Change the BaseCMapReaderFactory fetch-helper to return a Uint8Array

This moves more functionality into the base-class, rather than having to duplicate that in the extending classes.
For consistency, also updates the `BaseStandardFontDataFactory` and introduces more `async`/`await` in various relevant code.

src/display/base_factory.js

@@ -127,22 +127,27 @@ class BaseCMapReaderFactory {
       throw new Error("CMap name must be specified.");
     }
     const url = this.baseUrl + name + (this.isCompressed ? ".bcmap" : "");
-    const compressionType = this.isCompressed
-      ? CMapCompressionType.BINARY
-      : CMapCompressionType.NONE;
 
-    return this._fetchData(url, compressionType).catch(reason => {
-      throw new Error(
-        `Unable to load ${this.isCompressed ? "binary " : ""}CMap at: ${url}`
-      );
-    });
+    return this._fetch(url)
+      .then(cMapData => ({
+        cMapData,
+        compressionType: this.isCompressed
+          ? CMapCompressionType.BINARY
+          : CMapCompressionType.NONE,
+      }))
+      .catch(reason => {
+        throw new Error(
+          `Unable to load ${this.isCompressed ? "binary " : ""}CMap at: ${url}`
+        );
+      });
   }
 
   /**
    * @ignore
+   * @returns {Promise<Uint8Array>}
    */
-  _fetchData(url, compressionType) {
-    unreachable("Abstract method `_fetchData` called.");
+  async _fetch(url) {
+    unreachable("Abstract method `_fetch` called.");
   }
 }
 
@@ -168,16 +173,17 @@ class BaseStandardFontDataFactory {
     }
     const url = `${this.baseUrl}${filename}`;
 
-    return this._fetchData(url).catch(reason => {
+    return this._fetch(url).catch(reason => {
       throw new Error(`Unable to load font data at: ${url}`);
     });
   }
 
   /**
    * @ignore
+   * @returns {Promise<Uint8Array>}
    */
-  _fetchData(url) {
-    unreachable("Abstract method `_fetchData` called.");
+  async _fetch(url) {
+    unreachable("Abstract method `_fetch` called.");
   }
 }
 

src/display/display_utils.js

@@ -564,17 +564,14 @@ class DOMCMapReaderFactory extends BaseCMapReaderFactory {
   /**
    * @ignore
    */
-  _fetchData(url, compressionType) {
-    return fetchData(
+  async _fetch(url) {
+    const data = await fetchData(
       url,
       /* type = */ this.isCompressed ? "arraybuffer" : "text"
-    ).then(data => ({
-      cMapData:
-        data instanceof ArrayBuffer
-          ? new Uint8Array(data)
-          : stringToBytes(data),
-      compressionType,
-    }));
+    );
+    return data instanceof ArrayBuffer
+      ? new Uint8Array(data)
+      : stringToBytes(data);
   }
 }
 
@@ -582,10 +579,9 @@ class DOMStandardFontDataFactory extends BaseStandardFontDataFactory {
   /**
    * @ignore
    */
-  _fetchData(url) {
-    return fetchData(url, /* type = */ "arraybuffer").then(
-      data => new Uint8Array(data)
-    );
+  async _fetch(url) {
+    const data = await fetchData(url, /* type = */ "arraybuffer");
+    return new Uint8Array(data);
   }
 }
 

src/display/node_utils.js

@@ -113,10 +113,11 @@ class NodePackages {
   }
 }
 
-const fetchData = function (url) {
+async function fetchData(url) {
   const fs = NodePackages.get("fs");
-  return fs.promises.readFile(url).then(data => new Uint8Array(data));
-};
+  const data = await fs.promises.readFile(url);
+  return new Uint8Array(data);
+}
 
 class NodeFilterFactory extends BaseFilterFactory {}
 
@@ -134,8 +135,8 @@ class NodeCMapReaderFactory extends BaseCMapReaderFactory {
   /**
    * @ignore
    */
-  _fetchData(url, compressionType) {
-    return fetchData(url).then(data => ({ cMapData: data, compressionType }));
+  async _fetch(url) {
+    return fetchData(url);
   }
 }
 
@@ -143,7 +144,7 @@ class NodeStandardFontDataFactory extends BaseStandardFontDataFactory {
   /**
    * @ignore
    */
-  _fetchData(url) {
+  async _fetch(url) {
     return fetchData(url);
   }
 }