libutil: Add a stacked, recursive directory tree iterator

The concept is simple: Use the existing, platform dependent iterator
to walk a directory. If a directory entry is encountered, recurse into
it using the open_subdir handler, reconstruct the full path for any
entries discovered using the directory stack.

An additional function is added to skip a sub-hierarchy.

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

1 files changed, 215 insertions, 0 deletions

diff --git a/lib/util/src/dir_tree_iterator.c b/lib/util/src/dir_tree_iterator.c
new file mode 100644
index 0000000..88b6840
--- /dev/null
+++ b/lib/util/src/dir_tree_iterator.c
@@ -0,0 +1,215 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * dir_tree_iterator.c
+ *
+ * Copyright (C) 2023 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "util/dir_tree_iterator.h"
+#include "util/util.h"
+#include "sqfs/error.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct dir_stack_t {
+	struct dir_stack_t *next;
+	dir_iterator_t *dir;
+	char name[];
+} dir_stack_t;
+
+typedef struct {
+	dir_iterator_t base;
+
+	int state;
+	dir_stack_t *top;
+} dir_tree_iterator_t;
+
+static void pop(dir_tree_iterator_t *it)
+{
+	if (it->top != NULL) {
+		dir_stack_t *ent = it->top;
+		it->top = it->top->next;
+
+		sqfs_drop(ent->dir);
+		free(ent);
+	}
+}
+
+static int push(dir_tree_iterator_t *it, const char *name, dir_iterator_t *dir)
+{
+	dir_stack_t *ent = alloc_flex(sizeof(*ent), 1, strlen(name) + 1);
+
+	if (ent == NULL)
+		return SQFS_ERROR_ALLOC;
+
+	strcpy(ent->name, name);
+	ent->dir = sqfs_grab(dir);
+	ent->next = it->top;
+	it->top = ent;
+	return 0;
+}
+
+/*****************************************************************************/
+
+static void destroy(sqfs_object_t *obj)
+{
+	dir_tree_iterator_t *it = (dir_tree_iterator_t *)obj;
+
+	while (it->top != NULL)
+		pop(it);
+
+	free(it);
+}
+
+static int next(dir_iterator_t *base, dir_entry_t **out)
+{
+	dir_tree_iterator_t *it = (dir_tree_iterator_t *)base;
+	dir_iterator_t *sub = NULL;
+	dir_entry_t *ent = NULL;
+	dir_stack_t *sit = NULL;
+	size_t plen = 0;
+	int ret;
+
+	*out = NULL;
+
+	if (it->state != 0)
+		return it->state;
+
+	for (;;) {
+		if (it->top == NULL) {
+			ret = 1;
+			goto fail;
+		}
+
+		ret = it->top->dir->next(it->top->dir, &ent);
+		if (ret < 0)
+			goto fail;
+
+		if (ret > 0) {
+			pop(it);
+			continue;
+		}
+
+		if (!strcmp(ent->name, ".") || !strcmp(ent->name, "..")) {
+			free(ent);
+			ent = NULL;
+			continue;
+		}
+
+		break;
+	}
+
+	for (sit = it->top; sit != NULL; sit = sit->next) {
+		size_t len = strlen(sit->name);
+		if (len > 0)
+			plen += len + 1;
+	}
+
+	if (plen > 0) {
+		size_t slen = strlen(ent->name) + 1;
+		void *new = realloc(ent, sizeof(*ent) + plen + slen);
+		char *dst;
+
+		if (new == NULL) {
+			ret = SQFS_ERROR_ALLOC;
+			goto fail;
+		}
+
+		ent = new;
+		memmove(ent->name + plen, ent->name, slen);
+		dst = ent->name + plen;
+
+		for (sit = it->top; sit != NULL; sit = sit->next) {
+			size_t len = strlen(sit->name);
+			if (len > 0) {
+				*(--dst) = '/';
+				dst -= len;
+				memcpy(dst, sit->name, len);
+			}
+		}
+	}
+
+	if (S_ISDIR(ent->mode)) {
+		ret = it->top->dir->open_subdir(it->top->dir, &sub);
+		if (ret != 0)
+			goto fail;
+
+		ret = push(it, ent->name + plen, sub);
+		sqfs_drop(sub);
+		if (ret != 0)
+			goto fail;
+	}
+
+	*out = ent;
+	return it->state;
+fail:
+	free(ent);
+	it->state = ret;
+	return it->state;
+}
+
+static int read_link(dir_iterator_t *base, char **out)
+{
+	dir_tree_iterator_t *it = (dir_tree_iterator_t *)base;
+
+	if (it->top == NULL) {
+		*out = NULL;
+		return SQFS_ERROR_NO_ENTRY;
+	}
+
+	return it->top->dir->read_link(it->top->dir, out);
+}
+
+static int open_subdir(dir_iterator_t *base, dir_iterator_t **out)
+{
+	dir_tree_iterator_t *it = (dir_tree_iterator_t *)base;
+
+	if (it->top == NULL) {
+		*out = NULL;
+		return SQFS_ERROR_NO_ENTRY;
+	}
+
+	return it->top->dir->open_subdir(it->top->dir, out);
+}
+
+dir_iterator_t *dir_tree_iterator_create(const char *path)
+{
+	dir_tree_iterator_t *it = calloc(1, sizeof(*it));
+	dir_iterator_t *dir;
+	int ret;
+
+	if (it == NULL) {
+		perror(path);
+		return NULL;
+	}
+
+	dir = dir_iterator_create(path);
+	if (dir == NULL)
+		goto fail;
+
+	ret = push(it, "", dir);
+	dir = sqfs_drop(dir);
+	if (ret != 0) {
+		fprintf(stderr, "%s: out of memory\n", path);
+		goto fail;
+	}
+
+	sqfs_object_init(it, destroy, NULL);
+	((dir_iterator_t *)it)->dev = it->top->dir->dev;
+	((dir_iterator_t *)it)->next = next;
+	((dir_iterator_t *)it)->read_link = read_link;
+	((dir_iterator_t *)it)->open_subdir = open_subdir;
+
+	return (dir_iterator_t *)it;
+fail:
+	free(it);
+	return NULL;
+}
+
+void dir_tree_iterator_skip(dir_iterator_t *base)
+{
+	dir_tree_iterator_t *it = (dir_tree_iterator_t *)base;
+
+	pop(it);
+}