/* This file contains file and directory reading file system call handlers.

*

* The entry points into this file are:

* do_read perform the READ file system call

* do_getdents perform the GETDENTS file system call

*

* Created:

* April 2009 (D.C. van Moolenbroek)

*/

#include "inc.h"

#include <dirent.h>

#define DWORD_ALIGN(len) (((len) + sizeof(long) - 1) & ~(sizeof(long) - 1))

/*===========================================================================*

* do_read *

*===========================================================================*/

int do_read(void)

{

/* Read data from a file.

*/

struct inode *ino;

off_t pos;

size_t count, size;

vir_bytes off;

char *ptr;

int r, chunk;

if ((ino = find_inode(m_in.m_vfs_fs_readwrite.inode)) == NULL)

return EINVAL;

if (IS_DIR(ino)) return EISDIR;

if ((r = get_handle(ino)) != OK)

return r;

pos = m_in.m_vfs_fs_readwrite.seek_pos;

count = m_in.m_vfs_fs_readwrite.nbytes;

assert(count > 0);

/* Use the buffer from below to eliminate extra copying. */

size = sffs_table->t_readbuf(&ptr);

off = 0;

while (count > 0) {

chunk = MIN(count, size);

if ((r = sffs_table->t_read(ino->i_file, ptr, chunk, pos)) <= 0)

break;

chunk = r;

r = sys_safecopyto(m_in.m_source, m_in.m_vfs_fs_readwrite.grant, off,

(vir_bytes) ptr, chunk);

if (r != OK)

break;

count -= chunk;

off += chunk;

pos += chunk;

}

if (r < 0)

return r;

m_out.m_fs_vfs_readwrite.seek_pos = pos;

m_out.m_fs_vfs_readwrite.nbytes = off;

return OK;

}

/*===========================================================================*

* do_getdents *

*===========================================================================*/

int do_getdents(void)

{

/* Retrieve directory entries.

*/

char name[NAME_MAX+1];

struct inode *ino, *child;

struct dirent *dent;

struct sffs_attr attr;

size_t len, off, user_off, user_left;

off_t pos;

int r, namelen;

/* must be at least sizeof(struct dirent) + NAME_MAX */

static char buf[BLOCK_SIZE];

attr.a_mask = SFFS_ATTR_MODE;

if ((ino = find_inode(m_in.m_vfs_fs_getdents.inode)) == NULL)

return EINVAL;

if(m_in.m_vfs_fs_getdents.seek_pos >= ULONG_MAX) return EINVAL;

if (!IS_DIR(ino)) return ENOTDIR;

/* We are going to need at least one free inode to store children in. */

if (!have_free_inode()) return ENFILE;

/* If we don't have a directory handle yet, get one now. */

if ((r = get_handle(ino)) != OK)

return r;

off = 0;

user_off = 0;

user_left = m_in.m_vfs_fs_getdents.mem_size;

/* We use the seek position as file index number. The first position is for

* the "." entry, the second position is for the ".." entry, and the next

* position numbers each represent a file in the directory.

*/

for (pos = m_in.m_vfs_fs_getdents.seek_pos; ; pos++) {

/* Determine which inode and name to use for this entry.

* We have no idea whether the host will give us "." and/or "..",

* so generate our own and skip those from the host.

*/

if (pos == 0) {

/* Entry for ".". */

child = ino;

strcpy(name, ".");

get_inode(child);

}

else if (pos == 1) {

/* Entry for "..", but only when there is a parent. */

if (ino->i_parent == NULL)

continue;

child = ino->i_parent;

strcpy(name, "..");

get_inode(child);

}

else {

/* Any other entry, not being "." or "..". */

r = sffs_table->t_readdir(ino->i_dir, pos - 2, name,

sizeof(name), &attr);

if (r != OK) {

/* No more entries? Then close the handle and stop. */

if (r == ENOENT) {

put_handle(ino);

break;

}

/* FIXME: what if the error is ENAMETOOLONG? */

return r;

}

if (!strcmp(name, ".") || !strcmp(name, ".."))

continue;

if ((child = lookup_dentry(ino, name)) == NULL) {

child = get_free_inode();

/* We were promised a free inode! */

assert(child != NULL);

child->i_flags = MODE_TO_DIRFLAG(attr.a_mode);

add_dentry(ino, name, child);

}

}

/* record length incl. alignment. */

namelen = strlen(name);

len = _DIRENT_RECLEN(dent, namelen);

/* Is the user buffer too small to store another record?

* Note that we will be rerequesting the same dentry upon a subsequent

* getdents call this way, but we really need the name length for this.

*/

if (user_off + off + len > user_left) {

put_inode(child);

/* Is the user buffer too small for even a single record? */

if (user_off == 0 && off == 0)

return EINVAL;

break;

}

/* If our own buffer cannot contain the new record, copy out first. */

if (off + len > sizeof(buf)) {

r = sys_safecopyto(m_in.m_source, m_in.m_vfs_fs_getdents.grant,

user_off, (vir_bytes) buf, off);

if (r != OK) {

put_inode(child);

return r;

}

user_off += off;

user_left -= off;

off = 0;

}

/* Fill in the actual directory entry. */

dent = (struct dirent *) &buf[off];

dent->d_ino = INODE_NR(child);

dent->d_reclen = len;

dent->d_namlen = namelen;

dent->d_type = IS_DIR(child) ? DT_DIR : DT_REG;

strcpy(dent->d_name, name);

off += len;

put_inode(child);

}

/* If there is anything left in our own buffer, copy that out now. */

if (off > 0) {

r = sys_safecopyto(m_in.m_source, m_in.m_vfs_fs_getdents.grant, user_off,

(vir_bytes) buf, off);

if (r != OK)

return r;

user_off += off;

}

m_out.m_fs_vfs_getdents.seek_pos = pos;

m_out.m_fs_vfs_getdents.nbytes = user_off;

return OK;

}