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C++: Refactor {address,bytes32} constructors #646

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C++: Refactor {address,bytes32} constructors #646

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1fb93b4
Convert evmc::hex library into single hex.hpp header
chfast May 12, 2022
6d6852a
hex: Tune implementation
chfast May 12, 2022
a476d6e
hex: Use std::optional to report invalid input
chfast May 12, 2022
fe0d43f
C++: Rework hex literals parsing
chfast May 12, 2022
02a2af1
C++: Refactor {address,bytes32} constructors
chfast May 13, 2022
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139 changes: 30 additions & 109 deletions include/evmc/evmc.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@

#include <evmc/evmc.h>
#include <evmc/helpers.h>
#include <evmc/hex.hpp>

#include <functional>
#include <initializer_list>
Expand All @@ -30,34 +31,17 @@ struct address : evmc_address
/// Default and converting constructor.
///
/// Initializes bytes to zeros if not other @p init value provided.
constexpr address(evmc_address init = {}) noexcept : evmc_address{init} {}
inline constexpr address(evmc_address init = {}) noexcept : evmc_address{init} {}

/// Converting constructor from unsigned integer value.
///
/// This constructor assigns the @p v value to the last 8 bytes [12:19]
/// in big-endian order.
constexpr explicit address(uint64_t v) noexcept
: evmc_address{{0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
static_cast<uint8_t>(v >> 56),
static_cast<uint8_t>(v >> 48),
static_cast<uint8_t>(v >> 40),
static_cast<uint8_t>(v >> 32),
static_cast<uint8_t>(v >> 24),
static_cast<uint8_t>(v >> 16),
static_cast<uint8_t>(v >> 8),
static_cast<uint8_t>(v >> 0)}}
{}
inline constexpr explicit address(uint64_t v) noexcept : evmc_address{}
{
for (size_t i = sizeof(bytes) - sizeof(v); i < sizeof(bytes); ++i)
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Why is this better?

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It's just shorter.

bytes[i] = static_cast<uint8_t>(v >> (8 * (sizeof(bytes) - 1 - i)));
}

/// Explicit operator converting to bool.
inline constexpr explicit operator bool() const noexcept;
Expand All @@ -74,46 +58,17 @@ struct bytes32 : evmc_bytes32
/// Default and converting constructor.
///
/// Initializes bytes to zeros if not other @p init value provided.
constexpr bytes32(evmc_bytes32 init = {}) noexcept : evmc_bytes32{init} {}
inline constexpr bytes32(evmc_bytes32 init = {}) noexcept : evmc_bytes32{init} {}

/// Converting constructor from unsigned integer value.
///
/// This constructor assigns the @p v value to the last 8 bytes [24:31]
/// in big-endian order.
constexpr explicit bytes32(uint64_t v) noexcept
: evmc_bytes32{{0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
static_cast<uint8_t>(v >> 56),
static_cast<uint8_t>(v >> 48),
static_cast<uint8_t>(v >> 40),
static_cast<uint8_t>(v >> 32),
static_cast<uint8_t>(v >> 24),
static_cast<uint8_t>(v >> 16),
static_cast<uint8_t>(v >> 8),
static_cast<uint8_t>(v >> 0)}}
{}
inline constexpr explicit bytes32(uint64_t v) noexcept : evmc_bytes32{}
{
for (size_t i = sizeof(bytes) - sizeof(v); i < sizeof(bytes); ++i)
bytes[i] = static_cast<uint8_t>(v >> (8 * (sizeof(bytes) - 1 - i)));
}

/// Explicit operator converting to bool.
inline constexpr explicit operator bool() const noexcept;
Expand Down Expand Up @@ -280,71 +235,37 @@ inline constexpr bytes32::operator bool() const noexcept

namespace literals
{
namespace internal
{
constexpr int from_hex(char c) noexcept
{
return (c >= 'a' && c <= 'f') ? c - ('a' - 10) :
(c >= 'A' && c <= 'F') ? c - ('A' - 10) :
c - '0';
}

constexpr uint8_t byte(const char* s, size_t i) noexcept
{
return static_cast<uint8_t>((from_hex(s[2 * i]) << 4) | from_hex(s[2 * i + 1]));
}
/// Breaks compilation and reports error string in constexpr context.
inline void error([[maybe_unused]] const char* message) noexcept {}

/// Converts a raw literal into value of type T.
template <typename T>
T from_hex(const char*) noexcept;

template <>
constexpr bytes32 from_hex<bytes32>(const char* s) noexcept
constexpr T to(std::string_view s) noexcept
{
return {
{{byte(s, 0), byte(s, 1), byte(s, 2), byte(s, 3), byte(s, 4), byte(s, 5), byte(s, 6),
byte(s, 7), byte(s, 8), byte(s, 9), byte(s, 10), byte(s, 11), byte(s, 12), byte(s, 13),
byte(s, 14), byte(s, 15), byte(s, 16), byte(s, 17), byte(s, 18), byte(s, 19), byte(s, 20),
byte(s, 21), byte(s, 22), byte(s, 23), byte(s, 24), byte(s, 25), byte(s, 26), byte(s, 27),
byte(s, 28), byte(s, 29), byte(s, 30), byte(s, 31)}}};
}
if (s == "0")
return T{};

template <>
constexpr address from_hex<address>(const char* s) noexcept
{
return {
{{byte(s, 0), byte(s, 1), byte(s, 2), byte(s, 3), byte(s, 4), byte(s, 5), byte(s, 6),
byte(s, 7), byte(s, 8), byte(s, 9), byte(s, 10), byte(s, 11), byte(s, 12), byte(s, 13),
byte(s, 14), byte(s, 15), byte(s, 16), byte(s, 17), byte(s, 18), byte(s, 19)}}};
}
if (s[0] != '0' || s[1] != 'x')
error("literal must be in hexadecimal notation");

template <typename T, char... c>
constexpr T from_literal() noexcept
{
constexpr auto size = sizeof...(c);
constexpr char literal[] = {c...};
constexpr bool is_simple_zero = size == 1 && literal[0] == '0';
if (s.length() != 2 * sizeof(T) + 2)
error("literal must match the result type size");

static_assert(is_simple_zero || (literal[0] == '0' && literal[1] == 'x'),
"literal must be in hexadecimal notation");
static_assert(is_simple_zero || size == 2 * sizeof(T) + 2,
"literal must match the result type size");

return is_simple_zero ? T{} : from_hex<T>(&literal[2]);
T r{};
internal::from_hex(s, r.bytes);
return r;
}
} // namespace internal

/// Literal for evmc::address.
template <char... c>
constexpr address operator""_address() noexcept
constexpr address operator""_address(const char* s) noexcept
{
return internal::from_literal<address, c...>();
return to<address>(s);
}

/// Literal for evmc::bytes32.
template <char... c>
constexpr bytes32 operator""_bytes32() noexcept
constexpr bytes32 operator""_bytes32(const char* s) noexcept
{
return internal::from_literal<bytes32, c...>();
return to<bytes32>(s);
}
} // namespace literals

Expand Down
125 changes: 88 additions & 37 deletions include/evmc/hex.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,9 @@

#include <cstdint>
#include <iterator>
#include <optional>
#include <string>
#include <string_view>
#include <system_error>

namespace evmc
{
Expand All @@ -17,55 +17,106 @@ using bytes = std::basic_string<uint8_t>;
/// String view of uint8_t chars.
using bytes_view = std::basic_string_view<uint8_t>;

/// Hex decoding error codes.
enum class hex_errc
{
/// Invalid hex digit encountered during decoding.
invalid_hex_digit = 1,

/// Input contains incomplete hex byte (length is odd).
incomplete_hex_byte_pair = 2,
};
/// Encode a byte to a hex string.
inline std::string hex(uint8_t b) noexcept
{
static constexpr auto hex_digits = "0123456789abcdef";
return {hex_digits[b >> 4], hex_digits[b & 0xf]};
}

/// Obtains a reference to the static error category object for hex errors.
const std::error_category& hex_category() noexcept;
/// Encodes bytes as hex string.
inline std::string hex(bytes_view bs)
{
std::string str;
str.reserve(bs.size() * 2);
for (const auto b : bs)
str += hex(b);
return str;
}

/// Creates error_code object out of a hex error code value.
inline std::error_code make_error_code(hex_errc errc) noexcept
namespace internal
{
/// Extracts the nibble value out of a hex digit.
/// Returns -1 in case of invalid hex digit.
inline constexpr int from_hex_digit(char h) noexcept
{
return {static_cast<int>(errc), hex_category()};
if (h >= '0' && h <= '9')
return h - '0';
else if (h >= 'a' && h <= 'f')
return h - 'a' + 10;
else if (h >= 'A' && h <= 'F')
return h - 'A' + 10;
else
return -1;
}

/// Hex decoding exception.
struct hex_error : std::system_error
/// The constexpr variant of std::isspace().
inline constexpr bool isspace(char ch) noexcept
{
using system_error::system_error;
};
// Implementation taken from LLVM's libc.
return ch == ' ' || (static_cast<unsigned>(ch) - '\t') < 5;
}

/// Encode a byte to a hex string.
inline std::string hex(uint8_t b) noexcept
template <typename OutputIt>
inline constexpr bool from_hex(std::string_view hex, OutputIt result) noexcept
{
static constexpr auto hex_chars = "0123456789abcdef";
return {hex_chars[b >> 4], hex_chars[b & 0xf]};
// Omit the optional 0x prefix.
if (hex.size() >= 2 && hex[0] == '0' && hex[1] == 'x')
hex.remove_prefix(2);

constexpr int empty_mark = -1;
int hi_nibble = empty_mark;
for (const auto h : hex)
{
if (isspace(h))
continue;

const int v = from_hex_digit(h);
if (v < 0)
return false;

if (hi_nibble == empty_mark)
{
hi_nibble = v << 4;
}
else
{
*result++ = static_cast<uint8_t>(hi_nibble | v);
hi_nibble = empty_mark;
}
}

return hi_nibble == empty_mark;
}
} // namespace internal

/// Validates hex encoded string.
std::error_code validate_hex(std::string_view hex) noexcept;

/// Decodes hex encoded string to bytes.
///
/// Throws hex_error with the appropriate error code.
bytes from_hex(std::string_view hex);
/// @return True if the input is valid hex.
inline bool validate_hex(std::string_view hex) noexcept
{
struct noop_output_iterator
{
uint8_t sink = {};
uint8_t& operator*() noexcept { return sink; }
noop_output_iterator operator++(int) noexcept { return *this; } // NOLINT(cert-dcl21-cpp)
};

/// Encodes bytes as hex string.
std::string hex(bytes_view bs);
} // namespace evmc
return internal::from_hex(hex, noop_output_iterator{});
}

namespace std
/// Decodes hex encoded string to bytes.
///
/// In case the input is invalid the returned value is std::nullopt.
/// This can happen if a non-hex digit or odd number of digits is encountered.
/// Whitespace in the input is ignored.
inline std::optional<bytes> from_hex(std::string_view hex)
{
/// Template specialization of std::is_error_code_enum for evmc::hex_errc.
/// This enabled implicit conversions from evmc::hex_errc to std::error_code.
template <>
struct is_error_code_enum<evmc::hex_errc> : true_type
{};
} // namespace std
bytes bs;
bs.reserve(hex.size() / 2);
if (!internal::from_hex(hex, std::back_inserter(bs)))
return {};
return bs;
}
} // namespace evmc
1 change: 0 additions & 1 deletion lib/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,6 @@ target_compile_features(evmc_cpp INTERFACE cxx_std_17)
target_include_directories(evmc_cpp INTERFACE $<BUILD_INTERFACE:${EVMC_INCLUDE_DIR}>$<INSTALL_INTERFACE:include>)
target_link_libraries(evmc_cpp INTERFACE evmc::evmc)

add_subdirectory(hex)
add_subdirectory(instructions)
add_subdirectory(loader)
add_subdirectory(mocked_host)
Expand Down
18 changes: 0 additions & 18 deletions lib/hex/CMakeLists.txt
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