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      1 /*
      2  * Copyright (C) 2008 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 /*
     18  * Functions for dealing with try-catch info.
     19  */
     20 
     21 #include "DexCatch.h"
     22 
     23 /* Get the first handler offset for the given DexCode.
     24  * It's not 0 because the handlers list is prefixed with its size
     25  * (in entries) as a uleb128. */
     26 u4 dexGetFirstHandlerOffset(const DexCode* pCode) {
     27     if (pCode->triesSize == 0) {
     28         return 0;
     29     }
     30 
     31     const u1* baseData = dexGetCatchHandlerData(pCode);
     32     const u1* data = baseData;
     33 
     34     readUnsignedLeb128(&data);
     35 
     36     return data - baseData;
     37 }
     38 
     39 /* Get count of handler lists for the given DexCode. */
     40 u4 dexGetHandlersSize(const DexCode* pCode) {
     41     if (pCode->triesSize == 0) {
     42         return 0;
     43     }
     44 
     45     const u1* data = dexGetCatchHandlerData(pCode);
     46 
     47     return readUnsignedLeb128(&data);
     48 }
     49 
     50 /* Helper for dexFindCatchHandlerOffset(), which does an actual search
     51  * in the tries table. Returns -1 if there is no applicable handler. */
     52 int dexFindCatchHandlerOffset0(u2 triesSize, const DexTry* pTries,
     53         u4 address) {
     54     // Note: Signed type is important for max and min.
     55     int min = 0;
     56     int max = triesSize - 1;
     57 
     58     while (max >= min) {
     59         int guess = (min + max) >> 1;
     60         const DexTry* pTry = &pTries[guess];
     61         u4 start = pTry->startAddr;
     62 
     63         if (address < start) {
     64             max = guess - 1;
     65             continue;
     66         }
     67 
     68         u4 end = start + pTry->insnCount;
     69 
     70         if (address >= end) {
     71             min = guess + 1;
     72             continue;
     73         }
     74 
     75         // We have a winner!
     76         return (int) pTry->handlerOff;
     77     }
     78 
     79     // No match.
     80     return -1;
     81 }
     82 
     83 /* Get the handler offset just past the end of the one just iterated over.
     84  * This ends the iteration if it wasn't already. */
     85 u4 dexCatchIteratorGetEndOffset(DexCatchIterator* pIterator,
     86         const DexCode* pCode) {
     87     while (dexCatchIteratorNext(pIterator) != NULL) /* empty */ ;
     88 
     89     return (u4) (pIterator->pEncodedData - dexGetCatchHandlerData(pCode));
     90 }
     91