Add ability to store and retrieve a list of MapBuffer

Summary:
Add ability to store and retrieve a list of MapBuffer as an entry of MapBuffer.

```
Example:

MapBuffer1
{
 key1: "test string",
 key2: MapBuffer2,
 key3: [MapBuffer3, MapBuffer4]
}
```

Changelog:
[General][Added] Add ability to store and retrieve a list of MapBuffer

Reviewed By: JoshuaGross

Differential Revision: D38460204

fbshipit-source-id: 3e721418be2dca6d5f15f665753844d6f531e31c

ReactAndroid/src/main/java/com/facebook/react/common/mapbuffer/MapBuffer.kt

@@ -126,6 +126,16 @@ interface MapBuffer : Iterable<MapBuffer.Entry> {
    */
   fun getMapBuffer(key: Int): MapBuffer
 
+  /**
+   * Provides parsed [List<MapBuffer>] value if the entry for given key exists with [DataType.MAP]
+   * type
+   * @param key key to lookup [List<MapBuffer>] value for
+   * @return value associated with the requested key
+   * @throws IllegalArgumentException if the key doesn't exist
+   * @throws IllegalStateException if the data type doesn't match
+   */
+  fun getMapBufferList(key: Int): List<MapBuffer>
+
   /** Iterable entry representing parsed MapBuffer values */
   interface Entry {
     /**

ReactAndroid/src/main/java/com/facebook/react/common/mapbuffer/ReadableMapBuffer.kt

@@ -137,6 +137,24 @@ class ReadableMapBuffer : MapBuffer {
     return ReadableMapBuffer(ByteBuffer.wrap(newBuffer))
   }
 
+  private fun readMapBufferListValue(position: Int): List<ReadableMapBuffer> {
+    val readMapBufferList = arrayListOf<ReadableMapBuffer>()
+    var offset = offsetForDynamicData + buffer.getInt(position)
+    val sizeMapBufferList = buffer.getInt(offset)
+    offset += Int.SIZE_BYTES
+    var curLen = 0
+    while (curLen < sizeMapBufferList) {
+      val sizeMapBuffer = buffer.getInt(offset + curLen)
+      val newMapBuffer = ByteArray(sizeMapBuffer)
+      curLen = curLen + Int.SIZE_BYTES
+      buffer.position(offset + curLen)
+      buffer[newMapBuffer, 0, sizeMapBuffer]
+      readMapBufferList.add(ReadableMapBuffer(ByteBuffer.wrap(newMapBuffer)))
+      curLen = curLen + sizeMapBuffer
+    }
+    return readMapBufferList
+  }
+
   private fun getKeyOffsetForBucketIndex(bucketIndex: Int): Int {
     return HEADER_SIZE + BUCKET_SIZE * bucketIndex
   }
@@ -172,6 +190,9 @@ class ReadableMapBuffer : MapBuffer {
   override fun getMapBuffer(key: Int): ReadableMapBuffer =
       readMapBufferValue(getTypedValueOffsetForKey(key, MapBuffer.DataType.MAP))
 
+  override fun getMapBufferList(key: Int): List<ReadableMapBuffer> =
+      readMapBufferListValue(getTypedValueOffsetForKey(key, MapBuffer.DataType.MAP))
+
   override fun hashCode(): Int {
     buffer.rewind()
     return buffer.hashCode()

ReactAndroid/src/main/java/com/facebook/react/common/mapbuffer/WritableMapBuffer.kt

@@ -106,6 +106,8 @@ class WritableMapBuffer : MapBuffer {
 
   override fun getMapBuffer(key: Int): MapBuffer = verifyValue(key, values.get(key))
 
+  override fun getMapBufferList(key: Int): List<MapBuffer> = verifyValue(key, values.get(key))
+
   /** Generalizes verification of the value types based on the requested type. */
   private inline fun <reified T> verifyValue(key: Int, value: Any?): T {
     require(value != null) { "Key not found: $key" }