stat: New wrapper around the stat() family

This lets bfs transparently support the new statx() system call on
Linux, giving it access to file birth times.

1 files changed, 243 insertions, 0 deletions

diff --git a/stat.c b/stat.c
new file mode 100644
index 0000000..4f1c2fc
--- /dev/null
+++ b/stat.c
@@ -0,0 +1,243 @@
+/****************************************************************************
+ * bfs                                                                      *
+ * Copyright (C) 2018 Tavian Barnes <tavianator@tavianator.com>             *
+ *                                                                          *
+ * Permission to use, copy, modify, and/or distribute this software for any *
+ * purpose with or without fee is hereby granted.                           *
+ *                                                                          *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES *
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         *
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  *
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   *
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    *
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  *
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           *
+ ****************************************************************************/
+
+#include "stat.h"
+#include "util.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#if __linux__
+#	include <linux/stat.h>
+#	include <sys/syscall.h>
+#	include <sys/sysmacros.h>
+#elif __APPLE__
+#	define st_atim st_atimespec
+#	define st_ctim st_ctimespec
+#	define st_mtim st_mtimespec
+#	define st_birthtim st_birthtimespec
+#endif
+
+/**
+ * Check if we should retry a failed stat() due to a potentially broken link.
+ */
+static bool bfs_stat_retry(int ret, int at_flags, enum bfs_stat_flag flags) {
+	return ret != 0
+		&& !(at_flags & AT_SYMLINK_NOFOLLOW)
+		&& (flags & BFS_STAT_BROKEN_OK)
+		&& is_nonexistence_error(errno);
+}
+
+/**
+ * Convert a struct stat to a struct bfs_stat.
+ */
+static void bfs_stat_convert(const struct stat *statbuf, struct bfs_stat *buf) {
+	buf->mask = 0;
+
+	buf->dev = statbuf->st_dev;
+	buf->mask |= BFS_STAT_DEV;
+
+	buf->ino = statbuf->st_ino;
+	buf->mask |= BFS_STAT_INO;
+
+	buf->mode = statbuf->st_mode;
+	buf->mask |= BFS_STAT_TYPE | BFS_STAT_MODE;
+
+	buf->nlink = statbuf->st_nlink;
+	buf->mask |= BFS_STAT_NLINK;
+
+	buf->gid = statbuf->st_gid;
+	buf->mask |= BFS_STAT_GID;
+
+	buf->uid = statbuf->st_uid;
+	buf->mask |= BFS_STAT_UID;
+
+	buf->size = statbuf->st_size;
+	buf->mask |= BFS_STAT_SIZE;
+
+	buf->blocks = statbuf->st_blocks;
+	buf->mask |= BFS_STAT_BLOCKS;
+
+	buf->atime = statbuf->st_atim;
+	buf->mask |= BFS_STAT_ATIME;
+
+	buf->ctime = statbuf->st_ctim;
+	buf->mask |= BFS_STAT_CTIME;
+
+	buf->mtime = statbuf->st_mtim;
+	buf->mask |= BFS_STAT_MTIME;
+
+#if __APPLE__ || __FreeBSD__ || __NetBSD__
+	buf->btime = statbuf->st_birthtim;
+	buf->mask |= BFS_STAT_BTIME;
+#endif
+}
+
+/**
+ * bfs_stat() implementation backed by stat().
+ */
+static int bfs_stat_impl(int at_fd, const char *at_path, int at_flags, enum bfs_stat_flag flags, struct bfs_stat *buf) {
+	struct stat statbuf;
+	int ret = fstatat(at_fd, at_path, &statbuf, at_flags);
+
+	if (bfs_stat_retry(ret, at_flags, flags)) {
+		at_flags |= AT_SYMLINK_NOFOLLOW;
+		ret = fstatat(at_fd, at_path, &statbuf, at_flags);
+	}
+
+	if (ret == 0) {
+		bfs_stat_convert(&statbuf, buf);
+	}
+
+	return ret;
+}
+
+#ifdef STATX_BASIC_STATS
+
+/**
+ * Wrapper for the statx() system call, which has no native glibc wrapper.
+ */
+static int bfs_statx(int at_fd, const char *at_path, int at_flags, unsigned int mask, struct statx *buf) {
+	return syscall(__NR_statx, at_fd, at_path, at_flags, mask, buf);
+}
+
+/**
+ * bfs_stat() implementation backed by statx().
+ */
+static int bfs_statx_impl(int at_fd, const char *at_path, int at_flags, enum bfs_stat_flag flags, struct bfs_stat *buf) {
+	unsigned int mask = STATX_BASIC_STATS | STATX_BTIME;
+	struct statx xbuf;
+	int ret = bfs_statx(at_fd, at_path, at_flags, mask, &xbuf);
+
+	if (bfs_stat_retry(ret, at_flags, flags)) {
+		at_flags |= AT_SYMLINK_NOFOLLOW;
+		ret = bfs_statx(at_fd, at_path, at_flags, mask, &xbuf);
+	}
+
+	if (ret != 0) {
+		return ret;
+	}
+
+	if ((xbuf.stx_mask & STATX_BASIC_STATS) != STATX_BASIC_STATS) {
+		// Callers shouldn't have to check anything except BFS_STAT_BTIME
+		errno = EINVAL;
+		return -1;
+	}
+
+	buf->mask = 0;
+
+	buf->dev = makedev(xbuf.stx_dev_major, xbuf.stx_dev_minor);
+	buf->mask |= BFS_STAT_DEV;
+
+	if (xbuf.stx_mask & STATX_INO) {
+		buf->ino = xbuf.stx_ino;
+		buf->mask |= BFS_STAT_INO;
+	}
+
+	buf->mode = xbuf.stx_mode;
+	if (xbuf.stx_mask & STATX_TYPE) {
+		buf->mask |= BFS_STAT_TYPE;
+	}
+	if (xbuf.stx_mask & STATX_MODE) {
+		buf->mask |= BFS_STAT_MODE;
+	}
+
+	if (xbuf.stx_mask & STATX_NLINK) {
+		buf->nlink = xbuf.stx_nlink;
+		buf->mask |= BFS_STAT_NLINK;
+	}
+
+	if (xbuf.stx_mask & STATX_GID) {
+		buf->gid = xbuf.stx_gid;
+		buf->mask |= BFS_STAT_GID;
+	}
+
+	if (xbuf.stx_mask & STATX_UID) {
+		buf->uid = xbuf.stx_uid;
+		buf->mask |= BFS_STAT_UID;
+	}
+
+	if (xbuf.stx_mask & STATX_SIZE) {
+		buf->size = xbuf.stx_size;
+		buf->mask |= BFS_STAT_SIZE;
+	}
+
+	if (xbuf.stx_mask & STATX_BLOCKS) {
+		buf->blocks = xbuf.stx_blocks;
+		buf->mask |= BFS_STAT_BLOCKS;
+	}
+
+	if (xbuf.stx_mask & STATX_ATIME) {
+		buf->atime.tv_sec = xbuf.stx_atime.tv_sec;
+		buf->atime.tv_nsec = xbuf.stx_atime.tv_nsec;
+		buf->mask |= BFS_STAT_ATIME;
+	}
+
+	if (xbuf.stx_mask & STATX_BTIME) {
+		buf->btime.tv_sec = xbuf.stx_btime.tv_sec;
+		buf->btime.tv_nsec = xbuf.stx_btime.tv_nsec;
+		buf->mask |= BFS_STAT_BTIME;
+	}
+
+	if (xbuf.stx_mask & STATX_CTIME) {
+		buf->ctime.tv_sec = xbuf.stx_ctime.tv_sec;
+		buf->ctime.tv_nsec = xbuf.stx_ctime.tv_nsec;
+		buf->mask |= BFS_STAT_CTIME;
+	}
+
+	if (xbuf.stx_mask & STATX_MTIME) {
+		buf->mtime.tv_sec = xbuf.stx_mtime.tv_sec;
+		buf->mtime.tv_nsec = xbuf.stx_mtime.tv_nsec;
+		buf->mask |= BFS_STAT_MTIME;
+	}
+
+	return ret;
+}
+
+#endif // STATX_BASIC_STATS
+
+int bfs_stat(int at_fd, const char *at_path, int at_flags, enum bfs_stat_flag flags, struct bfs_stat *buf) {
+#ifdef STATX_BASIC_STATS
+	static bool has_statx = true;
+
+	if (has_statx) {
+		int ret = bfs_statx_impl(at_fd, at_path, at_flags, flags, buf);
+		if (ret != 0 && errno == ENOSYS) {
+			has_statx = false;
+		} else {
+			return ret;
+		}
+	}
+#endif
+
+	return bfs_stat_impl(at_fd, at_path, at_flags, flags, buf);
+}
+
+int bfs_fstat(int fd, struct bfs_stat *buf) {
+#ifdef AT_EMPTY_PATH
+	return bfs_stat(fd, "", AT_EMPTY_PATH, 0, buf);
+#else
+	struct stat statbuf;
+	int ret = fstat(fd, &statbuf);
+	if (ret == 0) {
+		bfs_stat_convert(&statbuf, buf);
+	}
+	return ret;
+#endif
+}