Add support for app bundle (#26)

Summary:
PR is related to #19

**Problem**
SoLoader cannot load `.so`libraries when an application is installed through [App Bundle](https://developer.android.com/platform/technology/app-bundle/) with config:
```
bundle {
    abi {
        enableSplit = true
    }
}
```

The reason is that app bundle installation consists of multiple apks. For instance:
- `base.apk`
- `split_config.arm64_v8a.apk`
- `split_config.xxxhdpi.apk`

`SoLoader` class creates `ApkSoSource` pointing only to  `base.apk`. But `*.so` files exist only in `split_config.arm64_v8a.apk`

**Solution**
Create separate `ApkSoSource` for each apk in the application folder. I couldn't figure out how to filter out apk without lib folder.

**Testing**
I haven't tried this with dynamic feature modules yet. So I can't say that it fully fixes #19. But at least it fixes facebook/fresco#2253
Any help with dynamic modules testing would be much appreciated.

**P.S.**
Due to some reasons, I can't wait for the new release of SoLoader lib, so I have published a temporary patched version to bintray in [my account](https://bintray.com/nnesterov/maven/patched-soloader)
with different grouipId `com.avito.android:patched-soloader:0.1.0`
If you are against publishing your lib in a different account, please let me know. I'll remove my version immediately.
Pull Request resolved: #26

Reviewed By: oprisnik

Differential Revision: D13669370

Pulled By: passy

fbshipit-source-id: dd605bf54662a38cb1fd04461e1e962f76da7d51

java/com/facebook/soloader/ApkSoSource.java

@@ -21,10 +21,7 @@
 import android.util.Log;
 import java.io.File;
 import java.io.IOException;
-import java.util.HashMap;
-import java.util.Map;
 import java.util.zip.ZipEntry;
-import javax.annotation.Nullable;
 
 /**
  * {@link SoSource} that extracts libraries from an APK to the filesystem.
@@ -47,10 +44,14 @@ public class ApkSoSource extends ExtractFromZipSoSource {
   private final int mFlags;
 
   public ApkSoSource(Context context, String name, int flags) {
+    this(context, new File(context.getApplicationInfo().sourceDir), name, flags);
+  }
+
+  public ApkSoSource(Context context, File apkPath, String name, int flags) {
     super(
         context,
         name,
-        new File(context.getApplicationInfo().sourceDir),
+        apkPath,
         // The regular expression matches libraries that would ordinarily be unpacked
         // during installation.
         "^lib/([^/]+)/([^/]+\\.so)$");

java/com/facebook/soloader/SoLoader.java

@@ -91,10 +91,10 @@ public class SoLoader {
 
   private static int sSoSourcesVersion = 0;
 
-  /** A backup SoSource to try if a lib file is corrupted */
+  /** A backup SoSources to try if a lib file is corrupted */
   @GuardedBy("sSoSourcesLock")
   @Nullable
-  private static UnpackingSoSource sBackupSoSource;
+  private static UnpackingSoSource[] sBackupSoSources;
 
   /**
    * A SoSource for the Context.ApplicationInfo.nativeLibsDir that can be updated if the application
@@ -121,9 +121,14 @@ public class SoLoader {
   /** Wrapper for System.loadLlibrary. */
   @Nullable private static SystemLoadLibraryWrapper sSystemLoadLibraryWrapper = null;
 
-  /** Name of the directory we use for extracted DSOs from built-in SO sources (APK, exopackage) */
+  /**
+   * Name of the directory we use for extracted DSOs from built-in SO sources (main APK, exopackage)
+   */
   private static final String SO_STORE_NAME_MAIN = "lib-main";
 
+  /** Name of the directory we use for extracted DSOs from split APKs */
+  private static final String SO_STORE_NAME_SPLITTED = "lib-";
+
   /** Enable the exopackage SoSource. */
   public static final int SOLOADER_ENABLE_EXOPACKAGE = (1 << 0);
 
@@ -230,7 +235,7 @@ private static void initSoSources(Context context, int flags, @Nullable SoFileLo
           //
 
           if ((flags & SOLOADER_ENABLE_EXOPACKAGE) != 0) {
-            sBackupSoSource = null;
+            sBackupSoSources = null;
             Log.d(TAG, "adding exo package source: " + SO_STORE_NAME_MAIN);
             soSources.add(0, new ExoSoSource(context, SO_STORE_NAME_MAIN));
           } else {
@@ -260,11 +265,34 @@ private static void initSoSources(Context context, int flags, @Nullable SoFileLo
             }
 
             if ((sFlags & SOLOADER_DISABLE_BACKUP_SOSOURCE) != 0) {
-              sBackupSoSource = null;
+              sBackupSoSources = null;
             } else {
-              sBackupSoSource = new ApkSoSource(context, SO_STORE_NAME_MAIN, apkSoSourceFlags);
-              Log.d(TAG, "adding backup  source: " + sBackupSoSource.toString());
-              soSources.add(0, sBackupSoSource);
+
+              final File mainApkDir = new File(context.getApplicationInfo().sourceDir);
+              ArrayList<UnpackingSoSource> backupSources = new ArrayList<>();
+              ApkSoSource mainApkSource =
+                  new ApkSoSource(context, mainApkDir, SO_STORE_NAME_MAIN, apkSoSourceFlags);
+              backupSources.add(mainApkSource);
+              Log.d(TAG, "adding backup source from : " + mainApkSource.toString());
+
+              if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
+                  && context.getApplicationInfo().splitSourceDirs != null) {
+                Log.d(TAG, "adding backup sources from split apks");
+                int splitIndex = 0;
+                for (String splitApkDir : context.getApplicationInfo().splitSourceDirs) {
+                  ApkSoSource splittedApkSource =
+                      new ApkSoSource(
+                          context,
+                          new File(splitApkDir),
+                          SO_STORE_NAME_SPLITTED + (splitIndex++),
+                          apkSoSourceFlags);
+                  Log.d(TAG, "adding backup source: " + splittedApkSource.toString());
+                  backupSources.add(splittedApkSource);
+                }
+              }
+
+              sBackupSoSources = backupSources.toArray(new UnpackingSoSource[backupSources.size()]);
+              soSources.addAll(0, backupSources);
             }
           }
         }
@@ -651,11 +679,17 @@ private static void doLoadLibraryBySoName(
           for (int i = 0; result == SoSource.LOAD_RESULT_NOT_FOUND && i < sSoSources.length; ++i) {
             SoSource currentSource = sSoSources[i];
             result = currentSource.loadLibrary(soName, loadFlags, oldPolicy);
-            if (result == SoSource.LOAD_RESULT_CORRUPTED_LIB_FILE && sBackupSoSource != null) {
+            if (result == SoSource.LOAD_RESULT_CORRUPTED_LIB_FILE && sBackupSoSources != null) {
               // Let's try from the backup source
               Log.d(TAG, "Trying backup SoSource for " + soName);
-              sBackupSoSource.prepare(soName);
-              result = sBackupSoSource.loadLibrary(soName, loadFlags, oldPolicy);
+              for (UnpackingSoSource backupSoSource : sBackupSoSources) {
+                backupSoSource.prepare(soName);
+                int resultFromBackup = backupSoSource.loadLibrary(soName, loadFlags, oldPolicy);
+                if (resultFromBackup == SoSource.LOAD_RESULT_LOADED) {
+                  result = resultFromBackup;
+                  break;
+                }
+              }
               break;
             }
           }