Fixed/simplified charset transformation

2026-01-06 12:54:11 +01:00 · 2020-01-31 17:11:36 +01:00
parent 54d6b2b70b
commit 47a0b5e361
4 changed files with 89 additions and 118 deletions
--- a/app/src/main/java/eu/faircode/email/UnknownCharsetProvider.java
+++ b/app/src/main/java/eu/faircode/email/UnknownCharsetProvider.java
@@ -0,0 +1,85 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+    FairEmail 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.
+    FairEmail 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 FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+    Copyright 2018-2020 by Marcel Bokhorst (M66B)
+*/
+
+import android.text.TextUtils;
+
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.nio.charset.spi.CharsetProvider;
+import java.util.Collections;
+import java.util.Iterator;
+
+import javax.mail.internet.MimeUtility;
+
+public class UnknownCharsetProvider extends CharsetProvider {
+    @Override
+    public Iterator<Charset> charsets() {
+        return Collections.emptyIterator();
+    }
+
+    @Override
+    public Charset charsetForName(String name) {
+        try {
+            Charset charset = charsetForMime(name);
+            return (charset == null ? StandardCharsets.ISO_8859_1 : charset);
+        } catch (Throwable ex) {
+            Log.e(ex);
+            return StandardCharsets.ISO_8859_1;
+        }
+    }
+
+    public static Charset charsetForMime(String name) {
+        // x-binaryenc
+        // UseInqueCodePage
+        // none
+        // unknown-8bit
+        // X-UNKNOWN
+        // https://javaee.github.io/javamail/FAQ#unsupen
+        // https://github.com/javaee/javamail/blob/master/mail/src/main/resources/META-INF/javamail.charset.map
+        try {
+            if (name == null)
+                name = "";
+
+            name = name.replace("\"", "");
+
+            int sp = name.indexOf(" ");
+            if (sp > 0)
+                name = name.substring(0, sp);
+
+            name = name.trim();
+
+            if (TextUtils.isEmpty(name))
+                return StandardCharsets.ISO_8859_1;
+
+            if ("x-IA5".equalsIgnoreCase(name))
+                return StandardCharsets.ISO_8859_1;
+            if ("ASCII".equalsIgnoreCase(name))
+                return StandardCharsets.ISO_8859_1;
+            if ("ISO8859-16".equalsIgnoreCase(name))
+                return StandardCharsets.ISO_8859_1;
+            if ("UTF-8//TRANSLIT".equalsIgnoreCase(name))
+                return StandardCharsets.UTF_8;
+
+            // Android will prevent recursion
+            String jname = MimeUtility.javaCharset(name);
+            return Charset.forName(jname);
+        } catch (Throwable ex) {
+            Log.e("Unknown charset " + name, ex);
+            return null;
+        }
+    }
+}