Replace std::ostringstream usage with fmt::format

Source/Core/AudioCommon/WaveFile.cpp

@@ -6,6 +6,8 @@
 
 #include <string>
 
+#include <fmt/format.h>
+
 #include "Common/CommonTypes.h"
 #include "Common/FileUtil.h"
 #include "Common/IOFile.h"
@@ -159,9 +161,9 @@ void WaveFileWriter::AddStereoSamplesBE(const short* sample_data, u32 count,
   {
     Stop();
     file_index++;
-    std::ostringstream filename;
-    filename << File::GetUserPath(D_DUMPAUDIO_IDX) << basename << file_index << ".wav";
-    Start(filename.str(), sample_rate_divisor);
+    const std::string filename =
+        fmt::format("{}{}{}.wav", File::GetUserPath(D_DUMPAUDIO_IDX), basename, file_index);
+    Start(filename, sample_rate_divisor);
     current_sample_rate_divisor = sample_rate_divisor;
   }
 

Source/Core/Common/Debug/Watches.cpp

@@ -7,6 +7,8 @@
 #include <locale>
 #include <sstream>
 
+#include <fmt/format.h>
+
 namespace Common::Debug
 {
 Watch::Watch(u32 address_, std::string name_, State is_enabled_)
@@ -107,13 +109,9 @@ void Watches::LoadFromStrings(const std::vector<std::string>& watches)
 std::vector<std::string> Watches::SaveToStrings() const
 {
   std::vector<std::string> watches;
+  watches.reserve(m_watches.size());
   for (const auto& watch : m_watches)
-  {
-    std::ostringstream ss;
-    ss.imbue(std::locale::classic());
-    ss << std::hex << watch.address << " " << watch.name;
-    watches.push_back(ss.str());
-  }
+    watches.emplace_back(fmt::format("{:x} {}", watch.address, watch.name));
   return watches;
 }
 

Source/Core/Core/NetPlayClient.cpp

@@ -11,7 +11,6 @@
 #include <memory>
 #include <mutex>
 #include <span>
-#include <sstream>
 #include <thread>
 #include <tuple>
 #include <type_traits>
@@ -535,10 +534,7 @@ void NetPlayClient::OnChatMessage(sf::Packet& packet)
   INFO_LOG_FMT(NETPLAY, "Player {} ({}) wrote: {}", player.name, player.pid, msg);
 
   // add to gui
-  std::ostringstream ss;
-  ss << player.name << '[' << char(pid + '0') << "]: " << msg;
-
-  m_dialog->AppendChat(ss.str());
+  m_dialog->AppendChat(fmt::format("{}[{}]: {}", player.name, pid, msg));
 }
 
 void NetPlayClient::OnChunkedDataStart(sf::Packet& packet)

Source/Core/InputCommon/ControllerInterface/CoreDevice.cpp

@@ -162,15 +162,12 @@ void Device::AddCombinedInput(std::string name, const std::pair<std::string, std
 std::string DeviceQualifier::ToString() const
 {
   if (source.empty() && (cid < 0) && name.empty())
-    return "";
+    return {};
 
-  std::ostringstream ss;
-  ss << source << '/';
   if (cid > -1)
-    ss << cid;
-  ss << '/' << name;
-
-  return ss.str();
+    return fmt::format("{}/{}/{}", source, cid, name);
+  else
+    return fmt::format("{}//{}", source, name);
 }
 
 //

Source/Core/InputCommon/ControllerInterface/DInput/DInputJoystick.cpp

@@ -7,9 +7,10 @@
 #include <limits>
 #include <mutex>
 #include <set>
-#include <sstream>
 #include <type_traits>
 
+#include <fmt/format.h>
+
 #include "Common/HRWrap.h"
 #include "Common/Logging/Log.h"
 #include "InputCommon/ControllerInterface/ControllerInterface.h"
@@ -266,37 +267,21 @@ void Joystick::UpdateInput()
 
 std::string Joystick::Button::GetName() const
 {
-  std::ostringstream ss;
-  ss << "Button " << (int)m_index;
-  return ss.str();
+  return fmt::format("Button {}", m_index);
 }
 
 std::string Joystick::Axis::GetName() const
 {
-  std::ostringstream ss;
-  // axis
-  if (m_index < 6)
-  {
-    ss << "Axis " << (char)('X' + (m_index % 3));
-    if (m_index > 2)
-      ss << 'r';
-  }
-  // slider
-  else
-  {
-    ss << "Slider " << (int)(m_index - 6);
-  }
-
-  ss << (m_range < 0 ? '-' : '+');
-  return ss.str();
+  const char sign = m_range < 0 ? '-' : '+';
+  if (m_index < 6)  // axis
+    return fmt::format("Axis {:c}{}{:c}", 'X' + m_index % 3, m_index > 2 ? "r" : "", sign);
+  else  // slider
+    return fmt::format("Slider {}{:c}", m_index - 6, sign);
 }
 
 std::string Joystick::Hat::GetName() const
 {
-  char tmpstr[] = "Hat . .";
-  tmpstr[4] = (char)('0' + m_index);
-  tmpstr[6] = "NESW"[m_direction];
-  return tmpstr;
+  return fmt::format("Hat {} {:c}", m_index, "NESW"[m_direction]);
 }
 
 // get / set state

Source/Core/UICommon/UICommon.cpp

@@ -16,6 +16,8 @@
 #include <wil/resource.h>
 #endif
 
+#include <fmt/format.h>
+
 #include "Common/Common.h"
 #include "Common/CommonPaths.h"
 #include "Common/Config/Config.h"
@@ -551,10 +553,8 @@ std::string FormatSize(u64 bytes, int decimals)
 
   // Don't need exact values, only 5 most significant digits
   const double unit_size = std::pow(2, unit * 10);
-  std::ostringstream ss;
-  ss << std::fixed << std::setprecision(decimals);
-  ss << bytes / unit_size << ' ' << Common::GetStringT(unit_symbols[unit]);
-  return ss.str();
+  return fmt::format("{:.{}Lf} {}", bytes / unit_size, decimals,
+                     Common::GetStringT(unit_symbols[unit]));
 }
 
 }  // namespace UICommon