--- /dev/null
+/* utimecmp.c -- compare file time stamps
+
+ Copyright (C) 2004 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+/* Written by Paul Eggert. */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "utimecmp.h"
+
+#if HAVE_INTTYPES_H
+# include <inttypes.h>
+#endif
+#if HAVE_STDINT_H
+# include <stdint.h>
+#endif
+
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include "hash.h"
+#include "timespec.h"
+#include "utimens.h"
+#include "xalloc.h"
+
+/* Verify a requirement at compile-time (unlike assert, which is runtime). */
+#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
+
+#ifndef MAX
+# define MAX(a, b) ((a) > (b) ? (a) : (b))
+#endif
+
+#ifndef SIZE_MAX
+# define SIZE_MAX ((size_t) -1)
+#endif
+
+/* The extra casts work around common compiler bugs. */
+#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
+/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
+ It is necessary at least when t == time_t. */
+#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
+ ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
+#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
+
+enum { BILLION = 1000 * 1000 * 1000 };
+
+/* Best possible resolution that utimens can set and stat can return,
+ due to system-call limitations. It must be a power of 10 that is
+ no greater than 1 billion. */
+#if HAVE_WORKING_UTIMES && defined ST_MTIM_NSEC
+enum { SYSCALL_RESOLUTION = 1000 };
+#else
+enum { SYSCALL_RESOLUTION = BILLION };
+#endif
+
+/* Describe a file system and its time stamp resolution in nanoseconds. */
+struct fs_res
+{
+ /* Device number of file system. */
+ dev_t dev;
+
+ /* An upper bound on the time stamp resolution of this file system,
+ ignoring any resolution that cannot be set via utimens. It is
+ represented by an integer count of nanoseconds. It must be
+ either 2 billion, or a power of 10 that is no greater than a
+ billion and is no less than SYSCALL_RESOLUTION. */
+ int resolution;
+
+ /* True if RESOLUTION is known to be exact, and is not merely an
+ upper bound on the true resolution. */
+ bool exact;
+};
+
+/* Hash some device info. */
+static size_t
+dev_info_hash (void const *x, size_t table_size)
+{
+ struct fs_res const *p = x;
+
+ /* Beware signed arithmetic gotchas. */
+ if (TYPE_SIGNED (dev_t) && SIZE_MAX < MAX (INT_MAX, TYPE_MAXIMUM (dev_t)))
+ {
+ uintmax_t dev = p->dev;
+ return dev % table_size;
+ }
+
+ return p->dev % table_size;
+}
+
+/* Compare two dev_info structs. */
+static bool
+dev_info_compare (void const *x, void const *y)
+{
+ struct fs_res const *a = x;
+ struct fs_res const *b = y;
+ return a->dev == b->dev;
+}
+
+/* Return -1, 0, 1 based on whether the destination file (with name
+ DST_NAME and status DST_STAT) is older than SRC_STAT, the same age
+ as SRC_STAT, or newer than SRC_STAT, respectively.
+
+ If OPTIONS & UTIMECMP_TRUNCATE_SOURCE, do the comparison after SRC is
+ converted to the destination's timestamp resolution as filtered through
+ utimens. In this case, return -2 if the exact answer cannot be
+ determined; this can happen only if the time stamps are very close and
+ there is some trouble accessing the file system (e.g., the user does not
+ have permission to futz with the destination's time stamps). */
+
+int
+utimecmp (char const *dst_name,
+ struct stat const *dst_stat,
+ struct stat const *src_stat,
+ int options)
+{
+ /* Things to watch out for:
+
+ The code uses a static hash table internally and is not safe in the
+ presence of signals, multiple threads, etc.
+
+ int and long int might be 32 bits. Many of the calculations store
+ numbers up to 2 billion, and multiply by 10; they have to avoid
+ multiplying 2 billion by 10, as this exceeds 32-bit capabilities.
+
+ time_t might be unsigned. */
+
+ verify (time_t_is_integer, (time_t) 0.5 == 0);
+ verify (twos_complement_arithmetic, -1 == ~1 + 1);
+
+ /* Destination and source time stamps. */
+ time_t dst_s = dst_stat->st_mtime;
+ time_t src_s = src_stat->st_mtime;
+ int dst_ns = TIMESPEC_NS (dst_stat->st_mtim);
+ int src_ns = TIMESPEC_NS (src_stat->st_mtim);
+
+ if (options & UTIMECMP_TRUNCATE_SOURCE)
+ {
+ /* Look up the time stamp resolution for the destination device. */
+
+ /* Hash table for devices. */
+ static Hash_table *ht;
+
+ /* Information about the destination file system. */
+ static struct fs_res *new_dst_res;
+ struct fs_res *dst_res;
+
+ /* Time stamp resolution in nanoseconds. */
+ int res;
+
+ if (! ht)
+ ht = hash_initialize (16, NULL, dev_info_hash, dev_info_compare, free);
+ if (! new_dst_res)
+ {
+ new_dst_res = xmalloc (sizeof *new_dst_res);
+ new_dst_res->resolution = 2 * BILLION;
+ new_dst_res->exact = false;
+ }
+ new_dst_res->dev = dst_stat->st_dev;
+ dst_res = hash_insert (ht, new_dst_res);
+ if (! dst_res)
+ xalloc_die ();
+
+ if (dst_res == new_dst_res)
+ {
+ /* NEW_DST_RES is now in use in the hash table, so allocate a
+ new entry next time. */
+ new_dst_res = NULL;
+ }
+
+ res = dst_res->resolution;
+
+ if (! dst_res->exact)
+ {
+ /* This file system's resolution is not known exactly.
+ Deduce it, and store the result in the hash table. */
+
+ time_t dst_a_s = dst_stat->st_atime;
+ time_t dst_c_s = dst_stat->st_ctime;
+ time_t dst_m_s = dst_s;
+ int dst_a_ns = TIMESPEC_NS (dst_stat->st_atim);
+ int dst_c_ns = TIMESPEC_NS (dst_stat->st_ctim);
+ int dst_m_ns = dst_ns;
+
+ /* Set RES to an upper bound on the file system resolution
+ (after truncation due to SYSCALL_RESOLUTION) by inspecting
+ the atime, ctime and mtime of the existing destination.
+ We don't know of any file system that stores atime or
+ ctime with a higher precision than mtime, so it's valid to
+ look at them too. */
+ {
+ bool odd_second = (dst_a_s | dst_c_s | dst_m_s) & 1;
+
+ if (SYSCALL_RESOLUTION == BILLION)
+ {
+ if (odd_second | dst_a_ns | dst_c_ns | dst_m_ns)
+ res = BILLION;
+ }
+ else
+ {
+ int a = dst_a_ns;
+ int c = dst_c_ns;
+ int m = dst_m_ns;
+
+ /* Write it this way to avoid mistaken GCC warning
+ about integer overflow in constant expression. */
+ int SR10 = SYSCALL_RESOLUTION; SR10 *= 10;
+
+ if ((a % SR10 | c % SR10 | m % SR10) != 0)
+ res = SYSCALL_RESOLUTION;
+ else
+ for (res = SR10, a /= SR10, c /= SR10, m /= SR10;
+ (res < dst_res->resolution
+ && (a % 10 | c % 10 | m % 10) == 0);
+ res *= 10, a /= 10, c /= 10, m /= 10)
+ if (res == BILLION)
+ {
+ if (! odd_second)
+ res *= 2;
+ break;
+ }
+ }
+
+ dst_res->resolution = res;
+ }
+
+ if (SYSCALL_RESOLUTION < res)
+ {
+ struct timespec timespec[2];
+ struct stat dst_status;
+
+ /* Ignore source time stamp information that must necessarily
+ be lost when filtered through utimens. */
+ src_ns -= src_ns % SYSCALL_RESOLUTION;
+
+ /* If the time stamps disagree widely enough, there's no need
+ to interrogate the file system to deduce the exact time
+ stamp resolution; return the answer directly. */
+ {
+ time_t s = src_s & ~ (res == 2 * BILLION);
+ if (src_s < dst_s || (src_s == dst_s && src_ns <= dst_ns))
+ return 1;
+ if (dst_s < s
+ || (dst_s == s && dst_ns < src_ns - src_ns % res))
+ return -1;
+ }
+
+ /* Determine the actual time stamp resolution for the
+ destination file system (after truncation due to
+ SYSCALL_RESOLUTION) by setting the access time stamp of the
+ destination to the existing access time, except with
+ trailing nonzero digits. */
+
+ timespec[0].tv_sec = dst_a_s;
+ timespec[0].tv_nsec = dst_a_ns;
+ timespec[1].tv_sec = dst_m_s | (res == 2 * BILLION);
+ timespec[1].tv_nsec = dst_m_ns + res / 9;
+
+ /* Set the modification time. But don't try to set the
+ modification time of symbolic links; on many hosts this sets
+ the time of the pointed-to file. */
+ if (S_ISLNK (dst_stat->st_mode)
+ || utimens (dst_name, timespec) != 0)
+ return -2;
+
+ /* Read the modification time that was set. It's safe to call
+ 'stat' here instead of worrying about 'lstat'; either the
+ caller used 'stat', or the caller used 'lstat' and found
+ something other than a symbolic link. */
+ {
+ int stat_result = stat (dst_name, &dst_status);
+
+ if (stat_result
+ | (dst_status.st_mtime ^ dst_m_s)
+ | (TIMESPEC_NS (dst_status.st_mtim) ^ dst_m_ns))
+ {
+ /* The modification time changed, or we can't tell whether
+ it changed. Change it back as best we can. */
+ timespec[1].tv_sec = dst_m_s;
+ timespec[1].tv_nsec = dst_m_ns;
+ utimens (dst_name, timespec);
+ }
+
+ if (stat_result != 0)
+ return -2;
+ }
+
+ /* Determine the exact resolution from the modification time
+ that was read back. */
+ {
+ int old_res = res;
+ int a = (BILLION * (dst_status.st_mtime & 1)
+ + TIMESPEC_NS (dst_status.st_mtim));
+
+ res = SYSCALL_RESOLUTION;
+
+ for (a /= res; a % 10 != 0; a /= 10)
+ {
+ if (res == BILLION)
+ {
+ res *= 2;
+ break;
+ }
+ res *= 10;
+ if (res == old_res)
+ break;
+ }
+ }
+ }
+
+ dst_res->resolution = res;
+ dst_res->exact = true;
+ }
+
+ /* Truncate the source's time stamp according to the resolution. */
+ src_s &= ~ (res == 2 * BILLION);
+ src_ns -= src_ns % res;
+ }
+
+ /* Compare the time stamps and return -1, 0, 1 accordingly. */
+ return (dst_s < src_s ? -1
+ : dst_s > src_s ? 1
+ : dst_ns < src_ns ? -1
+ : dst_ns > src_ns);
+}
projects / platform / upstream / coreutils.git / commitdiff