From 418cd07e176178301a7ede908a6a5003f1f6a700 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 19 Oct 2019 18:17:44 -0400
Subject: [PATCH] Adds a check against overrunning data.

---
 Outputs/CRT/CRT.cpp | 3 +++
 Outputs/CRT/CRT.hpp | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/Outputs/CRT/CRT.cpp b/Outputs/CRT/CRT.cpp
index 2a129284a..5b45513ea 100644
--- a/Outputs/CRT/CRT.cpp
+++ b/Outputs/CRT/CRT.cpp
@@ -406,6 +406,9 @@ void CRT::set_immediate_default_phase(float phase) {
 }
 
 void CRT::output_data(int number_of_cycles, size_t number_of_samples) {
+#ifndef NDEBUG
+	assert(number_of_samples <= allocated_data_length_);
+#endif
 	scan_target_->end_data(number_of_samples);
 	Scan scan;
 	scan.type = Scan::Type::Data;
diff --git a/Outputs/CRT/CRT.hpp b/Outputs/CRT/CRT.hpp
index 042521cc8..dd5985444 100644
--- a/Outputs/CRT/CRT.hpp
+++ b/Outputs/CRT/CRT.hpp
@@ -83,6 +83,10 @@ class CRT {
 		Outputs::Display::ScanTarget::Modals scan_target_modals_;
 		static const uint8_t DefaultAmplitude = 80;
 
+#ifndef NDEBUG
+		size_t allocated_data_length_ = 0;
+#endif
+
 	public:
 		/*!	Constructs the CRT with a specified clock rate, height and colour subcarrier frequency.
 			The requested number of buffers, each with the requested number of bytes per pixel,
@@ -221,6 +225,9 @@ class CRT {
 			@returns A pointer to the allocated area if room is available; @c nullptr otherwise.
 		*/
 		inline uint8_t *begin_data(std::size_t required_length, std::size_t required_alignment = 1) {
+#ifndef NDEBUG
+			allocated_data_length_ = required_length;
+#endif
 			return scan_target_->begin_data(required_length, required_alignment);
 		}