Added missing return in format_decimal(); Added first support for negative numbers

inc/format.h

@@ -40,21 +40,16 @@ constexpr inline void check_fmt_params() {
  *
  */
 
-// TODO: Error handling
 template <fmt_data_t fmt_data, std::integral arg_t>
 constexpr inline void format_arg(char* dest, arg_t arg) {
-    constexpr auto error_array = get_init_array<fmt_data.length>('f');
-
     detail::format_int(dest, arg, fmt_data);
 };
-// TODO: Error handling
+
 template <fmt_data_t fmt_data, std::floating_point arg_t>
 constexpr inline void format_arg(char* dest, arg_t arg) {
-    *(dest) = 'f';
-    *(dest + fmt_data.length - fmt_data.precision - 1) = '.';
-
     //detail::format_float(dest, arg, fmt_data);
 };
+
 // TODO: Error handling
 template<fmt_data_t fmt_data>
 constexpr inline void format_arg(char* dest, const char* arg) {
@@ -87,7 +82,7 @@ constexpr inline void format_args(char* dest, first_arg_t first_arg, args_t... a
 
 template <auto ast>
 consteval inline std::array<char, get_ast_output_len<ast>()> get_preproc_string() {
-    auto result = get_init_array<get_ast_output_len<ast>()>('0');
+    auto result = get_init_array<get_ast_output_len<ast>()>('f');
 
     int i = 0;
 

inc/format_impl.h

@@ -26,10 +26,44 @@ namespace detail {
  */
 
 
-#define FMT_POWERS_OF_10(factor)                                             \
+#define FMT_POWERS_OF_10(factor)                                               \
-  factor * 10, (factor)*100, (factor)*1000, (factor)*10000, (factor)*100000, \
+    factor * 10, (factor)*100, (factor)*1000, (factor)*10000, (factor)*100000, \
-      (factor)*1000000, (factor)*10000000, (factor)*100000000,               \
+        (factor)*1000000, (factor)*10000000, (factor)*100000000,               \
-      (factor)*1000000000
+        (factor)*1000000000
+
+template <typename T>
+constexpr int count_digits_fallback(T n) {
+    int count = 1;
+    for (;;) {
+        if (n < 10) return count;
+        if (n < 100) return count + 1;
+        if (n < 1000) return count + 2;
+        if (n < 10000) return count + 3;
+        n /= 10000u;
+        count += 4;
+    }
+}
+
+inline int do_count_digits(uint64_t n) {
+    // Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
+    static constexpr uint8_t bsr2log10[] = {
+        1,  1,  1,  2,  2,  2,  3,  3,  3,  4,  4,  4,  4,  5,  5,  5,
+        6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9,  10, 10, 10,
+        10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
+        15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
+    auto                            t = bsr2log10[__builtin_clzll(n | 1) ^ 63];
+    static constexpr const uint64_t zero_or_powers_of_10[] = {
+        0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
+        10000000000000000000ULL};
+    return t - (n < zero_or_powers_of_10[t]);
+}
+
+constexpr inline auto count_digits(uint64_t n) -> int {
+    if (!std::is_constant_evaluated()) {
+        return do_count_digits(n);
+    }
+    return count_digits_fallback(n);
+}
 
 
 // Converts value in the range [0, 100) to a string.
@@ -54,6 +88,8 @@ constexpr inline void copy2(char* dst, const char* src) {
 
 template <typename uint_t>
 constexpr inline void format_decimal(char* out, uint_t value, int size) {
+    if (count_digits(value) > size) return;
+
     out += size;
     while (value >= 100) {
         out -= 2;
@@ -61,46 +97,15 @@ constexpr inline void format_decimal(char* out, uint_t value, int size) {
         value /= 100;
     }
 
-    if (value < 10) *--out = static_cast<char>('0' + value);
+    if (value < 10) {
+        *--out = static_cast<char>('0' + value);
+        return;
+    }
 
     out -= 2;
     copy2(out, digits2(static_cast<size_t>(value)));
 }
 
-template <typename T>
-constexpr int count_digits_fallback(T n) {
-    int count = 1;
-    for (;;) {
-        if (n < 10) return count;
-        if (n < 100) return count + 1;
-        if (n < 1000) return count + 2;
-        if (n < 10000) return count + 3;
-        n /= 10000u;
-        count += 4;
-    }
-}
-
-inline int do_count_digits(uint64_t n) {
-  // Maps bsr(n) to ceil(log10(pow(2, bsr(n) + 1) - 1)).
-  static constexpr uint8_t bsr2log10[] = {
-      1,  1,  1,  2,  2,  2,  3,  3,  3,  4,  4,  4,  4,  5,  5,  5,
-      6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9,  10, 10, 10,
-      10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
-      15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20};
-  auto t = bsr2log10[__builtin_clzll(n | 1) ^ 63];
-  static constexpr const uint64_t zero_or_powers_of_10[] = {
-      0, 0, FMT_POWERS_OF_10(1U), FMT_POWERS_OF_10(1000000000ULL),
-      10000000000000000000ULL};
-  return t - (n < zero_or_powers_of_10[t]);
-}
-
-constexpr inline auto count_digits(uint64_t n) -> int {
-    if (!std::is_constant_evaluated()) {
-        return do_count_digits(n);
-    }
-    return count_digits_fallback(n);
-}
-
 
 /*
  *
@@ -116,8 +121,14 @@ constexpr inline void format_int(char* out, uint_t value, fmt_data_t fmt_node) {
 
 template <std::signed_integral uint_t>
 constexpr inline void format_int(char* out, uint_t value, fmt_data_t fmt_node) {
-    if (value < 0) value = -value;
+    auto       abs_value = static_cast<uint64_t>(value);
-    format_decimal(out, value, fmt_node.length);
+    const bool negative  = value < 0;
+
+    if (negative) abs_value = 0 - abs_value;
+    format_decimal(out + 1 * (negative), abs_value,
+                   fmt_node.length - 1 * (negative));
+
+    if (negative) *out = '-';
 }
 
 
@@ -130,8 +141,10 @@ constexpr inline void format_int(char* out, uint_t value, fmt_data_t fmt_node) {
 
 template <std::floating_point float_t>
 constexpr inline void format_float(char* out, float_t value,
-                                   fmt_data_t fmt_node) {
+                                   fmt_data_t fmt_data) {
-    // TODO
+
+    *(out)                                            = 'f';
+    *(out + fmt_data.length - fmt_data.precision - 1) = '.';
 }
 
 

src/main.cpp

@@ -4,11 +4,12 @@
 
 
 int main(int argc, char* argv[]) {
-    auto formatted = "Test: {:12} {:012.5} {:8}"_fmt(argv[0], argc, -1234);
+    auto formatted = "Test: {:12} {:012.5} {:8}"_fmt(argv[0], 123.45, -1234567);
 
     for (const auto& c : formatted)
         std::cout << c;
     std::cout << std::endl;
 
-    return formatted[6];
+//    return formatted[6];
+    return 0;
 }