Initial revision

1 files changed, 861 insertions, 0 deletions

diff --git a/ufs/dir.c b/ufs/dir.c
new file mode 100644
index 00000000..d088778e
--- /dev/null
+++ b/ufs/dir.c
@@ -0,0 +1,861 @@
+/* Directory management routines
+   Copyright (C) 1994 Free Software Foundation
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "ufs.h"
+#include "dir.h"
+
+#include <string.h>
+#include <stdio.h>
+
+enum slot_status
+{
+  /* This means we haven't yet found room for a new entry.  */
+  LOOKING,
+
+  /* This means that the specified entry is free and should be used. */
+  TAKE,
+
+  /* This means that the specified entry has enough room at the end
+     to hold the new entry. */
+  SHRINK,
+
+  /* This means that there is enough space in the block, but not in
+     any one single entry, so they all have to be shifted to make
+     room.  */
+  COMPRESS,
+
+  /* This means that the directory will have to be grown to hold the
+     entry. */
+  EXTEND,
+
+  /* For removal and rename, this means that this is the location
+     of the entry found.  */
+  HERE_TIS,
+};
+
+struct dirstat
+{
+  /* Type of followp operation expected */
+  enum lookup_type type;
+
+  /* One of the statuses above */
+  enum slot_status stat;
+
+  /* Mapped address and length of directory */
+  vm_address_t mapbuf;
+  vm_size_t mapextent;
+
+  /* Index of this directory block. */
+  int idx;
+  
+  /* For stat COMPRESS, this is the address (inside mapbuf) 
+     of the first direct in the directory block to be compressed. */
+  /* For stat HERE_TIS, SHRINK, and TAKE, this is the entry referenced. */
+  struct direct *entry;
+
+  /* For stat HERE_TIS, type REMOVE, this is the address of the immediately
+     previous direct in this directory block, or zero if this is the first. */
+  struct direct *preventry;
+};
+
+size_t diskfs_dirstat_size = sizeof (struct dirstat);
+
+static error_t					
+dirscanblock (vm_address_t blockoff, struct node *dp, int idx, char *name, 
+	      int namelen, enum lookup_type type, struct dirstat *ds,
+	      ino_t *inum);
+
+/* Implement the diskfs_lookup from the diskfs library.  See
+   <hurd/diskfs.h> for the interface specification.  */
+error_t
+diskfs_lookup (struct node *dp, char *name, enum lookup_type type,
+	       struct node **npp, struct dirstat *ds, struct protid *cred)
+{
+  error_t err;
+  ino_t inum;
+  int namelen;
+  int spec_dotdot;
+  struct node *np = 0;
+  int retry_dotdot = 0;
+  memory_object_t memobj;
+  vm_address_t buf;
+  vm_size_t buflen;
+  int blockaddr;
+  int idx;
+  
+  if (npp)
+    *npp = 0;
+
+  spec_dotdot = type & SPEC_DOTDOT;
+  type &= ~SPEC_DOTDOT;
+  
+  namelen = strlen (name);
+  
+  if (!S_ISDIR (dp->dn_stat.st_mode))
+    return ENOTDIR;
+  err = diskfs_access (dp, S_IEXEC, cred);
+  if (err)
+    return err;
+  
+ try_again:
+  if (ds)
+    {
+      ds->type = LOOKUP;
+      ds->mapbuf = 0;
+      ds->mapextent = 0;
+    }
+  if (ds && (type == CREATE || type == RENAME))
+    ds->stat = LOOKING;
+
+  /* Map in the directory contents. */
+  memobj = diskfs_get_filemap (dp);
+  mach_port_insert_right (mach_task_self (), memobj, memobj,
+			  MACH_MSG_TYPE_MAKE_SEND);
+  buf = 0;
+  /* We allow extra space in case we have to do an EXTEND. */
+  buflen = round_page (dp->dn_stat.st_size + DIRBLKSIZ);
+  if (type == LOOKUP)
+    /* Map read-only; we won't be writing */
+    err = vm_map (mach_task_self (), &buf, buflen, 0, 1, memobj, 0, 0, 
+		  VM_PROT_READ, VM_PROT_READ, 0);
+  else
+    err = vm_map (mach_task_self (), &buf, buflen, 0, 1, memobj, 0, 0, 
+		  VM_PROT_READ|VM_PROT_WRITE, VM_PROT_READ|VM_PROT_WRITE, 0);
+  mach_port_deallocate (mach_task_self (), memobj);
+
+  inum = 0;
+  
+  for (blockaddr = buf, idx = 0;
+       blockaddr - buf < dp->dn_stat.st_size;
+       blockaddr += DIRBLKSIZ, idx++)
+    {
+      err = dirscanblock (blockaddr, dp, idx, name, namelen, type, ds, &inum);
+      if (!err)
+	break;
+      if (err != ENOENT)
+	{
+	  vm_deallocate (mach_task_self (), buf, buflen);
+	  return err;
+	}
+    }
+
+  /* If err is set here, it's ENOENT, and we don't want to
+     think about that as an error yet. */
+  err = 0;
+
+  if (inum)
+    {
+      if (namelen != 2 || name[0] != '.' || name[1] != '.')
+	{
+	  if (inum == dp->dn->number)
+	    {
+	      np = dp;
+	      diskfs_nref (np);
+	    }
+	  else
+	    {
+	      err = iget (inum, &np);
+	      if (err)
+		goto out;
+	    }
+	}
+	  
+      /* We are looking up .. */
+      /* Check to see if this is the root of the filesystem. */
+      else if (dp->dn->number == 2)
+	{
+	  err = EAGAIN;
+	  goto out;
+	}
+	  
+      /* We can't just do iget, because we would then deadlock.
+	 So we do this.  Ick.  */
+      else if (retry_dotdot)
+	{
+	  /* Check to see that we got the same answer as last time. */
+	  if (inum != retry_dotdot)
+	    {
+	      /* Drop what we *thought* was .. (but isn't any more) and
+		 try *again*. */
+	      diskfs_nput (np);
+	      mutex_unlock (&dp->lock);
+	      err = iget (inum, &np);
+	      mutex_lock (&dp->lock);
+	      if (err)
+		goto out;
+	      retry_dotdot = inum;
+	      goto try_again;
+	    }
+	  /* Otherwise, we got it fine and np is already set properly. */
+	}
+      else if (!spec_dotdot)
+	{
+	  /* Lock them in the proper order, and then
+	     repeat the directory scan to see if this is still
+	     right.  */
+	  mutex_unlock (&dp->lock);
+	  err = iget (inum, &np);
+	  mutex_lock (&dp->lock);
+	  if (err)
+	    goto out;
+	  retry_dotdot = inum;
+	  goto try_again;
+	}
+      
+      /* Here below are the spec dotdot cases. */
+      else if (type == RENAME || type == REMOVE)
+	np = ifind (inum);
+      
+      else if (type == LOOKUP)
+	{
+	  diskfs_nput (dp);
+	  err = iget (inum, &np);
+	  if (err)
+	    goto out;
+	}
+      else
+	assert (0);
+    }
+  
+  /* If we will be modifying the directory, make sure it's allowed. */
+  if (type == RENAME
+      || (type == REMOVE && np)
+      || (type == CREATE && !np))
+    {
+      err = diskfs_checkdirmod (dp, np, cred);
+      if (err)
+	goto out;
+    }
+  
+  if ((type == CREATE || type == RENAME) && !np && ds && ds->type == LOOKING)
+    {
+      /* We didn't find any room, so mark ds to extend the dir */
+      ds->type = CREATE;
+      ds->stat = EXTEND;
+      ds->idx = idx;
+    }
+
+  /* Return to the user; if we can't, release the reference
+     (and lock) we acquired above.  */
+ out:
+  /* Deallocate or save the mapping. */
+  if ((err && err != ENOENT)
+      || !ds
+      || ds->type == LOOKUP)
+    vm_deallocate (mach_task_self (), buf, buflen);
+  else
+    {
+      ds->mapbuf = buf;
+      ds->mapextent = buflen;
+    }
+  
+  if (np)
+    {
+      if (err || !npp)
+	{
+	  if (!spec_dotdot)
+	    {
+	      /* Normal case */
+	      if (np == dp)
+		diskfs_nrele (np);
+	      else
+		diskfs_nput (np);
+	    }
+	  else if (type == RENAME || type == REMOVE)
+	    /* We just did ifind to get np; that allocates
+	       no new references, so we don't have anything to do */
+	    ;
+	  else if (type == LOOKUP)
+	    /* We did iget */
+	    diskfs_nput (np);
+	}
+      else if (npp)
+	*npp = np;
+    }
+
+  return err ? : np ? 0 : ENOENT;
+}
+
+/* Scan block at address BLKADDR (of node DP; block index IDX), for
+   name NAME of length NAMELEN.  Args TYPE, DS are as for
+   diskfs_lookup.  If found, set *INUM to the inode number, else
+   return ENOENT.  */
+static error_t
+dirscanblock (vm_address_t blockaddr, struct node *dp, int idx, char *name,
+	      int namelen, enum lookup_type type, 
+	      struct dirstat *ds, ino_t *inum)
+{
+  int nfree = 0;
+  int needed = 0;
+  int countup = 0;
+  vm_address_t currentoff, prevoff;
+  struct direct *entry;
+  int nentries = 0;
+
+  if (ds && ds->stat == LOOKING)
+    {
+      countup = 1;
+      needed = DIRSIZ (namelen);
+    }
+  
+  for (currentoff = blockaddr, prevoff = blockaddr;
+       currentoff < blockaddr + DIRBLKSIZ;
+       prevoff = currentoff, currentoff += entry->d_reclen)
+    {
+      entry = (struct direct *)currentoff;
+      
+      if (!entry->d_reclen
+	  || entry->d_reclen % 4
+	  || entry->d_namlen > MAXNAMLEN
+	  || currentoff + entry->d_reclen > blockaddr + DIRBLKSIZ
+	  || entry->d_name[entry->d_namlen]
+	  || DIRSIZ (entry->d_namlen) > entry->d_reclen
+	  || memchr (entry->d_name, '\0', entry->d_namlen))
+	{
+	  fprintf (stderr, "Bad directory entry: inode: %ld offset: %d\n",
+		  dp->dn->number, currentoff - blockaddr);
+	  return ENOENT;
+	}
+      
+      if (countup)
+	{
+	  int thisfree;
+	  
+	  if (entry->d_ino == 0)
+	    thisfree = entry->d_reclen;
+	  else
+	    thisfree = entry->d_reclen - DIRSIZ (entry->d_namlen);
+	  
+	  if (thisfree >= needed)
+	    {
+	      ds->type = CREATE;
+	      ds->stat = entry->d_ino == 0 ? TAKE : SHRINK;
+	      ds->entry = entry;
+	      ds->idx = idx;
+	      countup = 0;
+	    }
+	  else
+	    {
+	      nfree += thisfree;
+	      if (nfree >= needed)
+		{
+		  ds->type = CREATE;
+		  ds->stat = COMPRESS;
+		  ds->entry = (struct direct *) blockaddr;
+		  ds->idx = idx;
+		  countup = 0;
+		}
+	    }
+	}
+      
+      if (entry->d_ino)
+	nentries++;
+
+      if (entry->d_namlen == namelen
+	  && entry->d_name[0] == name[0]
+	  && entry->d_ino
+	  && !bcmp (entry->d_name, name, namelen))
+	break;
+    }
+
+  if (currentoff >= blockaddr + DIRBLKSIZ)
+    {
+      int i;
+      /* The name is not in this block. */
+
+      /* Because we scanned the entire block, we should write
+	 down how many entries there were. */
+      if (!dp->dn->dirents)
+	{
+	  dp->dn->dirents = malloc ((dp->dn_stat.st_size / DIRBLKSIZ + 1) 
+				* sizeof (int));
+	  for (i = 0; i < dp->dn_stat.st_size/DIRBLKSIZ; i++) 
+	    dp->dn->dirents[i] = -1;
+	}
+      /* Make sure the count is correct if there is one now. */
+      assert (dp->dn->dirents[idx] == -1
+	      || dp->dn->dirents[idx] == nentries);
+      dp->dn->dirents[idx] = nentries;
+
+      return ENOENT;
+    }
+  
+  /* We have found the required name. */
+
+  if (ds && type == CREATE)
+    ds->type = LOOKUP;		/* it's invalid now */
+  else if (ds && (type == REMOVE || type == RENAME))
+    {
+      ds->type = type;
+      ds->stat = HERE_TIS;
+      ds->entry = entry;
+      ds->idx = idx;
+      ds->preventry = (struct direct *) prevoff;
+    }
+
+  *inum = entry->d_ino;
+  return 0;
+}
+
+/* Following a lookup call for CREATE, this adds a node to a directory.
+   DP is the directory to be modified; NAME is the name to be entered;
+   NP is the node being linked in; DS is the cached information returned
+   by lookup; CRED describes the user making the call.  This call may
+   only be made if the directory has been held locked continuously since
+   the preceding lookup call, and only if that call returned ENOENT. */
+error_t
+diskfs_direnter(struct node *dp,
+		char *name,
+		struct node *np,
+		struct dirstat *ds,
+		struct protid *cred)
+{
+  struct direct *new;
+  int namelen = strlen (name);
+  int needed = DIRSIZ (namelen);
+  int oldneeded;
+  vm_address_t fromoff, tooff;
+  int totfreed;  
+  error_t err;
+
+  assert (ds->type == CREATE);
+  
+  switch (ds->stat)
+    {
+    case TAKE:
+      /* We are supposed to consume this slot. */
+      assert (ds->entry->d_ino == 0 && ds->entry->d_reclen >= needed);
+      
+      ds->entry->d_ino = np->dn->number;
+      ds->entry->d_namlen = namelen;
+      bcopy (name, ds->entry->d_name, namelen + 1);
+
+      break;
+      
+    case SHRINK:
+      /* We are supposed to take the extra space at the end
+	 of this slot. */
+      oldneeded = DIRSIZ (ds->entry->d_namlen);
+      assert (ds->entry->d_reclen - oldneeded >= needed);
+      
+      new = (struct direct *) ((vm_address_t) ds->entry + oldneeded);
+
+      new->d_ino = np->dn->number;
+      new->d_reclen = ds->entry->d_reclen - oldneeded;
+      new->d_namlen = namelen;
+      bcopy (name, new->d_name, namelen + 1);
+      
+      ds->entry->d_reclen = oldneeded;
+      
+      break;
+      
+    case COMPRESS:
+      /* We are supposed to move all the entries to the
+	 front of the block, giving each the minimum
+	 necessary room.  This should free up enough space
+	 for the new entry. */
+      fromoff = tooff = (vm_address_t) ds->entry;
+
+      while (fromoff < (vm_address_t) ds->entry + DIRBLKSIZ)
+	{
+	  struct direct *from = (struct direct *)fromoff;
+	  struct direct *to = (struct direct *) tooff;
+	  int fromreclen = from->d_reclen;
+
+	  if (from->d_ino != 0)
+	    {
+	      assert (fromoff >= tooff);
+
+	      bcopy (from, to, fromreclen);
+	      to->d_reclen = DIRSIZ (to->d_namlen);
+
+	      tooff += to->d_reclen;
+	    }
+	  fromoff += fromreclen;
+	}
+
+      totfreed = (vm_address_t) ds->entry + DIRBLKSIZ - tooff;
+      assert (totfreed >= needed);
+      
+      new = (struct direct *) tooff;
+      new->d_ino = np->dn->number;
+      new->d_reclen = totfreed;
+      new->d_namlen = namelen;
+      bcopy (name, new->d_name, namelen + 1);
+      break;
+
+    case EXTEND:
+      /* Extend the file. */
+      while (dp->dn_stat.st_size + DIRBLKSIZ > dp->allocsize)
+	if (err = diskfs_grow (dp, dp->dn_stat.st_size + DIRBLKSIZ, cred))
+	  {
+	    vm_deallocate (mach_task_self (), ds->mapbuf, ds->mapextent);
+	    return err;
+	  }
+
+      new = (struct direct *) (ds->mapbuf + dp->dn_stat.st_size);
+
+      dp->dn_stat.st_size += DIRBLKSIZ;
+      dp->dn_set_ctime = 1;
+
+      new->d_ino = np->dn->number;
+      new->d_reclen = DIRBLKSIZ;
+      new->d_namlen = namelen;
+      bcopy (name, new->d_name, namelen + 1);
+      break;
+      
+    default:
+      assert (0);
+    }
+
+  vm_deallocate (mach_task_self (), ds->mapbuf, ds->mapextent);
+        
+  if (ds->stat != EXTEND)
+    {
+      /* If we are keeping count of this block, then keep the count up 
+	 to date. */
+      if (dp->dn->dirents && dp->dn->dirents[ds->idx] != -1)
+	dp->dn->dirents[ds->idx]++;
+    }
+  else
+    {
+      /* It's cheap, so start a count here even if we aren't counting
+	 anything at all. */
+      if (dp->dn->dirents)
+	{
+	  dp->dn->dirents = realloc (dp->dn->dirents, 
+				     (ds->idx + 1) * sizeof (int));
+	  dp->dn->dirents[ds->idx] = 1;
+	}
+      else
+	{
+	  int i;
+	  dp->dn->dirents = malloc ((ds->idx + 1) * sizeof (int));
+	  for (i = 0; i < ds->idx; i++)
+	    dp->dn->dirents[i] = -1;
+	  dp->dn->dirents[ds->idx] = 1;
+	}
+    }
+  
+  diskfs_file_update (dp, 1);
+
+  if (dp->dirmod_reqs)
+    diskfs_notice_dirchange (dp, DIR_CHANGED_NEW, name);
+
+  return 0;
+}
+
+/* Following a lookup call for REMOVE, this removes the link from the
+   directory.  DP is the directory being changed and DS is the cached
+   information returned from lookup.  This call is only valid if the
+   directory has been locked continously since the call to lookup, and
+   only if that call succeeded.  */
+error_t
+diskfs_dirremove(struct node *dp,
+		 struct dirstat *ds)
+{
+  assert (ds->type == REMOVE);
+  assert (ds->stat == HERE_TIS);
+  
+  if (ds->preventry == 0)
+    ds->entry->d_ino = 0;
+  else
+    {
+      assert ((vm_address_t )ds->entry - (vm_address_t)ds->preventry
+	      == ds->preventry->d_reclen);
+      ds->preventry->d_reclen += ds->entry->d_reclen;
+    }
+
+  vm_deallocate (mach_task_self (), ds->mapbuf, ds->mapextent);
+
+  /* If we are keeping count of this block, then keep the count up
+     to date. */
+  if (dp->dn->dirents && dp->dn->dirents[ds->idx] != -1)
+    dp->dn->dirents[ds->idx]--;
+  
+  diskfs_file_update (dp, 1);
+
+  if (dp->dirmod_reqs)
+    diskfs_notice_dirchange (dp, DIR_CHANGED_UNLINK, ds->entry->d_name);
+
+  return 0;
+}
+  
+
+/* Following a lookup call for RENAME, this changes the inode number
+   on a directory entry.  DP is the directory being changed; NP is 
+   the new node being linked in; DP is the cached information returned 
+   by lookup.  This call is only valid if the directory has been locked
+   continuously since the call to lookup, and only if that call
+   succeeded.  */
+error_t
+diskfs_dirrewrite(struct node *dp, 
+		  struct node *np,
+		  struct dirstat *ds)
+{
+  assert (ds->type == RENAME);
+  assert (ds->stat == HERE_TIS);
+  
+  ds->entry->d_ino = np->dn->number;
+
+  vm_deallocate (mach_task_self (), ds->mapbuf, ds->mapextent);
+  
+  diskfs_file_update (dp, 1);
+
+  if (dp->dirmod_reqs)
+    diskfs_notice_dirchange (dp, DIR_CHANGED_RENUMBER, ds->entry->d_name);
+
+  return 0;
+}
+
+/* Tell if DP is an empty directory (has only "." and ".." entries). */
+/* This routine must be called from inside a catch_exception ().  */
+int
+diskfs_dirempty(struct node *dp,
+		struct protid *cred)
+{
+  struct direct *entry;
+  int curoff;
+  vm_address_t buf;
+  memory_object_t memobj;
+  error_t err;
+
+  memobj = diskfs_get_filemap (dp);
+  mach_port_insert_right (mach_task_self (), memobj, memobj,  
+			  MACH_MSG_TYPE_MAKE_SEND);
+  buf = 0;
+  
+  err = vm_map (mach_task_self (), &buf, dp->dn_stat.st_size, 0,
+		1, memobj, 0, 0, VM_PROT_READ, VM_PROT_READ, 0);
+  mach_port_deallocate (mach_task_self (), memobj);
+  assert (!err);
+
+  for (curoff = buf; 
+       curoff < buf + dp->dn_stat.st_size;
+       curoff += entry->d_reclen)
+    {
+      entry = (struct direct *) curoff;
+
+      if (entry->d_ino != 0
+	  && (entry->d_namlen > 2
+	      || entry->d_name[0] != '.'
+	      || (entry->d_name[1] != '.'
+		  && entry->d_name[1] != '\0')))
+	{
+	  vm_deallocate (mach_task_self (), buf, dp->dn_stat.st_size);
+	  return 0;
+	}
+    }
+  vm_deallocate (mach_task_self (), buf, dp->dn_stat.st_size);
+  return 1;
+}
+
+/* Make DS an invalid dirstat. */
+error_t
+diskfs_drop_dirstat (struct node *dp, struct dirstat *ds)
+{
+  if (ds->type != LOOKUP)
+    {
+      assert (ds->mapbuf);
+      vm_deallocate (mach_task_self (), ds->mapbuf, ds->mapextent);
+      ds->type = LOOKUP;
+    }
+  return 0;
+}
+
+
+/* Count the entries in directory block NB for directory DP and
+   write the answer down in its dirents array.  As a side affect
+   fill BUF with the block.  */
+static error_t
+count_dirents (struct node *dp, int nb, char *buf)
+{
+  int amt;
+  char *offinblk;
+  struct direct *entry;
+  int count = 0;
+  error_t err;
+
+  assert (dp->dn->dirents);
+  assert ((nb + 1) * DIRBLKSIZ <= dp->dn_stat.st_size);
+  
+  err = diskfs_node_rdwr (dp, buf, nb * DIRBLKSIZ, DIRBLKSIZ, 0, 0, &amt);
+  if (err)
+    return err;
+  assert (amt == DIRBLKSIZ);
+  
+  for (offinblk = buf;
+       offinblk < buf + DIRBLKSIZ;
+       offinblk += entry->d_reclen)
+    {
+      entry = (struct direct *) offinblk;
+      if (entry->d_ino)
+	count++;
+    }
+  
+  assert (dp->dn->dirents[nb] == -1 || dp->dn->dirents[nb] == count);
+  dp->dn->dirents[nb] = count;
+  return 0;
+}
+
+/* Implement the disikfs_get_directs callback as described in
+   <hurd/diskfs.h>. */
+error_t
+diskfs_get_directs (struct node *dp, 
+		    int entry, 
+		    int nentries,
+		    char **data,
+		    u_int *datacnt,
+		    vm_size_t bufsiz,
+		    int *amt)
+{
+  int blkno;
+  int nblks;
+  int curentry;
+  char buf[DIRBLKSIZ];
+  char *bufp;
+  int bufvalid;
+  error_t err;
+  int i;
+  char *datap;
+  struct direct *entryp;
+  int allocsize;
+  int checklen;
+
+  nblks = dp->dn_stat.st_size/DIRBLKSIZ;
+
+  if (!dp->dn->dirents)
+    {
+      dp->dn->dirents = malloc (nblks * sizeof (int));
+      for (i = 0; i < nblks; i++)
+	dp->dn->dirents[i] = -1;
+    }
+
+  /* Allocate enough space to hold the maximum we might return */
+  if (!bufsiz || bufsiz > dp->dn_stat.st_size)
+    allocsize = round_page (dp->dn_stat.st_size);
+  else
+    allocsize = round_page (bufsiz);
+
+  if (allocsize > *datacnt)
+    vm_allocate (mach_task_self (), (vm_address_t *) data, allocsize, 1);
+  
+  /* Scan through the entries to find ENTRY.  If we encounter
+     a -1 in the process then stop to fill it.  When we run
+     off the end, ENTRY is too big. */
+  curentry = 0;
+  bufvalid = 0;
+  for (blkno = 0; blkno < nblks; blkno++)
+    {
+      if (dp->dn->dirents[blkno] == -1)
+	{
+	  err = count_dirents (dp, blkno, buf);
+	  if (err)
+	    return err;
+	  bufvalid = 1;
+	}
+
+      if (curentry + dp->dn->dirents[blkno] > entry)
+	/* ENTRY starts in this block. */
+	break;
+
+      curentry += dp->dn->dirents[blkno];
+      
+      bufvalid = 0;
+    }
+  
+  if (blkno == nblks)
+    {
+      *datacnt = 0;
+      *amt = 0;
+      return 0;
+    }
+
+  /* Set bufp appropriately */
+  bufp = buf;
+  if (curentry != entry)
+    {
+      /* Look through the block to find out where to start,
+	 setting bufp appropriately.  */
+      if (!bufvalid)
+	{
+	  err = diskfs_node_rdwr (dp, buf, blkno * DIRBLKSIZ, DIRBLKSIZ,
+				  0, 0, &checklen);
+	  if (err)
+	    return err;
+	  assert (checklen == DIRBLKSIZ);
+	  bufvalid = 1;
+	}
+      for (i = 0, bufp = buf; 
+	   i < entry - curentry && bufp - buf < DIRBLKSIZ; 
+	   bufp += ((struct direct *)bufp)->d_reclen, i++)
+	;
+      /* Make sure we didn't run off the end. */
+      assert (bufp - buf < DIRBLKSIZ);
+    }      
+
+  i = 0;
+  datap = *data;
+
+  /* Copy the entries, one at a time. */
+  while (((nentries == -1) || (i < nentries))
+	 && (!bufsiz || (datap - *data < bufsiz) )
+	 && blkno < nblks)
+    {
+      if (!bufvalid)
+	{
+	  err = diskfs_node_rdwr (dp, buf, blkno * DIRBLKSIZ, DIRBLKSIZ, 
+				  0, 0, &checklen);
+	  if (err)
+	    return err;
+	  assert (checklen == DIRBLKSIZ);
+	  bufvalid = 1;
+	  bufp = buf;
+	}
+
+      entryp = (struct direct *)bufp;
+
+      if (entryp->d_ino)
+	{
+	  bcopy (bufp, datap, DIRSIZ (entryp->d_namlen));
+	  i++;
+	  datap += DIRSIZ (entryp->d_namlen);
+	}
+
+      bufp += entryp->d_reclen;
+      if (bufp - buf == DIRBLKSIZ)
+	{
+	  blkno++;
+	  bufvalid = 0;
+	}
+    }
+  
+  /* We've copied all we can.  If we allocated our own array
+     but didn't fill all of it, then free whatever memory we didn't use. */
+  if (allocsize > *datacnt)
+    {
+      if (round_page (datap - *data) < allocsize)
+	vm_deallocate (mach_task_self (), 
+		       (vm_address_t) (*data + round_page (datap - *data)),
+		       allocsize - round_page (datap - *data));
+    }
+  
+  /* Set variables for return */
+  *datacnt = datap - *data;
+  *amt = i;
+  return 0;
+}