From c90ee1365668f180d98d8b83c91d3094e953276f Mon Sep 17 00:00:00 2001
From: Ilya Gorbunov <ilya.gorbunov@jetbrains.com>
Date: Mon, 21 Nov 2016 21:21:47 +0300
Subject: [PATCH] Performance: use byte array buffer directly to read the
 entire contents of a file.  #KT-14883 Fixed

---
 libraries/stdlib/src/kotlin/io/FileReadWrite.kt | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/libraries/stdlib/src/kotlin/io/FileReadWrite.kt b/libraries/stdlib/src/kotlin/io/FileReadWrite.kt
index e00acd97a23..5a0011ad0fd 100644
--- a/libraries/stdlib/src/kotlin/io/FileReadWrite.kt
+++ b/libraries/stdlib/src/kotlin/io/FileReadWrite.kt
@@ -49,7 +49,18 @@ public inline fun File.printWriter(charset: Charset = Charsets.UTF_8): PrintWrit
  *
  * @return the entire content of this file as a byte array.
  */
-public fun File.readBytes(): ByteArray = FileInputStream(this).use { it.readBytes(length().toInt()) }
+public fun File.readBytes(): ByteArray = FileInputStream(this).use { input ->
+    var offset = 0
+    var remaining = this.length().toInt() // TODO: toIntExact()
+    val result = ByteArray(remaining)
+    while (remaining > 0) {
+        val read = input.read(result, offset, remaining)
+        if (read < 0) break
+        remaining -= read
+        offset += read
+    }
+    if (remaining == 0) result else result.copyOf(offset)
+}
 
 /**
  * Sets the content of this file as an [array] of bytes.