From b2139c0b1ef7b39bc6bb7bcd7666675b41b94afb Mon Sep 17 00:00:00 2001
From: Bananymous <bananymousosq@gmail.com>
Date: Mon, 4 Sep 2023 12:57:52 +0300
Subject: [PATCH] Kernel: Add basic support for O_NONBLOCK (only for tty)

---
 kernel/include/kernel/FS/Inode.h        | 1 +
 kernel/include/kernel/Terminal/TTY.h    | 3 ++-
 kernel/kernel/OpenFileDescriptorSet.cpp | 2 ++
 kernel/kernel/Terminal/TTY.cpp          | 6 ++++++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/include/kernel/FS/Inode.h b/kernel/include/kernel/FS/Inode.h
index a51258b96c..c159a64246 100644
--- a/kernel/include/kernel/FS/Inode.h
+++ b/kernel/include/kernel/FS/Inode.h
@@ -87,6 +87,7 @@ namespace Kernel
 
 		virtual BAN::ErrorOr<size_t> read(size_t, void*, size_t)		{ if (mode().ifdir()) return BAN::Error::from_errno(EISDIR); ASSERT_NOT_REACHED(); }
 		virtual BAN::ErrorOr<size_t> write(size_t, const void*, size_t)	{ if (mode().ifdir()) return BAN::Error::from_errno(EISDIR); ASSERT_NOT_REACHED(); }
+		virtual bool has_data() const									{ dwarnln("nonblock not supported"); return true; }
 		
 		virtual BAN::ErrorOr<void> truncate(size_t) { if (mode().ifdir()) return BAN::Error::from_errno(EISDIR); return BAN::Error::from_errno(ENOTSUP); }
 
diff --git a/kernel/include/kernel/Terminal/TTY.h b/kernel/include/kernel/Terminal/TTY.h
index fb5e68082d..5891df09c2 100644
--- a/kernel/include/kernel/Terminal/TTY.h
+++ b/kernel/include/kernel/Terminal/TTY.h
@@ -35,6 +35,7 @@ namespace Kernel
 
 		virtual BAN::ErrorOr<size_t> read(size_t, void*, size_t) override;
 		virtual BAN::ErrorOr<size_t> write(size_t, const void*, size_t) override;
+		virtual bool has_data() const override;
 
 	private:
 		void clear();
@@ -78,7 +79,7 @@ namespace Kernel
 		};
 
 	private:
-		Kernel::SpinLock m_lock;
+		mutable Kernel::SpinLock m_lock;
 
 		State m_state { State::Normal };
 		AnsiState m_ansi_state { };
diff --git a/kernel/kernel/OpenFileDescriptorSet.cpp b/kernel/kernel/OpenFileDescriptorSet.cpp
index 46e6f79425..bf3c19c741 100644
--- a/kernel/kernel/OpenFileDescriptorSet.cpp
+++ b/kernel/kernel/OpenFileDescriptorSet.cpp
@@ -234,6 +234,8 @@ namespace Kernel
 	{
 		TRY(validate_fd(fd));
 		auto& open_file = m_open_files[fd];
+		if ((open_file->flags & O_NONBLOCK) && !open_file->inode->has_data())
+			return 0;
 		size_t nread = TRY(open_file->inode->read(open_file->offset, buffer, count));
 		open_file->offset += nread;
 		return nread;
diff --git a/kernel/kernel/Terminal/TTY.cpp b/kernel/kernel/Terminal/TTY.cpp
index 9cf26cad15..906503ccc2 100644
--- a/kernel/kernel/Terminal/TTY.cpp
+++ b/kernel/kernel/Terminal/TTY.cpp
@@ -679,6 +679,12 @@ flush:
 		return count;
 	}
 
+	bool TTY::has_data() const
+	{
+		LockGuard _(m_lock);
+		return m_output.flush;
+	}
+
 	void TTY::putchar_current(uint8_t ch)
 	{
 		ASSERT(s_tty);