[R] Construct booster object in load.raw. (#7686)

R-package/R/xgb.load.raw.R

@@ -3,12 +3,21 @@
 #' User can generate raw memory buffer by calling xgb.save.raw
 #'
 #' @param buffer the buffer returned by xgb.save.raw
+#' @param as_booster Return the loaded model as xgb.Booster instead of xgb.Booster.handle.
 #'
 #' @export
-xgb.load.raw <- function(buffer) {
+xgb.load.raw <- function(buffer, as_booster = FALSE) {
   cachelist <- list()
   handle <- .Call(XGBoosterCreate_R, cachelist)
   .Call(XGBoosterLoadModelFromRaw_R, handle, buffer)
   class(handle) <- "xgb.Booster.handle"
-  return (handle)
+
+  if (as_booster) {
+    booster <- list(handle = handle, raw = NULL)
+    class(booster) <- "xgb.Booster"
+    booster <- xgb.Booster.complete(booster, saveraw = TRUE)
+    return(booster)
+  } else {
+    return (handle)
+  }
 }