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SwiftAndroid – P2P-Next
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https://trac.p2p-next.org/wiki/SwiftAndroid
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Porting Swift to Android
Introduction
This article details the steps taken in creating the Android port of the libswift library.
Required software
To build the Android application you will need the following:
Android SDK
a running Java environment
Preferably Eclipse with the SKD & AVDmanager plugin for creating Android apps
At least one Android emulator (I used versions 1.6 and 2.2)
the Android NDK that provides cross compilation tools for ARM processors
Compiling libswift
Libswift uses few libraries and it's very portable. Anyway the android NDK doesn't include any
library except libc. To compile libswift we will need the stdlib that needs to be compiled and
included in the NDK.
Statically compile swift is not a bit issue, it can be easily archived by using a different compiler
(not the NDK) that supports cross-compilation to ARM processor. The problem is that you will end
up with a standalone application that can't be linked to the hardware resources and doesn't have
any access permission for the system.
The trick is to be able to create a library that can be used by a java front-end application. We
can than give disk/network access right to the java application.
The above picture taken from http://marakana.com shows how the linking between the c++
library and the java front-end works. The Java Native Interface (jni) is been used to call the
native C++ library
Steps
Prepare the environment. Look at the requirement above
Create a new Eclispe project.
Create a scheletron of the native library calls in the src dir using the "native" key in the
declaration.
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SwiftAndroid – P2P-Next
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https://trac.p2p-next.org/wiki/SwiftAndroid
I used NativeLib?.java and implemented the functions start, stop, and progress (to
report the current download status)
Create the c header file based on the above scheletron.
in the "bin" dir run "javah -jni com. ... .NativeLib" in my case
this will create the file com_ .. _NativeLib.h in yourbin dir
create a jni dir in the base project dir
move the new header file in the jni dir
Put the Swift sources in the jni dir
an interface has to be provided to the jni header file
the new interface can be implemented based on the content of the previous header
file. This will also change data structures from/to jni/c++.
Create android's Makefile, called !Android.mk, inside the jni dir
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE
:= swift
LOCAL_SRC_FILES := swift.cpp sha1.cpp compat.cpp sendrecv.cpp send_control.cpp has
LOCAL_CFLAGS
+= -D__NEW__
include $(BUILD_SHARED_LIBRARY)
Now we need to compile everything using the NDK. As previously mentioned we need to
first include all the needed libraries, such as the stdlib, in the NDK to be able to compile.
There are several ways to archive it, I'll not mention them here since it's a long process
and Google will help you :-).
Create a project directory (in my case I called it swift) in the apps dir of the NDK root
directory.
Create a Application.mk in the above directory
APP_PROJECT_PATH := $(call my-dir)/project
APP_MODULES
:= swift_demo
In the above directory create a symbolic link called "project" that points to the root dir of
Eclipse's project
Run ndk-build located in NDK's root directory from your project dir
This should compile everything and create the library that we'll be using in our
application
If you have some errors than run: make APP=<name of your module> (in my case
"swift") from your NDK's root dir
Use "-B V1" options for debugging
If the compilation process went fine you will find the new library inside the "lib" dir in your
Eclipse project
Now the hardest part is done and the integration with the app's interface is almost
complete
Instantiate the NativeLib in your UI java application and call the native methods.
create a layout, file main.xml
IMPORTANT: you need to give rights to the application for using the internet and for
writing on the SD
add the line:
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
in your manifest file (AndroidManifest.xml).
Miscellaneous info
Modifications to libwsift:
all the unneeded files can be removed (everything except .cpp and .h files)
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SwiftAndroid – P2P-Next
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https://trac.p2p-next.org/wiki/SwiftAndroid
swift.cpp has to be modified and changed to accept function calls from java
providing library calls (I just implemented the start(root_hash, tracker) function)
handling and converting JNI datastructures in C++
_S_IREAD and _S_IWRITE are apparently undefined. for the moment I set them to
0000400 (read) and 0000200 (write)
NDK's compiler is way more strict that g++. Some things have to change.. like casting to
const some variables
an Android.mk file has to be created. This will substitute the Makefile
Video Player:
the video player will reproduce only audio tracks on the emulator > 1.5. It still works
correctly on the real device. The problem occurs with h264 video files (and mp4, m4v
container).
See Video playback regression in 1.5 ( http://code.google.com/p/android/issues/detail?id=2570&
q=videoview&
colspec=ID%20Type%20Version%20Security%20Status%20Owner%20Summary).
Provided zip in Next-Share/TUD/AndroidApp contains:
Application.mk -> for the NDK
SwiftBeta
-> for Eclipse-like projects
The actual application is located in SwiftBeta/bin/SwiftBeta.apk
To modify the swarms just change the onClick functions at lines 62-86 of:
SwiftBeta/src/com/tudelft/swift/swift.java
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