From 93708c0c1c450fa1a3b81197504ade4e6cd55ed0 Mon Sep 17 00:00:00 2001
From: Ben Vanik <ben.vanik@gmail.com>
Date: Mon, 9 Nov 2015 11:13:34 -0800
Subject: [PATCH] xe::format_string utility.

---
 src/xenia/base/string.cc | 23 +++++++++++++++++++++++
 src/xenia/base/string.h  | 10 ++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/xenia/base/string.cc b/src/xenia/base/string.cc
index 129323cf7..e6cf5b651 100644
--- a/src/xenia/base/string.cc
+++ b/src/xenia/base/string.cc
@@ -40,6 +40,29 @@ std::wstring to_wstring(const std::string& source) {
 #endif  // XE_PLATFORM_LINUX
 }
 
+std::string format_string(const char* format, va_list args) {
+  if (!format) {
+    return "";
+  }
+  size_t max_len = 64;
+  std::string new_s;
+  while (true) {
+    new_s.resize(max_len);
+    int ret =
+        std::vsnprintf(const_cast<char*>(new_s.data()), max_len, format, args);
+    if (ret > max_len) {
+      // Needed size is known (+2 for termination and avoid ambiguity).
+      max_len = ret + 2;
+    } else if (ret == -1 || ret >= max_len - 1) {
+      // Handle some buggy vsnprintf implementations.
+      max_len *= 2;
+    } else {
+      // Everything fit for sure.
+      return new_s;
+    }
+  }
+}
+
 std::string::size_type find_first_of_case(const std::string& target,
                                           const std::string& search) {
   const char* str = target.c_str();
diff --git a/src/xenia/base/string.h b/src/xenia/base/string.h
index a23951798..9cab4645f 100644
--- a/src/xenia/base/string.h
+++ b/src/xenia/base/string.h
@@ -10,6 +10,7 @@
 #ifndef XENIA_BASE_STRING_H_
 #define XENIA_BASE_STRING_H_
 
+#include <cstdarg>
 #include <cstdio>
 #include <string>
 #include <utility>
@@ -22,6 +23,15 @@ namespace xe {
 std::string to_string(const std::wstring& source);
 std::wstring to_wstring(const std::string& source);
 
+std::string format_string(const char* format, va_list args);
+inline std::string format_string(const char* format, ...) {
+  va_list va;
+  va_start(va, format);
+  auto result = format_string(format, va);
+  va_end(va);
+  return result;
+}
+
 // find_first_of string, case insensitive.
 std::string::size_type find_first_of_case(const std::string& target,
                                           const std::string& search);