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tmpfs/lib/src/fs.cc

Example file system for L4Re::Vfs.

Example file system for L4Re::Vfs.

/*
* (c) 2010 Adam Lackorzynski <adam@os.inf.tu-dresden.de>,
* Alexander Warg <warg@os.inf.tu-dresden.de>
* economic rights: Technische Universität Dresden (Germany)
* This file is part of TUD:OS and distributed under the terms of the
* GNU Lesser General Public License 2.1.
* Please see the COPYING-LGPL-2.1 file for details.
*/
#include <l4/l4re_vfs/backend>
#include <l4/cxx/string>
#include <l4/cxx/avl_tree>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <dirent.h>
#include <cstdio>
#include <cstdlib>
#include <cstring>
namespace {
using namespace L4Re::Vfs;
using cxx::Ref_ptr;
class File_data
{
public:
File_data() : _buf(0), _size(0) {}
unsigned long put(unsigned long offset,
unsigned long bufsize, void *srcbuf);
unsigned long get(unsigned long offset,
unsigned long bufsize, void *dstbuf);
unsigned long size(unsigned long offset);
unsigned long size() const { return _size; }
~File_data() noexcept { free(_buf); }
private:
void *_buf;
unsigned long _size;
};
unsigned long
File_data::put(unsigned long offset, unsigned long bufsize, void *srcbuf)
{
if (offset + bufsize > _size)
size(offset + bufsize);
if (!_buf)
return 0;
memcpy((char *)_buf + offset, srcbuf, bufsize);
return bufsize;
}
unsigned long
File_data::get(unsigned long offset, unsigned long bufsize, void *dstbuf)
{
unsigned long s = bufsize;
if (offset > _size)
return 0;
if (offset + bufsize > _size)
s = _size - offset;
memcpy(dstbuf, (char *)_buf + offset, s);
return s;
}
unsigned long
File_data::size(unsigned long offset)
{
if (offset != _size)
{
_size = offset;
_buf = realloc(_buf, _size);
}
if (_buf)
return 0;
return -ENOSPC;
}
class Node : public cxx::Avl_tree_node
{
public:
Node(const char *path, mode_t mode)
: _ref_cnt(0), _path(strdup(path))
{
memset(&_info, 0, sizeof(_info));
_info.st_mode = mode;
}
const char *path() const { return _path; }
struct stat64 *info() { return &_info; }
void add_ref() noexcept { ++_ref_cnt; }
int remove_ref() noexcept { return --_ref_cnt; }
bool is_dir() const { return S_ISDIR(_info.st_mode); }
virtual ~Node() { free(_path); }
private:
int _ref_cnt;
char *_path;
struct stat64 _info;
};
struct Node_get_key
{
typedef cxx::String Key_type;
static Key_type key_of(Node const *n)
{ return n->path(); }
};
struct Path_avl_tree_compare
{
bool operator () (const char *l, const char *r) const
{ return strcmp(l, r) < 0; }
bool operator () (const cxx::String l, const cxx::String r) const
{
int v = strncmp(l.start(), r.start(), cxx::min(l.len(), r.len()));
return v < 0 || (v == 0 && l.len() < r.len());
}
};
class Pers_file : public Node
{
public:
Pers_file(const char *name, mode_t mode)
: Node(name, (mode & 0777) | __S_IFREG) {}
File_data const &data() const { return _data; }
File_data &data() { return _data; }
private:
File_data _data;
};
class Pers_dir : public Node
{
private:
typedef cxx::Avl_tree<Node, Node_get_key, Path_avl_tree_compare> Tree;
Tree _tree;
public:
Pers_dir(const char *name, mode_t mode)
: Node(name, (mode & 0777) | __S_IFDIR) {}
Ref_ptr<Node> find_path(cxx::String);
bool add_node(Ref_ptr<Node> const &);
typedef Tree::Const_iterator Const_iterator;
Const_iterator begin() const { return _tree.begin(); }
Const_iterator end() const { return _tree.end(); }
};
Ref_ptr<Node> Pers_dir::find_path(cxx::String path)
{
return cxx::ref_ptr(_tree.find_node(path));
}
bool Pers_dir::add_node(Ref_ptr<Node> const &n)
{
bool e = _tree.insert(n.ptr()).second;
if (e)
n->add_ref();
return e;
}
class Tmpfs_dir : public Be_file
{
public:
explicit Tmpfs_dir(Ref_ptr<Pers_dir> const &d) noexcept
: _dir(d), _getdents_state(false) {}
int get_entry(const char *, int, mode_t, Ref_ptr<File> *) noexcept override;
ssize_t getdents(char *, size_t) noexcept override;
int fstat(struct stat64 *buf) const noexcept override;
int utime(const struct utimbuf *) noexcept override;
int fchmod(mode_t) noexcept override;
int mkdir(const char *, mode_t) noexcept override;
int unlink(const char *) noexcept override;
int rename(const char *, const char *) noexcept override;
int faccessat(const char *, int, int) noexcept override;
private:
int walk_path(cxx::String const &_s,
Ref_ptr<Node> *ret, cxx::String *remaining = 0);
Ref_ptr<Pers_dir> _dir;
bool _getdents_state;
Pers_dir::Const_iterator _getdents_iter;
};
class Tmpfs_file : public Be_file_pos
{
public:
explicit Tmpfs_file(Ref_ptr<Pers_file> const &f) noexcept
: Be_file_pos(), _file(f) {}
off64_t size() const noexcept;
int fstat(struct stat64 *buf) const noexcept override;
int ftruncate(off64_t p) noexcept override;
int ioctl(unsigned long, va_list) noexcept override;
int utime(const struct utimbuf *) noexcept override;
int fchmod(mode_t) noexcept override;
private:
ssize_t preadv(const struct iovec *v, int iovcnt, off64_t p) noexcept
override;
ssize_t pwritev(const struct iovec *v, int iovcnt, off64_t p) noexcept
override;
Ref_ptr<Pers_file> _file;
};
ssize_t Tmpfs_file::preadv(const struct iovec *v, int iovcnt, off64_t p)
noexcept
{
if (iovcnt < 0)
return -EINVAL;
ssize_t sum = 0;
for (int i = 0; i < iovcnt; ++i)
{
sum += _file->data().get(p, v[i].iov_len, v[i].iov_base);
p += v[i].iov_len;
}
return sum;
}
ssize_t Tmpfs_file::pwritev(const struct iovec *v, int iovcnt, off64_t p)
noexcept
{
if (iovcnt < 0)
return -EINVAL;
ssize_t sum = 0;
for (int i = 0; i < iovcnt; ++i)
{
sum += _file->data().put(p, v[i].iov_len, v[i].iov_base);
p += v[i].iov_len;
}
return sum;
}
int Tmpfs_file::fstat(struct stat64 *buf) const noexcept
{
_file->info()->st_size = _file->data().size();
memcpy(buf, _file->info(), sizeof(*buf));
return 0;
}
int Tmpfs_file::ftruncate(off64_t p) noexcept
{
if (p < 0)
return -EINVAL;
if (_file->data().size(p) == 0)
return 0;
return -EIO; // most likely ENOSPC, but can't report that
}
off64_t Tmpfs_file::size() const noexcept
{ return _file->data().size(); }
int
Tmpfs_file::ioctl(unsigned long v, va_list args) noexcept
{
switch (v)
{
case FIONREAD: // return amount of data still available
int *available = va_arg(args, int *);
*available = _file->data().size() - pos();
return 0;
};
return -EINVAL;
}
int
Tmpfs_file::utime(const struct utimbuf *times) noexcept
{
_file->info()->st_atime = times->actime;
_file->info()->st_mtime = times->modtime;
return 0;
}
int
Tmpfs_file::fchmod(mode_t m) noexcept
{
_file->info()->st_mode = m;
return 0;
}
int
Tmpfs_dir::faccessat(const char *path, int mode, int) noexcept
{
Ref_ptr<Node> node;
cxx::String name = path;
int err = walk_path(name, &node, &name);
if (err < 0)
return err;
if (mode == F_OK) // existence check
return 0;
struct stat64 *stats = node->info();
if ((mode & R_OK) && !(stats->st_mode & S_IRUSR))
return -EACCES;
if ((mode & W_OK) && !(stats->st_mode & S_IWUSR))
return -EACCES;
if ((mode & X_OK) && !(stats->st_mode & S_IXUSR))
return -EACCES;
return 0;
}
int
Tmpfs_dir::get_entry(const char *name, int flags, mode_t mode,
Ref_ptr<File> *file) noexcept
{
Ref_ptr<Node> path;
if (!*name)
{
*file = cxx::ref_ptr(this);
return 0;
}
cxx::String n = name;
int e = walk_path(n, &path, &n);
if (e == -ENOTDIR)
return e;
if (!(flags & O_CREAT) && e < 0)
return e;
if ((flags & O_CREAT) && e == -ENOENT)
{
Ref_ptr<Node> node(new Pers_file(n.start(), mode));
// when ENOENT is return, path is always a directory
bool e = cxx::ref_ptr_static_cast<Pers_dir>(path)->add_node(node);
if (!e)
return -ENOMEM;
path = node;
}
if (path->is_dir())
*file = cxx::ref_ptr(new Tmpfs_dir(cxx::ref_ptr_static_cast<Pers_dir>(path)));
else
*file = cxx::ref_ptr(new Tmpfs_file(cxx::ref_ptr_static_cast<Pers_file>(path)));
if (!*file)
return -ENOMEM;
return 0;
}
ssize_t
Tmpfs_dir::getdents(char *buf, size_t sz) noexcept
{
struct dirent64 *d = (struct dirent64 *)buf;
ssize_t ret = 0;
if (!_getdents_state)
{
_getdents_iter = _dir->begin();
_getdents_state = true;
}
else if (_getdents_iter == _dir->end())
{
_getdents_state = false;
return 0;
}
for (; _getdents_iter != _dir->end(); ++_getdents_iter)
{
unsigned l = strlen(_getdents_iter->path()) + 1;
if (l > sizeof(d->d_name))
l = sizeof(d->d_name);
unsigned n = offsetof (struct dirent64, d_name) + l;
n = (n + sizeof(long) - 1) & ~(sizeof(long) - 1);
if (n > sz)
break;
d->d_ino = 1;
d->d_off = 0;
memcpy(d->d_name, _getdents_iter->path(), l);
d->d_reclen = n;
d->d_type = DT_REG;
ret += n;
sz -= n;
d = (struct dirent64 *)((unsigned long)d + n);
}
return ret;
}
int
Tmpfs_dir::fstat(struct stat64 *buf) const noexcept
{
memcpy(buf, _dir->info(), sizeof(*buf));
return 0;
}
int
Tmpfs_dir::utime(const struct utimbuf *times) noexcept
{
_dir->info()->st_atime = times->actime;
_dir->info()->st_mtime = times->modtime;
return 0;
}
int
Tmpfs_dir::fchmod(mode_t m) noexcept
{
_dir->info()->st_mode = m;
return 0;
}
int
Tmpfs_dir::walk_path(cxx::String const &_s,
Ref_ptr<Node> *ret, cxx::String *remaining)
{
Ref_ptr<Pers_dir> p = _dir;
cxx::String s = _s;
Ref_ptr<Node> n;
while (1)
{
if (s.len() == 0)
{
*ret = p;
return 0;
}
cxx::String::Index sep = s.find("/");
if (sep - s.start() == 1 && *s.start() == '.')
{
s = s.substr(s.start() + 2);
continue;
}
n = p->find_path(s.head(sep - s.start()));
if (!n)
{
*ret = p;
if (remaining)
*remaining = s.head(sep - s.start());
return -ENOENT;
}
if (sep == s.end())
{
*ret = n;
return 0;
}
if (!n->is_dir())
return -ENOTDIR;
s = s.substr(sep + 1);
p = cxx::ref_ptr_static_cast<Pers_dir>(n);
}
*ret = n;
return 0;
}
int
Tmpfs_dir::mkdir(const char *name, mode_t mode) noexcept
{
Ref_ptr<Node> node = _dir;
cxx::String p = cxx::String(name);
cxx::String path, last = p;
cxx::String::Index s = p.rfind("/");
// trim /'s at the end
while (p.len() && s == p.end() - 1)
{
p.len(p.len() - 1);
s = p.rfind("/");
}
//printf("MKDIR '%s' p=%p %p\n", name, p.start(), s);
if (s != p.end())
{
path = p.head(s);
last = p.substr(s + 1, p.end() - s);
int e = walk_path(path, &node);
if (e < 0)
return e;
}
if (!node->is_dir())
return -ENOTDIR;
// due to path walking we can end up with an empty name
if (p.len() == 0 || p == cxx::String("."))
return 0;
Ref_ptr<Pers_dir> dnode = cxx::ref_ptr_static_cast<Pers_dir>(node);
Ref_ptr<Pers_dir> dir(new Pers_dir(last.start(), mode));
return dnode->add_node(dir) ? 0 : -EEXIST;
}
int
Tmpfs_dir::unlink(const char *name) noexcept
{
cxx::Ref_ptr<Node> n;
int e = walk_path(name, &n);
if (e < 0)
return -ENOENT;
printf("Unimplemented (if file exists): %s(%s)\n", __func__, name);
return -ENOMEM;
}
int
Tmpfs_dir::rename(const char *old, const char *newn) noexcept
{
printf("Unimplemented: %s(%s, %s)\n", __func__, old, newn);
return -ENOMEM;
}
class Tmpfs_fs : public Be_file_system
{
public:
Tmpfs_fs() : Be_file_system("tmpfs") {}
int mount(char const *source, unsigned long mountflags,
void const *data, cxx::Ref_ptr<File> *dir) noexcept override
{
(void)mountflags;
(void)source;
(void)data;
*dir = cxx::ref_ptr(new Tmpfs_dir(cxx::ref_ptr(new Pers_dir("root", 0777))));
if (!*dir)
return -ENOMEM;
return 0;
}
};
static Tmpfs_fs _tmpfs L4RE_VFS_FILE_SYSTEM_ATTRIBUTE;
}
avl_tree
AVL tree.
L4Re::Vfs::Be_file_system
Boilerplate class for implementing a L4Re::Vfs::File_system.
Definition backend:311
L4Re::Vfs::Be_file
Boiler plate class for implementing an open file for L4Re::Vfs.
Definition backend:31
cxx::Avl_tree_node
Node of an AVL tree.
Definition avl_tree:30
cxx::Avl_tree
A generic AVL tree.
Definition avl_tree:101
cxx::Ref_ptr
A reference-counting pointer with automatic cleanup.
Definition ref_ptr:71
cxx::String
Allocation free string class with explicit length field.
Definition string:31
cxx::String::start
Index start() const
Pointer to first character.
Definition string:54
cxx::String::end
Index end() const
Pointer to first byte behind the string.
Definition string:56
cxx::String::find
char const * find(char const *c) const
Find character. Return end() if not found.
Definition string:124
cxx::String::substr
String substr(unsigned long idx, unsigned long len=~0UL) const
Substring of length len starting at idx.
Definition string:84
cxx::String::head
String head(Index end) const
Return prefix up to index.
Definition string:68
cxx::String::Index
char const * Index
Character index type.
Definition string:35
cxx::String::rfind
char const * rfind(char const *c) const
Find right-most character. Return end() if not found.
Definition string:132
cxx::String::len
int len() const
Length.
Definition string:58
L4Re::Vfs
Virtual file system for interfaces in POSIX libc.
Definition backend:16