From 0534138668dd780cbdb413cd78c03c1ee878e651 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 25 Feb 2021 15:31:09 +0000
Subject: [PATCH] test: Refactor translate_signature in wasm_engine

This replaces the implementation in fizzy_engine with a template.
---
 test/utils/fizzy_engine.cpp | 29 +++-----------------------
 test/utils/wasm_engine.hpp  | 41 +++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 26 deletions(-)

diff --git a/test/utils/fizzy_engine.cpp b/test/utils/fizzy_engine.cpp
index 9055f19be..cbba53301 100644
--- a/test/utils/fizzy_engine.cpp
+++ b/test/utils/fizzy_engine.cpp
@@ -28,31 +28,6 @@ class FizzyEngine final : public WasmEngine
 
 namespace
 {
-ValType translate_valtype(char input)
-{
-    if (input == 'i')
-        return fizzy::ValType::i32;
-    else if (input == 'I')
-        return fizzy::ValType::i64;
-    else
-        throw std::runtime_error{"invalid type"};
-}
-
-FuncType translate_signature(std::string_view signature)
-{
-    const auto delimiter_pos = signature.find(':');
-    assert(delimiter_pos != std::string_view::npos);
-    const auto inputs = signature.substr(0, delimiter_pos);
-    const auto outputs = signature.substr(delimiter_pos + 1);
-
-    FuncType func_type;
-    std::transform(std::begin(inputs), std::end(inputs), std::back_inserter(func_type.inputs),
-        translate_valtype);
-    std::transform(std::begin(outputs), std::end(outputs), std::back_inserter(func_type.outputs),
-        translate_valtype);
-    return func_type;
-}
-
 fizzy::ExecutionResult env_adler32(fizzy::Instance& instance, const fizzy::Value* args, int)
 {
     assert(instance.memory != nullptr);
@@ -124,7 +99,9 @@ std::optional<WasmEngine::FuncRef> FizzyEngine::find_function(
     if (func_idx.has_value())
     {
         const auto func_type = m_instance->module->get_function_type(*func_idx);
-        const auto sig_type = translate_signature(signature);
+        FuncType sig_type;
+        std::tie(sig_type.inputs, sig_type.outputs) =
+            translate_function_signature<ValType, ValType::i32, ValType::i64>(signature);
         if (sig_type != func_type)
             return std::nullopt;
     }
diff --git a/test/utils/wasm_engine.hpp b/test/utils/wasm_engine.hpp
index d09e0e197..aaacd96f3 100644
--- a/test/utils/wasm_engine.hpp
+++ b/test/utils/wasm_engine.hpp
@@ -5,8 +5,11 @@
 #pragma once
 
 #include "bytes.hpp"
+#include <algorithm>
+#include <cassert>
 #include <memory>
 #include <optional>
+#include <stdexcept>
 #include <string_view>
 #include <vector>
 
@@ -58,8 +61,46 @@ class WasmEngine
     virtual Result execute(FuncRef func_ref, const std::vector<uint64_t>& args) = 0;
 };
 
+/// Throws exception if the signature is non-conformant.
+///
+/// A function signature consist of input and output types delimited by a colon. Zero number of
+/// types is allowed. A type is represented with a single character, where `i` means i32, and
+/// `I` means i64.
+///
+/// As an example `iI:i` translates to `(i32, i64) -> (i32)`, `I:` to `(i64) -> void`, etc.
 void validate_function_signature(std::string_view signature);
 
+/// Parses a validated signature and returns a pair of input and output type vectors of type
+/// `ValueType`.
+///
+/// Note that calling `validate_function_signature` first is advised for better error reporting.
+template <typename ValueType, ValueType i32_type, ValueType i64_type>
+std::pair<std::vector<ValueType>, std::vector<ValueType>> translate_function_signature(
+    std::string_view signature)
+{
+    constexpr auto translate_valtype = [](char input) {
+        if (input == 'i')
+            return i32_type;
+        else if (input == 'I')
+            return i64_type;
+        else
+            throw std::runtime_error{"invalid type"};
+    };
+
+    const auto delimiter_pos = signature.find(':');
+    assert(delimiter_pos != std::string_view::npos);
+    const auto inputs = signature.substr(0, delimiter_pos);
+    const auto outputs = signature.substr(delimiter_pos + 1);
+
+    std::vector<ValueType> input_types;
+    std::vector<ValueType> output_types;
+    std::transform(
+        std::begin(inputs), std::end(inputs), std::back_inserter(input_types), translate_valtype);
+    std::transform(std::begin(outputs), std::end(outputs), std::back_inserter(output_types),
+        translate_valtype);
+    return {std::move(input_types), std::move(output_types)};
+}
+
 std::unique_ptr<WasmEngine> create_fizzy_engine();
 std::unique_ptr<WasmEngine> create_fizzy_c_engine();
 std::unique_ptr<WasmEngine> create_wabt_engine();