Add fstree independend directory writer to libsquashfs.so

This commit adds a directory writer to libsquashfs that wrapps a meta
data writer and provides a higher-level interface for writing directory
entries. Under the hood it enforces the rules that squashfs insists
upon.

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

1 files changed, 287 insertions, 0 deletions

diff --git a/lib/sqfs/dir_writer.c b/lib/sqfs/dir_writer.c
new file mode 100644
index 0000000..3ef3bc7
--- /dev/null
+++ b/lib/sqfs/dir_writer.c
@@ -0,0 +1,287 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * dir_writer.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "sqfs/inode.h"
+#include "sqfs/dir.h"
+#include "util.h"
+
+#include <sys/stat.h>
+#include <endian.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stdio.h>
+
+typedef struct dir_entry_t {
+	struct dir_entry_t *next;
+	uint64_t inode_ref;
+	uint32_t inode_num;
+	uint16_t type;
+	size_t name_len;
+	char name[];
+} dir_entry_t;
+
+typedef struct index_ent_t {
+	struct index_ent_t *next;
+	dir_entry_t *ent;
+	uint64_t block;
+	uint32_t index;
+} index_ent_t;
+
+struct sqfs_dir_writer_t {
+	dir_entry_t *list;
+	dir_entry_t *list_end;
+
+	index_ent_t *idx;
+	index_ent_t *idx_end;
+
+	uint64_t dir_ref;
+	size_t dir_size;
+	size_t idx_size;
+	meta_writer_t *dm;
+};
+
+static int get_type(mode_t mode)
+{
+	switch (mode & S_IFMT) {
+	case S_IFSOCK: return SQFS_INODE_SOCKET;
+	case S_IFIFO:  return SQFS_INODE_FIFO;
+	case S_IFLNK:  return SQFS_INODE_SLINK;
+	case S_IFBLK:  return SQFS_INODE_BDEV;
+	case S_IFCHR:  return SQFS_INODE_CDEV;
+	case S_IFDIR:  return SQFS_INODE_DIR;
+	case S_IFREG:  return SQFS_INODE_FILE;
+	default:
+		assert(0);
+	}
+}
+
+static void writer_reset(sqfs_dir_writer_t *writer)
+{
+	dir_entry_t *ent;
+	index_ent_t *idx;
+
+	while (writer->idx != NULL) {
+		idx = writer->idx;
+		writer->idx = idx->next;
+		free(idx);
+	}
+
+	while (writer->list != NULL) {
+		ent = writer->list;
+		writer->list = ent->next;
+		free(ent);
+	}
+
+	writer->list_end = NULL;
+	writer->idx_end = NULL;
+	writer->dir_ref = 0;
+	writer->dir_size = 0;
+	writer->idx_size = 0;
+}
+
+sqfs_dir_writer_t *sqfs_dir_writer_create(meta_writer_t *dm)
+{
+	sqfs_dir_writer_t *writer = calloc(1, sizeof(*writer));
+
+	if (writer == NULL) {
+		perror("creating directory writer");
+		return NULL;
+	}
+
+	writer->dm = dm;
+	return writer;
+}
+
+void sqfs_dir_writer_destroy(sqfs_dir_writer_t *writer)
+{
+	writer_reset(writer);
+	free(writer);
+}
+
+int sqfs_dir_writer_begin(sqfs_dir_writer_t *writer)
+{
+	uint32_t offset;
+	uint64_t block;
+
+	writer_reset(writer);
+
+	meta_writer_get_position(writer->dm, &block, &offset);
+	writer->dir_ref = (block << 16) | offset;
+	return 0;
+}
+
+int sqfs_dir_writer_add_entry(sqfs_dir_writer_t *writer, const char *name,
+			      uint32_t inode_num, uint64_t inode_ref,
+			      mode_t mode)
+{
+	dir_entry_t *ent = alloc_flex(sizeof(*ent), 1, strlen(name));
+
+	if (ent == NULL) {
+		perror("creating directory entry");
+		return -1;
+	}
+
+	ent->inode_ref = inode_ref;
+	ent->inode_num = inode_num;
+	ent->type = get_type(mode);
+	ent->name_len = strlen(name);
+	memcpy(ent->name, name, ent->name_len);
+
+	if (writer->list_end == NULL) {
+		writer->list = writer->list_end = ent;
+	} else {
+		writer->list_end->next = ent;
+		writer->list_end = ent;
+	}
+
+	writer->dir_size += sizeof(ent) + ent->name_len;
+	return 0;
+}
+
+static size_t get_conseq_entry_count(uint32_t offset, dir_entry_t *head)
+{
+	size_t size, count = 0;
+	dir_entry_t *it;
+	int32_t diff;
+
+	size = (offset + sizeof(sqfs_dir_header_t)) % SQFS_META_BLOCK_SIZE;
+
+	for (it = head; it != NULL; it = it->next) {
+		if ((it->inode_ref >> 16) != (head->inode_ref >> 16))
+			break;
+
+		diff = it->inode_num - head->inode_num;
+
+		if (diff > 32767 || diff < -32767)
+			break;
+
+		size += sizeof(sqfs_dir_entry_t) + it->name_len;
+
+		if (count > 0 && size > SQFS_META_BLOCK_SIZE)
+			break;
+
+		count += 1;
+
+		if (count == SQFS_MAX_DIR_ENT)
+			break;
+	}
+
+	return count;
+}
+
+static int add_header(sqfs_dir_writer_t *writer, size_t count,
+		      dir_entry_t *ref, uint64_t block)
+{
+	sqfs_dir_header_t hdr;
+	index_ent_t *idx;
+
+	hdr.count = htole32(count - 1);
+	hdr.start_block = htole32(ref->inode_ref >> 16);
+	hdr.inode_number = htole32(ref->inode_num);
+
+	if (meta_writer_append(writer->dm, &hdr, sizeof(hdr)))
+		return -1;
+
+	idx = calloc(1, sizeof(*idx));
+	if (idx == NULL) {
+		perror("creating directory index entry");
+		return -1;
+	}
+
+	idx->ent = ref;
+	idx->block = block;
+	idx->index = writer->dir_size;
+
+	if (writer->idx_end == NULL) {
+		writer->idx = writer->idx_end = idx;
+	} else {
+		writer->idx_end->next = idx;
+		writer->idx_end = idx;
+	}
+
+	writer->dir_size += sizeof(hdr);
+	writer->idx_size += 1;
+	return 0;
+}
+
+int sqfs_dir_writer_end(sqfs_dir_writer_t *writer)
+{
+	dir_entry_t *it, *first;
+	sqfs_dir_entry_t ent;
+	uint16_t *diff_u16;
+	size_t i, count;
+	uint32_t offset;
+	uint64_t block;
+
+	for (it = writer->list; it != NULL; ) {
+		meta_writer_get_position(writer->dm, &block, &offset);
+		count = get_conseq_entry_count(offset, it);
+
+		if (add_header(writer, count, it, block))
+			return -1;
+
+		first = it;
+
+		for (i = 0; i < count; ++i) {
+			ent.offset = htole16(it->inode_ref & 0x0000FFFF);
+			ent.inode_diff = it->inode_num - first->inode_num;
+			ent.type = htole16(it->type);
+			ent.size = htole16(it->name_len - 1);
+
+			diff_u16 = (uint16_t *)&ent.inode_diff;
+			*diff_u16 = htole16(*diff_u16);
+
+			if (meta_writer_append(writer->dm, &ent, sizeof(ent)))
+				return -1;
+
+			if (meta_writer_append(writer->dm, it->name, it->name_len))
+				return -1;
+
+			it = it->next;
+		}
+	}
+
+	return 0;
+}
+
+size_t sqfs_dir_writer_get_size(sqfs_dir_writer_t *writer)
+{
+	return writer->dir_size;
+}
+
+uint64_t sqfs_dir_writer_get_dir_reference(sqfs_dir_writer_t *writer)
+{
+	return writer->dir_ref;
+}
+
+size_t sqfs_dir_writer_get_index_size(sqfs_dir_writer_t *writer)
+{
+	return writer->idx_size;
+}
+
+int sqfs_dir_writer_write_index(sqfs_dir_writer_t *writer,
+				meta_writer_t *im)
+{
+	sqfs_dir_index_t ent;
+	index_ent_t *idx;
+
+	for (idx = writer->idx; idx != NULL; idx = idx->next) {
+		ent.start_block = htole32(idx->block);
+		ent.index = htole32(idx->index);
+		ent.size = htole32(idx->ent->name_len - 1);
+
+		if (meta_writer_append(im, &ent, sizeof(ent)))
+			return -1;
+
+		if (meta_writer_append(im, idx->ent->name, idx->ent->name_len))
+			return -1;
+	}
+
+	return 0;
+}