Add libsimple_close_range

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 142 insertions, 0 deletions

diff --git a/close_range.c b/close_range.c
new file mode 100644
index 0000000..540eba0
--- /dev/null
+++ b/close_range.c
@@ -0,0 +1,142 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+#ifdef __linux__
+# include <sys/syscall.h>
+#endif
+
+
+static int
+uintpcmp(const void *av, const void *bv)
+{
+	const unsigned int *ap = av;
+	const unsigned int *bp = bv;
+	const unsigned int a = *ap;
+	const unsigned int b = *bp;
+	return a < b ? -1 : a > b;
+}
+
+static unsigned int *
+list_fds(unsigned int min, unsigned int max, size_t *count)
+{
+	DIR *dir;
+	int ignore_fd;
+	unsigned int *ret = NULL, *new;
+	size_t size = 0;
+	struct dirent *f;
+	unsigned long int fd;
+	char *end;
+
+	*count = 0;
+
+	dir = opendir("/dev/fd");
+	if (!dir)
+		return NULL;
+	ignore_fd = dirfd(dir);
+
+	errno = 0;
+	while ((f = readdir(dir))) {
+		if (!isdigit(f->d_name[0]))
+			continue;
+		fd = strtoul(f->d_name, &end, 10);
+		if ((int)fd == ignore_fd || (unsigned int)fd < min || (unsigned int)fd > max)
+			continue;
+		if (*end || fd > INT_MAX || (!fd && errno))
+			continue;
+		if (*count == size) {
+			size += 16;
+			new = realloc(ret, size * sizeof(*ret));
+			if (!new)
+				goto fail;
+			ret = new;
+		}
+		ret[(*count)++] = (unsigned int)fd;
+	}
+
+	if (errno) {
+	fail:
+		closedir(dir);
+	fail_closed:
+		free(ret);
+		return NULL;
+	}
+
+	if (closedir(dir))
+		goto fail_closed;
+
+	return ret;
+}
+
+int
+libsimple_close_range(unsigned int first, unsigned int last, unsigned int *next) /* TODO test */
+{
+	int saved_errno;
+
+	*next = first;
+
+	if (first > last) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	if (first > INT_MAX)
+		return 0;
+	if (last > INT_MAX)
+		last = INT_MAX;
+
+	saved_errno = errno;
+
+#if defined(__linux__) && defined(__NR_close_range)
+	if (!syscall(__NR_close_range, first, last, 0))
+		return 0;
+	else if (errno != ENOSYS)
+		return -1;
+#endif
+
+	if (last - first > 100) { /* TODO best limit should be researched */
+		unsigned int *fds;
+		size_t n, i;
+		fds = list_fds(first, last, &n);
+		if (!fds)
+			goto fallback;
+		qsort(fds, n, sizeof(*fds), uintpcmp);
+		for (i = 0; i < n; i++) {
+			if (close((int)fds[i]) && errno != EBADF) {
+				if (i + 1 < n)
+					*next = fds[i + 1];
+				else
+					*next = fds[i] + (fds[i] < LIBSIMPLE_CLOSE_RANGE_MAX);
+				free(fds);
+				return -1;
+			}
+		}
+		free(fds);
+		goto out;
+	}
+
+fallback:
+	do {
+		if (close((int)first) && errno != EBADF) {
+			*next = first + (first < LIBSIMPLE_CLOSE_RANGE_MAX);
+			return -1;
+		}
+	} while (first++ < last);
+
+out:
+	*next = last + (last < LIBSIMPLE_CLOSE_RANGE_MAX);
+	errno = saved_errno;
+	return 0;
+}
+
+
+#else
+#include "test.h"
+
+int
+main(void)
+{
+	return 0;
+}
+
+#endif