block writer: move block comaprison to utility function

Slightly modify the byte-for-byte comparison function to compare an
arbitrary range in a file and move it to libutil. Instead of calling
it for each block in the block writer, simply let it check an entire
range in the block writer and compute the range position/size of the
reference ahead, before looking for potential matches.

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

2 files changed, 15 insertions, 46 deletions

diff --git a/lib/sqfs/Makemodule.am b/lib/sqfs/Makemodule.am
index ad3d42d..b1c9d94 100644
--- a/lib/sqfs/Makemodule.am
+++ b/lib/sqfs/Makemodule.am
@@ -44,7 +44,7 @@ libsquashfs_la_LIBADD += $(ZSTD_LIBS) $(PTHREAD_LIBS)
 
 # directly "import" stuff from libutil
 libsquashfs_la_SOURCES += lib/util/str_table.c lib/util/alloc.c
-libsquashfs_la_SOURCES += lib/util/xxhash.c
+libsquashfs_la_SOURCES += lib/util/xxhash.c lib/util/file_cmp.c
 libsquashfs_la_SOURCES += lib/util/hash_table.c include/util/hash_table.h
 libsquashfs_la_SOURCES += lib/util/rbtree.c include/util/rbtree.h
 libsquashfs_la_SOURCES += lib/util/array.c include/util/array.h
diff --git a/lib/sqfs/block_writer.c b/lib/sqfs/block_writer.c
index 10f5ada..7709fb3 100644
--- a/lib/sqfs/block_writer.c
+++ b/lib/sqfs/block_writer.c
@@ -54,44 +54,20 @@ static int store_block_location(block_writer_default_t *wr, sqfs_u64 offset,
 	return array_append(&(wr->blocks), &info);
 }
 
-static int compare_blocks(block_writer_default_t *wr, sqfs_u64 loc_a,
-			  sqfs_u64 loc_b, size_t size)
-{
-	sqfs_u8 *ptr_a = wr->scratch, *ptr_b = ptr_a + SCRATCH_SIZE / 2;
-	size_t diff;
-	int ret;
-
-	while (size > 0) {
-		diff = SCRATCH_SIZE / 2;
-		diff = diff > size ? size : diff;
-
-		ret = wr->file->read_at(wr->file, loc_a, ptr_a, diff);
-		if (ret != 0)
-			return ret;
-
-		ret = wr->file->read_at(wr->file, loc_b, ptr_b, diff);
-		if (ret != 0)
-			return ret;
-
-		if (memcmp(ptr_a, ptr_b, diff) != 0)
-			return 1;
-
-		size -= diff;
-		loc_a += diff;
-		loc_b += diff;
-	}
-
-	return 0;
-}
-
 static int deduplicate_blocks(block_writer_default_t *wr, size_t count,
 			      size_t *out)
 {
 	const blk_info_t *blocks = wr->blocks.data;
-	sqfs_u64 loc_a, loc_b;
-	size_t i, j, sz;
+	sqfs_u64 loc_a, loc_b, sz;
+	size_t i, j;
 	int ret;
 
+	sz = 0;
+	loc_a = blocks[wr->file_start].offset;
+
+	for (i = 0; i < count; ++i)
+		sz += SIZE_FROM_HASH(blocks[wr->file_start + i].hash);
+
 	for (i = 0; i < wr->file_start; ++i) {
 		for (j = 0; j < count; ++j) {
 			if (blocks[i + j].hash == 0)
@@ -108,21 +84,14 @@ static int deduplicate_blocks(block_writer_default_t *wr, size_t count,
 		if (wr->flags & SQFS_BLOCK_WRITER_HASH_COMPARE_ONLY)
 			break;
 
-		for (j = 0; j < count; ++j) {
-			sz = SIZE_FROM_HASH(blocks[i + j].hash);
+		loc_b = blocks[i].offset;
 
-			loc_a = blocks[i + j].offset;
-			loc_b = blocks[wr->file_start + j].offset;
-
-			ret = compare_blocks(wr, loc_a, loc_b, sz);
-			if (ret < 0)
-				return ret;
-			if (ret > 0)
-				break;
-		}
-
-		if (j == count)
+		ret = check_file_range_equal(wr->file, wr->scratch,
+					     SCRATCH_SIZE, loc_a, loc_b, sz);
+		if (ret == 0)
 			break;
+		if (ret < 0)
+			return ret;
 	}
 
 	*out = i;