mirror of
https://github.com/M66B/FairEmail.git
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104 lines
3.3 KiB
Java
104 lines
3.3 KiB
Java
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 android.text.TextUtils;
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import java.nio.charset.Charset;
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import java.nio.charset.StandardCharsets;
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class CharsetHelper {
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private static final int MAX_SAMPLE_SIZE = 8192;
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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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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 Charset detect(String text) {
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try {
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byte[] octets = text.getBytes(StandardCharsets.ISO_8859_1);
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byte[] sample;
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if (octets.length < MAX_SAMPLE_SIZE)
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sample = octets;
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else {
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sample = new byte[MAX_SAMPLE_SIZE];
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System.arraycopy(octets, 0, sample, 0, MAX_SAMPLE_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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if ("US-ASCII".equals(detected) ||
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"ISO-8859-1".equals(detected) ||
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"ISO-8859-2".equals(detected) ||
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"windows-1250".equals(detected) ||
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"windows-1252".equals(detected) ||
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"windows-1257".equals(detected) ||
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"UTF-8".equals(detected))
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Log.w("compact_enc_det result=" + detected);
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else
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// ISO-2022-JP, GB18030
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Log.e("compact_enc_det result=" + detected);
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if (TextUtils.isEmpty(detected))
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return null;
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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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}
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