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Diffstat (limited to 'gnulib/lib/utimecmp.c')
| m--------- | gnulib | 0 | ||||
| -rw-r--r-- | gnulib/lib/utimecmp.c | 356 |
2 files changed, 356 insertions, 0 deletions
diff --git a/gnulib b/gnulib deleted file mode 160000 -Subproject 4fc10daa05477586fea99b6b3ca02a87d1102fa diff --git a/gnulib/lib/utimecmp.c b/gnulib/lib/utimecmp.c new file mode 100644 index 00000000..63a0c9a8 --- /dev/null +++ b/gnulib/lib/utimecmp.c @@ -0,0 +1,356 @@ +/* utimecmp.c -- compare file time stamps + + Copyright (C) 2004-2007, 2009-2010 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 3 of the License, 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, see <http://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +#include <config.h> + +#include "utimecmp.h" + +#include <limits.h> +#include <stdbool.h> +#include <stdint.h> +#include <stdlib.h> +#include <time.h> +#include <unistd.h> + +#include "hash.h" +#include "intprops.h" +#include "stat-time.h" +#include "utimens.h" +#include "verify.h" +#include "xalloc.h" + +#ifndef MAX +# define MAX(a, b) ((a) > (b) ? (a) : (b)) +#endif + +#define 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_UTIMENSAT +enum { SYSCALL_RESOLUTION = 1 }; +#elif ((HAVE_FUTIMESAT || HAVE_WORKING_UTIMES) \ + && (defined HAVE_STRUCT_STAT_ST_ATIM_TV_NSEC \ + || defined HAVE_STRUCT_STAT_ST_ATIMESPEC_TV_NSEC \ + || defined HAVE_STRUCT_STAT_ST_ATIMENSEC \ + || defined HAVE_STRUCT_STAT_ST_ATIM_ST__TIM_TV_NSEC \ + || defined HAVE_STRUCT_STAT_ST_SPARE1)) +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. + + DST_NAME may be NULL if OPTIONS is 0. + + 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 (TYPE_IS_INTEGER (time_t)); + verify (TYPE_TWOS_COMPLEMENT (int)); + + /* Destination and source time stamps. */ + time_t dst_s = dst_stat->st_mtime; + time_t src_s = src_stat->st_mtime; + int dst_ns = get_stat_mtime_ns (dst_stat); + int src_ns = get_stat_mtime_ns (src_stat); + + 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; + + /* Quick exit, if possible. Since the worst resolution is 2 + seconds, anything that differs by more than that does not + needs source truncation. */ + if (dst_s == src_s && dst_ns == src_ns) + return 0; + if (dst_s <= src_s - 2) + return -1; + if (src_s <= dst_s - 2) + return 1; + + 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; + +#ifdef _PC_TIMESTAMP_RESOLUTION + /* If the system will tell us the resolution, we're set! */ + if (! dst_res->exact) + { + res = pathconf (dst_name, _PC_TIMESTAMP_RESOLUTION); + if (0 < res) + { + dst_res->resolution = res; + dst_res->exact = true; + } + } +#endif + + 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 = get_stat_atime_ns (dst_stat); + int dst_c_ns = get_stat_ctime_ns (dst_stat); + 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) + ? lutimens (dst_name, timespec) + : utimens (dst_name, timespec)) != 0) + return -2; + + /* Read the modification time that was set. */ + { + int stat_result = (S_ISLNK (dst_stat->st_mode) + ? lstat (dst_name, &dst_status) + : stat (dst_name, &dst_status)); + + if (stat_result + | (dst_status.st_mtime ^ dst_m_s) + | (get_stat_mtime_ns (&dst_status) ^ 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; + if (S_ISLNK (dst_stat->st_mode)) + lutimens (dst_name, timespec); + else + 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) + + get_stat_mtime_ns (&dst_status)); + + 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); +} |