1 files changed, 82 insertions, 0 deletions
diff --git a/bg/ResponseMetaData.js b/bg/ResponseMetaData.js
new file mode 100644
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--- /dev/null
+++ b/bg/ResponseMetaData.js
@@ -0,0 +1,82 @@
+/**
+* GNU LibreJS - A browser add-on to block nonfree nontrivial JavaScript.
+*
+* Copyright (C) 2018 Giorgio Maone <giorgio@maone.net>
+*
+* This file is part of GNU LibreJS.
+*
+* GNU LibreJS 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.
+*
+* GNU LibreJS 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 GNU LibreJS.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+  This class parses HTTP response headers to extract both the
+  MIME Content-type and the character set to be used, if specified,
+  to parse textual data through a decoder.
+*/
+
+class ResponseMetaData {
+  constructor(request) {
+    let {responseHeaders} = request;
+    this.headers = {};
+    for (let h of responseHeaders) {
+      if (/^\s*Content-(Type|Disposition)\s*$/i.test(h.name)) {
+        let propertyName =  h.name.split("-")[1].trim();
+        propertyName = `content${propertyName.charAt(0).toUpperCase()}${propertyName.substring(1).toLowerCase()}`;
+        this[propertyName] = h.value;
+        this.headers[propertyName] = h;
+      }
+    }
+    this.forcedUTF8 = false;
+  }
+
+  get charset() {
+    let charset = "";
+    if (this.contentType) {
+      let m = this.contentType.match(/;\s*charset\s*=\s*(\S+)/);
+      if (m) {
+        charset = m[1];
+      }
+    }
+    Object.defineProperty(this, "charset", { value: charset, writable: false, configurable: true });
+    return charset;
+  }
+
+  get isUTF8() {
+    return /^utf-8$/i.test(this.charset);
+  }
+
+  forceUTF8() {
+    if (!(this.forcedUTF8 || this.isUTF8)) {
+      let h = this.headers.contentType;
+      if (h) {
+        h.value = h.value.replace(/;\s*charset\s*=.*|$/, "; charset=utf8");
+        this.forcedUTF8 = true;
+      } // if the header doesn't exist the browser should default to UTF-8 anyway
+    }
+    return this.forcedUTF8;
+  }
+
+  createDecoder() {
+    if (this.charset) {
+      try {
+        return new TextDecoder(this.charset);
+      } catch (e) {
+        console.error(e);
+      }
+    }
+    return new TextDecoder("utf-8");
+  }
+};
+
+module.exports = { ResponseMetaData };