-    writeObject(this.ref, dict, buffer, originalTransform);
+    await writeObject(this.ref, dict, buffer, originalTransform);
 
     changes[0].data = buffer.join("");
 
@@ -2814,7 +2814,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const buffer = [`${this.ref.num} ${this.ref.gen} obj\n`];
-    writeDict(dict, buffer, originalTransform);
+    await writeDict(dict, buffer, originalTransform);
     buffer.push("\nendobj\n");
 
     return [{ ref: this.ref, data: buffer.join(""), xfa }];
@@ -2873,7 +2873,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
         }
         parent.set("V", name);
         parentBuffer = [`${this.parent.num} ${this.parent.gen} obj\n`];
-        writeDict(parent, parentBuffer, parentTransform);
+        await writeDict(parent, parentBuffer, parentTransform);
         parentBuffer.push("\nendobj\n");
       } else if (this.parent instanceof Dict) {
         this.parent.set("V", name);
@@ -2897,7 +2897,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const buffer = [`${this.ref.num} ${this.ref.gen} obj\n`];
-    writeDict(dict, buffer, originalTransform);
+    await writeDict(dict, buffer, originalTransform);
     buffer.push("\nendobj\n");
 
     const newRefs = [{ ref: this.ref, data: buffer.join(""), xfa }];

src/core/document.js

@@ -297,7 +297,7 @@ class Page {
       );
     }
 
-    writeObject(this.ref, pageDict, buffer, transform);
+    await writeObject(this.ref, pageDict, buffer, transform);
     if (savedDict) {
       pageDict.set("Annots", savedDict);
     }

src/core/writer.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { bytesToString, warn } from "../shared/util.js";
+import { bytesToString, info, stringToBytes, warn } from "../shared/util.js";
 import { Dict, Name, Ref } from "./primitives.js";
 import {
   escapePDFName,
@@ -25,36 +25,87 @@ import { SimpleDOMNode, SimpleXMLParser } from "./xml_parser.js";
 import { BaseStream } from "./base_stream.js";
 import { calculateMD5 } from "./crypto.js";
 
-function writeObject(ref, obj, buffer, transform) {
+async function writeObject(ref, obj, buffer, transform) {
   buffer.push(`${ref.num} ${ref.gen} obj\n`);
   if (obj instanceof Dict) {
-    writeDict(obj, buffer, transform);
+    await writeDict(obj, buffer, transform);
   } else if (obj instanceof BaseStream) {
-    writeStream(obj, buffer, transform);
+    await writeStream(obj, buffer, transform);
   }
   buffer.push("\nendobj\n");
 }
 
-function writeDict(dict, buffer, transform) {
+async function writeDict(dict, buffer, transform) {
   buffer.push("<<");
   for (const key of dict.getKeys()) {
     buffer.push(` /${escapePDFName(key)} `);
-    writeValue(dict.getRaw(key), buffer, transform);
+    await writeValue(dict.getRaw(key), buffer, transform);
   }
   buffer.push(">>");
 }
 
-function writeStream(stream, buffer, transform) {
+async function writeStream(stream, buffer, transform) {
   let string = stream.getString();
   if (transform !== null) {
     string = transform.encryptString(string);
   }
+
+  // eslint-disable-next-line no-undef
+  if (typeof CompressionStream === "undefined") {
+    stream.dict.set("Length", string.length);
+    await writeDict(stream.dict, buffer, transform);
+    buffer.push(" stream\n", string, "\nendstream");
+    return;
+  }
+
+  const filter = await stream.dict.getAsync("Filter");
+  const flateDecode = Name.get("FlateDecode");
+
+  // If the string is too small there is no real benefit
+  // in compressing it.
+  // The number 256 is arbitrary, but it should be reasonable.
+  const MIN_LENGTH_FOR_COMPRESSING = 256;
+
+  if (
+    string.length >= MIN_LENGTH_FOR_COMPRESSING ||
+    (Array.isArray(filter) && filter.includes(flateDecode)) ||
+    (filter instanceof Name && filter.name === flateDecode.name)
+  ) {
+    try {
+      const byteArray = stringToBytes(string);
+      // eslint-disable-next-line no-undef
+      const cs = new CompressionStream("deflate");
+      const writer = cs.writable.getWriter();
+      writer.write(byteArray);
+      writer.close();
+
+      // Response::text doesn't return the correct data.
+      const buf = await new Response(cs.readable).arrayBuffer();
+      string = bytesToString(new Uint8Array(buf));
+
+      if (Array.isArray(filter)) {
+        if (!filter.includes(flateDecode)) {
+          filter.push(flateDecode);
+        }
+      } else if (!filter) {
+        stream.dict.set("Filter", flateDecode);
+      } else if (
+        !(filter instanceof Name) ||
+        filter.name !== flateDecode.name
+      ) {
+        stream.dict.set("Filter", [filter, flateDecode]);
+      }
+    } catch (ex) {
+      info(`writeStream - cannot compress data: "${ex}".`);
+    }
+  }
+
   stream.dict.set("Length", string.length);
-  writeDict(stream.dict, buffer, transform);
+  await writeDict(stream.dict, buffer, transform);
   buffer.push(" stream\n", string, "\nendstream");
 }
 
-function writeArray(array, buffer, transform) {
+async function writeArray(array, buffer, transform) {
   buffer.push("[");
   let first = true;
   for (const val of array) {
@@ -63,18 +114,18 @@ function writeArray(array, buffer, transform) {
     } else {
       first = false;
     }
-    writeValue(val, buffer, transform);
+    await writeValue(val, buffer, transform);
   }
   buffer.push("]");
 }
 
-function writeValue(value, buffer, transform) {
+async function writeValue(value, buffer, transform) {
   if (value instanceof Name) {
     buffer.push(`/${escapePDFName(value.name)}`);
   } else if (value instanceof Ref) {
     buffer.push(`${value.num} ${value.gen} R`);
   } else if (Array.isArray(value)) {
-    writeArray(value, buffer, transform);
+    await writeArray(value, buffer, transform);
   } else if (typeof value === "string") {
     if (transform !== null) {
       value = transform.encryptString(value);
@@ -85,9 +136,9 @@ function writeValue(value, buffer, transform) {
   } else if (typeof value === "boolean") {
     buffer.push(value.toString());
   } else if (value instanceof Dict) {
-    writeDict(value, buffer, transform);
+    await writeDict(value, buffer, transform);
   } else if (value instanceof BaseStream) {
-    writeStream(value, buffer, transform);
+    await writeStream(value, buffer, transform);
   } else if (value === null) {
     buffer.push("null");
   } else {
@@ -160,7 +211,7 @@ function writeXFADataForAcroform(str, newRefs) {
   return buffer.join("");
 }
 
-function updateAcroform({
+async function updateAcroform({
   xref,
   acroForm,
   acroFormRef,
@@ -206,7 +257,7 @@ function updateAcroform({
   }
 
   const buffer = [];
-  writeObject(acroFormRef, dict, buffer, transform);
+  await writeObject(acroFormRef, dict, buffer, transform);
 
   newRefs.push({ ref: acroFormRef, data: buffer.join("") });
 }
@@ -234,7 +285,7 @@ function updateXFA({ xfaData, xfaDatasetsRef, newRefs, xref }) {
   newRefs.push({ ref: xfaDatasetsRef, data });
 }
 
-function incrementalUpdate({
+async function incrementalUpdate({
   originalData,
   xrefInfo,
   newRefs,
@@ -247,7 +298,7 @@ function incrementalUpdate({
   acroForm = null,
   xfaData = null,
 }) {
-  updateAcroform({
+  await updateAcroform({
     xref,
     acroForm,
     acroFormRef,
@@ -328,7 +379,7 @@ function incrementalUpdate({
   newXref.set("Length", tableLength);
 
   buffer.push(`${refForXrefTable.num} ${refForXrefTable.gen} obj\n`);
-  writeDict(newXref, buffer, null);
+  await writeDict(newXref, buffer, null);
   buffer.push(" stream\n");
 
   const bufferLen = buffer.reduce((a, str) => a + str.length, 0);

test/pdfs/.gitignore

@@ -590,3 +590,4 @@
 !copy_paste_ligatures.pdf
 !issue16316.pdf
 !issue14565.pdf
+!multiline.pdf

test/test_manifest.json

@@ -7580,5 +7580,19 @@
       "rounds": 1,
       "annotations": true,
       "type": "eq"
+   },
+   {
+      "id": "multiline_compress",
+      "file": "pdfs/multiline.pdf",
+      "md5": "4727c7d1e4e5c7d45fded8ab7a2e05e5",
+      "rounds": 1,
+      "type": "eq",
+      "save": true,
+      "print": true,
+      "annotationStorage": {
+         "24R": {
+            "value": "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz\nabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"
+         }
+      }
    }
 ]

test/unit/annotation_spec.js

@@ -2115,6 +2115,58 @@ describe("annotation", function () {
       );
     });
 
+    it("should compress and save text", async function () {
+      const textWidgetRef = Ref.get(123, 0);
+      const xref = new XRefMock([
+        { ref: textWidgetRef, data: textWidgetDict },
+        helvRefObj,
+      ]);
+      partialEvaluator.xref = xref;
+      const task = new WorkerTask("test save");
+
+      const annotation = await AnnotationFactory.create(
+        xref,
+        textWidgetRef,
+        pdfManagerMock,
+        idFactoryMock
+      );
+      const annotationStorage = new Map();
+      const value = "a".repeat(256);
+      annotationStorage.set(annotation.data.id, { value });
+
+      const data = await annotation.save(
+        partialEvaluator,
+        task,
+        annotationStorage
+      );
+      expect(data.length).toEqual(2);
+      const [oldData, newData] = data;
+      expect(oldData.ref).toEqual(Ref.get(123, 0));
+      expect(newData.ref).toEqual(Ref.get(2, 0));
+
+      oldData.data = oldData.data.replace(/\(D:\d+\)/, "(date)");
+      expect(oldData.data).toEqual(
+        "123 0 obj\n" +
+          "<< /Type /Annot /Subtype /Widget /FT /Tx /DA (/Helv 5 Tf) /DR " +
+          "<< /Font << /Helv 314 0 R>>>> /Rect [0 0 32 10] " +
+          `/V (${value}) /AP << /N 2 0 R>> /M (date)>>\nendobj\n`
+      );
+
+      const compressedData = [
+        120, 156, 211, 15, 169, 80, 112, 242, 117, 86, 40, 84, 112, 10, 81, 208,
+        247, 72, 205, 41, 83, 48, 85, 8, 73, 83, 48, 84, 48, 0, 66, 8, 25, 146,
+        171, 96, 164, 96, 172, 103, 96, 174, 16, 146, 162, 160, 145, 56, 194,
+        129, 166, 66, 72, 150, 130, 107, 136, 66, 160, 130, 171, 175, 51, 0,
+        222, 235, 111, 133,
+      ];
+      const compressedStream = String.fromCharCode(...compressedData);
+      expect(newData.data).toEqual(
+        "2 0 obj\n<< /Subtype /Form /Resources " +
+          "<< /Font << /Helv 314 0 R>>>> /BBox [0 0 32 10] /Filter /FlateDecode /Length 68>> stream\n" +
+          `${compressedStream}\nendstream\nendobj\n`
+      );
+    });
+
     it("should get field object for usage in JS sandbox", async function () {
       const textWidgetRef = Ref.get(123, 0);
       const xDictRef = Ref.get(141, 0);

test/unit/writer_spec.js

@@ -20,7 +20,7 @@ import { StringStream } from "../../src/core/stream.js";
 
 describe("Writer", function () {
   describe("Incremental update", function () {
-    it("should update a file with new objects", function () {
+    it("should update a file with new objects", async function () {
       const originalData = new Uint8Array();
       const newRefs = [
         { ref: Ref.get(123, 0x2d), data: "abc\n" },
@@ -37,7 +37,7 @@ describe("Writer", function () {
         info: {},
       };
 
-      let data = incrementalUpdate({ originalData, xrefInfo, newRefs });
+      let data = await incrementalUpdate({ originalData, xrefInfo, newRefs });
       data = bytesToString(data);
 
       const expected =
@@ -60,7 +60,7 @@ describe("Writer", function () {
       expect(data).toEqual(expected);
     });
 
-    it("should update a file, missing the /ID-entry, with new objects", function () {
+    it("should update a file, missing the /ID-entry, with new objects", async function () {
       const originalData = new Uint8Array();
       const newRefs = [{ ref: Ref.get(123, 0x2d), data: "abc\n" }];
       const xrefInfo = {
@@ -74,7 +74,7 @@ describe("Writer", function () {
         info: {},
       };
 
-      let data = incrementalUpdate({ originalData, xrefInfo, newRefs });
+      let data = await incrementalUpdate({ originalData, xrefInfo, newRefs });
       data = bytesToString(data);
 
       const expected =
@@ -96,7 +96,7 @@ describe("Writer", function () {
   });
 
   describe("writeDict", function () {
-    it("should write a Dict", function () {
+    it("should write a Dict", async function () {
       const dict = new Dict(null);
       dict.set("A", Name.get("B"));
       dict.set("B", Ref.get(123, 456));
@@ -121,7 +121,7 @@ describe("Writer", function () {
       dict.set("NullVal", null);
 
       const buffer = [];
-      writeDict(dict, buffer, null);
+      await writeDict(dict, buffer, null);
 
       const expected =
         "<< /A /B /B 123 456 R /C 789 /D (hello world) " +
@@ -134,14 +134,14 @@ describe("Writer", function () {
       expect(buffer.join("")).toEqual(expected);
     });
 
-    it("should write a Dict in escaping PDF names", function () {
+    it("should write a Dict in escaping PDF names", async function () {
       const dict = new Dict(null);
       dict.set("\xfeA#", Name.get("hello"));
       dict.set("B", Name.get("#hello"));
       dict.set("C", Name.get("he\xfello\xff"));
 
       const buffer = [];
-      writeDict(dict, buffer, null);
+      await writeDict(dict, buffer, null);
 
       const expected = "<< /#feA#23 /hello /B /#23hello /C /he#fello#ff>>";
 
@@ -150,7 +150,7 @@ describe("Writer", function () {
   });
 
   describe("XFA", function () {
-    it("should update AcroForm when no datasets in XFA array", function () {
+    it("should update AcroForm when no datasets in XFA array", async function () {
       const originalData = new Uint8Array();
       const newRefs = [];
 
@@ -176,7 +176,7 @@ describe("Writer", function () {
         info: {},
       };
 
-      let data = incrementalUpdate({
+      let data = await incrementalUpdate({
         originalData,
         xrefInfo,
         newRefs,