Use DecompressionStream in async code

Usually, content stream or fonts are compressed using FlateDecode.
So use the DecompressionStream API to decompress those streams
in the async code path.

Author: calixteman

src/core/cmap.js

@@ -699,6 +699,12 @@ class CMapFactory {
     if (encoding instanceof Name) {
       return createBuiltInCMap(encoding.name, fetchBuiltInCMap);
     } else if (encoding instanceof BaseStream) {
+      if (encoding.isAsync) {
+        const bytes = await encoding.asyncGetBytes();
+        if (bytes) {
+          encoding = new Stream(bytes, 0, bytes.length, encoding.dict);
+        }
+      }
       const parsedCMap = await parseCMap(
         /* cMap = */ new CMap(),
         /* lexer = */ new Lexer(encoding),

src/core/document.js

@@ -61,14 +61,14 @@ import {
   RefSetCache,
 } from "./primitives.js";
 import { getXfaFontDict, getXfaFontName } from "./xfa_fonts.js";
+import { NullStream, Stream } from "./stream.js";
 import { BaseStream } from "./base_stream.js";
 import { calculateMD5 } from "./calculate_md5.js";
 import { Catalog } from "./catalog.js";
 import { clearGlobalCaches } from "./cleanup_helper.js";
 import { DatasetReader } from "./dataset_reader.js";
 import { Intersector } from "./intersector.js";
 import { Linearization } from "./parser.js";
-import { NullStream } from "./stream.js";
 import { ObjectLoader } from "./object_loader.js";
 import { OperatorList } from "./operator_list.js";
 import { PartialEvaluator } from "./evaluator.js";
@@ -271,9 +271,31 @@ class Page {
     const content = await this.pdfManager.ensure(this, "content");
 
     if (content instanceof BaseStream && !content.isImageStream) {
+      if (content.isAsync) {
+        const bytes = await content.asyncGetBytes();
+        if (bytes) {
+          return new Stream(bytes, 0, bytes.length, content.dict);
+        }
+      }
       return content;
     }
     if (Array.isArray(content)) {
+      const promises = [];
+      for (let i = 0, ii = content.length; i < ii; i++) {
+        const item = content[i];
+        if (item instanceof BaseStream && item.isAsync) {
+          promises.push(
+            item.asyncGetBytes().then(bytes => {
+              if (bytes) {
+                content[i] = new Stream(bytes, 0, bytes.length, item.dict);
+              }
+            })
+          );
+        }
+      }
+      if (promises.length > 0) {
+        await Promise.all(promises);
+      }
       return new StreamsSequenceStream(
         content,
         this.#onSubStreamError.bind(this)

src/core/evaluator.js

@@ -1706,7 +1706,7 @@ class PartialEvaluator {
     return null;
   }
 
-  getOperatorList({
+  async getOperatorList({
     stream,
     task,
     resources,
@@ -1715,6 +1715,13 @@ class PartialEvaluator {
     fallbackFontDict = null,
     prevRefs = null,
   }) {
+    if (stream.isAsync) {
+      const bytes = await stream.asyncGetBytes();
+      if (bytes) {
+        stream = new Stream(bytes, 0, bytes.length, stream.dict);
+      }
+    }
+
     const objId = stream.dict?.objId;
     const seenRefs = new RefSet(prevRefs);
 
@@ -2373,7 +2380,7 @@ class PartialEvaluator {
     });
   }
 
-  getTextContent({
+  async getTextContent({
     stream,
     task,
     resources,
@@ -2389,6 +2396,13 @@ class PartialEvaluator {
     prevRefs = null,
     intersector = null,
   }) {
+    if (stream.isAsync) {
+      const bytes = await stream.asyncGetBytes();
+      if (bytes) {
+        stream = new Stream(bytes, 0, bytes.length, stream.dict);
+      }
+    }
+
     const objId = stream.dict?.objId;
     const seenRefs = new RefSet(prevRefs);
 
@@ -4565,8 +4579,16 @@ class PartialEvaluator {
       if (fontFile) {
         if (!(fontFile instanceof BaseStream)) {
           throw new FormatError("FontFile should be a stream");
-        } else if (fontFile.isEmpty) {
-          throw new FormatError("FontFile is empty");
+        } else {
+          if (fontFile.isAsync) {
+            const bytes = await fontFile.asyncGetBytes();
+            if (bytes) {
+              fontFile = new Stream(bytes, 0, bytes.length, fontFile.dict);
+            }
+          }
+          if (fontFile.isEmpty) {
+            throw new FormatError("FontFile is empty");
+          }
         }
       }
     } catch (ex) {

src/core/flate_stream.js

@@ -122,6 +122,8 @@ const fixedDistCodeTab = [
 ];
 
 class FlateStream extends DecodeStream {
+  #isAsync = true;
+
   constructor(str, maybeLength) {
     super(maybeLength);
 
@@ -162,7 +164,9 @@ class FlateStream extends DecodeStream {
 
   async asyncGetBytes() {
     this.stream.reset();
-    const bytes = this.stream.getBytes();
+    const bytes = this.stream.isAsync
+      ? await this.stream.asyncGetBytes()
+      : this.stream.getBytes();
 
     try {
       const { readable, writable } = new DecompressionStream("deflate");
@@ -200,6 +204,7 @@ class FlateStream extends DecodeStream {
       // decoder.
       // We already get the bytes from the underlying stream, so we just reuse
       // them to avoid get them again.
+      this.#isAsync = false;
       this.stream = new Stream(
         bytes,
         2 /* = header size (see ctor) */,
@@ -212,7 +217,7 @@ class FlateStream extends DecodeStream {
   }
 
   get isAsync() {
-    return true;
+    return this.#isAsync;
   }
 
   getBits(bits) {

src/core/stream.js

@@ -51,6 +51,7 @@ class Stream extends BaseStream {
     const strEnd = this.end;
 
     if (!length) {
+      this.pos = strEnd;
       return bytes.subarray(pos, strEnd);
     }
     let end = pos + length;

test/unit/cff_parser_spec.js

@@ -68,6 +68,7 @@ describe("CFFParser", function () {
   });
 
   beforeEach(function () {
+    fontData.reset();
     parser = new CFFParser(fontData, {}, SEAC_ANALYSIS_ENABLED);
     cff = parser.parse();
   });
@@ -168,6 +169,7 @@ describe("CFFParser", function () {
   });
 
   it("parses a CharString endchar with 4 args w/seac enabled", function () {
+    fontData.reset();
     const cffParser = new CFFParser(
       fontData,
       {},
@@ -197,6 +199,7 @@ describe("CFFParser", function () {
   });
 
   it("parses a CharString endchar with 4 args w/seac disabled", function () {
+    fontData.reset();
     const cffParser = new CFFParser(
       fontData,
       {},