Merge pull request #160 from CrustyAuklet/to_chars

To chars

CMakeLists.txt

@@ -23,6 +23,7 @@ set(SNITCH_WITH_MULTITHREADING             ON  CACHE BOOL "Make the testing fram
 set(SNITCH_WITH_TIMINGS                    ON  CACHE BOOL "Measure the time taken by each test case -- disable to speed up tests.")
 set(SNITCH_WITH_SHORTHAND_MACROS           ON  CACHE BOOL "Use short names for test macros -- disable if this causes conflicts.")
 set(SNITCH_CONSTEXPR_FLOAT_USE_BITCAST     ON  CACHE BOOL "Use std::bit_cast if available to implement exact constexpr float-to-string conversion.")
+set(SNITCH_APPEND_TO_CHARS                 ON  CACHE BOOL "Use std::to_chars for string conversions -- disable for greater compatability with a slight performance cost.")
 set(SNITCH_DEFAULT_WITH_COLOR              ON  CACHE BOOL "Enable terminal colors by default -- can also be controlled by command line interface.")
 set(SNITCH_DECOMPOSE_SUCCESSFUL_ASSERTIONS OFF CACHE BOOL "Enable expression decomposition even for successful assertions -- more expensive.")
 set(SNITCH_WITH_ALL_REPORTERS              ON  CACHE BOOL "Allow all built-in reporters to be selected from the command line -- disable for faster compilation.")

include/snitch/snitch_append.hpp

@@ -45,47 +45,53 @@ SNITCH_EXPORT [[nodiscard]] bool append_fast(small_string_span ss, double f) noe
     return could_fit;
 }
 
-[[nodiscard]] constexpr std::size_t num_digits(large_uint_t x) noexcept {
-    return x >= 10u ? 1u + num_digits(x / 10u) : 1u;
+template<large_uint_t Base = 10u, unsigned_integral T>
+[[nodiscard]] constexpr std::size_t num_digits(T x) noexcept {
+    return x >= Base ? 1u + num_digits<Base>(x / Base) : 1u;
 }
 
-[[nodiscard]] constexpr std::size_t num_digits(large_int_t x) noexcept {
-    return x >= 10 ? 1u + num_digits(x / 10) : x <= -10 ? 1u + num_digits(x / 10) : x > 0 ? 1u : 2u;
+template<large_int_t Base = 10, signed_integral T>
+[[nodiscard]] constexpr std::size_t num_digits(T x) noexcept {
+    return (x >= Base || x <= -Base) ? 1u + num_digits<Base>(x / Base) : x > 0 ? 1u : 2u;
 }
 
-constexpr std::array<char, 10> digits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
+constexpr std::array<char, 16> digits = {'0', '1', '2', '3', '4', '5', '6', '7',
+                                         '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
 constexpr std::size_t max_uint_length = num_digits(std::numeric_limits<large_uint_t>::max());
 constexpr std::size_t max_int_length  = max_uint_length + 1;
 
-[[nodiscard]] constexpr bool append_constexpr(small_string_span ss, large_uint_t i) noexcept {
+template<large_uint_t Base = 10u, unsigned_integral T>
+[[nodiscard]] constexpr bool append_constexpr(small_string_span ss, T i) noexcept {
     if (i != 0u) {
         small_string<max_uint_length> tmp;
-        tmp.resize(num_digits(i));
+        tmp.resize(num_digits<Base>(i));
         std::size_t k = 1;
-        for (large_uint_t j = i; j != 0u; j /= 10u, ++k) {
-            tmp[tmp.size() - k] = digits[j % 10u];
+        for (large_uint_t j = i; j != 0u; j /= Base, ++k) {
+            tmp[tmp.size() - k] = digits[j % Base];
         }
         return append_constexpr(ss, tmp);
     } else {
         return append_constexpr(ss, "0");
     }
 }
 
-[[nodiscard]] constexpr bool append_constexpr(small_string_span ss, large_int_t i) noexcept {
+template<large_int_t Base = 10, signed_integral T>
+[[nodiscard]] constexpr bool append_constexpr(small_string_span ss, T i) noexcept {
     if (i > 0) {
         small_string<max_int_length> tmp;
-        tmp.resize(num_digits(i));
+        tmp.resize(num_digits<Base>(i));
         std::size_t k = 1;
-        for (large_int_t j = i; j != 0; j /= 10, ++k) {
-            tmp[tmp.size() - k] = digits[j % 10];
+        for (large_int_t j = i; j != 0; j /= Base, ++k) {
+            tmp[tmp.size() - k] = digits[j % Base];
         }
         return append_constexpr(ss, tmp);
     } else if (i < 0) {
         small_string<max_int_length> tmp;
-        tmp.resize(num_digits(i));
+        tmp.resize(num_digits<Base>(i));
         std::size_t k = 1;
-        for (large_int_t j = i; j != 0; j /= 10, ++k) {
-            tmp[tmp.size() - k] = digits[-(j % 10)];
+        for (large_int_t j = i; j != 0; j /= Base, ++k) {
+            tmp[tmp.size() - k] = digits[-(j % Base)];
         }
         tmp[0] = '-';
         return append_constexpr(ss, tmp);
@@ -98,15 +104,15 @@ constexpr std::size_t max_int_length  = max_uint_length + 1;
 constexpr std::size_t min_exp_digits = 2u;
 
 [[nodiscard]] constexpr std::size_t num_exp_digits(fixed_exp_t x) noexcept {
-    const std::size_t exp_digits = num_digits(static_cast<large_uint_t>(x > 0 ? x : -x));
+    const std::size_t exp_digits = num_digits<10>(static_cast<large_uint_t>(x > 0 ? x : -x));
     return exp_digits < min_exp_digits ? min_exp_digits : exp_digits;
 }
 
 [[nodiscard]] constexpr std::size_t num_digits(const signed_fixed_data& x) noexcept {
     // +1 for fractional separator '.'
     // +1 for exponent separator 'e'
     // +1 for exponent sign
-    return num_digits(static_cast<large_uint_t>(x.digits)) + num_exp_digits(x.exponent) +
+    return num_digits<10>(static_cast<large_uint_t>(x.digits)) + num_exp_digits(x.exponent) +
            (x.sign ? 1u : 0u) + 3u;
 }
 
@@ -135,7 +141,7 @@ set_precision(signed_fixed_data fd, std::size_t p) noexcept {
     // and round-half-to-even is the default rounding mode for IEEE 754 floats. We don't follow
     // the current rounding mode, but we can at least follow the default.
 
-    std::size_t base_digits = num_digits(static_cast<large_uint_t>(fd.digits));
+    std::size_t base_digits = num_digits<10>(static_cast<large_uint_t>(fd.digits));
 
     bool only_zero = true;
     while (base_digits > p) {
@@ -144,12 +150,13 @@ set_precision(signed_fixed_data fd, std::size_t p) noexcept {
                 only_zero = false;
             }
             fd.digits = fd.digits / 10u;
+            base_digits -= 1u;
         } else {
-            fd.digits = round_half_to_even(fd.digits, only_zero);
+            fd.digits   = round_half_to_even(fd.digits, only_zero);
+            base_digits = num_digits<10>(static_cast<large_uint_t>(fd.digits));
         }
 
         fd.exponent += 1;
-        base_digits -= 1u;
     }
 
     return fd;

include/snitch/snitch_concepts.hpp

@@ -6,18 +6,25 @@
 #include <type_traits>
 
 namespace snitch {
+
+template<typename T>
+concept integral = std::is_integral_v<T>;
+
 template<typename T>
-concept signed_integral = std::is_signed_v<T>;
+concept signed_integral = integral<T> && std::is_signed_v<T>;
 
 template<typename T>
-concept unsigned_integral = std::is_unsigned_v<T>;
+concept unsigned_integral = integral<T> && std::is_unsigned_v<T>;
 
 template<typename T>
 concept floating_point = std::is_floating_point_v<T>;
 
 template<typename T, typename U>
 concept convertible_to = std::is_convertible_v<T, U>;
 
+template<typename T, typename U>
+concept same_as = std::is_same_v<T, U>;
+
 template<typename T>
 concept enumeration = std::is_enum_v<T>;
 

include/snitch/snitch_config.hpp.config

@@ -65,6 +65,9 @@
 #if !defined(SNITCH_CONSTEXPR_FLOAT_USE_BITCAST)
 #cmakedefine01 SNITCH_CONSTEXPR_FLOAT_USE_BITCAST
 #endif
+#if !defined(SNITCH_APPEND_TO_CHARS)
+#cmakedefine01 SNITCH_APPEND_TO_CHARS
+#endif
 #if !defined(SNITCH_DECOMPOSE_SUCCESSFUL_ASSERTIONS)
 #cmakedefine01 SNITCH_DECOMPOSE_SUCCESSFUL_ASSERTIONS
 #endif
@@ -111,6 +114,13 @@
 #    define SNITCH_CONSTEXPR_FLOAT_USE_BITCAST 0
 #endif
 
+#if (!defined(__cpp_lib_to_chars)) || (defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE <= 11) ||     \
+    (defined(_LIBCPP_VERSION) && _LIBCPP_VERSION <= 14000) ||                                      \
+    (defined(_MSC_VER) && _MSC_VER <= 1924)
+#    undef SNITCH_APPEND_TO_CHARS
+#    define SNITCH_APPEND_TO_CHARS 0
+#endif
+
 #if SNITCH_SHARED_LIBRARY
 #    if defined(_MSC_VER)
 #        if defined(SNITCH_EXPORTS)

meson_options.txt

@@ -19,6 +19,7 @@ option('with_multithreading'             ,type: 'boolean', value: true, descript
 option('with_timings'                    ,type: 'boolean' ,value: true, description: 'Measure the time taken by each test case -- disable to speed up tests.')
 option('with_shorthand_macros'           ,type: 'boolean' ,value: true, description: 'Use short names for test macros -- disable if this causes conflicts.')
 option('constexpr_float_use_bitcast'     ,type: 'boolean' ,value: true, description: 'Use std::bit_cast if available to implement exact constexpr float-to-string conversion.')
+option('snitch_append_to_chars'          ,type: 'boolean' ,value: true, description: 'Use std::to_chars for string conversions -- disable for greater compatability with a slight performance cost.')
 option('default_with_color'              ,type: 'boolean' ,value: true, description: 'Enable terminal colors by default -- can also be controlled by command line interface.')
 option('decompose_successful_assertions' ,type: 'boolean' ,value: true, description: 'Enable expression decomposition even for successful assertions -- more expensive.')
 option('with_all_reporters'              ,type: 'boolean' ,value: true, description: 'Allow all built-in reporters to be selected from the command line -- disable for faster compilation.')

snitch/meson.build

@@ -38,6 +38,7 @@ conf_data = configuration_data({
   'SNITCH_WITH_TIMINGS'                    : get_option('with_timings').to_int(),
   'SNITCH_WITH_SHORTHAND_MACROS'           : get_option('with_shorthand_macros').to_int(),
   'SNITCH_CONSTEXPR_FLOAT_USE_BITCAST'     : get_option('constexpr_float_use_bitcast').to_int(),
+  'SNITCH_APPEND_TO_CHARS'                 : get_option('snitch_append_to_chars').to_int(),
   'SNITCH_DEFAULT_WITH_COLOR'              : get_option('default_with_color').to_int(),
   'SNITCH_DECOMPOSE_SUCCESSFUL_ASSERTIONS' : get_option('decompose_successful_assertions').to_int(),
   'SNITCH_WITH_ALL_REPORTERS'              : get_option('with_all_reporters').to_int(),

src/snitch_append.cpp

@@ -1,65 +1,74 @@
 #include "snitch/snitch_append.hpp"
 
-#include <cinttypes> // for format strings
-#include <cstdio> // for std::snprintf
+#include "snitch/snitch_concepts.hpp"
+#include "snitch/snitch_string.hpp"
+
+#include <cstdint> // for std::uintptr_t
 #include <cstring> // for std::memmove
+#if SNITCH_APPEND_TO_CHARS
+#    include <charconv> // for std::to_chars
+#    include <system_error> // for std::errc
+#endif
 
 namespace snitch::impl {
 namespace {
 using snitch::small_string_span;
-
-template<typename T>
-constexpr const char* get_format_code() noexcept {
-    if constexpr (std::is_same_v<T, const void*>) {
-#if defined(_MSC_VER)
-        return "0x%p";
-#else
-        return "%p";
-#endif
-    } else if constexpr (std::is_same_v<T, std::uintmax_t>) {
-        return "%" PRIuMAX;
-    } else if constexpr (std::is_same_v<T, std::intmax_t>) {
-        return "%" PRIdMAX;
-    } else if constexpr (std::is_same_v<T, float>) {
-        return "%.6e";
-    } else if constexpr (std::is_same_v<T, double>) {
-        return "%.15e";
-    } else {
-        static_assert(!std::is_same_v<T, T>, "unsupported type");
+using namespace std::literals;
+
+#if SNITCH_APPEND_TO_CHARS
+template<floating_point T>
+bool append_to(small_string_span ss, T value) noexcept {
+    constexpr auto fmt       = std::chars_format::scientific;
+    constexpr auto precision = same_as<float, std::remove_cvref_t<T>> ? 6 : 15;
+    auto [end, err] = std::to_chars(ss.end(), ss.begin() + ss.capacity(), value, fmt, precision);
+    if (err != std::errc{}) {
+        // Not enough space, try into a temporary string that *should* be big enough,
+        // and copy whatever we can. 32 characters is enough for all integers and floating
+        // point values encoded on 64 bit or less.
+        small_string<32> fallback;
+        auto [end2, err2] = std::to_chars(
+            fallback.end(), fallback.begin() + fallback.capacity(), value, fmt, precision);
+        if (err2 != std::errc{}) {
+            return false;
+        }
+        fallback.grow(end2 - fallback.begin());
+        return append(ss, fallback);
     }
-}
 
-template<typename T>
-bool append_fmt(small_string_span ss, T value) noexcept {
-    if (ss.available() <= 1) {
-        // snprintf will always print a null-terminating character,
-        // so abort early if only space for one or zero character, as
-        // this would clobber the original string.
-        return false;
-    }
+    ss.grow(end - ss.end());
+    return true;
+}
 
-    // Calculate required length.
-    const int return_code = std::snprintf(nullptr, 0, get_format_code<T>(), value);
-    if (return_code < 0) {
-        return false;
+template<large_int_t Base = 10, integral T>
+bool append_to(small_string_span ss, T value) noexcept {
+    auto [end, err] = std::to_chars(ss.end(), ss.begin() + ss.capacity(), value, Base);
+    if (err != std::errc{}) {
+        // Not enough space, try into a temporary string that *should* be big enough,
+        // and copy whatever we can. 32 characters is enough for all integers and floating
+        // point values encoded on 64 bit or less.
+        small_string<32> fallback;
+        auto [end2, err2] =
+            std::to_chars(fallback.end(), fallback.begin() + fallback.capacity(), value, Base);
+        if (err2 != std::errc{}) {
+            return false;
+        }
+        fallback.grow(end2 - fallback.begin());
+        return append(ss, fallback);
     }
+    ss.grow(end - ss.end());
+    return true;
+}
+#else
+template<floating_point T>
+bool append_to(small_string_span ss, T value) noexcept {
+    return append_constexpr(ss, value);
+}
 
-    // 'return_code' holds the number of characters that are required,
-    // excluding the null-terminating character, which always gets appended,
-    // so we need to +1.
-    const std::size_t length    = static_cast<std::size_t>(return_code) + 1;
-    const bool        could_fit = length <= ss.available();
-
-    const std::size_t offset     = ss.size();
-    const std::size_t prev_space = ss.available();
-    ss.resize(std::min(ss.size() + length, ss.capacity()));
-    std::snprintf(ss.begin() + offset, prev_space, get_format_code<T>(), value);
-
-    // Pop the null-terminating character, always printed unfortunately.
-    ss.pop_back();
-
-    return could_fit;
+template<large_int_t Base = 10, integral T>
+bool append_to(small_string_span ss, T value) noexcept {
+    return append_constexpr<Base>(ss, value);
 }
+#endif
 } // namespace
 
 bool append_fast(small_string_span ss, std::string_view str) noexcept {
@@ -80,24 +89,42 @@ bool append_fast(small_string_span ss, std::string_view str) noexcept {
 bool append_fast(small_string_span ss, const void* ptr) noexcept {
     if (ptr == nullptr) {
         return append(ss, nullptr);
-    } else {
-        return append_fmt(ss, ptr);
     }
+
+    if (!append_fast(ss, "0x"sv)) {
+        return false;
+    }
+
+    const auto int_ptr = reinterpret_cast<std::uintptr_t>(ptr);
+
+    // Pad with zeros.
+    constexpr std::size_t max_digits = 2 * sizeof(void*);
+    std::size_t           padding    = max_digits - num_digits<16>(int_ptr);
+    while (padding > 0) {
+        constexpr std::string_view zeroes = "0000000000000000";
+        const std::size_t          batch  = std::min(zeroes.size(), padding);
+        if (!append_fast(ss, zeroes.substr(0, batch))) {
+            return false;
+        }
+
+        padding -= batch;
+    }
+    return append_to<16>(ss, int_ptr);
 }
 
 bool append_fast(small_string_span ss, large_uint_t i) noexcept {
-    return append_fmt(ss, i);
+    return append_to(ss, i);
 }
 
 bool append_fast(small_string_span ss, large_int_t i) noexcept {
-    return append_fmt(ss, i);
+    return append_to(ss, i);
 }
 
 bool append_fast(small_string_span ss, float f) noexcept {
-    return append_fmt(ss, f);
+    return append_to(ss, f);
 }
 
 bool append_fast(small_string_span ss, double d) noexcept {
-    return append_fmt(ss, d);
+    return append_to(ss, d);
 }
 } // namespace snitch::impl