Add support for shared object name mapping in SoLoader

Summary:
The class MergedSoMapping is responsible for mapping library names and
invoking the proper JNI_OnLoad.  The default implementation simply reports
that no libraries are merged, so there is no change in behavior.

Differential Revision: D3845378

fbshipit-source-id: 9f31b3419255568361a8dcbcb31b36e34d3a7177

java/com/facebook/soloader/BUCK

@@ -2,7 +2,7 @@ include_defs("//oss_defs/SOLOADER_DEFS")
 
 android_library(
   name = 'soloader',
-  srcs = glob(['*.java']),
+  srcs = glob(['*.java'], excludes = ['MergedSoMapping.java']),
   tests = [
     '//javatests/com/facebook/soloader:soloader',
   ],
@@ -12,12 +12,18 @@ android_library(
     # has to run very early in the app startup process.
     # Definitely do *not* depend on guava.
     '//deps:jsr-305',
+    ':mapping-stub',
   ],
   visibility = [
     'PUBLIC',
   ],
 )
 
+java_library(
+  name = 'mapping-stub',
+  srcs = ['MergedSoMapping.java'],
+)
+
 project_config(
   src_target = ':soloader',
 )

java/com/facebook/soloader/MergedSoMapping.java

@@ -0,0 +1,14 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.soloader;
+
+class MergedSoMapping {
+  static String mapLibName(String preMergedLibName) {
+    return null;
+  }
+
+  static void invokeJniOnload(String preMergedLibName) {
+    throw new IllegalArgumentException(
+        "Unknown library: " + preMergedLibName);
+  }
+}

java/com/facebook/soloader/SoLoader.java

@@ -291,8 +291,11 @@ public static synchronized void loadLibrary(String shortName, int loadFlags)
       }
     }
 
+    String mergedLibName = MergedSoMapping.mapLibName(shortName);
+    String nameToLoad = mergedLibName != null ? mergedLibName : shortName;
+
     try {
-      loadLibraryBySoName(System.mapLibraryName(shortName), loadFlags);
+      loadLibraryBySoName(System.mapLibraryName(nameToLoad), loadFlags);
     } catch (IOException ex) {
       throw new RuntimeException(ex);
     } catch (UnsatisfiedLinkError ex) {
@@ -302,6 +305,10 @@ public static synchronized void loadLibrary(String shortName, int loadFlags)
       }
       throw ex;
     }
+
+    if (mergedLibName != null) {
+      MergedSoMapping.invokeJniOnload(shortName);
+    }
   }
 
   /**