Fixed/simplified charset transformation

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -45,7 +45,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
 import java.nio.charset.Charset;
-import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -1252,37 +1251,11 @@ public class MessageHelper {
 
             try {
                 ContentType ct = new ContentType(part.getContentType());
-
                 String charset = ct.getParameter("charset");
-                if (charset == null)
+                if (UnknownCharsetProvider.charsetForMime(charset) == null)
-                    charset = StandardCharsets.ISO_8859_1.name();
-                else {
-                    charset = charset.replace("\"", "");
-                    charset = MimeUtility.javaCharset(charset);
-
-                    boolean supported = false;
-                    try {
-                        supported = Charset.isSupported(charset);
-                    } catch (IllegalCharsetNameException ex) {
-                        Log.e(charset, ex);
-                    }
-
-                    if (!supported) {
-                        // x-binaryenc
-                        // UseInqueCodePage
-                        // none
-                        // unknown-8bit
-                        // X-UNKNOWN
-                        Log.e("Unsupported encoding charset=" + charset);
                     warnings.add(context.getString(R.string.title_no_charset, charset));
-                        charset = StandardCharsets.ISO_8859_1.name();
-                    }
-                }
-
-                result = new String(result.getBytes(Charset.forName(charset)));
             } catch (ParseException ex) {
-                Log.w(ex);
+                Log.e(ex);
-                warnings.add(Log.formatThrowable(ex, false));
             }
 
             if (part == plain)

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;
+        }
+    }
+}

app/src/main/resources/META-INF/javamail.charset.map

@@ -1,88 +0,0 @@
-### JDK-to-MIME charset mapping table ####
-### This should be the first mapping table ###
-
-### FairEmail
-
-8859_16		ISO-8859-1
-iso8859_16	ISO-8859-1
-ISO8859-16	ISO-8859-1
-
-ascii       ISO-8859-1
-ASCII       ISO-8859-1
-
-### Inherited
-
-8859_1		ISO-8859-1
-iso8859_1	ISO-8859-1
-ISO8859-1	ISO-8859-1
-
-8859_2		ISO-8859-2
-iso8859_2	ISO-8859-2
-ISO8859-2	ISO-8859-2
-
-8859_3		ISO-8859-3
-iso8859_3	ISO-8859-3
-ISO8859-3	ISO-8859-3
-
-8859_4		ISO-8859-4
-iso8859_4	ISO-8859-4
-ISO8859-4	ISO-8859-4
-
-8859_5		ISO-8859-5
-iso8859_5	ISO-8859-5
-ISO8859-5	ISO-8859-5
-
-8859_6		ISO-8859-6
-iso8859_6	ISO-8859-6
-ISO8859-6	ISO-8859-6
-
-8859_7		ISO-8859-7
-iso8859_7	ISO-8859-7
-ISO8859-7	ISO-8859-7
-
-8859_8		ISO-8859-8
-iso8859_8	ISO-8859-8
-ISO8859-8	ISO-8859-8
-
-8859_9		ISO-8859-9
-iso8859_9	ISO-8859-9
-ISO8859-9	ISO-8859-9
-
-SJIS		Shift_JIS
-JIS		ISO-2022-JP
-ISO2022JP	ISO-2022-JP
-EUC_JP		euc-jp
-KOI8_R		koi8-r
-EUC_CN		euc-cn
-EUC_TW		euc-tw
-EUC_KR		euc-kr
-
---DIVIDER: this line *must* start with "--" and end with "--" --
-
-#### XXX-to-JDK charset mapping table ####
-
-iso-2022-cn     ISO2022CN
-iso-2022-kr     ISO2022KR
-utf-8           UTF8
-utf8		UTF8
-ja_jp.iso2022-7 ISO2022JP
-ja_jp.eucjp     EUCJIS
-
-# these two are not needed in 1.1.6.  (since EUC_KR exists
-# and KSC5601 will map to the correct converter)
-euc-kr          KSC5601
-euckr           KSC5601
-
-# in JDK 1.1.6 we will no longer need the "us-ascii" convert
-us-ascii        ISO-8859-1
-x-us-ascii      ISO-8859-1
-
-# Chinese charsets are a mess and widely misrepresented.
-# gb18030 is a superset of gbk, which is a supserset of cp936/ms936,
-# which is a superset of gb2312.
-# https://bugzilla.gnome.org/show_bug.cgi?id=446783
-# map all of these to gb18030.
-gb2312		GB18030
-cp936		GB18030
-ms936		GB18030
-gbk		GB18030

app/src/main/resources/META-INF/services/java.nio.charset.spi.CharsetProvider

@@ -0,0 +1 @@
+eu.faircode.email.UnknownCharsetProvider