From a323486a9bf40d60eb1a7914aaf38bb412c74ea0 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Wed, 26 Jul 2017 15:01:17 +0100
Subject: Add pure assembly example for summing

---
 docs/assembly.rst | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/docs/assembly.rst b/docs/assembly.rst
index 2f5b8812..5288089f 100644
--- a/docs/assembly.rst
+++ b/docs/assembly.rst
@@ -96,6 +96,29 @@ you really know what you are doing.
                 }
             }
         }
+
+        // Same as above, but accomplish the entire code within inline assembly.
+        function sumPureAsm(uint[] _data) returns (uint o_sum) {
+            assembly {
+               // Load the length (first 32 bytes)
+               let len := mload(_data)
+
+               // Skip over the length field.
+               _data := add(_data, 0x20)
+
+               // Set up a bound.
+               let end := add(_data, len)
+
+               // Iterate until the bound is not met.
+               for {} lt(_data, end) {} {
+                   o_sum := add(o_sum, mload(_data))
+                   _data := add(_data, 0x20)
+               }
+
+               // NOTE: after this point it is not safe to use _data in Solidity code
+               //       because its offsets are in an invalid position
+            }
+        }
     }
 
 
-- 
cgit v1.2.3


From 34503d98d7d95fc3a55a60be854809524c1f204e Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 27 Jul 2017 15:08:32 +0100
Subject: Move init/cond into the for loop

---
 docs/assembly.rst | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/assembly.rst b/docs/assembly.rst
index 5288089f..377a6530 100644
--- a/docs/assembly.rst
+++ b/docs/assembly.rst
@@ -106,13 +106,13 @@ you really know what you are doing.
                // Skip over the length field.
                _data := add(_data, 0x20)
 
-               // Set up a bound.
-               let end := add(_data, len)
-
                // Iterate until the bound is not met.
-               for {} lt(_data, end) {} {
+               for
+                   { let end := add(_data, len) }
+                   lt(_data, end)
+                   { _data := add(_data, 0x20) }
+               {
                    o_sum := add(o_sum, mload(_data))
-                   _data := add(_data, 0x20)
                }
 
                // NOTE: after this point it is not safe to use _data in Solidity code
-- 
cgit v1.2.3


From 9358001ba4074d94d9daa566d225e1f8b2305009 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 10 Aug 2017 17:47:35 +0100
Subject: Use temporary variable for sum example

---
 docs/assembly.rst | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/docs/assembly.rst b/docs/assembly.rst
index 377a6530..bdb708a9 100644
--- a/docs/assembly.rst
+++ b/docs/assembly.rst
@@ -104,19 +104,21 @@ you really know what you are doing.
                let len := mload(_data)
 
                // Skip over the length field.
-               _data := add(_data, 0x20)
+               //
+               // Keep temporary variable so it can be incremented in place.
+               //
+               // NOTE: incrementing _data would result in an unusable
+               //       _data variable after this assembly block
+               let data := add(_data, 0x20)
 
                // Iterate until the bound is not met.
                for
-                   { let end := add(_data, len) }
-                   lt(_data, end)
-                   { _data := add(_data, 0x20) }
+                   { let end := add(data, len) }
+                   lt(data, end)
+                   { data := add(data, 0x20) }
                {
-                   o_sum := add(o_sum, mload(_data))
+                   o_sum := add(o_sum, mload(data))
                }
-
-               // NOTE: after this point it is not safe to use _data in Solidity code
-               //       because its offsets are in an invalid position
             }
         }
     }
-- 
cgit v1.2.3