2020-10-09 15:43:02 +00:00
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package eu.faircode.email;
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/*
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This file is part of FairEmail.
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FairEmail is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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FairEmail is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FairEmail. If not, see <http://www.gnu.org/licenses/>.
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Copyright 2018-2020 by Marcel Bokhorst (M66B)
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*/
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import java.nio.charset.Charset;
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import java.nio.charset.StandardCharsets;
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import java.nio.charset.UnsupportedCharsetException;
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class CharsetHelper {
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2020-10-14 20:36:27 +00:00
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private static final int MAX_DETECT_SIZE = 8192;
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2020-10-14 18:54:28 +00:00
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static {
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System.loadLibrary("compact_enc_det");
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}
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private static native String jni_detect(byte[] chars);
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2020-10-09 15:43:02 +00:00
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static boolean isUTF8(String text) {
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// Get extended ASCII characters
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byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
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int bytes;
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for (int i = 0; i < octets.length; i++) {
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if ((octets[i] & 0b10000000) == 0b00000000)
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bytes = 1;
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else if ((octets[i] & 0b11100000) == 0b11000000)
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bytes = 2;
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else if ((octets[i] & 0b11110000) == 0b11100000)
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bytes = 3;
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else if ((octets[i] & 0b11111000) == 0b11110000)
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bytes = 4;
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else if ((octets[i] & 0b11111100) == 0b11111000)
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bytes = 5;
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else if ((octets[i] & 0b11111110) == 0b11111100)
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bytes = 6;
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else
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return false;
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if (i + bytes > octets.length)
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return false;
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while (--bytes > 0)
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if ((octets[++i] & 0b11000000) != 0b10000000)
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return false;
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}
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return true;
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}
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static boolean isISO8859(String text) {
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// https://en.wikipedia.org/wiki/ISO/IEC_8859-1
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int c;
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byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
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for (byte b : octets) {
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c = b & 0xFF;
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if (c < 32)
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return false;
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if (c >= 127 && c < 160)
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return false;
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}
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return true;
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}
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static boolean isISO2022JP(String text) {
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// https://en.wikipedia.org/wiki/ISO/IEC_2022
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// https://www.sljfaq.org/afaq/encodings.html#encodings-ISO-2022-JP
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try {
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Charset.forName("ISO-2022-JP");
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} catch (UnsupportedCharsetException ex) {
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return false;
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}
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int c;
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int escapes = 0;
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boolean escaped = false;
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boolean parenthesis = false;
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boolean dollar = false;
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byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
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for (byte b : octets) {
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c = b & 0xFF;
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if (c > 0x7F)
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return false;
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if (escaped) {
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escaped = false;
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if (c == '(')
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parenthesis = true;
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else if (c == '$')
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dollar = true;
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} else if (parenthesis) {
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parenthesis = false;
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if (c == 'B' || c == 'J')
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escapes++;
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} else if (dollar) {
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dollar = false;
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if (c == '@' || c == 'B')
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escapes++;
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} else if (c == 0x1B)
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escaped = true;
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if (escapes >= 3)
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return true;
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}
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return false;
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}
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2020-10-10 06:57:03 +00:00
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static Charset detect(String text) {
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try {
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2020-10-10 11:20:24 +00:00
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byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
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2020-10-14 20:36:27 +00:00
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byte[] sample;
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if (octets.length < MAX_DETECT_SIZE)
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sample = octets;
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else {
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sample = new byte[MAX_DETECT_SIZE];
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System.arraycopy(octets, 0, sample, 0, MAX_DETECT_SIZE);
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}
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Log.i("compact_enc_det sample=" + sample.length);
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String detected = jni_detect(sample);
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Log.i("compact_enc_det result=" + detected);
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2020-10-10 06:57:03 +00:00
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return Charset.forName(detected);
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} catch (Throwable ex) {
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Log.w(ex);
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return null;
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}
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}
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2020-10-09 15:43:02 +00:00
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}
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