Block processor: add flags to manage hashing & sparse block detection

This commit adds 2 new user settable flags to the block processor:
 - A flag to ignore sparse blocks and treat them like normal
   data blocks.
 - A flag to disable checksum computation altogether.

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

2 files changed, 21 insertions, 3 deletions

diff --git a/include/sqfs/block.h b/include/sqfs/block.h
index 7cc815c..582f128 100644
--- a/include/sqfs/block.h
+++ b/include/sqfs/block.h
@@ -97,6 +97,19 @@ typedef enum {
 	SQFS_BLK_DONT_DEDUPLICATE = 0x0008,
 
 	/**
+	 * @brief Supress sparse block detection.
+	 *
+	 * If set, sparse blocks are no longer checked and flagged as such and
+	 * are instead processed like normal blocks.
+	 */
+	SQFS_BLK_IGNORE_SPARSE = 0x0010,
+
+	/**
+	 * @brief Don't compute block data checksums.
+	 */
+	SQFS_BLK_DONT_HASH = 0x0020,
+
+	/**
 	 * @brief Set by the @ref sqfs_block_processor_t if it determines a
 	 *        block of a file to be sparse, i.e. only zero bytes.
 	 */
@@ -135,7 +148,7 @@ typedef enum {
 	/**
 	 * @brief The combination of all flags that are user settable.
 	 */
-	SQFS_BLK_USER_SETTABLE_FLAGS = 0x000F,
+	SQFS_BLK_USER_SETTABLE_FLAGS = 0x003F,
 } SQFS_BLK_FLAGS;
 
 #endif /* SQFS_BLOCK_H */
diff --git a/lib/sqfs/block_processor/common.c b/lib/sqfs/block_processor/common.c
index bfcc3d5..b40ec0f 100644
--- a/lib/sqfs/block_processor/common.c
+++ b/lib/sqfs/block_processor/common.c
@@ -144,12 +144,17 @@ static int process_block(sqfs_block_t *block, sqfs_compressor_t *cmp,
 		}
 	}
 
-	if (is_zero_block(block->data, block->size)) {
+	if (!(block->flags & SQFS_BLK_IGNORE_SPARSE) &&
+	    is_zero_block(block->data, block->size)) {
 		block->flags |= SQFS_BLK_IS_SPARSE;
 		return 0;
 	}
 
-	block->checksum = xxh32(block->data, block->size);
+	if (block->flags & SQFS_BLK_DONT_HASH) {
+		block->checksum = 0;
+	} else {
+		block->checksum = xxh32(block->data, block->size);
+	}
 
 	if (block->flags & (SQFS_BLK_IS_FRAGMENT | SQFS_BLK_DONT_COMPRESS))
 		return 0;