Move condensed-sparse-file handling to libsquashfs

Add another helper function for getting a blocks from a condensed sparse
file, then rewrite the data writer to use that instead, using an
sqfs_file_t pointer instead of direct file i/o.

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

5 files changed, 123 insertions, 79 deletions

diff --git a/include/data_writer.h b/include/data_writer.h
index c9b416c..4d5fa12 100644
--- a/include/data_writer.h
+++ b/include/data_writer.h
@@ -97,8 +97,9 @@ int write_data_from_file(data_writer_t *data, file_info_t *fi,
 
   Returns 0 on success, prints errors to stderr.
  */
-int write_data_from_fd_condensed(data_writer_t *data, file_info_t *fi,
-				 int infd, sqfs_sparse_map_t *map, int flags);
+int write_data_from_file_condensed(data_writer_t *data, sqfs_file_t *file,
+				   file_info_t *fi,
+				   const sqfs_sparse_map_t *map, int flags);
 
 data_writer_stats_t *data_writer_get_stats(data_writer_t *data);
 
diff --git a/include/sqfs/io.h b/include/sqfs/io.h
index cf6f1fa..bbc3da9 100644
--- a/include/sqfs/io.h
+++ b/include/sqfs/io.h
@@ -189,6 +189,35 @@ SQFS_API int sqfs_file_create_block(sqfs_file_t *file, uint64_t offset,
 				    size_t size, void *user, uint32_t flags,
 				    sqfs_block_t **out);
 
+/**
+ * @brief Read a chunk from a condensed version of a sparse file and turn it
+ *        into a block that can be fed to a block processor.
+ *
+ * @member sqfs_file_t
+ *
+ * This function works on condensed sparse files, i.e. a sparse file that had
+ * its holdes removed. The given mapping describes the original data region
+ * that are actually packed next to each other. The function emulates the
+ * orignal sparse file by zero-initializing the block data, then figuring
+ * out which regions overlap the block, working out their physical location and
+ * stitching the block together.
+ *
+ * @param file A pointer to a file implementation.
+ * @param offset A byte offset into the file.
+ * @param size The number of bytes to read, starting at the given offset.
+ * @param user A user pointer to set for the block.
+ * @param flags The flags to store in the newly created block.
+ * @param map Describes the data regions of the original sparse file.
+ * @param out Returns a pointer to a block on success.
+ *
+ * @return Zero on success, an @ref E_SQFS_ERROR identifier on failure.
+ */
+SQFS_API int sqfs_file_create_block_dense(sqfs_file_t *file, uint64_t offset,
+					  size_t size, void *user,
+					  uint32_t flags,
+					  const sqfs_sparse_map_t *map,
+					  sqfs_block_t **out);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/sqfs/io.c b/lib/sqfs/io.c
index 4afb489..b41fc4a 100644
--- a/lib/sqfs/io.c
+++ b/lib/sqfs/io.c
@@ -37,3 +37,69 @@ int sqfs_file_create_block(sqfs_file_t *file, uint64_t offset,
 	*out = blk;
 	return 0;
 }
+
+int sqfs_file_create_block_dense(sqfs_file_t *file, uint64_t offset,
+				 size_t size, void *user, uint32_t flags,
+				 const sqfs_sparse_map_t *map,
+				 sqfs_block_t **out)
+{
+	sqfs_block_t *blk = alloc_flex(sizeof(*blk), 1, size);
+	size_t dst_start, diff, count;
+	const sqfs_sparse_map_t *it;
+	uint64_t poffset, src_start;
+	int err;
+
+	if (blk == NULL)
+		return SQFS_ERROR_ALLOC;
+
+	poffset = 0;
+
+	for (it = map; it != NULL; it = it->next) {
+		if (it->offset + it->count <= offset) {
+			poffset += it->count;
+			continue;
+		}
+
+		if (it->offset >= offset + size) {
+			poffset += it->count;
+			continue;
+		}
+
+		count = size;
+
+		if (offset + count >= it->offset + it->count)
+			count = it->offset + it->count - offset;
+
+		if (it->offset < offset) {
+			diff = offset - it->offset;
+
+			src_start = poffset + diff;
+			dst_start = 0;
+			count -= diff;
+		} else if (it->offset > offset) {
+			diff = it->offset - offset;
+
+			src_start = poffset;
+			dst_start = diff;
+		} else {
+			src_start = poffset;
+			dst_start = 0;
+		}
+
+		err = file->read_at(file, src_start,
+				    blk->data + dst_start, count);
+		if (err) {
+			free(blk);
+			return err;
+		}
+
+		poffset += it->count;
+	}
+
+	blk->user = user;
+	blk->size = size;
+	blk->flags = flags;
+
+	*out = blk;
+	return 0;
+}
diff --git a/lib/sqfshelper/data_writer.c b/lib/sqfshelper/data_writer.c
index a6d0297..92592c9 100644
--- a/lib/sqfshelper/data_writer.c
+++ b/lib/sqfshelper/data_writer.c
@@ -390,77 +390,15 @@ int write_data_from_file(data_writer_t *data, file_info_t *fi,
 	return 0;
 }
 
-static int check_map_valid(const sqfs_sparse_map_t *map, file_info_t *fi)
-{
-	const sqfs_sparse_map_t *m;
-	uint64_t offset;
-
-	if (map != NULL) {
-		offset = map->offset;
-
-		for (m = map; m != NULL; m = m->next) {
-			if (m->offset < offset)
-				goto fail_map;
-			offset = m->offset + m->count;
-		}
-
-		if (offset > fi->size)
-			goto fail_map_size;
-	}
-
-	return 0;
-fail_map_size:
-	fprintf(stderr, "%s: sparse file map spans beyond file size\n",
-		fi->input_file);
-	return -1;
-fail_map:
-	fprintf(stderr,
-		"%s: sparse file map is unordered or self overlapping\n",
-		fi->input_file);
-	return -1;
-}
-
-static int get_sparse_block(sqfs_block_t *blk, file_info_t *fi, int infd,
-			    sqfs_sparse_map_t **sparse_map, uint64_t offset,
-			    size_t diff)
-{
-	sqfs_sparse_map_t *map = *sparse_map;
-	size_t start, count;
-
-	while (map != NULL && map->offset < offset + diff) {
-		start = 0;
-		count = map->count;
-
-		if (map->offset < offset)
-			count -= offset - map->offset;
-
-		if (map->offset > offset)
-			start = map->offset - offset;
-
-		if (start + count > diff)
-			count = diff - start;
-
-		if (read_data(fi->input_file, infd, blk->data + start, count))
-			return -1;
-
-		map = map->next;
-	}
-
-	*sparse_map = map;
-	return 0;
-}
-
-int write_data_from_fd_condensed(data_writer_t *data, file_info_t *fi,
-				 int infd, sqfs_sparse_map_t *map, int flags)
+int write_data_from_file_condensed(data_writer_t *data, sqfs_file_t *file,
+				   file_info_t *fi,
+				   const sqfs_sparse_map_t *map, int flags)
 {
 	uint32_t blk_flags = BLK_FIRST_BLOCK;
 	size_t diff, i = 0;
 	sqfs_block_t *blk;
 	uint64_t offset;
 
-	if (check_map_valid(map, fi))
-		return -1;
-
 	if (flags & DW_DONT_COMPRESS)
 		blk_flags |= SQFS_BLK_DONT_COMPRESS;
 
@@ -474,17 +412,13 @@ int write_data_from_fd_condensed(data_writer_t *data, file_info_t *fi,
 			diff = fi->size - offset;
 		}
 
-		blk = alloc_flex(sizeof(*blk), 1, diff);
-		blk->size = diff;
-		blk->index = i++;
-		blk->user = fi;
-		blk->flags = blk_flags;
-
-		if (get_sparse_block(blk, fi, infd, &map, offset, diff)) {
-			free(blk);
+		if (sqfs_file_create_block_dense(file, offset, diff, fi,
+						 blk_flags, map, &blk)) {
 			return -1;
 		}
 
+		blk->index = i++;
+
 		if (is_zero_block(blk->data, blk->size)) {
 			data->stats.sparse_blocks += 1;
 
diff --git a/tar/tar2sqfs.c b/tar/tar2sqfs.c
index ca00579..84d56f4 100644
--- a/tar/tar2sqfs.c
+++ b/tar/tar2sqfs.c
@@ -225,12 +225,24 @@ fail_arg:
 static int write_file(tar_header_decoded_t *hdr, file_info_t *fi,
 		      data_writer_t *data)
 {
+	const sqfs_sparse_map_t *it;
 	sqfs_file_t *file;
+	uint64_t sum;
 	int ret;
 
 	if (hdr->sparse != NULL) {
-		ret = write_data_from_fd_condensed(data, fi, STDIN_FILENO,
-						   hdr->sparse, 0);
+		for (sum = 0, it = hdr->sparse; it != NULL; it = it->next)
+			sum += it->count;
+
+		file = sqfs_get_stdin_file(sum);
+		if (file == NULL) {
+			perror("packing files");
+			return -1;
+		}
+
+		ret = write_data_from_file_condensed(data, file, fi,
+						     hdr->sparse, 0);
+		file->destroy(file);
 		if (ret)
 			return -1;
 
@@ -243,10 +255,12 @@ static int write_file(tar_header_decoded_t *hdr, file_info_t *fi,
 		return -1;
 	}
 
-	if (write_data_from_file(data, fi, file, 0))
+	ret = write_data_from_file(data, fi, file, 0);
+	file->destroy(file);
+
+	if (ret)
 		return -1;
 
-	file->destroy(file);
 	return skip_padding(STDIN_FILENO, fi->size);
 }