minix/lib/libsffs/read.c

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/* 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;
}