libdex/DexCatch.c

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Functions for dealing with try-catch info.
 */

#include "DexCatch.h"

/* Get the first handler offset for the given DexCode. 
 * It's not 0 because the handlers list is prefixed with its size
 * (in entries) as a uleb128. */
u4 dexGetFirstHandlerOffset(const DexCode* pCode) {
    if (pCode->triesSize == 0) {
        return 0;
    }
    
    const u1* baseData = dexGetCatchHandlerData(pCode);
    const u1* data = baseData;

    readUnsignedLeb128(&data);

    return data - baseData;
}

/* Get count of handler lists for the given DexCode. */
u4 dexGetHandlersSize(const DexCode* pCode) {
    if (pCode->triesSize == 0) {
        return 0;
    }

    const u1* data = dexGetCatchHandlerData(pCode);

    return readUnsignedLeb128(&data);
}

/* Helper for dexFindCatchHandlerOffset(), which does an actual search
 * in the tries table. Returns -1 if there is no applicable handler. */
int dexFindCatchHandlerOffset0(u2 triesSize, const DexTry* pTries,
        u4 address) {
    // Note: Signed type is important for max and min.
    int min = 0;
    int max = triesSize - 1;

    while (max >= min) {
        int guess = (min + max) >> 1;
        const DexTry* pTry = &pTries[guess];
        u4 start = pTry->startAddr;

        if (address < start) {
            max = guess - 1;
            continue;
        }

        u4 end = start + pTry->insnCount;

        if (address >= end) {
            min = guess + 1;
            continue;
        }

        // We have a winner!
        return (int) pTry->handlerOff;
    }

    // No match.
    return -1;
}

/* Get the handler offset just past the end of the one just iterated over.
 * This ends the iteration if it wasn't already. */
u4 dexCatchIteratorGetEndOffset(DexCatchIterator* pIterator,
        const DexCode* pCode) {
    while (dexCatchIteratorNext(pIterator) != NULL) /* empty */ ;

    return (u4) (pIterator->pEncodedData - dexGetCatchHandlerData(pCode));
}