genode/repos/os/include/vfs/rom_file_system.h
2015-07-06 12:22:27 +02:00

139 lines
3.1 KiB
C++

/*
* \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"; }
/*********************************
** Directory-service interface **
********************************/
/*
* Overwrite the default open function to update the ROM dataspace
* each time when opening the corresponding file.
*/
Open_result open(char const *path, unsigned,
Vfs_handle **out_handle) override
{
Open_result const result =
Single_file_system::open(path, 0, out_handle);
_rom.update();
return result;
}
/********************************
** File I/O service interface **
********************************/
Stat_result stat(char const *path, Stat &out) override
{
Stat_result result = Single_file_system::stat(path, out);
_rom.update();
out.size = _rom.is_valid() ? _rom.size() : 0;
return result;
}
/********************************
** File I/O service interface **
********************************/
Write_result write(Vfs_handle *, char const *, file_size,
file_size &count_out) override
{
count_out = 0;
return WRITE_ERR_INVALID;
}
Read_result read(Vfs_handle *vfs_handle, char *dst, file_size count,
file_size &out_count) override
{
/* file read limit is the size of the dataspace */
file_size const max_size = _rom.size();
/* current read offset */
file_size const read_offset = vfs_handle->seek();
/* maximum read offset, clamped to dataspace size */
file_size 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 */
file_size 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_ */