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| 1 // Copyright (c) 2014 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef BASE_ANDROID_JNI_INT_WRAPPER_H_ |
| 6 #define BASE_ANDROID_JNI_INT_WRAPPER_H_ |
| 7 |
| 8 // Wrapper used to receive int when calling Java from native. |
| 9 // The wrapper disallows automatic conversion of long to int. |
| 10 // This is to avoid a common anti-pattern where a Java int is used |
| 11 // to receive a native pointer. Please use a Java long to receive |
| 12 // native pointers, so that the code works on both 32-bit and 64-bit |
| 13 // platforms. Note the wrapper allows other lossy conversions into |
| 14 // jint that could be consider anti-patterns, such as from size_t. |
| 15 |
| 16 // Checking is only done in debugging builds. |
| 17 |
| 18 #ifdef NDEBUG |
| 19 |
| 20 typedef jint JniIntWrapper; |
| 21 |
| 22 // This inline is sufficiently trivial that it does not change the |
| 23 // final code generated by g++. |
| 24 inline jint as_jint(JniIntWrapper wrapper) { |
| 25 return wrapper; |
| 26 } |
| 27 |
| 28 #else |
| 29 |
| 30 class JniIntWrapper { |
| 31 public: |
| 32 JniIntWrapper() : i_(0) {} |
| 33 JniIntWrapper(int i) : i_(i) {} |
| 34 JniIntWrapper(const JniIntWrapper& ji) : i_(ji.i_) {} |
| 35 template <class T> JniIntWrapper(const T& t) : i_(t) {} |
| 36 jint as_jint() const { return i_; } |
| 37 private: |
| 38 // If you get an "is private" error at the line below it is because you used |
| 39 // an implicit conversion to convert a long to an int when calling Java. |
| 40 // We disallow this, as a common anti-pattern allows converting a native |
| 41 // pointer (intptr_t) to a Java int. Please use a Java long to represent |
| 42 // a native pointer. If you want a lossy conversion, please use an |
| 43 // explicit conversion in your C++ code. Note an error is only seen when |
| 44 // compiling on a 64-bit platform, as intptr_t is indistinguishable from |
| 45 // int on 32-bit platforms. |
| 46 JniIntWrapper(long); |
| 47 jint i_; |
| 48 }; |
| 49 |
| 50 inline jint as_jint(const JniIntWrapper& wrapper) { |
| 51 return wrapper.as_jint(); |
| 52 } |
| 53 |
| 54 #endif // NDEBUG |
| 55 |
| 56 #endif // BASE_ANDROID_JNI_INT_WRAPPER_H_ |
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