// Copyright 2014 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef BASE_ANDROID_JNI_INT_WRAPPER_H_ #define BASE_ANDROID_JNI_INT_WRAPPER_H_ // Wrapper used to receive int when calling Java from native. // The wrapper disallows automatic conversion of long to int. // This is to avoid a common anti-pattern where a Java int is used // to receive a native pointer. Please use a Java long to receive // native pointers, so that the code works on both 32-bit and 64-bit // platforms. Note the wrapper allows other lossy conversions into // jint that could be consider anti-patterns, such as from size_t. // Checking is only done in debugging builds. #ifdef NDEBUG typedef jint JniIntWrapper; // This inline is sufficiently trivial that it does not change the // final code generated by g++. inline jint as_jint(JniIntWrapper wrapper) { return wrapper; } #else class JniIntWrapper { public: JniIntWrapper() : i_(0) {} JniIntWrapper(int i) : i_(i) {} JniIntWrapper(const JniIntWrapper& ji) : i_(ji.i_) {} template JniIntWrapper(const T& t) : i_(t) {} jint as_jint() const { return i_; } private: // If you get an "is private" error at the line below it is because you used // an implicit conversion to convert a long to an int when calling Java. // We disallow this, as a common anti-pattern allows converting a native // pointer (intptr_t) to a Java int. Please use a Java long to represent // a native pointer. If you want a lossy conversion, please use an // explicit conversion in your C++ code. Note an error is only seen when // compiling on a 64-bit platform, as intptr_t is indistinguishable from // int on 32-bit platforms. JniIntWrapper(long); jint i_; }; inline jint as_jint(const JniIntWrapper& wrapper) { return wrapper.as_jint(); } #endif // NDEBUG #endif // BASE_ANDROID_JNI_INT_WRAPPER_H_