4 files changed, 120 insertions, 2 deletions

diff --git a/mkfs/Makemodule.am b/mkfs/Makemodule.am
index ad3f166..7b0b353 100644
--- a/mkfs/Makemodule.am
+++ b/mkfs/Makemodule.am
@@ -1,6 +1,7 @@
 mksquashfs_SOURCES = mkfs/mksquashfs.c mkfs/options.c mkfs/options.h
+mksquashfs_SOURCES += mkfs/meta_writer.c mkfs/meta_writer.h
 mksquashfs_SOURCES += include/squashfs.h
-mksquashfs_LDADD = libfstree.a libcompress.a
+mksquashfs_LDADD = libutil.a libfstree.a libcompress.a
 
 if WITH_LZMA
 mksquashfs_LDADD += $(XZ_LIBS)
diff --git a/mkfs/meta_writer.c b/mkfs/meta_writer.c
new file mode 100644
index 0000000..97db1c1
--- /dev/null
+++ b/mkfs/meta_writer.c
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "meta_writer.h"
+#include "util.h"
+
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+meta_writer_t *meta_writer_create(int fd, compressor_t *cmp)
+{
+	meta_writer_t *m = calloc(1, sizeof(*m));
+
+	if (m == NULL) {
+		perror("creating meta data writer");
+		return NULL;
+	}
+
+	m->cmp = cmp;
+	m->outfd = fd;
+	return m;
+}
+
+void meta_writer_destroy(meta_writer_t *m)
+{
+	free(m);
+}
+
+int meta_writer_flush(meta_writer_t *m)
+{
+	ssize_t ret, count;
+
+	if (m->offset == 0)
+		return 0;
+
+	ret = m->cmp->do_block(m->cmp, m->data + 2, m->offset);
+	if (ret < 0)
+		return -1;
+
+	if (ret > 0) {
+		((uint16_t *)m->data)[0] = htole16(ret);
+		count = ret + 2;
+	} else {
+		((uint16_t *)m->data)[0] = htole16(m->offset | 0x8000);
+		count = m->offset + 2;
+	}
+
+	ret = write_retry(m->outfd, m->data, count);
+
+	if (ret < 0) {
+		perror("writing meta data");
+		return -1;
+	}
+
+	if (ret < count) {
+		fputs("meta data written to file was truncated\n", stderr);
+		return -1;
+	}
+
+	memset(m->data, 0, sizeof(m->data));
+	m->offset = 0;
+	m->block_offset += count;
+	return 0;
+}
+
+int meta_writer_append(meta_writer_t *m, const void *data, size_t size)
+{
+	size_t diff;
+
+	while (size != 0) {
+		diff = sizeof(m->data) - 2 - m->offset;
+
+		if (diff == 0) {
+			if (meta_writer_flush(m))
+				return -1;
+			diff = sizeof(m->data) - 2;
+		}
+
+		if (diff > size)
+			diff = size;
+
+		memcpy(m->data + 2 + m->offset, data, diff);
+		m->offset += diff;
+		size -= diff;
+		data = (const char *)data + diff;
+	}
+
+	if (m->offset == (sizeof(m->data) - 2))
+		return meta_writer_flush(m);
+
+	return 0;
+}
diff --git a/mkfs/meta_writer.h b/mkfs/meta_writer.h
new file mode 100644
index 0000000..bfa4160
--- /dev/null
+++ b/mkfs/meta_writer.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef META_WRITER_H
+#define META_WRITER_H
+
+#include "squashfs.h"
+#include "compress.h"
+
+typedef struct {
+	uint8_t data[SQFS_META_BLOCK_SIZE + 2];
+	size_t offset;
+	size_t block_offset;
+	int outfd;
+	compressor_t *cmp;
+} meta_writer_t;
+
+meta_writer_t *meta_writer_create(int fd, compressor_t *cmp);
+
+void meta_writer_destroy(meta_writer_t *m);
+
+int meta_writer_flush(meta_writer_t *m);
+
+int meta_writer_append(meta_writer_t *m, const void *data, size_t size);
+
+#endif /* META_WRITER_H */
diff --git a/mkfs/options.c b/mkfs/options.c
index e3371aa..fedf404 100644
--- a/mkfs/options.c
+++ b/mkfs/options.c
@@ -263,7 +263,8 @@ void process_command_line(options_t *opt, int argc, char **argv)
 			break;
 		case 'b':
 			opt->blksz = read_number("Block size", optarg,
-						 1024, 0xFFFFFFFF);
+						 SQFS_META_BLOCK_SIZE,
+						 0xFFFFFFFF);
 			break;
 		case 'B':
 			opt->devblksz = read_number("Device block size", optarg,