Kernel/LibC: Add basic pipe() syscall and command

You can now create pipes :)

kernel/kernel/FS/Pipe.cpp

@@ -0,0 +1,88 @@
+#include <kernel/FS/Pipe.h>
+#include <kernel/LockGuard.h>
+#include <kernel/RTC.h>
+
+namespace Kernel
+{
+
+	BAN::ErrorOr<BAN::RefPtr<Inode>> Pipe::create(const Credentials& credentials)
+	{
+		Pipe* pipe = new Pipe(credentials);
+		if (pipe == nullptr)
+			return BAN::Error::from_errno(ENOMEM);
+		return BAN::RefPtr<Inode>::adopt(pipe);
+	}
+	
+	Pipe::Pipe(const Credentials& credentials)
+		: m_uid(credentials.euid())
+		, m_gid(credentials.egid())
+	{
+		uint64_t current_time = BAN::to_unix_time(RTC::get_current_time());
+		m_atime = { .tv_sec = current_time, .tv_nsec = 0 };
+		m_mtime = { .tv_sec = current_time, .tv_nsec = 0 };
+		m_ctime = { .tv_sec = current_time, .tv_nsec = 0 };
+	}
+
+	void Pipe::clone_writing()
+	{
+		LockGuard _(m_lock);
+		ASSERT(m_writing_count > 0);
+		m_writing_count++;
+	}
+	
+	void Pipe::close_writing()
+	{
+		LockGuard _(m_lock);
+		ASSERT(m_writing_count > 0);
+		m_writing_count--;
+		if (m_writing_count == 0)
+			m_semaphore.unblock();
+	}
+
+	BAN::ErrorOr<size_t> Pipe::read(size_t, void* buffer, size_t count)
+	{
+		m_lock.lock();
+		while (m_buffer.empty())
+		{
+			if (m_writing_count == 0)
+				return 0;
+			m_lock.unlock();
+			m_semaphore.block();
+			m_lock.lock();
+		}
+
+		size_t to_copy = BAN::Math::min<size_t>(count, m_buffer.size());
+		memcpy(buffer, m_buffer.data(), to_copy);
+
+		memmove(m_buffer.data(), m_buffer.data() + to_copy, m_buffer.size() - to_copy);
+		MUST(m_buffer.resize(m_buffer.size() - to_copy));
+
+		uint64_t current_time = BAN::to_unix_time(RTC::get_current_time());
+		m_atime = { .tv_sec = current_time, .tv_nsec = 0 };
+
+		m_semaphore.unblock();
+
+		m_lock.unlock();
+
+		return to_copy;
+	}
+	
+	BAN::ErrorOr<size_t> Pipe::write(size_t, const void* buffer, size_t count)
+	{
+		LockGuard _(m_lock);
+
+		size_t old_size = m_buffer.size();
+
+		TRY(m_buffer.resize(old_size + count));
+		memcpy(m_buffer.data() + old_size, buffer, count);
+
+		uint64_t current_time = BAN::to_unix_time(RTC::get_current_time());
+		m_mtime = { .tv_sec = current_time, .tv_nsec = 0 };
+		m_ctime = { .tv_sec = current_time, .tv_nsec = 0 };
+
+		m_semaphore.unblock();
+
+		return count;
+	}
+	
+}