vfs: ROM file system

os/include/vfs/rom_file_system.h

@@ -0,0 +1,114 @@
+/*
+ * \brief  ROM filesystem
+ * \author Norman Feske
+ * \date   2014-04-14
+ */
+
+/*
+ * Copyright (C) 2014 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__VFS__ROM_FILE_SYSTEM_H_
+#define _INCLUDE__VFS__ROM_FILE_SYSTEM_H_
+
+#include <os/attached_rom_dataspace.h>
+#include <vfs/file_system.h>
+
+namespace Vfs { class Rom_file_system; }
+
+
+class Vfs::Rom_file_system : public Single_file_system
+{
+	private:
+
+		struct Label
+		{
+			enum { LABEL_MAX_LEN = 64 };
+			char string[LABEL_MAX_LEN];
+
+			Label(Xml_node config)
+			{
+				/* obtain label from config */
+				string[0] = 0;
+				try { config.attribute("label").value(string, sizeof(string)); }
+				catch (...)
+				{
+					/* use VFS node name if label was not provided */
+					string[0] = 0;
+					try { config.attribute("name").value(string, sizeof(string)); }
+					catch (...) { }
+				}
+			}
+		} _label;
+
+		Genode::Attached_rom_dataspace _rom;
+
+	public:
+
+		Rom_file_system(Xml_node config)
+		:
+			Single_file_system(NODE_TYPE_FILE, name(), config),
+			_label(config),
+			_rom(_label.string)
+		{ }
+
+		static char const *name() { return "rom"; }
+
+
+		/********************************
+		 ** File I/O service interface **
+		 ********************************/
+
+		Stat_result stat(char const *path, Stat &out) override
+		{
+			Stat_result result = Single_file_system::stat(path, out);
+			out.size = _rom.size();
+			return result;
+		}
+
+
+		/********************************
+		 ** File I/O service interface **
+		 ********************************/
+
+		Write_result write(Vfs_handle *, char const *, size_t, size_t &count_out) override
+		{
+			count_out = 0;
+			return WRITE_ERR_INVALID;
+		}
+
+		Read_result read(Vfs_handle *vfs_handle, char *dst, size_t count,
+		                 size_t &out_count) override
+		{
+			/* file read limit is the size of the dataspace */
+			size_t const max_size = _rom.size();
+
+			/* current read offset */
+			size_t const read_offset = vfs_handle->seek();
+
+			/* maximum read offset, clamped to dataspace size */
+			size_t const end_offset = min(count + read_offset, max_size);
+
+			/* source address within the dataspace */
+			char const *src = _rom.local_addr<char>() + read_offset;
+
+			/* check if end of file is reached */
+			if (read_offset >= end_offset) {
+				out_count = 0;
+				return READ_OK;
+			}
+
+			/* copy-out bytes from ROM dataspace */
+			size_t const num_bytes = end_offset - read_offset;
+
+			memcpy(dst, src, num_bytes);
+
+			out_count = num_bytes;
+			return READ_OK;
+		}
+};
+
+#endif /* _INCLUDE__VFS__ROM_FILE_SYSTEM_H_ */