examples: Add "Precompiles VM" example

examples/CMakeLists.txt

@@ -10,6 +10,8 @@ if(NOT CMAKE_CXX_STANDARD)
 endif()
 set(CMAKE_DEBUG_POSTFIX "")
 
+add_subdirectory(example_precompiles_vm)
+
 
 add_library(evmc-example-host STATIC example_host.cpp)
 target_link_libraries(evmc-example-host PRIVATE evmc)

examples/example_precompiles_vm/CMakeLists.txt

@@ -0,0 +1,8 @@
+# EVMC: Ethereum Client-VM Connector API.
+# Copyright 2019 The EVMC Authors.
+# Licensed under the Apache License, Version 2.0.
+
+add_library(evmc-example-precompiles-vm SHARED example_precompiles_vm.cpp)
+target_link_libraries(evmc-example-precompiles-vm PRIVATE evmc)
+set_source_files_properties(example_precompiles_vm.cpp PROPERTIES
+    COMPILE_DEFINITIONS PROJECT_VERSION="${PROJECT_VERSION}")

examples/example_precompiles_vm/example_precompiles_vm.cpp

@@ -0,0 +1,127 @@
+/* EVMC: Ethereum Client-VM Connector API.
+ * Copyright 2019 The EVMC Authors.
+ * Licensed under the Apache License, Version 2.0.
+ */
+
+#include <evmc/evmc.h>
+#include <evmc/utils.h>
+#include <algorithm>
+
+static evmc_result execute_identity(const evmc_message* msg)
+{
+    auto result = evmc_result{};
+
+    // Check the gas cost.
+    auto gas_cost = 15 + 3 * ((int64_t(msg->input_size) + 31) / 32);
+    auto gas_left = msg->gas - gas_cost;
+    if (gas_left < 0)
+    {
+        result.status_code = EVMC_OUT_OF_GAS;
+        return result;
+    }
+
+    // Execute.
+    auto data = new uint8_t[msg->input_size];
+    std::copy_n(msg->input_data, msg->input_size, data);
+
+    // Return the result.
+    result.status_code = EVMC_SUCCESS;
+    result.output_data = data;
+    result.output_size = msg->input_size;
+    result.release = [](const evmc_result* result) { delete[] result->output_data; };
+    result.gas_left = gas_left;
+    return result;
+}
+
+static evmc_result execute_empty(const evmc_message* msg)
+{
+    auto result = evmc_result{};
+    result.status_code = EVMC_SUCCESS;
+    result.gas_left = msg->gas;
+    return result;
+}
+
+static evmc_result not_implemented()
+{
+    auto result = evmc_result{};
+    result.status_code = EVMC_INTERNAL_ERROR;
+    return result;
+}
+
+static evmc_result execute(evmc_instance*,
+                           evmc_context*,
+                           enum evmc_revision rev,
+                           const evmc_message* msg,
+                           const uint8_t*,
+                           size_t)
+{
+    // The EIP-1352 (https://eips.ethereum.org/EIPS/eip-1352) defines
+    // the range 0 - 0xffff (2 bytes) of addresses reserved for precompiled contracts.
+    // Check if the destination address is within the reserved range.
+
+    constexpr auto prefix_size = sizeof(evmc_address) - 2;
+    const auto& dst = msg->destination;
+    // Check if the address prefix is all zeros.
+    if (std::all_of(&dst.bytes[0], &dst.bytes[prefix_size], [](uint8_t x) { return x == 0; }))
+    {
+        // If not, reject the execution request.
+        auto result = evmc_result{};
+        result.status_code = EVMC_REJECTED;
+        return result;
+    }
+
+    // Extract the precompiled contract id from last 2 bytes of the destination address.
+    const auto id = (dst.bytes[prefix_size] << 8) | dst.bytes[prefix_size + 1];
+    switch (id)
+    {
+    case 0x0001:  // ECDSARECOVER
+        return not_implemented();
+
+    case 0x0002:  // SHA256
+        return not_implemented();
+
+    case 0x0003:  // RIPEMD160
+        return not_implemented();
+
+    case 0x0004:  // Identity
+        return execute_identity(msg);
+
+    case 0x0005:  // EXPMOD
+        if (rev < EVMC_BYZANTIUM)
+            return execute_empty(msg);
+        return not_implemented();
+
+    case 0x0006:  // SNARKV
+        if (rev < EVMC_BYZANTIUM)
+            return execute_empty(msg);
+        return not_implemented();
+
+    case 0x0007:  // BNADD
+        if (rev < EVMC_BYZANTIUM)
+            return execute_empty(msg);
+        return not_implemented();
+
+    case 0x0008:  // BNMUL
+        if (rev < EVMC_BYZANTIUM)
+            return execute_empty(msg);
+        return not_implemented();
+
+    default:  // As if empty code was executed.
+        return execute_empty(msg);
+    }
+}
+
+extern "C" EVMC_EXPORT evmc_instance* evmc_create_example_precompiles_vm()
+{
+    static struct evmc_instance instance = {
+        EVMC_ABI_VERSION,
+        "example_precompiles_vm",
+        PROJECT_VERSION,
+        [](evmc_instance*) {},
+        execute,
+        [](evmc_instance*) { return evmc_capabilities_flagset{EVMC_CAPABILITY_PRECOMPILES}; },
+        nullptr,
+        nullptr,
+    };
+    return &instance;
+}

test/vmtester/CMakeLists.txt

@@ -13,6 +13,7 @@ set_source_files_properties(vmtester.cpp PROPERTIES COMPILE_DEFINITIONS PROJECT_
 install(TARGETS evmc-vmtester RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 
 add_test(NAME vmtester/examplevm COMMAND evmc-vmtester $<TARGET_FILE:evmc-example-vm>)
+add_test(NAME vmtester/example_precompiles_vm COMMAND evmc-vmtester $<TARGET_FILE:evmc-example-precompiles-vm>)
 
 add_test(NAME vmtester/help COMMAND evmc-vmtester --version --help)
 set_tests_properties(vmtester/help PROPERTIES PASS_REGULAR_EXPRESSION "Usage:")