USB: Separate the descriptor copy logic

The descriptor copy code is not actually the same in HIDv4 and VEN,
so it did not make a lot of sense to put it in USB/Common.cpp.
Separate and move it to HIDv4 and VEN.

This cleanup is important because there are even more differences
between HIDv4 and HIDv5.

4 files changed, 77 insertions, 80 deletions

diff --git a/Source/Core/Core/IOS/USB/Common.cpp b/Source/Core/Core/IOS/USB/Common.cpp
index a9627b0974..a91ac518b1 100644
--- a/Source/Core/Core/IOS/USB/Common.cpp
+++ b/Source/Core/Core/IOS/USB/Common.cpp
@@ -6,7 +6,6 @@
 
 #include <algorithm>
 
-#include "Common/Align.h"
 #include "Common/Assert.h"
 #include "Common/CommonTypes.h"
 #include "Common/StringUtil.h"
@@ -70,82 +69,26 @@ bool Device::HasClass(const u8 device_class) const
   });
 }
 
-static void CopyToBufferAligned(std::vector<u8>* buffer, const void* data, const size_t size)
+void DeviceDescriptor::Swap()
 {
-  buffer->insert(buffer->end(), static_cast<const u8*>(data), static_cast<const u8*>(data) + size);
-  const size_t number_of_padding_bytes = Common::AlignUp(size, 4) - size;
-  buffer->insert(buffer->end(), number_of_padding_bytes, 0);
+  bcdUSB = Common::swap16(bcdUSB);
+  idVendor = Common::swap16(idVendor);
+  idProduct = Common::swap16(idProduct);
+  bcdDevice = Common::swap16(bcdDevice);
 }
 
-static void CopyDescriptorToBuffer(std::vector<u8>* buffer, DeviceDescriptor descriptor)
+void ConfigDescriptor::Swap()
 {
-  descriptor.bcdUSB = Common::swap16(descriptor.bcdUSB);
-  descriptor.idVendor = Common::swap16(descriptor.idVendor);
-  descriptor.idProduct = Common::swap16(descriptor.idProduct);
-  descriptor.bcdDevice = Common::swap16(descriptor.bcdDevice);
-  CopyToBufferAligned(buffer, &descriptor, descriptor.bLength);
+  wTotalLength = Common::swap16(wTotalLength);
 }
 
-static void CopyDescriptorToBuffer(std::vector<u8>* buffer, ConfigDescriptor descriptor)
+void InterfaceDescriptor::Swap()
 {
-  descriptor.wTotalLength = Common::swap16(descriptor.wTotalLength);
-  CopyToBufferAligned(buffer, &descriptor, descriptor.bLength);
 }
 
-static void CopyDescriptorToBuffer(std::vector<u8>* buffer, InterfaceDescriptor descriptor)
+void EndpointDescriptor::Swap()
 {
-  CopyToBufferAligned(buffer, &descriptor, descriptor.bLength);
-}
-
-static void CopyDescriptorToBuffer(std::vector<u8>* buffer, EndpointDescriptor descriptor)
-{
-  descriptor.wMaxPacketSize = Common::swap16(descriptor.wMaxPacketSize);
-  // IOS only copies 8 bytes from the endpoint descriptor, regardless of the actual length
-  CopyToBufferAligned(buffer, &descriptor, sizeof(descriptor));
-}
-
-std::vector<u8> Device::GetDescriptorsUSBV4() const
-{
-  return GetDescriptors([](const auto& descriptor) { return true; });
-}
-
-std::vector<u8> Device::GetDescriptorsUSBV5(const u8 interface, const u8 alt_setting) const
-{
-  return GetDescriptors([interface, alt_setting](const auto& descriptor) {
-    // The USBV5 interfaces present each interface as a different device,
-    // and the descriptors are filtered by alternate setting.
-    return descriptor.bInterfaceNumber == interface && descriptor.bAlternateSetting == alt_setting;
-  });
-}
-
-std::vector<u8>
-Device::GetDescriptors(std::function<bool(const InterfaceDescriptor&)> predicate) const
-{
-  std::vector<u8> buffer;
-
-  const auto device_descriptor = GetDeviceDescriptor();
-  CopyDescriptorToBuffer(&buffer, device_descriptor);
-
-  const auto configurations = GetConfigurations();
-  for (size_t c = 0; c < configurations.size(); ++c)
-  {
-    const auto& config_descriptor = configurations[c];
-    CopyDescriptorToBuffer(&buffer, config_descriptor);
-
-    const auto interfaces = GetInterfaces(static_cast<u8>(c));
-    for (size_t i = interfaces.size(); i-- > 0;)
-    {
-      const auto& descriptor = interfaces[i];
-      if (!predicate(descriptor))
-        continue;
-
-      CopyDescriptorToBuffer(&buffer, descriptor);
-      for (const auto& endpoint_descriptor : GetEndpoints(
-               static_cast<u8>(c), descriptor.bInterfaceNumber, descriptor.bAlternateSetting))
-        CopyDescriptorToBuffer(&buffer, endpoint_descriptor);
-    }
-  }
-  return buffer;
+  wMaxPacketSize = Common::swap16(wMaxPacketSize);
 }
 
 std::string Device::GetErrorName(const int error_code) const
diff --git a/Source/Core/Core/IOS/USB/Common.h b/Source/Core/Core/IOS/USB/Common.h
index 9efb6630a1..2013716a07 100644
--- a/Source/Core/Core/IOS/USB/Common.h
+++ b/Source/Core/Core/IOS/USB/Common.h
@@ -44,6 +44,7 @@ constexpr u16 USBHDR(u8 dir, u8 type, u8 recipient, u8 request)
 
 struct DeviceDescriptor
 {
+  void Swap();
   u8 bLength;
   u8 bDescriptorType;
   u16 bcdUSB;
@@ -62,6 +63,7 @@ struct DeviceDescriptor
 
 struct ConfigDescriptor
 {
+  void Swap();
   u8 bLength;
   u8 bDescriptorType;
   u16 wTotalLength;
@@ -74,6 +76,7 @@ struct ConfigDescriptor
 
 struct InterfaceDescriptor
 {
+  void Swap();
   u8 bLength;
   u8 bDescriptorType;
   u8 bInterfaceNumber;
@@ -87,6 +90,7 @@ struct InterfaceDescriptor
 
 struct EndpointDescriptor
 {
+  void Swap();
   u8 bLength;
   u8 bDescriptorType;
   u8 bEndpointAddress;
@@ -158,8 +162,6 @@ public:
   u16 GetVid() const;
   u16 GetPid() const;
   bool HasClass(u8 device_class) const;
-  std::vector<u8> GetDescriptorsUSBV4() const;
-  std::vector<u8> GetDescriptorsUSBV5(u8 interface, u8 alt_setting) const;
 
   virtual DeviceDescriptor GetDeviceDescriptor() const = 0;
   virtual std::vector<ConfigDescriptor> GetConfigurations() const = 0;
@@ -178,7 +180,6 @@ public:
   virtual int SubmitTransfer(std::unique_ptr<IsoMessage> message) = 0;
 
 protected:
-  std::vector<u8> GetDescriptors(std::function<bool(const InterfaceDescriptor&)> predicate) const;
   u64 m_id = 0xFFFFFFFFFFFFFFFF;
 };
 }  // namespace USB
diff --git a/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp b/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
index edcf8b18c3..b0a1606e6c 100644
--- a/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
+++ b/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
@@ -210,6 +210,40 @@ void USB_HIDv4::TriggerDeviceChangeReply()
   m_devicechange_hook_request.reset();
 }
 
+template <typename T>
+static void CopyDescriptorToBuffer(std::vector<u8>* buffer, T descriptor)
+{
+  const size_t size = sizeof(descriptor);
+  descriptor.Swap();
+  buffer->insert(buffer->end(), reinterpret_cast<const u8*>(&descriptor),
+                 reinterpret_cast<const u8*>(&descriptor) + size);
+  const size_t number_of_padding_bytes = Common::AlignUp(size, 4) - size;
+  buffer->insert(buffer->end(), number_of_padding_bytes, 0);
+}
+
+static std::vector<u8> GetDescriptors(const USB::Device& device)
+{
+  std::vector<u8> buffer;
+
+  CopyDescriptorToBuffer(&buffer, device.GetDeviceDescriptor());
+  const auto configurations = device.GetConfigurations();
+  for (size_t c = 0; c < configurations.size(); ++c)
+  {
+    CopyDescriptorToBuffer(&buffer, configurations[c]);
+    const auto interfaces = device.GetInterfaces(static_cast<u8>(c));
+    for (size_t i = interfaces.size(); i-- > 0;)
+    {
+      CopyDescriptorToBuffer(&buffer, interfaces[i]);
+      for (const auto& endpoint_descriptor : device.GetEndpoints(
+               static_cast<u8>(c), interfaces[i].bInterfaceNumber, interfaces[i].bAlternateSetting))
+      {
+        CopyDescriptorToBuffer(&buffer, endpoint_descriptor);
+      }
+    }
+  }
+  return buffer;
+}
+
 std::vector<u8> USB_HIDv4::GetDeviceEntry(const USB::Device& device) const
 {
   std::lock_guard<std::mutex> id_map_lock{m_id_map_mutex};
@@ -219,7 +253,7 @@ std::vector<u8> USB_HIDv4::GetDeviceEntry(const USB::Device& device) const
   //   4-8 bytes: device ID
   //   the rest of the buffer is device descriptors data
   std::vector<u8> entry(8);
-  const std::vector<u8> descriptors = device.GetDescriptorsUSBV4();
+  const std::vector<u8> descriptors = GetDescriptors(device);
   const u32 entry_size = Common::swap32(static_cast<u32>(entry.size() + descriptors.size()));
   const u32 ios_device_id = Common::swap32(m_device_ids.at(device.GetId()));
   std::memcpy(entry.data(), &entry_size, sizeof(entry_size));
diff --git a/Source/Core/Core/IOS/USB/USB_VEN/VEN.cpp b/Source/Core/Core/IOS/USB/USB_VEN/VEN.cpp
index 552d278863..27fb03087d 100644
--- a/Source/Core/Core/IOS/USB/USB_VEN/VEN.cpp
+++ b/Source/Core/Core/IOS/USB/USB_VEN/VEN.cpp
@@ -186,20 +186,39 @@ IPCCommandResult USB_VEN::GetDeviceInfo(USBV5Device& device, const IOCtlRequest&
   if (request.buffer_out == 0 || request.buffer_out_size != 0xc0)
     return GetDefaultReply(IPC_EINVAL);
 
-  const auto host_device = GetDeviceById(device.host_id);
+  const std::shared_ptr<USB::Device> host_device = GetDeviceById(device.host_id);
   const u8 alt_setting = Memory::Read_U8(request.buffer_in + 8);
-  auto descriptors = host_device->GetDescriptorsUSBV5(device.interface_number, alt_setting);
-  if (descriptors.empty())
-    return GetDefaultReply(IPC_ENOENT);
-
-  descriptors.resize(request.buffer_out_size - 20);
-  if (descriptors.size() > request.buffer_out_size - 20)
-    WARN_LOG(IOS_USB, "Buffer is too large. Only the first 172 bytes will be copied.");
 
   Memory::Memset(request.buffer_out, 0, request.buffer_out_size);
   Memory::Write_U32(Memory::Read_U32(request.buffer_in), request.buffer_out);
   Memory::Write_U32(1, request.buffer_out + 4);
-  Memory::CopyToEmu(request.buffer_out + 20, descriptors.data(), descriptors.size());
+
+  USB::DeviceDescriptor device_descriptor = host_device->GetDeviceDescriptor();
+  device_descriptor.Swap();
+  Memory::CopyToEmu(request.buffer_out + 20, &device_descriptor, sizeof(device_descriptor));
+
+  // VEN only cares about the first configuration.
+  USB::ConfigDescriptor config_descriptor = host_device->GetConfigurations()[0];
+  config_descriptor.Swap();
+  Memory::CopyToEmu(request.buffer_out + 40, &config_descriptor, sizeof(config_descriptor));
+
+  std::vector<USB::InterfaceDescriptor> interfaces = host_device->GetInterfaces(0);
+  auto it = std::find_if(interfaces.begin(), interfaces.end(), [&](const auto& interface) {
+    return interface.bInterfaceNumber == device.interface_number &&
+           interface.bAlternateSetting == alt_setting;
+  });
+  if (it == interfaces.end())
+    return GetDefaultReply(IPC_EINVAL);
+  it->Swap();
+  Memory::CopyToEmu(request.buffer_out + 52, &*it, sizeof(*it));
+
+  auto endpoints = host_device->GetEndpoints(0, it->bInterfaceNumber, it->bAlternateSetting);
+  for (size_t i = 0; i < endpoints.size(); ++i)
+  {
+    endpoints[i].Swap();
+    Memory::CopyToEmu(request.buffer_out + 64 + 8 * static_cast<u8>(i), &endpoints[i],
+                      sizeof(endpoints[i]));
+  }
 
   return GetDefaultReply(IPC_SUCCESS);
 }