From d06de33bc3fef366f2d70d80e91df6ae4b9b5d5f Mon Sep 17 00:00:00 2001
From: vub <Vitalik Buterin>
Date: Fri, 10 Mar 2017 09:48:05 -0500
Subject: [PATCH] Whoops, actually added the file this time

---
 casper4/remove_rlp_last.se | 58 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 casper4/remove_rlp_last.se

diff --git a/casper4/remove_rlp_last.se b/casper4/remove_rlp_last.se
new file mode 100644
index 0000000..8ff70e3
--- /dev/null
+++ b/casper4/remove_rlp_last.se
@@ -0,0 +1,58 @@
+macro calldatachar($x):
+    div(calldataload($x), 2**248)
+
+macro calldatabytes_as_int($x, $b):
+    div(calldataload($x), 256**(32-$b))
+
+
+c0 = calldatachar(0)
+if c0 < 192:
+    ~invalid()
+elif c0 < 248:
+    pos = 1
+    L = c0 - 192
+else:
+    pos = 1 + (c0 - 247)
+    if calldatachar(1) == 0:
+        ~invalid()
+    L = calldatabytes_as_int(1, c0 - 247)
+if pos + L != ~calldatasize():
+    ~invalid()
+startpos = pos
+
+lastpos = 0
+while pos < ~calldatasize():
+    c = calldatachar(pos)
+    if c < 128:
+        lastpos = pos
+        pos += 1
+    elif c < 184:
+        L = c - 128
+        lastpos = pos
+        pos += L + 1
+    elif c < 192:
+        if calldatachar(pos + 1) == 0:
+            ~invalid()
+        L = calldatabytes_as_int(pos + 1, c - 183)
+        lastpos = pos
+        pos += L + (c - 183) + 1
+    else:
+        ~invalid()
+
+
+newlen = lastpos - startpos
+newmemindex = 1000
+if newlen < 56:
+    ~mstore8(newmemindex, 192 + newlen)
+    ~calldatacopy(newmemindex + 1, startpos, newlen)
+    ~return(newmemindex, 1 + newlen)
+else:
+    _log = 0
+    _newlen = newlen
+    while _newlen:
+        _log += 1
+        _newlen = ~div(_newlen, 256)
+    ~mstore8(newmemindex, 247 + _log)
+    ~mstore(newmemindex + 1, newlen * (256 ** (32 - _log)))
+    ~calldatacopy(newmemindex + 1 + _log, startpos, newlen)
+    ~return(newmemindex, 1 + _log + newlen)