Make the data writer padding hookable

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

2 files changed, 12 insertions, 0 deletions

diff --git a/include/sqfs/data_writer.h b/include/sqfs/data_writer.h
index a895b7a..210a08d 100644
--- a/include/sqfs/data_writer.h
+++ b/include/sqfs/data_writer.h
@@ -125,6 +125,15 @@ struct sqfs_block_hooks_t {
 	 *              fragment block.
 	 */
 	void (*notify_fragment_discard)(void *user, const sqfs_block_t *block);
+
+	/**
+	 * @brief Gets called before writing a block of padding bytes to disk.
+	 *
+	 * @param user A user pointer.
+	 * @param block The padding bytes that are about to be written.
+	 * @param count The number of padding bytes in the block.
+	 */
+	void (*prepare_padding)(void *user, sqfs_u8 *block, size_t count);
 };
 
 #ifdef __cplusplus
diff --git a/lib/sqfs/data_writer/block.c b/lib/sqfs/data_writer/block.c
index 7c52bb4..01e1387 100644
--- a/lib/sqfs/data_writer/block.c
+++ b/lib/sqfs/data_writer/block.c
@@ -70,6 +70,9 @@ static int allign_file(sqfs_data_writer_t *proc, sqfs_block_t *blk)
 	if (padding == 0)
 		return SQFS_ERROR_ALLOC;
 
+	if (proc->hooks != NULL && proc->hooks->prepare_padding != NULL)
+		proc->hooks->prepare_padding(proc->user_ptr, padding, diff);
+
 	chksum = crc32(0, padding, diff);
 
 	ret = proc->file->write_at(proc->file, size, padding, diff);