ArrayBufferUtil (#2215)

* Rename StringUtil to ArrayBufferUtil

* Update docs

* Rename file string-util.js to array-buffer-util.js

1 files changed, 76 insertions, 0 deletions

diff --git a/ext/js/data/sandbox/array-buffer-util.js b/ext/js/data/sandbox/array-buffer-util.js
new file mode 100644
index 00000000..13988e76
--- /dev/null
+++ b/ext/js/data/sandbox/array-buffer-util.js
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2021-2022  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Class containing generic ArrayBuffer utility functions.
+ */
+class ArrayBufferUtil {
+    /**
+     * Decodes the contents of an ArrayBuffer using UTF8.
+     * @param {ArrayBuffer} arrayBuffer The input ArrayBuffer.
+     * @returns {string} A UTF8-decoded string.
+     */
+    static arrayBufferUtf8Decode(arrayBuffer) {
+        try {
+            return new TextDecoder('utf-8').decode(arrayBuffer);
+        } catch (e) {
+            return decodeURIComponent(escape(this.arrayBufferToBinaryString(arrayBuffer)));
+        }
+    }
+
+    /**
+     * Converts the contents of an ArrayBuffer to a base64 string.
+     * @param {ArrayBuffer} arrayBuffer The input ArrayBuffer.
+     * @returns {string} A base64 string representing the binary content.
+     */
+    static arrayBufferToBase64(arrayBuffer) {
+        return btoa(this.arrayBufferToBinaryString(arrayBuffer));
+    }
+
+    /**
+     * Converts the contents of an ArrayBuffer to a binary string.
+     * @param {ArrayBuffer} arrayBuffer The input ArrayBuffer.
+     * @returns {string} A string representing the binary content.
+     */
+    static arrayBufferToBinaryString(arrayBuffer) {
+        const bytes = new Uint8Array(arrayBuffer);
+        try {
+            return String.fromCharCode(...bytes);
+        } catch (e) {
+            let binary = '';
+            for (let i = 0, ii = bytes.byteLength; i < ii; ++i) {
+                binary += String.fromCharCode(bytes[i]);
+            }
+            return binary;
+        }
+    }
+
+    /**
+     * Converts a base64 string to an ArrayBuffer.
+     * @param {string} content The binary content string encoded in base64.
+     * @returns {ArrayBuffer} A new `ArrayBuffer` object corresponding to the specified content.
+     */
+    static base64ToArrayBuffer(content) {
+        const binaryContent = atob(content);
+        const length = binaryContent.length;
+        const array = new Uint8Array(length);
+        for (let i = 0; i < length; ++i) {
+            array[i] = binaryContent.charCodeAt(i);
+        }
+        return array.buffer;
+    }
+}