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#ifndef LIBDEX_DEXCATCH_H_
22#define LIBDEX_DEXCATCH_H_
23
24#include "DexFile.h"
25#include "Leb128.h"
26
27/*
28 * Catch handler entry, used while iterating over catch_handler_items.
29 */
30struct DexCatchHandler {
31    u4          typeIdx;    /* type index of the caught exception type */
32    u4          address;    /* handler address */
33};
34
35/* Get the first handler offset for the given DexCode.
36 * It's not 0 because the handlers list is prefixed with its size
37 * (in entries) as a uleb128. */
38u4 dexGetFirstHandlerOffset(const DexCode* pCode);
39
40/* Get count of handler lists for the given DexCode. */
41u4 dexGetHandlersSize(const DexCode* pCode);
42
43/*
44 * Iterator over catch handler data. This structure should be treated as
45 * opaque.
46 */
47struct DexCatchIterator {
48    const u1* pEncodedData;
49    bool catchesAll;
50    u4 countRemaining;
51    DexCatchHandler handler;
52};
53
54/* Initialize a DexCatchIterator to emptiness. This mostly exists to
55 * squelch innocuous warnings. */
56DEX_INLINE void dexCatchIteratorClear(DexCatchIterator* pIterator) {
57    pIterator->pEncodedData = NULL;
58    pIterator->catchesAll = false;
59    pIterator->countRemaining = 0;
60    pIterator->handler.typeIdx = 0;
61    pIterator->handler.address = 0;
62}
63
64/* Initialize a DexCatchIterator with a direct pointer to encoded handlers. */
65DEX_INLINE void dexCatchIteratorInitToPointer(DexCatchIterator* pIterator,
66    const u1* pEncodedData)
67{
68    s4 count = readSignedLeb128(&pEncodedData);
69
70    if (count <= 0) {
71        pIterator->catchesAll = true;
72        count = -count;
73    } else {
74        pIterator->catchesAll = false;
75    }
76
77    pIterator->pEncodedData = pEncodedData;
78    pIterator->countRemaining = count;
79}
80
81/* Initialize a DexCatchIterator to a particular handler offset. */
82DEX_INLINE void dexCatchIteratorInit(DexCatchIterator* pIterator,
83    const DexCode* pCode, u4 offset)
84{
85    dexCatchIteratorInitToPointer(pIterator,
86            dexGetCatchHandlerData(pCode) + offset);
87}
88
89/* Get the next item from a DexCatchIterator. Returns NULL if at end. */
90DEX_INLINE DexCatchHandler* dexCatchIteratorNext(DexCatchIterator* pIterator) {
91    if (pIterator->countRemaining == 0) {
92        if (! pIterator->catchesAll) {
93            return NULL;
94        }
95
96        pIterator->catchesAll = false;
97        pIterator->handler.typeIdx = kDexNoIndex;
98    } else {
99        u4 typeIdx = readUnsignedLeb128(&pIterator->pEncodedData);
100        pIterator->handler.typeIdx = typeIdx;
101        pIterator->countRemaining--;
102    }
103
104    pIterator->handler.address = readUnsignedLeb128(&pIterator->pEncodedData);
105    return &pIterator->handler;
106}
107
108/* Get the handler offset just past the end of the one just iterated over.
109 * This ends the iteration if it wasn't already. */
110u4 dexCatchIteratorGetEndOffset(DexCatchIterator* pIterator,
111    const DexCode* pCode);
112
113/* Helper for dexFindCatchHandler(). Do not call directly. */
114int dexFindCatchHandlerOffset0(u2 triesSize, const DexTry* pTries,
115        u4 address);
116
117/* Find the handler associated with a given address, if any.
118 * Initializes the given iterator and returns true if a match is
119 * found. Returns false if there is no applicable handler. */
120DEX_INLINE bool dexFindCatchHandler(DexCatchIterator *pIterator,
121        const DexCode* pCode, u4 address) {
122    u2 triesSize = pCode->triesSize;
123    int offset = -1;
124
125    // Short-circuit the overwhelmingly common cases.
126    switch (triesSize) {
127        case 0: {
128            break;
129        }
130        case 1: {
131            const DexTry* tries = dexGetTries(pCode);
132            u4 start = tries[0].startAddr;
133
134            if (address < start) {
135                break;
136            }
137
138            u4 end = start + tries[0].insnCount;
139
140            if (address >= end) {
141                break;
142            }
143
144            offset = tries[0].handlerOff;
145            break;
146        }
147        default: {
148            offset = dexFindCatchHandlerOffset0(triesSize, dexGetTries(pCode),
149                    address);
150        }
151    }
152
153    if (offset < 0) {
154        dexCatchIteratorClear(pIterator); // This squelches warnings.
155        return false;
156    } else {
157        dexCatchIteratorInit(pIterator, pCode, offset);
158        return true;
159    }
160}
161
162#endif  // LIBDEX_DEXCATCH_H_
163