Implement a version of the directory iterator for Unix

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 177 insertions, 0 deletions

diff --git a/lib/util/src/unix_dir_iterator.c b/lib/util/src/unix_dir_iterator.c
new file mode 100644
index 0000000..e712a45
--- /dev/null
+++ b/lib/util/src/unix_dir_iterator.c
@@ -0,0 +1,169 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * unix_dir_iterator.c
+ *
+ * Copyright (C) 2023 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "util/dir_iterator.h"
+#include "util/util.h"
+#include "sqfs/error.h"
+
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <string.h>
+#include <errno.h>
+
+typedef struct {
+	dir_iterator_t base;
+
+	struct dirent *ent;
+	struct stat sb;
+	int state;
+	DIR *dir;
+} unix_dir_iterator_t;
+
+static void dir_destroy(sqfs_object_t *obj)
+{
+	unix_dir_iterator_t *it = (unix_dir_iterator_t *)obj;
+
+	closedir(it->dir);
+	free(it);
+}
+
+static int dir_read_link(dir_iterator_t *base, char **out)
+{
+	unix_dir_iterator_t *it = (unix_dir_iterator_t *)base;
+	size_t size;
+	char *str;
+
+	*out = NULL;
+
+	if (it->state != 0 || it->ent == NULL) {
+		fputs("[BUG] no entry loaded, cannot readlink\n", stderr);
+		return SQFS_ERROR_INTERNAL;
+	}
+
+	if (S_ISLNK(it->sb.st_mode)) {
+		fprintf(stderr, "[BUG] %s is not a symlink, cannot readlink\n",
+			it->ent->d_name);
+		it->state = SQFS_ERROR_INTERNAL;
+		return SQFS_ERROR_INTERNAL;
+	}
+
+	if ((sizeof(it->sb.st_size) > sizeof(size_t)) &&
+	    it->sb.st_size > SIZE_MAX) {
+		goto fail_ov;
+	}
+
+	if (SZ_ADD_OV((size_t)it->sb.st_size, 1, &size))
+		goto fail_ov;
+
+	str = calloc(1, size);
+	if (str == NULL) {
+		perror(it->ent->d_name);
+		it->state = SQFS_ERROR_ALLOC;
+		return it->state;
+	}
+
+	if (readlinkat(dirfd(it->dir), it->ent->d_name,
+		       str, (size_t)it->sb.st_size) < 0) {
+		fprintf(stderr, "%s: readlink: %s\n", it->ent->d_name,
+			strerror(errno));
+		free(str);
+		it->state = SQFS_ERROR_INTERNAL;
+		return it->state;
+	}
+
+	str[it->sb.st_size] = '\0';
+
+	*out = str;
+	return it->state;
+fail_ov:
+	fprintf(stderr, "%s: link target too long\n", it->ent->d_name);
+	return SQFS_ERROR_OVERFLOW;
+}
+
+static int dir_next(dir_iterator_t *base, dir_entry_t **out)
+{
+	unix_dir_iterator_t *it = (unix_dir_iterator_t *)base;
+	dir_entry_t *decoded;
+	size_t len;
+
+	if (it->state != 0)
+		return it->state;
+
+	errno = 0;
+	it->ent = readdir(it->dir);
+
+	if (it->ent == NULL) {
+		if (errno != 0) {
+			perror("readdir");
+			it->state = SQFS_ERROR_INTERNAL;
+		} else {
+			it->state = 1;
+		}
+
+		return it->state;
+	}
+
+	if (fstatat(dirfd(it->dir), it->ent->d_name, &it->sb, AT_SYMLINK_NOFOLLOW)) {
+		perror(it->ent->d_name);
+		it->state = SQFS_ERROR_INTERNAL;
+		return it->state;
+	}
+
+	len = strlen(it->ent->d_name);
+
+	decoded = alloc_flex(sizeof(*decoded), 1, len + 1);
+	if (decoded == NULL) {
+		perror(it->ent->d_name);
+		it->state = SQFS_ERROR_ALLOC;
+		return it->state;
+	}
+
+	memcpy(decoded->name, it->ent->d_name, len);
+	decoded->mtime = it->sb.st_mtime;
+	decoded->dev = it->sb.st_dev;
+	decoded->rdev = it->sb.st_rdev;
+	decoded->uid = it->sb.st_uid;
+	decoded->gid = it->sb.st_gid;
+	decoded->mode = it->sb.st_mode;
+
+	*out = decoded;
+	return it->state;
+}
+
+dir_iterator_t *dir_iterator_create(const char *path)
+{
+	unix_dir_iterator_t *it = calloc(1, sizeof(*it));
+
+	if (it == NULL) {
+		perror(path);
+		return NULL;
+	}
+
+	it->state = 0;
+	it->dir = opendir(path);
+
+	if (it->dir == NULL) {
+		perror(path);
+		free(it);
+		return NULL;
+	}
+
+	if (fstat(dirfd(it->dir), &it->sb)) {
+		perror(path);
+		closedir(it->dir);
+		free(it);
+		return NULL;
+	}
+
+	sqfs_object_init(it, dir_destroy, NULL);
+	((dir_iterator_t *)it)->dev = it->sb.st_dev;
+	((dir_iterator_t *)it)->next = dir_next;
+	((dir_iterator_t *)it)->read_link = dir_read_link;
+
+	return (dir_iterator_t *)it;
+}
diff --git a/lib/util/src/w32_dir_iterator.c b/lib/util/src/w32_dir_iterator.c
index 1a330ae..9ec8b18 100644
--- a/lib/util/src/w32_dir_iterator.c
+++ b/lib/util/src/w32_dir_iterator.c
@@ -47,6 +47,13 @@ static sqfs_s64 w32time_to_unix(const FILETIME *ft)
 	return w32ts - UNIX_EPOCH_ON_W32;
 }
 
+static int dir_iterator_read_link(dir_iterator_t *it, char **out)
+{
+	(void)it;
+	*out = NULL;
+	return SQFS_ERROR_UNSUPPORTED;
+}
+
 static int dir_iterator_next(dir_iterator_t *it, dir_entry_t **out)
 {
 	dir_iterator_win32_t *w32 = (dir_iterator_win32_t *)it;
@@ -177,6 +184,7 @@ dir_iterator_t *dir_iterator_create(const char *path)
 	sqfs_object_init(it, dir_iterator_destroy, NULL);
 
 	((dir_iterator_t *)it)->next = dir_iterator_next;
+	((dir_iterator_t *)it)->read_link = dir_iterator_read_link;
 
 	it->state = STATE_HAVE_ENTRY;
 	it->dirhnd = dirhnd;