[Java] Add Java bindings for memtables and sst format.

Summary:
Add Java bindings for memtables and sst format.  Specifically,
add two abstract Java classses --- MemTableConfig and SstFormatConfig.
Each MemTable / SST implementation should has its own config class
extends MemTableConfig / SstFormatConfig respectively and pass it
to Options via setMemTableConfig / setSstConfig.

Test Plan:
make rocksdbjava
make jdb_test
make jdb_bench
java/jdb_bench.sh \
  --benchmarks=fillseq,readrandom,readwhilewriting \
  --memtablerep=hash_skiplist \
  --use_plain_table=1 \
  --key_size=20 \
  --prefix_size=12 \
  --value_size=100 \
  --cache_size=17179869184 \
  --disable_wal=0 \
  --sync=0 \

Reviewers: haobo, ankgup87, sdong

Reviewed By: haobo

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D17997

java/rocksjni/options.cc

@@ -17,6 +17,9 @@
 #include "rocksdb/db.h"
 #include "rocksdb/options.h"
 #include "rocksdb/statistics.h"
+#include "rocksdb/memtablerep.h"
+#include "rocksdb/table.h"
+#include "rocksdb/slice_transform.h"
 
 /*
  * Class:     org_rocksdb_Options
@@ -479,6 +482,27 @@ jlong Java_org_rocksdb_Options_maxManifestFileSize(
   return reinterpret_cast<rocksdb::Options*>(jhandle)->max_manifest_file_size;
 }
 
+/*
+ * Method:    memTableFactoryName
+ * Signature: (J)Ljava/lang/String
+ */
+jstring Java_org_rocksdb_Options_memTableFactoryName(
+    JNIEnv* env, jobject jobj, jlong jhandle) {
+  auto opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  rocksdb::MemTableRepFactory* tf = opt->memtable_factory.get();
+
+  // Should never be nullptr.
+  // Default memtable factory is SkipListFactory
+  assert(tf);
+
+  // temporarly fix for the historical typo
+  if (strcmp(tf->Name(), "HashLinkListRepFactory") == 0) {
+    return env->NewStringUTF("HashLinkedListRepFactory");
+  }
+
+  return env->NewStringUTF(tf->Name());
+}
+
 /*
  * Class:     org_rocksdb_Options
  * Method:    setMaxManifestFileSize
@@ -490,6 +514,16 @@ void Java_org_rocksdb_Options_setMaxManifestFileSize(
       static_cast<int64_t>(max_manifest_file_size);
 }
 
+/*
+ * Method:    setMemTableFactory
+ * Signature: (JJ)V
+ */
+void Java_org_rocksdb_Options_setMemTableFactory(
+    JNIEnv* env, jobject jobj, jlong jhandle, jlong jfactory_handle) {
+  reinterpret_cast<rocksdb::Options*>(jhandle)->memtable_factory.reset(
+      reinterpret_cast<rocksdb::MemTableRepFactory*>(jfactory_handle));
+}
+
 /*
  * Class:     org_rocksdb_Options
  * Method:    tableCacheNumshardbits
@@ -533,6 +567,16 @@ void Java_org_rocksdb_Options_setTableCacheRemoveScanCountLimit(
       jhandle)->table_cache_remove_scan_count_limit = static_cast<int>(limit);
 }
 
+/*
+ * Method:    useFixedLengthPrefixExtractor
+ * Signature: (JI)V
+ */
+void Java_org_rocksdb_Options_useFixedLengthPrefixExtractor(
+    JNIEnv* env, jobject jobj, jlong jhandle, jint jprefix_length) {
+  reinterpret_cast<rocksdb::Options*>(jhandle)->prefix_extractor.reset(
+      rocksdb::NewFixedPrefixTransform(static_cast<size_t>(jprefix_length)));
+}
+
 /*
  * Class:     org_rocksdb_Options
  * Method:    walTtlSeconds
@@ -597,6 +641,16 @@ void Java_org_rocksdb_Options_setAllowOsBuffer(
       static_cast<bool>(allow_os_buffer);
 }
 
+/*
+ * Method:    setTableFactory
+ * Signature: (JJ)V
+ */
+void Java_org_rocksdb_Options_setTableFactory(
+    JNIEnv* env, jobject jobj, jlong jhandle, jlong jfactory_handle) {
+  reinterpret_cast<rocksdb::Options*>(jhandle)->table_factory.reset(
+      reinterpret_cast<rocksdb::TableFactory*>(jfactory_handle));
+}
+
 /*
  * Class:     org_rocksdb_Options
  * Method:    allowMmapReads
@@ -787,6 +841,22 @@ void Java_org_rocksdb_Options_setAllowThreadLocal(
       static_cast<bool>(allow_thread_local);
 }
 
+/*
+ * Method:    tableFactoryName
+ * Signature: (J)Ljava/lang/String
+ */
+jstring Java_org_rocksdb_Options_tableFactoryName(
+    JNIEnv* env, jobject jobj, jlong jhandle) {
+  auto opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  rocksdb::TableFactory* tf = opt->table_factory.get();
+
+  // Should never be nullptr.
+  // Default memtable factory is SkipListFactory
+  assert(tf);
+
+  return env->NewStringUTF(tf->Name());
+}
+
 //////////////////////////////////////////////////////////////////////////////
 // WriteOptions