Merge pull request #217 from ethereum/cpp-host

cpp: Add evmc::host - wrapper around Host context / interface

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## [6.2.0] - Unreleased
 
+- Added: [[#217](https://github.com/ethereum/evmc/pull/217)]
+  The `evmc::host` C++ wrapper for EVMC host context and interface
+  to be used by VM implementations.
 - Deprecated: [[#196](https://github.com/ethereum/evmc/pull/196)]
   The `EVMC_CONSTANTINOPLE2` revision name is deprecated, replaced with `EVMC_PETERSBURG`.
 

include/evmc/evmc.hpp

@@ -76,4 +76,92 @@ public:
 private:
     evmc_instance* const m_instance = nullptr;
 };
+
+
+/// Wrapper around EVMC host context / host interface.
+class host
+{
+    evmc_context* context = nullptr;
+    evmc_tx_context tx_context = {};
+
+public:
+    host(evmc_context* context) noexcept : context{context} {}
+
+    bool account_exists(const evmc_address& address) noexcept
+    {
+        return context->host->account_exists(context, &address);
+    }
+
+    evmc_bytes32 get_storage(const evmc_address& address, const evmc_bytes32& key) noexcept
+    {
+        return context->host->get_storage(context, &address, &key);
+    }
+
+    evmc_storage_status set_storage(const evmc_address& address,
+                                    const evmc_bytes32& key,
+                                    const evmc_bytes32& value) noexcept
+    {
+        return context->host->set_storage(context, &address, &key, &value);
+    }
+
+    evmc_uint256be get_balance(const evmc_address& address) noexcept
+    {
+        return context->host->get_balance(context, &address);
+    }
+
+    size_t get_code_size(const evmc_address& address) noexcept
+    {
+        return context->host->get_code_size(context, &address);
+    }
+
+    evmc_bytes32 get_code_hash(const evmc_address& address) noexcept
+    {
+        return context->host->get_code_hash(context, &address);
+    }
+
+    size_t copy_code(const evmc_address& address,
+                     size_t code_offset,
+                     uint8_t* buffer_data,
+                     size_t buffer_size) noexcept
+    {
+        return context->host->copy_code(context, &address, code_offset, buffer_data, buffer_size);
+    }
+
+    void selfdestruct(const evmc_address& address, const evmc_address& beneficiary)
+    {
+        context->host->selfdestruct(context, &address, &beneficiary);
+    }
+
+    result call(const evmc_message& message) noexcept
+    {
+        return result{context->host->call(context, &message)};
+    }
+
+    /// Gets the transaction and block context from the Host.
+    ///
+    /// The implementation caches the received transaction context
+    /// by assuming that the block timestamp should never be zero.
+    ///
+    /// @return Reference to the cached transaction context.
+    const evmc_tx_context& get_tx_context() noexcept
+    {
+        if (tx_context.block_timestamp == 0)
+            tx_context = context->host->get_tx_context(context);
+        return tx_context;
+    }
+
+    evmc_bytes32 get_block_hash(int64_t number) noexcept
+    {
+        return context->host->get_block_hash(context, number);
+    }
+
+    void emit_log(const evmc_address& address,
+                  const uint8_t* data,
+                  size_t data_size,
+                  const evmc_bytes32 topics[],
+                  size_t topics_count) noexcept
+    {
+        context->host->emit_log(context, &address, data, data_size, topics, topics_count);
+    }
+};
 }  // namespace evmc

test/unittests/CMakeLists.txt

@@ -15,5 +15,5 @@ add_executable(
     test_loader.cpp
 )
 
-target_link_libraries(evmc-test PRIVATE loader-mocked evmc-example-vm-static instructions GTest::gtest GTest::main)
+target_link_libraries(evmc-test PRIVATE loader-mocked evmc-example-vm-static evmc-example-host instructions GTest::gtest GTest::main)
 set_target_properties(evmc-test PROPERTIES RUNTIME_OUTPUT_DIRECTORY ..)

test/unittests/test_cpp.cpp

@@ -2,9 +2,11 @@
 // Copyright 2019 The EVMC Authors.
 // Licensed under the Apache License, Version 2.0.
 
+#include "../../examples/example_host.h"
 #include "../../examples/example_vm.h"
 
 #include <evmc/evmc.hpp>
+#include <evmc/helpers.hpp>
 
 #include <gtest/gtest.h>
 
@@ -61,3 +63,38 @@ TEST(cpp, vm_set_option)
     auto vm = evmc::vm{&raw_instance};
     EXPECT_EQ(vm.set_option("1", "2"), EVMC_SET_OPTION_INVALID_NAME);
 }
+
+TEST(cpp, host)
+{
+    // Use example host to execute all methods from the C++ host wrapper.
+
+    auto* host_context = example_host_create_context();
+    auto host = evmc::host{host_context};
+
+    auto a = evmc_address{{1}};
+    auto v = evmc_bytes32{{7, 7, 7}};
+
+    EXPECT_FALSE(host.account_exists(a));
+
+    EXPECT_EQ(host.set_storage(a, {}, v), EVMC_STORAGE_MODIFIED);
+    EXPECT_EQ(host.set_storage(a, {}, v), EVMC_STORAGE_UNCHANGED);
+    EXPECT_EQ(host.get_storage(a, {}), v);
+
+    EXPECT_TRUE(is_zero(host.get_balance(a)));
+
+    EXPECT_EQ(host.get_code_size(a), 0);
+    EXPECT_EQ(host.get_code_hash(a), evmc_bytes32{});
+    EXPECT_EQ(host.copy_code(a, 0, nullptr, 0), 0);
+
+    host.selfdestruct(a, a);
+    EXPECT_EQ(host.call({}).gas_left, 0);
+
+    auto* tx = &host.get_tx_context();
+    EXPECT_EQ(&host.get_tx_context(), tx);
+
+    EXPECT_EQ(host.get_block_hash(0), evmc_bytes32{});
+
+    host.emit_log(a, nullptr, 0, nullptr, 0);
+
+    example_host_destroy_context(host_context);
+}