tools: Add skip_space_iterator struct

This restores the option to filter-out whitespace before parsing hex.
This is useful e.g. when loading hex from a file.

test/unittests/CMakeLists.txt

@@ -23,6 +23,7 @@ add_executable(
     loader_mock.h
     loader_test.cpp
     mocked_host_test.cpp
+    skip_space_iterator_test.cpp
     tooling_test.cpp
     hex_test.cpp
 )

test/unittests/skip_space_iterator_test.cpp

@@ -0,0 +1,83 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2022 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+
+#include <tools/evmc/skip_space_iterator.hpp>
+#include <gtest/gtest.h>
+
+using evmc::skip_space_iterator;
+
+namespace
+{
+std::string remove_space(std::string_view in)
+{
+    // Copy input to additional buffer. This helps with out-of-buffer reads detection by sanitizers.
+    const auto in_buffer = std::make_unique<char[]>(in.size());
+    const auto begin = in_buffer.get();
+    const auto end = begin + in.size();
+    std::copy(in.begin(), in.end(), begin);
+
+    // Filter the input.
+    std::string out;
+    std::copy(skip_space_iterator{begin, end}, skip_space_iterator{end, end},
+              std::back_inserter(out));
+    return out;
+}
+}  // namespace
+
+TEST(skip_space_iterator, empty)
+{
+    EXPECT_EQ(remove_space(""), "");
+    EXPECT_EQ(remove_space(" "), "");
+    EXPECT_EQ(remove_space("  "), "");
+}
+
+TEST(skip_space_iterator, filter_middle)
+{
+    EXPECT_EQ(remove_space("x y"), "xy");
+    EXPECT_EQ(remove_space("x  y"), "xy");
+}
+
+TEST(skip_space_iterator, filter_front)
+{
+    EXPECT_EQ(remove_space(" x"), "x");
+    EXPECT_EQ(remove_space("  x"), "x");
+}
+
+TEST(skip_space_iterator, filter_back)
+{
+    EXPECT_EQ(remove_space("x "), "x");
+    EXPECT_EQ(remove_space("x  "), "x");
+}
+
+TEST(skip_space_iterator, filter_mixed)
+{
+    EXPECT_EQ(remove_space(" x y z "), "xyz");
+    EXPECT_EQ(remove_space("  x  y  z  "), "xyz");
+}
+
+TEST(skip_space_iterator, isspace)
+{
+    // Test internal isspace() compliance with std::isspace().
+    // The https://en.cppreference.com/w/cpp/string/byte/isspace has the list of "space" characters.
+
+    for (int i = int{std::numeric_limits<char>::min()}; i <= std::numeric_limits<char>::max(); ++i)
+    {
+        const auto c = static_cast<char>(i);
+        EXPECT_EQ(evmc::isspace(c), (std::isspace(c) != 0));
+        switch (c)
+        {
+        case ' ':
+        case '\f':
+        case '\n':
+        case '\r':
+        case '\t':
+        case '\v':
+            EXPECT_TRUE(evmc::isspace(c));
+            break;
+        default:
+            EXPECT_FALSE(evmc::isspace(c));
+            break;
+        }
+    }
+}

tools/evmc/CMakeLists.txt

@@ -5,7 +5,7 @@
 hunter_add_package(CLI11)
 find_package(CLI11 REQUIRED)
 
-add_executable(evmc-tool main.cpp)
+add_executable(evmc-tool main.cpp skip_space_iterator.hpp)
 add_executable(evmc::tool ALIAS evmc-tool)
 set_target_properties(evmc-tool PROPERTIES OUTPUT_NAME evmc)
 set_source_files_properties(main.cpp PROPERTIES

tools/evmc/main.cpp

@@ -2,6 +2,7 @@
 // Copyright 2019-2020 The EVMC Authors.
 // Licensed under the Apache License, Version 2.0.
 
+#include "skip_space_iterator.hpp"
 #include <CLI/CLI.hpp>
 #include <evmc/hex.hpp>
 #include <evmc/loader.h>
@@ -19,12 +20,13 @@ evmc::bytes load_from_hex(const std::string& str)
     {
         const auto path = str.substr(1);
         std::ifstream file{path};
-        const std::string content{std::istreambuf_iterator<char>{file},
-                                  std::istreambuf_iterator<char>{}};
-        auto o = evmc::from_hex(content);
-        if (!o)
+        const std::istreambuf_iterator<char> file_begin{file};
+        const std::istreambuf_iterator<char> file_end;
+        evmc::bytes out;
+        if (!evmc::from_hex(evmc::skip_space_iterator{file_begin, file_end},
+                            evmc::skip_space_iterator{file_end, file_end}, std::back_inserter(out)))
             throw std::invalid_argument{"invalid hex in " + path};
-        return std::move(*o);
+        return out;
     }
 
     return evmc::from_hex(str).value();  // Should be validated already.

tools/evmc/skip_space_iterator.hpp

@@ -0,0 +1,60 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2022 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+#pragma once
+
+#include <iterator>
+
+namespace evmc
+{
+/// The constexpr variant of std::isspace().
+inline constexpr bool isspace(char ch) noexcept
+{
+    // Implementation taken from LLVM's libc.
+    return ch == ' ' || (static_cast<unsigned>(ch) - '\t') < 5;
+}
+
+/// The input filter iterator which skips whitespace characters from the base input iterator.
+template <typename BaseIterator>
+struct skip_space_iterator
+{
+    using difference_type = typename std::iterator_traits<BaseIterator>::difference_type;
+    using value_type = typename std::iterator_traits<BaseIterator>::value_type;
+    using pointer = typename std::iterator_traits<BaseIterator>::pointer;
+    using reference = typename std::iterator_traits<BaseIterator>::reference;
+    using iterator_category = std::input_iterator_tag;
+
+private:
+    BaseIterator base;
+    BaseIterator base_end;
+    value_type value;
+
+    constexpr void forward_to_next_value()
+    {
+        for (; base != base_end; ++base)
+        {
+            value = *base;
+            if (isspace(value) == 0)
+                break;
+        }
+    }
+
+public:
+    constexpr skip_space_iterator(BaseIterator it, BaseIterator end) noexcept
+      : base{it}, base_end{end}
+    {
+        forward_to_next_value();
+    }
+
+    constexpr auto operator*() { return value; }
+
+    constexpr void operator++()
+    {
+        ++base;
+        forward_to_next_value();
+    }
+
+    constexpr bool operator!=(const skip_space_iterator& o) { return base != o.base; }
+    constexpr bool operator==(const skip_space_iterator& o) { return base == o.base; }
+};
+}  // namespace evmc