From 81a44afbb4f42297d5a6eac2ea836aa36f93278b Mon Sep 17 00:00:00 2001
From: Myles Busig <mdbusig@gmail.com>
Date: Wed, 27 Mar 2024 00:32:54 -0600
Subject: [PATCH] Add log

---
 include/mtl/log.hpp | 62 +++++++++++++++++++++++++++++++++++++++++++++
 src/gba/log.cpp     | 62 +++++++++++++++++++++++++++++++++++++++++++++
 src/log.cpp         | 29 +++++++++++++++++++++
 3 files changed, 153 insertions(+)
 create mode 100644 include/mtl/log.hpp
 create mode 100644 src/gba/log.cpp
 create mode 100644 src/log.cpp

diff --git a/include/mtl/log.hpp b/include/mtl/log.hpp
new file mode 100644
index 0000000..e5f74ad
--- /dev/null
+++ b/include/mtl/log.hpp
@@ -0,0 +1,62 @@
+#pragma once
+
+#include <cstdint>
+
+#include "mtl/string_stream.hpp"
+
+namespace mtl {
+
+namespace log {
+
+/**
+ * \brief Log stream
+ *
+ * String stream that overrides sync() to flush the stream to the correct
+ * output depending on the platform. Each flush is treated as a separate message.
+ * The capacity of the stream depends on the platform.
+ *
+ * See mtl::string_stream for information on when the stream is flushed.
+ */
+class stream : public string_stream {
+private:
+	uint32_t m_log_level;
+
+public:
+	stream(istring& str, uint32_t log_level);
+	~stream();
+
+	using string_stream::operator=;
+	using string_stream::operator<<;
+
+	void flush() override;
+};
+
+/**
+ * \brief Stub log stream
+ *
+ * Implements all of the log stream functions as a NOP. Replaces all of
+ * the log streams when logging is disabled.
+ *
+ * TODO: Enable logging disabling.
+ */
+class stream_stub {
+public:
+	stream_stub(istring&, uint32_t) { }
+
+	void flush() { }
+	void clear() { }
+
+	template <typename T>
+	stream_stub& operator<<(T) {
+		return *this;
+	}
+};
+
+extern stream debug;
+extern stream info;
+extern stream warn;
+extern stream error;
+
+} // namespace log
+
+} // namespace mtl
diff --git a/src/gba/log.cpp b/src/gba/log.cpp
new file mode 100644
index 0000000..8f7fa14
--- /dev/null
+++ b/src/gba/log.cpp
@@ -0,0 +1,62 @@
+#include "mtl/log.hpp"
+
+#include "mtl/string.hpp"
+#include "mtl/string_view.hpp"
+#include "mtl/string_stream.hpp"
+
+namespace mtl {
+
+namespace log {
+/**
+ * \brief MGBA debug registers and constants
+ */
+namespace reg {
+/**
+ * \brief MGBA debug enable register.
+ *
+ * When 0xC0DE is written to the register, debug output is enabled.
+ * When 0 is written to the register, debug output is disabled.
+ * Will be set to 0x1DEA when successfully enabled.
+ */
+static volatile uint16_t& enable = *reinterpret_cast<uint16_t*>(0x4FFF780);
+/**
+ * \brief MGBA debug flags register.
+ *
+ * When 0x100 | LOG_LEVEL, the message buffer is flushed. MGBA levels are:
+ *
+ * Fatal: 0 (stops the emulator, unused)
+ * Error: 1
+ * Warn:  2
+ * Info:  3
+ * Debug: 4
+ */
+static volatile uint16_t& flags = *reinterpret_cast<uint16_t*>(0x4FFF700);
+/**
+ * \brief MGBA debug string register.
+ *
+ * Max length of 0x100 (256) including null terminator.
+ */
+static string_ext string(reinterpret_cast<char*>(0x4FFF600), 256);
+}; // namespace reg
+
+stream::stream(istring& buf, uint32_t log_level)
+	: string_stream(buf), m_log_level(log_level) {
+	reg::enable = 0xC0DE;
+}
+stream::~stream() {
+	reg::enable = 0;
+}
+
+void stream::flush() {
+	reg::flags = 0x100 | m_log_level;
+	clear();
+}
+
+stream debug(reg::string, 4);
+stream info(reg::string, 3);
+stream warn(reg::string, 2);
+stream error(reg::string, 1);
+
+} // namespace log
+
+} // namespace mtl
diff --git a/src/log.cpp b/src/log.cpp
new file mode 100644
index 0000000..9103e26
--- /dev/null
+++ b/src/log.cpp
@@ -0,0 +1,29 @@
+#include "mtl/log.hpp"
+
+#include <cstdint>
+#include <cstdio>
+
+namespace mtl {
+
+namespace log {
+
+static string<512> buffer;
+
+stream::stream(istring& buf, uint32_t log_level)
+	: string_stream(buf), m_log_level(log_level) { }
+stream::~stream() { }
+
+void stream::flush() {
+	fwrite(buffer.c_str(), 1, buffer.length(), stdin);
+	clear();
+}
+
+stream debug(buffer, 4);
+stream info(buffer, 3);
+stream warn(buffer, 2);
+stream error(buffer, 1);
+
+} // namespace log
+
+} // namespace mtl
+