Added tutorial 19

Author: willitscale

README.md

@@ -21,6 +21,7 @@ The companion to the Youtube tutorials
 - [Learning Solidity : Tutorial 16 Time Based Events](https://www.youtube.com/watch?v=HGw-yalqdgs)
 - [Learning Solidity : Tutorial 17 Polymorphism](https://www.youtube.com/watch?v=l_E5F5qnbtk)
 - [Learning Solidity : Tutorial 18 Randomness and Gambling](https://www.youtube.com/watch?v=3wY5PRliphE)
+- [Learning Solidity : Tutorial 19 Nested Arrays and Storage](https://www.youtube.com/watch?v=zkNHRJEuYQg)
 
 ### Support
 

tutorial-19/NestedArrays.sol

@@ -0,0 +1,65 @@
+pragma solidity ^0.4.0;
+
+contract NestedArrays {
+
+    uint[][] private nested;
+
+    function getArray() public {
+        nested.push([1,2,3]);
+    }
+
+    // [1, 3, 2, 4]
+    function toBytes(uint[] _array)
+        public
+        returns (bytes _ptr) {
+        assembly {
+            let len := mload(_array)
+            _ptr := msize()
+            
+            // Bytes
+            mstore(_ptr, mul(add(len, 2), 0x20))
+            
+            // Array 
+            mstore(add(_ptr, 0x20), 0x20)
+            mstore(add(_ptr, 0x40), len)
+            
+            let idx := 0
+            loop:
+            jumpi(end, eq(len, idx))
+            mstore(add(_ptr, add(mul(idx,0x20),0x60)), mload(add(_array, add(0x20, mul(idx, 0x20)))))
+            idx := add(idx, 1)
+            jump(loop)
+            
+            end:
+            // Without return statements memory is overridden
+            mstore(0x40, add(mul(len, 0x20), 0x20))
+        }
+    }
+    
+    // ["0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x20","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x04","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x01","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x03","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x02","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x00","0x04"]
+    function toArray(bytes _bytes)
+        public
+        returns (uint[] _ptr) {
+        assembly {
+            
+            // First 32 bytes are byte array properties
+            // Next 32 bytes are the data size of the array elements
+            let len := mload(add(_bytes, 0x40))
+            _ptr := msize()
+            
+            // Array
+            mstore(_ptr, len)
+            
+            let idx := 0
+            loop:
+            jumpi(end, eq(len, idx))
+            mstore(add(_ptr, add(mul(idx,0x20),0x20)), mload(add(_bytes, add(0x60, mul(idx, 0x20)))))
+            idx := add(idx, 1)
+            jump(loop)
+            
+            end:
+            mstore(0x40, add(_ptr,add(mul(len, 0x20), 0x40)))
+        }
+    }
+  
+}