fmt: draft 2

static/text/20250822_fmt_min.cpp

@@ -0,0 +1,65 @@
+#include <cstring>
+
+struct String_Buffer
+{
+	char* str;
+	int cap;
+	int len = 0;
+};
+
+namespace fmt
+{
+
+void write(String_Buffer& buf, const char* str, int len)
+{
+	int remaining_cap = buf.cap - buf.len - 1; // leave one byte for NUL
+	int write_len = len > remaining_cap ? remaining_cap : len;
+	if (write_len > 0)
+		memcpy(buf.str + buf.len, str, write_len);
+	buf.len += len;
+}
+
+void write_value(String_Buffer& buf, const char* value)
+{
+	write(buf, value, strlen(value));
+}
+
+bool next_hole(String_Buffer& buf, const char*& fstr)
+{
+	const char* prefix = fstr;
+	while (*fstr != 0) {
+		if (*fstr == '{') {
+			int len = fstr - prefix;
+			++fstr;
+			if (*fstr == '}') {
+				++fstr;
+				write(buf, prefix, len);
+				return true;
+			}
+			if (*fstr == '{') {
+				write(buf, prefix, len);
+				prefix = fstr;
+				++fstr;
+			}
+		}
+		++fstr;
+	}
+	write(buf, prefix, fstr - prefix);
+	return false;
+}
+
+template<typename T>
+void format_value(String_Buffer& buf, const char*& fstr, const T& value)
+{
+	if (next_hole(buf, fstr))
+		write_value(buf, value);
+}
+
+template<typename... Args>
+void format(String_Buffer& buf, const char* fstr, const Args&... args)
+{
+	(format_value(buf, fstr, args), ...);
+	while (next_hole(buf, fstr)) {}
+}
+
+}