98 lines
4.2 KiB
Markdown
98 lines
4.2 KiB
Markdown
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# libnativehelper
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libnativehelper is a collection of JNI related utilities used in Android.
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There are several header and binary libraries here and not all of the
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functionality fits together well. The header libraries are mostly C++
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based. The binary libraries are entirely written in C with no C++
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dependencies. This is by design as the code here can be distributed in
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multiple ways, including mainline modules, so keeping the size down
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benefits everyone with smaller downloads and a stable ABI.
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## Header Libraries
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### jni_headers
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This is a header library that contains provides the API represented in
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the JNI Specification 1.6. Any project in Android that depends on
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`jni.h` should depend on this.
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See:
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* [jni.h](include_jni/jni.h)
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### libnativehelper_header_only
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These headers provide utilities that defined entirely within the
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headers. There are scoped resource classes that make common JNI
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patterns of acquiring and releasing resources safer to use than the
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JNI specification equivalents. Examples being `ScopedLocalRef` to
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manage the lifetime of local references and `ScopedUtfChars` to manage
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the lifetime of Java strings in native code and provide access to utf8
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characters.
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See:
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* [nativehelper/nativehelper_utils.h](header_only_include/nativehelper/nativehelper_utils.h)
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* [nativehelper/scoped_utf_chars.h](header_only_include/nativehelper/scoped_utf_chars.h)
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* [nativehelper/scoped_bytes.h](header_only_include/nativehelper/scoped_bytes.h)
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* [nativehelper/scoped_string_chars.h](header_only_include/nativehelper/scoped_string_chars.h)
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* [nativehelper/scoped_primitive_array.h](header_only_include/nativehelper/scoped_primitive_array.h)
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* [nativehelper/scoped_local_ref.h](header_only_include/nativehelper/scoped_local_ref.h)
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* [nativehelper/scoped_local_frame.h](header_only_include/nativehelper/scoped_local_frame.h)
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### jni_platform_headers
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The `jni_macros.h` header provide compile time checking of JNI methods
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implemented in C++. They ensure the C++ method declaration match the
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Java signature they are associated with.
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See:
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* [nativehelper/jni_macros.h](include_platform_header_only/nativehelper/jni_macros.h)
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## Libraries
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### libnativehelper
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A shared library distributed in the ART module that provides helper
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routines built on Java APIs. This library depends on details that are
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private to libcore and use should be restricted to platform code and
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within the ART module.
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This library also contains the JNI invocation API from the JNI
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Specification and the glue that connects the ART runtime to the API
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implementation. The glue logic is platform only as it is used with the
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Zygote and the standalone dalvikvm.
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See:
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* [nativehelper/JNIHelp.h](include/nativehelper/JNIHelp.h)
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* [nativehelper/JniInvocation.h](include_platform/nativehelper/JniInvocation.h)
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* [nativehelper/JNIPlatformHelp.h](include_platform/nativehelper/JNIPlatformHelp.h)
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* [nativehelper/ScopedBytes.h](include/nativehelper/ScopedBytes.h)
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* [nativehelper/ScopedUtfChars.h](include/nativehelper/ScopedUtfChars.h)
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* [nativehelper/ScopedLocalFrame.h](include/nativehelper/ScopedLocalFrame.h)
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* [nativehelper/ScopedLocalRef.h](include/nativehelper/ScopedLocalRef.h)
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* [nativehelper/ScopedPrimitiveArray.h](include/nativehelper/ScopedPrimitiveArray.h)
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* [nativehelper/ScopedStringChars.h](include/nativehelper/ScopedStringChars.h)
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* [nativehelper/toStringArray.h](include/nativehelper/toStringArray.h)
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### libnativehelper_compat_libc++
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This shared and static library contains a subset of the helper
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routines in libnativehelper based on public Java API. This code can be
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statically linked as the Java APIs it depends on are considered
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stable. The name of this library is a misnomer since it contains no
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C++ code.
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See:
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* [nativehelper/JNIHelp.h](include/nativehelper/JNIHelp.h)
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* [nativehelper/ScopedBytes.h](include/nativehelper/ScopedBytes.h)
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* [nativehelper/ScopedUtfChars.h](include/nativehelper/ScopedUtfChars.h)
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* [nativehelper/ScopedLocalFrame.h](include/nativehelper/ScopedLocalFrame.h)
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* [nativehelper/ScopedLocalRef.h](include/nativehelper/ScopedLocalRef.h)
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* [nativehelper/ScopedPrimitiveArray.h](include/nativehelper/ScopedPrimitiveArray.h)
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* [nativehelper/ScopedStringChars.h](include/nativehelper/ScopedStringChars.h)
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* [nativehelper/toStringArray.h](include/nativehelper/toStringArray.h)
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