Shamelessly copied fmtlib code for decimal formatting; Added comment with idea about error handling

CMakeLists.txt

@@ -17,7 +17,7 @@ add_executable(logger src/main.cpp)
 if(MSVC)
     target_compile_options(logger PRIVATE /W4 /WX)
 else()
-    target_compile_options(logger PRIVATE -Wall -Wextra -pedantic)
+    target_compile_options(logger PRIVATE -O3 -Wall -Wextra -pedantic -fno-exceptions)
 endif()
 
 

inc/format.h

@@ -2,9 +2,11 @@
 #define LOGGER_FORMAT_H
 
 
+#include <cstring>
+
 #include "parse.h"
 #include "utility.h"
-#include <cstring>
+#include "format_impl.h"
 
 
 namespace detail {
@@ -32,16 +34,6 @@ constexpr void check_fmt_params() {
 }
 
 
-/*
- *
- * Type-specific formatting functions
- *      (Most of this code is shamelessly stolen from fmtlib)
- */
-
-
-// TODO
-
-
 /*
  *
  *  Formatting wrapper functions
@@ -50,14 +42,12 @@ constexpr void check_fmt_params() {
 
 
 template <std::integral arg_t>
-constexpr void format_arg(char* dest, fmt_data_t fmt_data, arg_t) {
-    *(dest + fmt_data.position) = 'i';
-    //    dest = dest + fmt_data.position;
-    //    format_int(dest, fmt_data.length, arg);
+constexpr void format_arg(char* dest, fmt_data_t fmt_data, arg_t arg) {
+    detail::format_integral(dest, arg, fmt_data);
 };
+
 template <std::floating_point arg_t>
 constexpr void format_arg(char* dest, fmt_data_t fmt_data, arg_t) {
-    dest    = dest + fmt_data.position;
     *(dest) = 'f';
     *(dest + fmt_data.length - fmt_data.precision - 1) = '.';
 };
@@ -66,7 +56,7 @@ constexpr void format_arg(char* dest, fmt_data_t fmt_data, const char* arg) {
     const std::size_t len = const_strlen(arg);
     if (len > fmt_data.length) return;
 
-    dest = dest + fmt_data.position + fmt_data.length - len;
+    dest = dest + fmt_data.length - len;
 
     if (!std::is_constant_evaluated()) {
         std::memcpy(dest, arg, len);
@@ -84,7 +74,7 @@ constexpr void format_args(char*) {
 
 template <auto fmt_data_array, typename first_arg_t, typename... args_t>
 constexpr void format_args(char* dest, first_arg_t first_arg, args_t... args) {
-    format_arg(dest, fmt_data_array[0], first_arg);
+    format_arg(dest + fmt_data_array[0].position, fmt_data_array[0], first_arg);
     format_args<drop_first(fmt_data_array)>(dest, args...);
 }
 
@@ -117,7 +107,7 @@ consteval std::array<char, get_ast_output_len<ast>()> get_preproc_string() {
 
 
 template <detail::ConstString s, typename... args_t>
-constexpr std::array<char, detail::get_output_len<s>()> format(args_t... args) {
+constexpr auto format(args_t... args) {
     constexpr auto ast      = detail::parse_string<s>().value;
     constexpr auto fmt_data = detail::get_fmt_data<ast>();
 
@@ -128,6 +118,7 @@ constexpr std::array<char, detail::get_output_len<s>()> format(args_t... args) {
     return result;
 }
 
+
 template<detail::ConstString t_s>
 class fmt_literal_obj_t {
     public:

inc/format_impl.h

@@ -0,0 +1,105 @@
+#ifndef LOGGER_FORMAT_IMPL_H
+#define LOGGER_FORMAT_IMPL_H
+
+
+/*
+ *
+ * ****************************************************************
+ * Disclaimer: Most of this code is shamelessly stolen from fmtlib
+ * ****************************************************************
+ *
+ */
+
+
+#include "utility.h"
+
+
+namespace detail {
+
+
+/*
+ *
+ * Utility functions
+ *
+ */
+
+
+// Converts value in the range [0, 100) to a string.
+constexpr inline const char* digits2(size_t value) {
+    // GCC generates slightly better code when value is pointer-size.
+    return &"0001020304050607080910111213141516171819"
+            "2021222324252627282930313233343536373839"
+            "4041424344454647484950515253545556575859"
+            "6061626364656667686970717273747576777879"
+            "8081828384858687888990919293949596979899"[value * 2];
+}
+
+
+constexpr inline void copy2(char* dst, const char* src) {
+    if (!std::is_constant_evaluated()) {
+        std::memcpy(dst, src, 2);
+        return;
+    }
+
+    *dst++ = static_cast<char>(*src++);
+    *dst   = static_cast<char>(*src);
+}
+
+template <typename UInt>
+constexpr inline void format_decimal(char* out, UInt value, int size) {
+    // TODO: Error handling (Maybe calculate "ffff..." as a constant expression
+    //       and then set the out pointer with a branchless statement)
+
+    out += size;
+    while (value >= 100) {
+        out -= 2;
+        copy2(out, digits2(static_cast<size_t>(value % 100)));
+        value /= 100;
+    }
+
+    if (value < 10) *--out = static_cast<char>('0' + value);
+
+    out -= 2;
+    copy2(out, digits2(static_cast<size_t>(value)));
+}
+
+
+/*
+ *
+ * Integral types
+ *
+ */
+
+
+template <std::unsigned_integral uint_t>
+constexpr inline void format_integral(char* out, uint_t value,
+                                      fmt_data_t fmt_node) {
+    format_decimal(out, value, fmt_node.length);
+}
+
+template <std::signed_integral uint_t>
+constexpr inline void format_integral(char* out, uint_t value,
+                                      fmt_data_t fmt_node) {
+    if (value < 0) value = -value;
+    format_decimal(out, value, fmt_node.length);
+}
+
+
+/*
+ *
+ * Floating point types
+ *
+ */
+
+
+template <std::floating_point float_t>
+constexpr inline void format_integral(char* out, float_t value,
+                                      fmt_data_t fmt_node) {
+    // TODO
+}
+
+
+} // namespace detail
+
+
+#endif // LOGGER_FORMAT_IMPL_H

src/main.cpp

@@ -1,14 +1,14 @@
-#include <iostream>
+//#include <iostream>
 
 #include <Logger.h>
 
 
-int main() {
-    constexpr auto formatted = "Test: {:012.5} {:6} {:8}"_fmt(142.4334, "abcdef", -1234);
+int main(int argc, char* argv[]) {
+    auto formatted = "Test: {:12} {:012.5} {:8}"_fmt(argv[0], argc, -1234);
 
     for (const auto& c : formatted)
         std::cout << c;
     std::cout << std::endl;
 
-    return 0;
+    return formatted[6];
 }