From 955d8921b9c37f48477102a16785bd7af6663e94 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 30 May 2018 01:38:20 -0700
Subject: [PATCH] ircd::fs: Add basic fd wrapper object.

---
 include/ircd/fs/fd.h |  51 +++++++++++++++++++
 include/ircd/fs/fs.h |   1 +
 ircd/fs.cc           | 115 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 167 insertions(+)
 create mode 100644 include/ircd/fs/fd.h

diff --git a/include/ircd/fs/fd.h b/include/ircd/fs/fd.h
new file mode 100644
index 000000000..043276bc3
--- /dev/null
+++ b/include/ircd/fs/fd.h
@@ -0,0 +1,51 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_FS_FD_H
+
+namespace ircd::fs
+{
+	struct fd;
+}
+
+/// Object for maintaining state to an open file or directory. Instances can
+/// be used with various functions around ircd::fs.
+struct ircd::fs::fd
+{
+	struct opts;
+
+	int fdno{-1};
+
+  public:
+	operator const int &() const
+	{
+		return fdno;
+	}
+
+	fd(const string_view &path, const opts &);
+	fd(const string_view &path);
+	fd() = default;
+	fd(fd &&) noexcept;
+	fd(const fd &) = delete;
+	fd &operator=(fd &&) noexcept;
+	fd &operator=(const fd &) = delete;
+	~fd() noexcept(false);
+};
+
+struct ircd::fs::fd::opts
+{
+	ulong flags {0};
+	ulong mask {0};
+	bool ate {false};
+
+	opts(const std::ios::open_mode &);
+	opts() = default;
+};
diff --git a/include/ircd/fs/fs.h b/include/ircd/fs/fs.h
index 8c7797527..c7c6e0a17 100644
--- a/include/ircd/fs/fs.h
+++ b/include/ircd/fs/fs.h
@@ -91,6 +91,7 @@ namespace ircd::fs
 	extern aio *aioctx;
 }
 
+#include "fd.h"
 #include "read.h"
 #include "write.h"
 #include "stdin.h"
diff --git a/ircd/fs.cc b/ircd/fs.cc
index d2c406e66..fde33e608 100644
--- a/ircd/fs.cc
+++ b/ircd/fs.cc
@@ -260,6 +260,121 @@ ircd::fs::write__std(const string_view &path,
 	return buf;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// fs/fd.h
+//
+// TODO: x-platform
+//
+
+namespace ircd::fs
+{
+	thread_local char path_buf[2048];
+	static const char *path_str(const string_view &);
+	static uint posix_flags(const std::ios::open_mode &mode);
+}
+
+uint
+ircd::fs::posix_flags(const std::ios::open_mode &mode)
+{
+	static const auto rdwr
+	{
+		std::ios::in | std::ios::out
+	};
+
+	uint ret{0};
+	if((mode & rdwr) == rdwr)
+		ret |= O_RDWR;
+	else if(mode & std::ios::out)
+		ret |= O_WRONLY;
+	else
+		ret |= O_RDONLY;
+
+	ret |= mode & std::ios::trunc? O_TRUNC : 0;
+	ret |= mode & std::ios::app? O_APPEND : 0;
+	ret |= ret & O_WRONLY? O_CREAT : 0;
+	ret |= ret & O_RDWR && ret & (O_TRUNC | O_APPEND)? O_CREAT : 0;
+	return ret;
+}
+
+const char *
+ircd::fs::path_str(const string_view &s)
+{
+	return data(strlcpy(path_buf, s));
+}
+
+//
+// fd::opts
+//
+
+ircd::fs::fd::opts::opts(const std::ios::open_mode &mode)
+:flags
+{
+	posix_flags(mode)
+	| O_CLOEXEC
+}
+,mask
+{
+	flags & O_CREAT?
+		S_IRUSR | S_IWUSR:
+		0U
+}
+,ate
+{
+	bool(mode & std::ios::ate)
+}
+{
+}
+
+//
+// fd::fd
+//
+
+ircd::fs::fd::fd(const string_view &path)
+:fd{path, opts{}}
+{
+}
+
+ircd::fs::fd::fd(const string_view &path,
+                 const opts &opts)
+:fdno
+{
+	int(syscall(::open, path_str(path), int(opts.flags), mode_t(opts.mask)))
+}
+{
+	if(opts.ate)
+		syscall(::lseek, fdno, 0, SEEK_END);
+}
+
+ircd::fs::fd::fd(fd &&o)
+noexcept
+:fdno
+{
+	std::move(o.fdno)
+}
+{
+	o.fdno = -1;
+}
+
+ircd::fs::fd &
+ircd::fs::fd::operator=(fd &&o)
+noexcept
+{
+	this->~fd();
+	fdno = std::move(o.fdno);
+	o.fdno = -1;
+	return *this;
+}
+
+ircd::fs::fd::~fd()
+noexcept(false)
+{
+	if(fdno < 0)
+		return;
+
+	syscall(::close, fdno);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // fs.h / misc