From d128fe45d7bccfdb675e50afe2e0bfaac7310f26 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <chfast@gmail.com>
Date: Thu, 6 Sep 2018 18:21:05 +0200
Subject: [PATCH] Introduce EVMC_STORAGE_NON_EXISTING_ACCOUNT for set_storage()
 Host method

---
 bindings/go/evmc/host.go  |  8 ++++++--
 examples/example_host.cpp | 30 +++++++++++++++++++++++++-----
 include/evmc/evmc.h       | 14 +++++++++-----
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/bindings/go/evmc/host.go b/bindings/go/evmc/host.go
index 0a97aa8..7a3dea0 100644
--- a/bindings/go/evmc/host.go
+++ b/bindings/go/evmc/host.go
@@ -72,7 +72,7 @@ func goByteSlice(data *C.uint8_t, size C.size_t) []byte {
 type HostContext interface {
 	AccountExists(addr common.Address) bool
 	GetStorage(addr common.Address, key common.Hash) common.Hash
-	SetStorage(addr common.Address, key common.Hash, value common.Hash) StorageStatus
+	SetStorage(addr common.Address, key common.Hash, value common.Hash) (StorageStatus, error)
 	GetBalance(addr common.Address) (common.Hash, error)
 	GetCodeSize(addr common.Address) (int, error)
 	GetCodeHash(addr common.Address) (common.Hash, error)
@@ -106,7 +106,11 @@ func getStorage(pResult *C.struct_evmc_uint256be, pCtx unsafe.Pointer, pAddr *C.
 func setStorage(pCtx unsafe.Pointer, pAddr *C.struct_evmc_address, pKey *C.struct_evmc_uint256be, pVal *C.struct_evmc_uint256be) C.enum_evmc_storage_status {
 	idx := int((*C.struct_extended_context)(pCtx).index)
 	ctx := getHostContext(idx)
-	return C.enum_evmc_storage_status(ctx.SetStorage(goAddress(*pAddr), goHash(*pKey), goHash(*pVal)))
+	status, err := ctx.SetStorage(goAddress(*pAddr), goHash(*pKey), goHash(*pVal))
+	if err != nil {
+		return C.EVMC_STORAGE_NON_EXISTING_ACCOUNT
+	}
+	return C.enum_evmc_storage_status(status)
 }
 
 //export getBalance
diff --git a/examples/example_host.cpp b/examples/example_host.cpp
index e675f86..af285c0 100644
--- a/examples/example_host.cpp
+++ b/examples/example_host.cpp
@@ -24,6 +24,11 @@ bool operator<(const evmc_uint256be& a, const evmc_uint256be& b)
     return std::memcmp(a.bytes, b.bytes, sizeof(a)) < 0;
 }
 
+bool operator==(const evmc_uint256be& a, const evmc_uint256be& b)
+{
+    return std::memcmp(a.bytes, b.bytes, sizeof(a)) == 0;
+}
+
 struct account
 {
     evmc_uint256be balance = {};
@@ -63,11 +68,26 @@ static enum evmc_storage_status set_storage(evmc_context* context,
                                             const evmc_uint256be* key,
                                             const evmc_uint256be* value)
 {
-    (void)context;
-    (void)address;
-    (void)key;
-    (void)value;
-    return EVMC_STORAGE_UNCHANGED;
+    example_host_context* host = static_cast<example_host_context*>(context);
+    auto accountIt = host->accounts.find(*address);
+    if (accountIt == host->accounts.end())
+        return EVMC_STORAGE_NON_EXISTING_ACCOUNT;
+
+    auto storageIt = accountIt->second.storage.find(*key);
+    if (storageIt == accountIt->second.storage.end())
+    {
+        accountIt->second.storage.emplace(std::make_pair(*key, *value));
+        return EVMC_STORAGE_ADDED;
+    }
+    else if (storageIt->second == *value)
+    {
+        return EVMC_STORAGE_UNCHANGED;
+    }
+    else
+    {
+        storageIt->second = *value;
+        return EVMC_STORAGE_MODIFIED;
+    }
 }
 
 static bool get_balance(evmc_uint256be* result, evmc_context* context, const evmc_address* address)
diff --git a/include/evmc/evmc.h b/include/evmc/evmc.h
index ca18da5..e71585a 100644
--- a/include/evmc/evmc.h
+++ b/include/evmc/evmc.h
@@ -459,21 +459,25 @@ enum evmc_storage_status
     /**
      * A storage item has been deleted: X -> 0.
      */
-    EVMC_STORAGE_DELETED = 4
+    EVMC_STORAGE_DELETED = 4,
+
+    /**
+     * An attempt to modify storage of an non-existing account.
+     */
+    EVMC_STORAGE_NON_EXISTING_ACCOUNT = 5
 };
 
 
 /**
  * Set storage callback function.
  *
- * This callback function is used by an EVM to update the given contract
- * storage entry.
+ * This callback function is used by an EVM to update the given contract storage entry.
+ *
  * @param context  The pointer to the Host execution context.
- *                 @see ::evmc_context.
  * @param address  The address of the contract.
  * @param key      The index of the storage entry.
  * @param value    The value to be stored.
- * @return         The effect on the storage item, @see ::evmc_storage_status.
+ * @return         The effect on the storage item. @see ::evmc_storage_status.
  */
 typedef enum evmc_storage_status (*evmc_set_storage_fn)(struct evmc_context* context,
                                                         const struct evmc_address* address,