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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.text;
     18 
     19 import android.text.Layout.Directions;
     20 
     21 /**
     22  * Access the ICU bidi implementation.
     23  * @hide
     24  */
     25 /* package */ class AndroidBidi {
     26 
     27     public static int bidi(int dir, char[] chs, byte[] chInfo, int n, boolean haveInfo) {
     28         if (chs == null || chInfo == null) {
     29             throw new NullPointerException();
     30         }
     31 
     32         if (n < 0 || chs.length < n || chInfo.length < n) {
     33             throw new IndexOutOfBoundsException();
     34         }
     35 
     36         switch(dir) {
     37             case Layout.DIR_REQUEST_LTR: dir = 0; break;
     38             case Layout.DIR_REQUEST_RTL: dir = 1; break;
     39             case Layout.DIR_REQUEST_DEFAULT_LTR: dir = -2; break;
     40             case Layout.DIR_REQUEST_DEFAULT_RTL: dir = -1; break;
     41             default: dir = 0; break;
     42         }
     43 
     44         int result = runBidi(dir, chs, chInfo, n, haveInfo);
     45         result = (result & 0x1) == 0 ? Layout.DIR_LEFT_TO_RIGHT : Layout.DIR_RIGHT_TO_LEFT;
     46         return result;
     47     }
     48 
     49     /**
     50      * Returns run direction information for a line within a paragraph.
     51      *
     52      * @param dir base line direction, either Layout.DIR_LEFT_TO_RIGHT or
     53      *     Layout.DIR_RIGHT_TO_LEFT
     54      * @param levels levels as returned from {@link #bidi}
     55      * @param lstart start of the line in the levels array
     56      * @param chars the character array (used to determine whitespace)
     57      * @param cstart the start of the line in the chars array
     58      * @param len the length of the line
     59      * @return the directions
     60      */
     61     public static Directions directions(int dir, byte[] levels, int lstart,
     62             char[] chars, int cstart, int len) {
     63         if (len == 0) {
     64             return Layout.DIRS_ALL_LEFT_TO_RIGHT;
     65         }
     66 
     67         int baseLevel = dir == Layout.DIR_LEFT_TO_RIGHT ? 0 : 1;
     68         int curLevel = levels[lstart];
     69         int minLevel = curLevel;
     70         int runCount = 1;
     71         for (int i = lstart + 1, e = lstart + len; i < e; ++i) {
     72             int level = levels[i];
     73             if (level != curLevel) {
     74                 curLevel = level;
     75                 ++runCount;
     76             }
     77         }
     78 
     79         // add final run for trailing counter-directional whitespace
     80         int visLen = len;
     81         if ((curLevel & 1) != (baseLevel & 1)) {
     82             // look for visible end
     83             while (--visLen >= 0) {
     84                 char ch = chars[cstart + visLen];
     85 
     86                 if (ch == '\n') {
     87                     --visLen;
     88                     break;
     89                 }
     90 
     91                 if (ch != ' ' && ch != '\t') {
     92                     break;
     93                 }
     94             }
     95             ++visLen;
     96             if (visLen != len) {
     97                 ++runCount;
     98             }
     99         }
    100 
    101         if (runCount == 1 && minLevel == baseLevel) {
    102             // we're done, only one run on this line
    103             if ((minLevel & 1) != 0) {
    104                 return Layout.DIRS_ALL_RIGHT_TO_LEFT;
    105             }
    106             return Layout.DIRS_ALL_LEFT_TO_RIGHT;
    107         }
    108 
    109         int[] ld = new int[runCount * 2];
    110         int maxLevel = minLevel;
    111         int levelBits = minLevel << Layout.RUN_LEVEL_SHIFT;
    112         {
    113             // Start of first pair is always 0, we write
    114             // length then start at each new run, and the
    115             // last run length after we're done.
    116             int n = 1;
    117             int prev = lstart;
    118             curLevel = minLevel;
    119             for (int i = lstart, e = lstart + visLen; i < e; ++i) {
    120                 int level = levels[i];
    121                 if (level != curLevel) {
    122                     curLevel = level;
    123                     if (level > maxLevel) {
    124                         maxLevel = level;
    125                     } else if (level < minLevel) {
    126                         minLevel = level;
    127                     }
    128                     // XXX ignore run length limit of 2^RUN_LEVEL_SHIFT
    129                     ld[n++] = (i - prev) | levelBits;
    130                     ld[n++] = i - lstart;
    131                     levelBits = curLevel << Layout.RUN_LEVEL_SHIFT;
    132                     prev = i;
    133                 }
    134             }
    135             ld[n] = (lstart + visLen - prev) | levelBits;
    136             if (visLen < len) {
    137                 ld[++n] = visLen;
    138                 ld[++n] = (len - visLen) | (baseLevel << Layout.RUN_LEVEL_SHIFT);
    139             }
    140         }
    141 
    142         // See if we need to swap any runs.
    143         // If the min level run direction doesn't match the base
    144         // direction, we always need to swap (at this point
    145         // we have more than one run).
    146         // Otherwise, we don't need to swap the lowest level.
    147         // Since there are no logically adjacent runs at the same
    148         // level, if the max level is the same as the (new) min
    149         // level, we have a series of alternating levels that
    150         // is already in order, so there's no more to do.
    151         //
    152         boolean swap;
    153         if ((minLevel & 1) == baseLevel) {
    154             minLevel += 1;
    155             swap = maxLevel > minLevel;
    156         } else {
    157             swap = runCount > 1;
    158         }
    159         if (swap) {
    160             for (int level = maxLevel - 1; level >= minLevel; --level) {
    161                 for (int i = 0; i < ld.length; i += 2) {
    162                     if (levels[ld[i]] >= level) {
    163                         int e = i + 2;
    164                         while (e < ld.length && levels[ld[e]] >= level) {
    165                             e += 2;
    166                         }
    167                         for (int low = i, hi = e - 2; low < hi; low += 2, hi -= 2) {
    168                             int x = ld[low]; ld[low] = ld[hi]; ld[hi] = x;
    169                             x = ld[low+1]; ld[low+1] = ld[hi+1]; ld[hi+1] = x;
    170                         }
    171                         i = e + 2;
    172                     }
    173                 }
    174             }
    175         }
    176         return new Directions(ld);
    177     }
    178 
    179     private native static int runBidi(int dir, char[] chs, byte[] chInfo, int n, boolean haveInfo);
    180 }