Cleanup new code, add docs and error handling

src/core/gdbstub/hio.h

@@ -1,4 +1,4 @@
-// Copyright 2022 Citra Emulator Project
+// Copyright 2023 Citra Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
@@ -11,11 +11,14 @@
 namespace GDBStub {
 
 /**
+ * A request from a debugged application to perform some I/O with the GDB client.
+ * This structure is also used to encode the reply back to the application.
+ *
  * Based on the Rosalina implementation:
  * https://github.com/LumaTeam/Luma3DS/blob/master/sysmodules/rosalina/include/gdb.h#L46C27-L62
  */
 struct PackedGdbHioRequest {
-    char magic[4]; // "GDB\x00"
+    char magic[4]; // "GDB\0"
     u32 version;
 
     // Request
@@ -31,14 +34,24 @@ struct PackedGdbHioRequest {
     bool ctrl_c;
 };
 
+/**
+ * Set the current HIO request to the given address. This is how the debugged
+ * app indicates to the gdbstub that it wishes to perform a request.
+ *
+ *  @param address The memory address of the \ref PackedGdbHioRequest.
+ */
 void SetHioRequest(const VAddr address);
 
-bool HandleHioReply(const u8* const command_buffer, const u32 command_length);
+/**
+ * If there is a pending HIO request, send it to the client.
+ *
+ * @returns whethere any request was sent to the client.
+ */
+bool HandlePendingHioRequestPacket();
 
-bool HasPendingHioRequest();
-
-bool WaitingForHioReply();
-
-std::string BuildHioRequestPacket();
+/**
+ * Process an HIO reply from the client.
+ */
+void HandleHioReply(const u8* const command_buffer, const u32 command_length);
 
 } // namespace GDBStub