Add string_format and vstring_format

luna/Format.cpp

@@ -468,3 +468,42 @@ Result<usize> cstyle_format(const char* format, callback_t callback, void* arg,
 
     return state.count;
 }
+
+struct StringFormatInfo
+{
+    char* buffer;
+    size_t remaining;
+};
+
+Result<usize> vstring_format(char* buf, size_t max, const char* format, va_list ap)
+{
+    StringFormatInfo info = {.buffer = buf, .remaining = max - 1};
+
+    usize result = TRY(cstyle_format(
+        format,
+        [](char c, void* arg) -> Result<void> {
+            StringFormatInfo* info_arg = (StringFormatInfo*)arg;
+            if (!info_arg->remaining) return {};
+            *(info_arg->buffer) = c;
+            info_arg->buffer++;
+            info_arg->remaining--;
+            return {};
+        },
+        &info, ap));
+
+    *(info.buffer) = 0;
+
+    return result;
+}
+
+Result<usize> string_format(char* buf, size_t max, const char* format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+
+    usize result = TRY(vstring_format(buf, max, format, ap));
+
+    va_end(ap);
+
+    return result;
+}

luna/Format.h

@@ -6,3 +6,5 @@
 typedef Result<void> (*callback_t)(char, void*);
 
 Result<usize> cstyle_format(const char* format, callback_t callback, void* arg, va_list ap);
+Result<usize> vstring_format(char* buf, size_t max, const char* format, va_list ap);
+Result<usize> string_format(char* buf, size_t max, const char* format, ...);