Add getAttachments to PDFDocument

README.md

@@ -71,6 +71,7 @@ Install with: `npm install @cantoo/pdf-lib`
   - [Embed PDF Pages](#embed-pdf-pages)
   - [Embed Font and Measure Text](#embed-font-and-measure-text)
   - [Add Attachments](#add-attachments)
+  - [Extract Attachments](#extract-attachments)
   - [Set Document Metadata](#set-document-metadata)
   - [Read Document Metadata](#read-document-metadata)
   - [Set Viewer Preferences](#set-viewer-preferences)
@@ -117,6 +118,7 @@ Install with: `npm install @cantoo/pdf-lib`
 - Set viewer preferences
 - Read viewer preferences
 - Add attachments
+- Extract attachments
 
 ## Motivation
 
@@ -765,6 +767,23 @@ const pdfBytes = await pdfDoc.save()
 //   • Rendered in an <iframe>
 ```
 
+### Extract Attachments
+
+If you load a PDF that has `cars.csv` as an attachment, you can use the
+following to extract the attachments:
+
+<!-- prettier-ignore -->
+```js
+const pdfDoc = await PDFDocument.load(...)
+const attachments = pdfDoc.getAttachments()
+const csv = attachments.find(({ name }) => name === 'cars.csv')
+fs.writeFileSync(csv.name, csv.data)
+```
+
+> NOTE: If you are building a pdf file with this library, any attachments you've
+> added won't be returned by this function until after you call `save` on the
+> document.
+
 ### Set Document Metadata
 
 _This example produces [this PDF](assets/pdfs/examples/set_document_metadata.pdf)_.

src/api/PDFDocument.ts

@@ -27,6 +27,10 @@ import {
   PDFCatalog,
   PDFContext,
   PDFDict,
+  PDFArray,
+  decodePDFRawStream,
+  PDFStream,
+  PDFRawStream,
   PDFHexString,
   PDFName,
   PDFObjectCopier,
@@ -940,6 +944,47 @@ export default class PDFDocument {
     this.embeddedFiles.push(embeddedFile);
   }
 
+  private getRawAttachments() {
+    if (!this.catalog.has(PDFName.of('Names'))) return [];
+    const Names = this.catalog.lookup(PDFName.of('Names'), PDFDict);
+
+    if (!Names.has(PDFName.of('EmbeddedFiles'))) return [];
+    const EmbeddedFiles = Names.lookup(PDFName.of('EmbeddedFiles'), PDFDict);
+
+    if (!EmbeddedFiles.has(PDFName.of('Names'))) return [];
+    const EFNames = EmbeddedFiles.lookup(PDFName.of('Names'), PDFArray);
+
+    const rawAttachments = [];
+    for (let idx = 0, len = EFNames.size(); idx < len; idx += 2) {
+      const fileName = EFNames.lookup(idx) as PDFHexString | PDFString;
+      const fileSpec = EFNames.lookup(idx + 1, PDFDict);
+      rawAttachments.push({ fileName, fileSpec });
+    }
+
+    return rawAttachments;
+  }
+
+  /**
+   * Get all attachments that are embedded in this document.
+   *
+   * > **NOTE:** If you build a document with this library, this won't return
+   * > anything until you call [[save]] on the document.
+   *
+   * @returns Array of attachments with name and data
+   */
+  getAttachments() {
+    const rawAttachments = this.getRawAttachments();
+    return rawAttachments.map(({ fileName, fileSpec }) => {
+      const stream = fileSpec
+        .lookup(PDFName.of('EF'), PDFDict)
+        .lookup(PDFName.of('F'), PDFStream) as PDFRawStream;
+      return {
+        name: fileName.decodeText(),
+        data: decodePDFRawStream(stream).decode(),
+      };
+    });
+  }
+
   /**
    * Embed a font into this document. The input data can be provided in multiple
    * formats:

tests/api/PDFDocument.spec.ts

@@ -37,6 +37,9 @@ const normalPdfBytes = fs.readFileSync('assets/pdfs/normal.pdf');
 const withViewerPrefsPdfBytes = fs.readFileSync(
   'assets/pdfs/with_viewer_prefs.pdf',
 );
+const hasAttachmentPdfBytes = fs.readFileSync(
+  'assets/pdfs/examples/add_attachments.pdf',
+);
 
 describe(`PDFDocument`, () => {
   describe(`load() method`, () => {
@@ -573,4 +576,143 @@ describe(`PDFDocument`, () => {
       expect(pdfDoc.defaultWordBreaks).toEqual(srcDoc.defaultWordBreaks);
     });
   });
+
+  describe(`attach() method`, () => {
+    it(`Saves to the same value after attaching a file`, async () => {
+      const pdfDoc1 = await PDFDocument.create({ updateMetadata: false });
+      const pdfDoc2 = await PDFDocument.create({ updateMetadata: false });
+
+      const jpgAttachmentBytes = fs.readFileSync(
+        'assets/images/cat_riding_unicorn.jpg',
+      );
+      const pdfAttachmentBytes = fs.readFileSync(
+        'assets/pdfs/us_constitution.pdf',
+      );
+
+      await pdfDoc1.attach(jpgAttachmentBytes, 'cat_riding_unicorn.jpg', {
+        mimeType: 'image/jpeg',
+        description: 'Cool cat riding a unicorn! 🦄🐈🕶️',
+        creationDate: new Date('2019/12/01'),
+        modificationDate: new Date('2020/04/19'),
+      });
+
+      await pdfDoc1.attach(pdfAttachmentBytes, 'us_constitution.pdf', {
+        mimeType: 'application/pdf',
+        description: 'Constitution of the United States 🇺🇸🦅',
+        creationDate: new Date('1787/09/17'),
+        modificationDate: new Date('1992/05/07'),
+      });
+
+      await pdfDoc2.attach(jpgAttachmentBytes, 'cat_riding_unicorn.jpg', {
+        mimeType: 'image/jpeg',
+        description: 'Cool cat riding a unicorn! 🦄🐈🕶️',
+        creationDate: new Date('2019/12/01'),
+        modificationDate: new Date('2020/04/19'),
+      });
+
+      await pdfDoc2.attach(pdfAttachmentBytes, 'us_constitution.pdf', {
+        mimeType: 'application/pdf',
+        description: 'Constitution of the United States 🇺🇸🦅',
+        creationDate: new Date('1787/09/17'),
+        modificationDate: new Date('1992/05/07'),
+      });
+
+      const savedDoc1 = await pdfDoc1.save();
+      const savedDoc2 = await pdfDoc2.save();
+
+      expect(savedDoc1).toEqual(savedDoc2);
+    });
+  });
+
+  describe(`getAttachments() method`, () => {
+    it(`Can read attachments from an existing pdf file`, async () => {
+      const pdfDoc = await PDFDocument.load(hasAttachmentPdfBytes);
+      const attachments = pdfDoc.getAttachments();
+      expect(attachments.length).toEqual(2);
+      const jpgAttachmentExtractedBytes = attachments.find(
+        (attachment) => attachment.name === 'cat_riding_unicorn.jpg',
+      )!;
+      const pdfAttachmentExtractedBytes = attachments.find(
+        (attachment) => attachment.name === 'us_constitution.pdf',
+      )!;
+      expect(pdfAttachmentExtractedBytes).toBeDefined();
+      expect(jpgAttachmentExtractedBytes).toBeDefined();
+      const jpgAttachmentBytes = fs.readFileSync(
+        'assets/images/cat_riding_unicorn.jpg',
+      );
+      const pdfAttachmentBytes = fs.readFileSync(
+        'assets/pdfs/us_constitution.pdf',
+      );
+      expect(jpgAttachmentBytes).toEqual(
+        Buffer.from(jpgAttachmentExtractedBytes.data),
+      );
+      expect(pdfAttachmentBytes).toEqual(
+        Buffer.from(pdfAttachmentExtractedBytes.data),
+      );
+    });
+
+    it(`Saves to the same value after round tripping`, async () => {
+      const pdfDoc1 = await PDFDocument.create({ updateMetadata: false });
+      const pdfDoc2 = await PDFDocument.create({ updateMetadata: false });
+
+      const jpgAttachmentBytes = fs.readFileSync(
+        'assets/images/cat_riding_unicorn.jpg',
+      );
+      const pdfAttachmentBytes = fs.readFileSync(
+        'assets/pdfs/us_constitution.pdf',
+      );
+
+      await pdfDoc1.attach(jpgAttachmentBytes, 'cat_riding_unicorn.jpg', {
+        mimeType: 'image/jpeg',
+        description: 'Cool cat riding a unicorn! 🦄🐈🕶️',
+        creationDate: new Date('2019/12/01'),
+        modificationDate: new Date('2020/04/19'),
+      });
+
+      await pdfDoc1.attach(pdfAttachmentBytes, 'us_constitution.pdf', {
+        mimeType: 'application/pdf',
+        description: 'Constitution of the United States 🇺🇸🦅',
+        creationDate: new Date('1787/09/17'),
+        modificationDate: new Date('1992/05/07'),
+      });
+
+      // This is the currently documented behavior before save has been called
+      const noAttachments = pdfDoc1.getAttachments();
+      expect(noAttachments).toEqual([]);
+
+      const savedDoc1 = await pdfDoc1.save();
+      const attachments = pdfDoc1.getAttachments();
+      const jpgAttachmentExtractedBytes = attachments.find(
+        (attachment) => attachment.name === 'cat_riding_unicorn.jpg',
+      )!;
+      const pdfAttachmentExtractedBytes = attachments.find(
+        (attachment) => attachment.name === 'us_constitution.pdf',
+      )!;
+
+      await pdfDoc2.attach(
+        jpgAttachmentExtractedBytes.data,
+        'cat_riding_unicorn.jpg',
+        {
+          mimeType: 'image/jpeg',
+          description: 'Cool cat riding a unicorn! 🦄🐈🕶️',
+          creationDate: new Date('2019/12/01'),
+          modificationDate: new Date('2020/04/19'),
+        },
+      );
+
+      await pdfDoc2.attach(
+        pdfAttachmentExtractedBytes.data,
+        'us_constitution.pdf',
+        {
+          mimeType: 'application/pdf',
+          description: 'Constitution of the United States 🇺🇸🦅',
+          creationDate: new Date('1787/09/17'),
+          modificationDate: new Date('1992/05/07'),
+        },
+      );
+
+      const savedDoc2 = await pdfDoc2.save();
+      expect(savedDoc1).toEqual(savedDoc2);
+    });
+  });
 });