in cassovary-core/src/main/scala/com/twitter/cassovary/util/io/ListOfEdgesGraphReader.scala [133:147]
def readEdgesBySource(): Int2ObjectOpenHashMap[ReusableArrayBuffer] = {
val edgesBySource = new Int2ObjectOpenHashMap[ReusableArrayBuffer]()
val nodeIds = twoNodeIdsIterator()
nodeIds foreach { case (internalFromId, internalToId) =>
if (edgesBySource.containsKey(internalFromId)) {
edgesBySource.get(internalFromId) += internalToId
} else {
val buf = new ReusableArrayBuffer(4)
buf += internalFromId
buf += internalToId
edgesBySource.put(internalFromId, buf)
}
}
edgesBySource
}