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diff lib/i-ring.c @ 7639:1670d42131d7

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Make fts (in FTS_CWDFD mode) more efficient by caching a few open file descriptors. This also averts a failure on systems with native openat support when a traversed directory lacks "x" access. * lib/fts_.h: Include "i-ring.h" (struct FTS) [fts_fd_ring]: New member. * lib/fts.c (RESTORE_INITIAL_CWD): Also call fd_ring_clear. (FCHDIR): Add parentheses. (fd_ring_check, fd_ring_print) [!FTS_DEBUG]: Define away. (cwd_advance_fd): Add a 3rd parameter. Adjust all callers. When descending, rather than simply closing the previous fts_cwd_fd value, push that file descriptor onto the ring. (same_fd, fd_ring_print, fd_ring_check) [FTS_DEBUG]: New functions. (fts_open): Initialize the new fd_ring member. (fts_close): Clear the ring. (fts_safe_changedir): When possible, use our new fd_ring to skip the diropen and fstat and dev/ino comparison that would normally accompany a virtual `chdir ("..")'. * modules/fts (Depends-on): Add i-ring. * modules/i-ring: New module. * lib/i-ring.c, lib/i-ring.h, lib/i-ring-test.c: New files. * m4/i-ring.m4: New file.
author Jim Meyering <jim@meyering.net>
date Sun, 12 Nov 2006 17:35:38 +0000
parents
children bbbbbf4cd1c5
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+/* a simple ring buffer
+   Copyright (C) 2006 Free Software Foundation, Inc.
+
+   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+#include "i-ring.h"
+
+#include <stdlib.h>
+
+void
+i_ring_init (I_ring *ir, int default_val)
+{
+  int i;
+  ir->ir_empty = true;
+  ir->ir_front = 0;
+  ir->ir_back = 0;
+  for (i = 0; i < I_RING_SIZE; i++)
+    ir->ir_data[i] = default_val;
+  ir->ir_default_val = default_val;
+}
+
+bool
+i_ring_empty (I_ring const *ir)
+{
+  return ir->ir_empty;
+}
+
+int
+i_ring_push (I_ring *ir, int val)
+{
+  unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
+  int old_val = ir->ir_data[dest_idx];
+  ir->ir_data[dest_idx] = val;
+  ir->ir_front = dest_idx;
+  if (dest_idx == ir->ir_back)
+    ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
+  ir->ir_empty = false;
+  return old_val;
+}
+
+int
+i_ring_pop (I_ring *ir)
+{
+  int top_val;
+  if (i_ring_empty (ir))
+    abort ();
+  top_val = ir->ir_data[ir->ir_front];
+  ir->ir_data[ir->ir_front] = ir->ir_default_val;
+  if (ir->ir_front == ir->ir_back)
+    ir->ir_empty = true;
+  else
+    ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);
+  return top_val;
+}