Android NDK: read file from assets inside of shared library

Question

In my app I have to pass a file from assets folder to shared library. I cannot do it with use of jni right now. I'm using precompiled shared library in my project, in which I have hardcoded path to my file, but I'm getting error "No such file or directory". So in my .apk file I have .so file in libs/armeabi-v7a folder and my file in /assets folder.

I have tried to do it like this:

char *cert_file = "/assets/cacert.cert";
av_strdup(cert_file);

And some other paths, but it doesn't work.

Is it possible at all?

Answer 1

Your assets are packaged into your apk, so you can't refer to them directly during runtime like in the sample code you provided. You have 2 options here:

• Process the assets as an input stream, using

Context.getAssets().open('cacert.cert')

• Copy out your asset to a local file in your files dir, and then reference the filename of the copied file.

Answer 2

Building off of the answer by @Sistr , I used getBuffer along with AASSET_MODE_BUFFER (instead of AAsset_read).

However, I was trying to write the buffer to an ofstream. I got signal crashes using the <<operator:

ofstream myStream(<some file>, ios_base::binary);
auto buffer = AAsset_getBuffer(asset);
myStream << buffer;

I presume this is because the buffer pointer points to the asset without a NULL character at the end (I was reading a text asset; Android source code). Using the write function worked:

ofstream myStream(<some file>, ios_base::binary);
auto buffer = AAsset_getBuffer(asset);
myStream.write((char *)buffer, AAsset_getLength(asset));

This is because the <<operator does not have to call strlen to find out how many characters to write since it is explicitly given by AAsset_getLength.