update from main archive 960105 cvs/libc-970107 cvs/libc-970106

1 files changed, 105 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/getdents.c b/sysdeps/unix/sysv/linux/getdents.c
new file mode 100644
index 0000000000..0504393e67
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/getdents.c
@@ -0,0 +1,105 @@
+/* Copyright (C) 1993, 1995, 1996, 1997 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <dirent.h>
+#include <stddef.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include <linux/posix_types.h>
+
+#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
+
+
+extern int __getdents __P ((int fd, char *buf, size_t nbytes));
+
+/* For Linux we need a special version of this file since the
+   definition of `struct dirent' is not the same for the kernel and
+   the libc.  There is one additional field which might be introduced
+   in the kernel structure in the future.
+
+   He is the kernel definition of `struct dirent' as of 2.1.20:  */
+
+struct kernel_dirent
+  {
+    long int d_ino;
+    __kernel_off_t d_off;
+    unsigned short int d_reclen;
+    char d_name[256];
+  };
+
+
+/* The problem here is that we cannot simply read the next NBYTES
+   bytes.  We need to take the additional field into account.  We use
+   some heuristic.  Assume the directory contains names with at least
+   3 characters we can compute a maximum number of entries which fit
+   in the buffer.  Taking this number allows us to specify a correct
+   number of bytes to read.  If we should be wrong, we can reset the
+   file descriptor.  */
+int __getdirentries __P ((int fd, char *buf, size_t nbytes, off_t *basep));
+int
+__getdirentries (fd, buf, nbytes, basep)
+     int fd;
+     char *buf;
+     size_t nbytes;
+     off_t *basep;
+{
+  off_t base = __lseek (fd, (off_t) 0, SEEK_CUR);
+  size_t red_nbytes;
+  struct kernel_dirent *kdp;
+  struct dirent *dp;
+  int retval;
+
+  red_nbytes = nbytes - (nbytes / (offsetof (struct dirent, d_name) + 3));
+
+  dp = (struct dirent *) buf;
+  kdp = (struct kernel_dirent *) (buf + (nbytes - red_nbytes));
+
+  retval = __getdents (fd, (char *) kdp, red_nbytes);
+
+  while ((char *) kdp < buf + (nbytes - red_nbytes) + retval)
+    {
+      dp->d_ino = kdp->d_ino;
+      dp->d_off = kdp->d_off;
+      dp->d_reclen = (kdp->d_reclen
+		      + (offsetof (struct dirent, d_name)
+			 - offsetof (struct kernel_dirent, d_name)));
+      dp->d_type = DT_UNKNOWN;
+      memmove (dp->d_name, kdp->d_name,
+	       kdp->d_reclen - offsetof (struct kernel_dirent, d_name));
+
+      dp = (struct dirent *) (((char *) dp) + dp->d_reclen);
+      kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
+
+      if ((char *) dp >= (char *) kdp)
+	{
+	  /* Our heuristic failed.  We read too many entries.  Reset
+	     the stream.  */
+	  off_t used = ((char *) kdp - (char *) buf) - (nbytes - red_nbytes);
+	  base = __lseek (fd, retval - used, SEEK_CUR);
+	}
+    }
+
+  if (basep)
+    *basep = base;
+
+  return (char *) dp - (char *) buf;
+}
+
+weak_alias (__getdirentries, getdirentries)