1436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby/* 2436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * Copyright (C) 2011 The Android Open Source Project 3436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * 4436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * Licensed under the Apache License, Version 2.0 (the "License"); 5436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * you may not use this file except in compliance with the License. 6436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * You may obtain a copy of the License at 7436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * 8436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * http://www.apache.org/licenses/LICENSE-2.0 9436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * 10436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * Unless required by applicable law or agreed to in writing, software 11436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * distributed under the License is distributed on an "AS IS" BASIS, 12436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * See the License for the specific language governing permissions and 14436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * limitations under the License. 15436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby */ 16436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby 17436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hambypackage com.android.settings.bluetooth; 18436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby 19436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hambyimport android.text.InputFilter; 20436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hambyimport android.text.Spanned; 21436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby 22436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby/** 23436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * This filter will constrain edits so that the text length is not 24436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * greater than the specified number of bytes using UTF-8 encoding. 25436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * <p>The JNI method used by {@link android.server.BluetoothService} 26436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * to convert UTF-16 to UTF-8 doesn't support surrogate pairs, 27436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * therefore code points outside of the basic multilingual plane 28436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * (0000-FFFF) will be encoded as a pair of 3-byte UTF-8 characters, 29436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * rather than a single 4-byte UTF-8 encoding. Dalvik implements this 30436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * conversion in {@code convertUtf16ToUtf8()} in 31436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * {@code dalvik/vm/UtfString.c}. 32436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * <p>This JNI method is unlikely to change in the future due to 33436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * backwards compatibility requirements. It's also unclear whether 34436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * the installed base of Bluetooth devices would correctly handle the 35436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * encoding of surrogate pairs in UTF-8 as 4 bytes rather than 6. 36436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * However, this filter will still work in scenarios where surrogate 37436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * pairs are encoded as 4 bytes, with the caveat that the maximum 38436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby * length will be constrained more conservatively than necessary. 39436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby */ 40436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hambyclass Utf8ByteLengthFilter implements InputFilter { 41436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby private final int mMaxBytes; 42436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby 43436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby Utf8ByteLengthFilter(int maxBytes) { 44436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby mMaxBytes = maxBytes; 45436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 46436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby 47436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby public CharSequence filter(CharSequence source, int start, int end, 48436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby Spanned dest, int dstart, int dend) { 49436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby int srcByteCount = 0; 50436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // count UTF-8 bytes in source substring 51436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby for (int i = start; i < end; i++) { 52436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby char c = source.charAt(i); 53436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby srcByteCount += (c < (char) 0x0080) ? 1 : (c < (char) 0x0800 ? 2 : 3); 54436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 55436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby int destLen = dest.length(); 56436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby int destByteCount = 0; 57436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // count UTF-8 bytes in destination excluding replaced section 58436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby for (int i = 0; i < destLen; i++) { 59436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby if (i < dstart || i >= dend) { 60436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby char c = dest.charAt(i); 61436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby destByteCount += (c < (char) 0x0080) ? 1 : (c < (char) 0x0800 ? 2 : 3); 62436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 63436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 64436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby int keepBytes = mMaxBytes - destByteCount; 65436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby if (keepBytes <= 0) { 66436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby return ""; 67436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } else if (keepBytes >= srcByteCount) { 68436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby return null; // use original dest string 69436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } else { 70436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // find end position of largest sequence that fits in keepBytes 71436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby for (int i = start; i < end; i++) { 72436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby char c = source.charAt(i); 73436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby keepBytes -= (c < (char) 0x0080) ? 1 : (c < (char) 0x0800 ? 2 : 3); 74436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby if (keepBytes < 0) { 75436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby return source.subSequence(start, i); 76436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 77436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 78436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // If the entire substring fits, we should have returned null 79436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // above, so this line should not be reached. If for some 80436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby // reason it is, return null to use the original dest string. 81436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby return null; 82436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 83436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby } 84436b29e68e6608bed9e8e7d54385b8f62d89208eJake Hamby} 85