Cleanup: move deduplication code from data writer to fstree

Since it is actually completely independend of libsqfs and only works
on file_info_t lists, it can be safely moved over to libfstree and
the data writer becomes less cluttered as a result.

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

4 files changed, 154 insertions, 128 deletions

diff --git a/include/fstree.h b/include/fstree.h
index 687b693..c327fc6 100644
--- a/include/fstree.h
+++ b/include/fstree.h
@@ -297,4 +297,25 @@ void tree_node_sort_recursive(tree_node_t *root);
 /* resolve a path to a tree node. Returns NULL on failure and sets errno */
 tree_node_t *fstree_node_from_path(fstree_t *fs, const char *path);
 
+/*
+  Walk through 'list' to find a file with a fragment that has
+  the same size ('frag_size') and checksum ('chksum') as 'fi'.
+  Processing stopps if 'fi' itself is found in the list.
+
+  Returns NULL if no such fragment could be found.
+*/
+file_info_t *fragment_by_chksum(file_info_t *fi, uint32_t chksum,
+				size_t frag_size, file_info_t *list,
+				size_t block_size);
+
+/*
+  Walk through 'list' to find a file that contains the same sequence of blocks
+  as 'file', comparing size and checksum. Processing stops if 'file' is found
+  in the list.
+
+  Returns NULL if no such fragment could be found.
+ */
+uint64_t find_equal_blocks(file_info_t *file, file_info_t *list,
+			   size_t block_size);
+
 #endif /* FSTREE_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 8258136..4288ef1 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -4,7 +4,7 @@ libfstree_a_SOURCES += lib/fstree/gen_inode_table.c lib/fstree/get_path.c
 libfstree_a_SOURCES += lib/fstree/node_stat.c lib/fstree/mknode.c
 libfstree_a_SOURCES += lib/fstree/add_by_path.c lib/fstree/xattr.c
 libfstree_a_SOURCES += lib/fstree/node_from_path.c include/fstree.h
-libfstree_a_SOURCES += lib/fstree/gen_file_list.c
+libfstree_a_SOURCES += lib/fstree/gen_file_list.c lib/fstree/deduplicate.c
 libfstree_a_CFLAGS = $(AM_CFLAGS)
 libfstree_a_CPPFLAGS = $(AM_CPPFLAGS)
 
diff --git a/lib/fstree/deduplicate.c b/lib/fstree/deduplicate.c
new file mode 100644
index 0000000..9ae4440
--- /dev/null
+++ b/lib/fstree/deduplicate.c
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "config.h"
+#include "fstree.h"
+
+#include <string.h>
+
+file_info_t *fragment_by_chksum(file_info_t *fi, uint32_t chksum,
+				size_t frag_size, file_info_t *list,
+				size_t block_size)
+{
+	file_info_t *it;
+
+	for (it = list; it != NULL; it = it->next) {
+		if (it == fi) {
+			it = NULL;
+			break;
+		}
+
+		if (!(it->flags & FILE_FLAG_HAS_FRAGMENT))
+			continue;
+
+		if (it->flags & FILE_FLAG_FRAGMENT_IS_DUPLICATE)
+			continue;
+
+		if ((it->size % block_size) != frag_size)
+			continue;
+
+		if (it->fragment_chksum == chksum)
+			break;
+	}
+
+	return it;
+}
+
+static size_t get_block_count(file_info_t *fi, size_t block_size)
+{
+	size_t count = fi->size / block_size;
+
+	if ((fi->size % block_size) && !(fi->flags & FILE_FLAG_HAS_FRAGMENT))
+		++count;
+
+	while (count > 0 && fi->blocks[count - 1].size == 0)
+		--count;
+
+	return count;
+}
+
+static size_t find_first_match(file_info_t *file, file_info_t *cmp,
+			       size_t idx, size_t cmp_blk_count)
+{
+	size_t i;
+
+	for (i = 0; i < cmp_blk_count; ++i) {
+		if (memcmp(file->blocks + idx, cmp->blocks + i,
+			   sizeof(file->blocks[idx])) == 0) {
+			break;
+		}
+	}
+
+	return i;
+}
+
+uint64_t find_equal_blocks(file_info_t *file, file_info_t *list,
+			   size_t block_size)
+{
+	size_t start, first_match, i, j, block_count, cmp_blk_count;
+	uint64_t location;
+	file_info_t *it;
+
+	block_count = get_block_count(file, block_size);
+	if (block_count == 0)
+		return 0;
+
+	for (start = 0; start < block_count; ++start) {
+		if (file->blocks[start].size != 0)
+			break;
+	}
+
+	for (it = list; it != NULL; it = it->next) {
+		if (it == file) {
+			it = NULL;
+			break;
+		}
+
+		if (it->flags & FILE_FLAG_BLOCKS_ARE_DUPLICATE)
+			continue;
+
+		cmp_blk_count = get_block_count(it, block_size);
+		if (cmp_blk_count == 0)
+			continue;
+
+		first_match = find_first_match(file, it, start, cmp_blk_count);
+		if (first_match == cmp_blk_count)
+			continue;
+
+		i = start;
+		j = first_match;
+
+		while (i < block_count && j < cmp_blk_count) {
+			if (file->blocks[i].size == 0) {
+				++i;
+				continue;
+			}
+
+			if (it->blocks[j].size == 0) {
+				++j;
+				continue;
+			}
+
+			if (memcmp(it->blocks + j, file->blocks + i,
+				   sizeof(file->blocks[i])) != 0) {
+				break;
+			}
+
+			++i;
+			++j;
+		}
+
+		if (i == block_count)
+			break;
+	}
+
+	if (it == NULL)
+		return 0;
+
+	location = it->startblock;
+
+	for (i = 0; i < first_match; ++i)
+		location += it->blocks[i].size & ((1 << 24) - 1);
+
+	return location;
+}
diff --git a/lib/sqfs/data_writer.c b/lib/sqfs/data_writer.c
index fddb9d3..4324f06 100644
--- a/lib/sqfs/data_writer.c
+++ b/lib/sqfs/data_writer.c
@@ -126,133 +126,6 @@ int data_writer_flush_fragments(data_writer_t *data)
 	return 0;
 }
 
-static file_info_t *fragment_by_chksum(file_info_t *fi, uint32_t chksum,
-				       size_t frag_size, file_info_t *list,
-				       size_t block_size)
-{
-	file_info_t *it;
-
-	for (it = list; it != NULL; it = it->next) {
-		if (it == fi) {
-			it = NULL;
-			break;
-		}
-
-		if (!(it->flags & FILE_FLAG_HAS_FRAGMENT))
-			continue;
-
-		if (it->flags & FILE_FLAG_FRAGMENT_IS_DUPLICATE)
-			continue;
-
-		if ((it->size % block_size) != frag_size)
-			continue;
-
-		if (it->fragment_chksum == chksum)
-			break;
-	}
-
-	return it;
-}
-
-static size_t get_block_count(file_info_t *fi, size_t block_size)
-{
-	size_t count = fi->size / block_size;
-
-	if ((fi->size % block_size) && !(fi->flags & FILE_FLAG_HAS_FRAGMENT))
-		++count;
-
-	while (count > 0 && fi->blocks[count - 1].size == 0)
-		--count;
-
-	return count;
-}
-
-static size_t find_first_match(file_info_t *file, file_info_t *cmp,
-			       size_t idx, size_t cmp_blk_count)
-{
-	size_t i;
-
-	for (i = 0; i < cmp_blk_count; ++i) {
-		if (memcmp(file->blocks + idx, cmp->blocks + i,
-			   sizeof(file->blocks[idx])) == 0) {
-			break;
-		}
-	}
-
-	return i;
-}
-
-static uint64_t find_equal_blocks(file_info_t *file, file_info_t *list,
-				  size_t block_size)
-{
-	size_t start, first_match, i, j, block_count, cmp_blk_count;
-	uint64_t location;
-	file_info_t *it;
-
-	block_count = get_block_count(file, block_size);
-	if (block_count == 0)
-		return 0;
-
-	for (start = 0; start < block_count; ++start) {
-		if (file->blocks[start].size != 0)
-			break;
-	}
-
-	for (it = list; it != NULL; it = it->next) {
-		if (it == file) {
-			it = NULL;
-			break;
-		}
-
-		if (it->flags & FILE_FLAG_BLOCKS_ARE_DUPLICATE)
-			continue;
-
-		cmp_blk_count = get_block_count(it, block_size);
-		if (cmp_blk_count == 0)
-			continue;
-
-		first_match = find_first_match(file, it, start, cmp_blk_count);
-		if (first_match == cmp_blk_count)
-			continue;
-
-		i = start;
-		j = first_match;
-
-		while (i < block_count && j < cmp_blk_count) {
-			if (file->blocks[i].size == 0) {
-				++i;
-				continue;
-			}
-
-			if (it->blocks[j].size == 0) {
-				++j;
-				continue;
-			}
-
-			if (memcmp(it->blocks + j, file->blocks + i,
-				   sizeof(file->blocks[i])) != 0) {
-				break;
-			}
-
-			++i;
-			++j;
-		}
-
-		if (i == block_count)
-			break;
-	}
-
-	if (it == NULL)
-		return 0;
-
-	location = it->startblock;
-
-	for (i = 0; i < first_match; ++i)
-		location += it->blocks[i].size & ((1 << 24) - 1);
-
-	return location;
-}
-
 static int flush_data_block(data_writer_t *data, size_t size,
 			    file_info_t *fi, int flags, file_info_t *list)
 {