[XAM] Improvement rollup. Content, enumerators...

- [Kernel] Create guest object for XEnumerator.
- [XAM] Split content data into host/guest variants.
- [XAM] Correct message return type from RESULT to HRESULT.
- [XAM] Add a new dummy content device for ODD.
- [XAM] Implement XamContentAggregateCreateEnumerator.
- [XAM] Implement XamGetPrivateEnumStructureFromHandle.
- [XAM] Implement XMsgCompleteIORequest (sketchy).
- [XAM] Implement XamGetOverlappedResult (sketchy).
- [XAM] Implement XamTaskSchedule (sketchy).

src/xenia/base/string_util.h

@@ -34,6 +34,11 @@
 namespace xe {
 namespace string_util {
 
+enum class Safety {
+  IDontKnowWhatIAmDoing,
+  IKnowWhatIAmDoing,
+};
+
 inline size_t copy_truncating(char* dest, const std::string_view source,
                               size_t dest_buffer_count) {
   if (!dest_buffer_count) {
@@ -68,6 +73,44 @@ inline size_t copy_and_swap_truncating(char16_t* dest,
   return chars_copied;
 }
 
+template <Safety safety = Safety::IDontKnowWhatIAmDoing>
+inline size_t copy_maybe_truncating(char* dest, const std::string_view source,
+                                    size_t dest_buffer_count) {
+  static_assert(safety == Safety::IKnowWhatIAmDoing);
+  if (!dest_buffer_count) {
+    return 0;
+  }
+  size_t chars_copied = std::min(source.size(), dest_buffer_count);
+  std::memcpy(dest, source.data(), chars_copied);
+  return chars_copied;
+}
+
+template <Safety safety = Safety::IDontKnowWhatIAmDoing>
+inline size_t copy_maybe_truncating(char16_t* dest,
+                                    const std::u16string_view source,
+                                    size_t dest_buffer_count) {
+  static_assert(safety == Safety::IKnowWhatIAmDoing);
+  if (!dest_buffer_count) {
+    return 0;
+  }
+  size_t chars_copied = std::min(source.size(), dest_buffer_count);
+  std::memcpy(dest, source.data(), chars_copied * sizeof(char16_t));
+  return chars_copied;
+}
+
+template <Safety safety = Safety::IDontKnowWhatIAmDoing>
+inline size_t copy_and_swap_maybe_truncating(char16_t* dest,
+                                             const std::u16string_view source,
+                                             size_t dest_buffer_count) {
+  static_assert(safety == Safety::IKnowWhatIAmDoing);
+  if (!dest_buffer_count) {
+    return 0;
+  }
+  size_t chars_copied = std::min(source.size(), dest_buffer_count);
+  xe::copy_and_swap(dest, source.data(), chars_copied);
+  return chars_copied;
+}
+
 inline std::string to_hex_string(uint32_t value) {
   return fmt::format("{:08X}", value);
 }