From 0b06077c55413edafb1210d385f313d980008031 Mon Sep 17 00:00:00 2001
From: andri lim <jangko128@gmail.com>
Date: Tue, 8 Oct 2019 20:40:27 +0700
Subject: [PATCH] compile time toBytes

---
 stint/private/endians2_priv.nim | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/stint/private/endians2_priv.nim b/stint/private/endians2_priv.nim
index 8abf73f..cf3a53e 100644
--- a/stint/private/endians2_priv.nim
+++ b/stint/private/endians2_priv.nim
@@ -1,4 +1,4 @@
-import ./bitops2_priv, ./datatypes
+import ./bitops2_priv, ./datatypes, ./uint_bitwise_ops
 
 import stew/endians2
 export endians2
@@ -9,13 +9,29 @@ func swapBytes*(x: UintImpl): UintImpl {.inline.} =
 
   UintImpl(hi: hi, lo: lo)
 
+func copyMem(x: UintImpl): auto {.compileTime.} =
+  const size = bitsof(x) div 8
+  var ret: array[size, byte]
+
+  type DT = type x.leastSignificantWord
+  for i in 0 ..< size:
+    let pos = i * 8
+    ret[i] = byte((x shr pos).leastSignificantWord and 0xFF.DT)
+  ret
+
 func toBytes*(x: UintImpl, endian: Endianness = system.cpuEndian): auto {.inline.} =
   # TODO can't use bitsof in return type (compiler bug?), hence return auto
-  # TODO compile-time version
   var ret: array[bitsof(x) div 8, byte]
-  if endian == system.cpuEndian:
-    copyMem(addr ret[0], unsafeAddr x, ret.len)
+  when nimvm:
+    if endian == system.cpuEndian:
+      ret = copyMem(x)
+    else:
+      let v = swapBytes(x)
+      ret = copyMem(v)
   else:
-    let v = swapBytes(x)
-    copyMem(addr ret[0], unsafeAddr v, ret.len)
+    if endian == system.cpuEndian:
+      copyMem(addr ret[0], unsafeAddr x, ret.len)
+    else:
+      let v = swapBytes(x)
+      copyMem(addr ret[0], unsafeAddr v, ret.len)
   ret