From 3795115641bf5c1d1a3d60313408ba462057ba18 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Mon, 13 Apr 2026 16:18:00 +0200
Subject: kstd/format: add support for char formatting

---
 .../include/kstd/bits/format/formatter/char.hpp    | 94 ++++++++++++++++++++++
 libs/kstd/include/kstd/format                      |  1 +
 libs/kstd/tests/src/format.cpp                     |  8 +-
 3 files changed, 99 insertions(+), 4 deletions(-)
 create mode 100644 libs/kstd/include/kstd/bits/format/formatter/char.hpp

(limited to 'libs/kstd')

diff --git a/libs/kstd/include/kstd/bits/format/formatter/char.hpp b/libs/kstd/include/kstd/bits/format/formatter/char.hpp
new file mode 100644
index 0000000..ddfefe5
--- /dev/null
+++ b/libs/kstd/include/kstd/bits/format/formatter/char.hpp
@@ -0,0 +1,94 @@
+#ifndef KSTD_BITS_FORMAT_FORMATTER_CHAR_HPP
+#define KSTD_BITS_FORMAT_FORMATTER_CHAR_HPP
+
+#include "../context.hpp"
+#include "../error.hpp"
+#include "../formatter.hpp"
+#include "../parse_context.hpp"
+#include "../specifiers.hpp"
+#include "integral.hpp"
+
+#include <iterator>
+
+namespace kstd
+{
+
+  template<>
+  struct formatter<char> : formatter<unsigned char>
+  {
+    bits::format::specifiers specifiers{};
+
+    constexpr auto parse(format_parse_context & context) -> format_parse_context::iterator
+    {
+      specifiers = bits::format::parse_format_specifiers(context);
+
+      auto it = context.begin();
+      auto const end = context.end();
+
+      if (specifiers.alternative_form || specifiers.zero_pad || specifiers.sign != bits::format::sign_mode::none)
+      {
+        bits::format::error("Invalid format specifiers for 'char'");
+      }
+
+      if (it != end && *it != '}')
+      {
+        if (*it == 'c' || *it == 'b' || *it == 'B' || *it == 'd' || *it == 'o' || *it == 'x' || *it == 'X')
+        {
+          specifiers.type = *it;
+          std::advance(it, 1);
+        }
+        else
+        {
+          bits::format::error("Invalid type specifier for char.");
+        }
+      }
+
+      if (it != end && *it != '}')
+      {
+        bits::format::error("Missing terminating '}' in format string.");
+      }
+
+      return it;
+    }
+
+    auto format(char value, format_context & context) const -> void
+    {
+      if (specifiers.type == '\0' || specifiers.type == 'c')
+      {
+        auto final_width = 0uz;
+
+        if (specifiers.mode == bits::format::width_mode::static_value)
+        {
+          final_width = specifiers.width_value;
+        }
+        else if (specifiers.mode == bits::format::width_mode::dynamic_argument_id)
+        {
+          auto const & arg = context.arg(specifiers.width_value);
+          final_width = bits::format::extrat_dynamic_width(arg);
+        }
+
+        auto padding =
+            bits::format::calculate_format_padding(final_width, 1, specifiers.align, bits::format::alignment::left);
+
+        for (auto i = 0uz; i < padding.left; ++i)
+        {
+          context.push(specifiers.fill);
+        }
+
+        context.push(value);
+
+        for (auto i = 0uz; i < padding.right; ++i)
+        {
+          context.push(specifiers.fill);
+        }
+      }
+      else
+      {
+        formatter<unsigned char>::format(static_cast<unsigned char>(value), context);
+      }
+    }
+  };
+
+}  // namespace kstd
+
+#endif
\ No newline at end of file
diff --git a/libs/kstd/include/kstd/format b/libs/kstd/include/kstd/format
index d11c221..047ea5c 100644
--- a/libs/kstd/include/kstd/format
+++ b/libs/kstd/include/kstd/format
@@ -7,6 +7,7 @@
 #include "bits/format/formatter.hpp"              // IWYU pragma: export
 #include "bits/format/formatter/bool.hpp"         // IWYU pragma: export
 #include "bits/format/formatter/byte.hpp"         // IWYU pragma: export
+#include "bits/format/formatter/char.hpp"         // IWYU pragma: export
 #include "bits/format/formatter/cstring.hpp"      // IWYU pragma: export
 #include "bits/format/formatter/integral.hpp"     // IWYU pragma: export
 #include "bits/format/formatter/ordering.hpp"     // IWYU pragma: export
diff --git a/libs/kstd/tests/src/format.cpp b/libs/kstd/tests/src/format.cpp
index 4915e50..73c8102 100644
--- a/libs/kstd/tests/src/format.cpp
+++ b/libs/kstd/tests/src/format.cpp
@@ -40,21 +40,21 @@ SCENARIO("Formatting to a new string", "[format]")
 
     WHEN("calling format with the same number of arguments as there are placeholders")
     {
-      auto result = kstd::format(fmt, 1, true, -100);
+      auto result = kstd::format(fmt, 1, true, 'a');
 
       THEN("the result is the formatted string")
       {
-        REQUIRE(result == "Here are some placeholders: 1 true -100");
+        REQUIRE(result == "Here are some placeholders: 1 true a");
       }
     }
 
     WHEN("calling format with too many arguments")
     {
-      auto result = kstd::format(fmt, 2, false, -200, 4, 5, 6);
+      auto result = kstd::format(fmt, 2, false, 'b', 4, 5, 6);
 
       THEN("the result is the formatted string")
       {
-        REQUIRE(result == "Here are some placeholders: 2 false -200");
+        REQUIRE(result == "Here are some placeholders: 2 false b");
       }
     }
   }
-- 
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