Blockhash correction and some tests

libevm/ExtVMFace.h

@@ -148,7 +148,7 @@ public:
 	virtual void revert() {}
 
 	/// Hash of a block if within the last 256 blocks, or h256() otherwise.
-	h256 prevhash(u256 _number) { return _number < currentBlock.number && _number > (std::max<u256>(257, currentBlock.number) - 257) ? lastHashes[(unsigned)(currentBlock.number - 1 - _number)] : h256(); }	// TODO: CHECK!!!
+	h256 blockhash(u256 _number) { return _number < currentBlock.number && _number >= (std::max<u256>(256, currentBlock.number) - 256) ? lastHashes[(unsigned)(currentBlock.number - 1 - _number)] : h256(); }	// TODO: CHECK!!!
 
 	/// Get the code at the given location in code ROM.
 	byte getCode(u256 _n) const { return _n < code.size() ? code[(size_t)_n] : 0; }

libevm/VM.h

@@ -559,7 +559,7 @@ inline bytesConstRef VM::go(ExtVMFace& _ext, OnOpFunc const& _onOp, uint64_t _st
 			m_stack.push_back(_ext.gasPrice);
 			break;
 		case Instruction::BLOCKHASH:
-			m_stack.back() = (u256)_ext.prevhash(m_stack.back());
+			m_stack.back() = (u256)_ext.blockhash(m_stack.back());
 			break;
 		case Instruction::COINBASE:
 			m_stack.push_back((u160)_ext.currentBlock.coinbaseAddress);

test/vmBlockInfoTestFiller.json

@@ -1,8 +1,92 @@
 {
-    "prevhash": {
+    "blockhashNotExistingBlock": {
         "env" : {
         "previousHash" : "5e20a0453cecd065ea59c37ac63e079ee08998b6045136a8ce6635c7912ec0b6",
-        "currentNumber" : "0",
+        "currentNumber" : "1",
+        "currentGasLimit" : "1000000",
+        "currentDifficulty" : "256",
+        "currentTimestamp" : 1,
+        "currentCoinbase" : "2adc25665018aa1fe0e6bc666dac8fc2697ff9ba"
+        },
+        "pre" : {
+        "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+            "balance" : "1000000000000000000",
+            "nonce" : 0,
+            "code" : "{ [[ 0 ]] (BLOCKHASH 2) }",
+            "storage": {}
+        }
+        },
+        "exec" : {
+            "address" : "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6",
+            "origin" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "caller" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "value" : "1000000000000000000",
+            "data" : "",
+            "gasPrice" : "100000000000000",
+            "gas" : "10000"
+        }
+    },
+
+    "blockhashMyBlock": {
+        "env" : {
+        "previousHash" : "5e20a0453cecd065ea59c37ac63e079ee08998b6045136a8ce6635c7912ec0b6",
+        "currentNumber" : "1",
+        "currentGasLimit" : "1000000",
+        "currentDifficulty" : "256",
+        "currentTimestamp" : 1,
+        "currentCoinbase" : "2adc25665018aa1fe0e6bc666dac8fc2697ff9ba"
+        },
+        "pre" : {
+        "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+            "balance" : "1000000000000000000",
+            "nonce" : 0,
+            "code" : "{ [[ 0 ]] (BLOCKHASH 1) }",
+            "storage": {}
+        }
+        },
+        "exec" : {
+            "address" : "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6",
+            "origin" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "caller" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "value" : "1000000000000000000",
+            "data" : "",
+            "gasPrice" : "100000000000000",
+            "gas" : "10000"
+        }
+    },
+
+    "blockhash258Block": {
+        "env" : {
+        "previousHash" : "5e20a0453cecd065ea59c37ac63e079ee08998b6045136a8ce6635c7912ec0b6",
+        "currentNumber" : "258",
+        "currentGasLimit" : "1000000",
+        "currentDifficulty" : "256",
+        "currentTimestamp" : 1,
+        "currentCoinbase" : "2adc25665018aa1fe0e6bc666dac8fc2697ff9ba"
+        },
+        "pre" : {
+        "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+            "balance" : "1000000000000000000",
+            "nonce" : 0,
+            "code" : "{ [[ 0 ]] (BLOCKHASH 1) }",
+            "storage": {}
+        }
+        },
+        "exec" : {
+            "address" : "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6",
+            "origin" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "caller" : "cd1722f3947def4cf144679da39c4c32bdc35681",
+            "value" : "1000000000000000000",
+            "data" : "",
+            "gasPrice" : "100000000000000",
+            "gas" : "10000"
+        }
+    },
+
+    "blockhash257Block": {
+        "env" : {
+        "previousHash" : "5e20a0453cecd065ea59c37ac63e079ee08998b6045136a8ce6635c7912ec0b6",
+        "currentNumber" : "257",
         "currentGasLimit" : "1000000",
         "currentDifficulty" : "256",
         "currentTimestamp" : 1,
@@ -12,7 +96,7 @@
         "0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
             "balance" : "1000000000000000000",
             "nonce" : 0,
-            "code" : "{ [[ 0 ]] (PREVHASH) }",
+            "code" : "{ [[ 0 ]] (BLOCKHASH 0) }",
             "storage": {}
         }
         },