libsparse: add function to resparse a file and a utility to use it
Add sparse_file_repsarse, which splits chunks in an existing sparse
file such that the maximum size of a chunk, plus a header and footer,
is smaller than the given size. This will allow multiple smaller
sparse files to result in the same data as a large sparse file.
Change-Id: I177abdb958a23d5afd394ff265c5b0c6a3ff22fa
diff --git a/libsparse/sparse.c b/libsparse/sparse.c
index c560ec9..77f02fc 100644
--- a/libsparse/sparse.c
+++ b/libsparse/sparse.c
@@ -24,6 +24,7 @@
#include "output_file.h"
#include "backed_block.h"
#include "sparse_defs.h"
+#include "sparse_format.h"
struct sparse_file *sparse_file_new(unsigned int block_size, int64_t len)
{
@@ -188,6 +189,104 @@
return ret;
}
+static int out_counter_write(void *priv, const void *data, int len)
+{
+ int64_t *count = priv;
+ *count += len;
+ return 0;
+}
+
+static struct backed_block *move_chunks_up_to_len(struct sparse_file *from,
+ struct sparse_file *to, unsigned int len)
+{
+ int64_t count = 0;
+ struct output_file *out_counter;
+ struct backed_block *last_bb = NULL;
+ struct backed_block *bb;
+ struct backed_block *start;
+ int64_t file_len = 0;
+
+ /*
+ * overhead is sparse file header, initial skip chunk, split chunk, end
+ * skip chunk, and crc chunk.
+ */
+ int overhead = sizeof(sparse_header_t) + 4 * sizeof(chunk_header_t) +
+ sizeof(uint32_t);
+ len -= overhead;
+
+ start = backed_block_iter_new(from->backed_block_list);
+ out_counter = open_output_callback(out_counter_write, &count,
+ to->block_size, to->len, false, true, 0, false);
+ if (!out_counter) {
+ return NULL;
+ }
+
+ for (bb = start; bb; bb = backed_block_iter_next(bb)) {
+ count = 0;
+ /* will call out_counter_write to update count */
+ sparse_file_write_block(out_counter, bb);
+ if (file_len + count > len) {
+ /*
+ * If the remaining available size is more than 1/8th of the
+ * requested size, split the chunk. Results in sparse files that
+ * are at least 7/8ths of the requested size
+ */
+ if (!last_bb || (len - file_len > (len / 8))) {
+ backed_block_split(from->backed_block_list, bb, len - file_len);
+ last_bb = bb;
+ }
+ goto out;
+ }
+ file_len += count;
+ last_bb = bb;
+ }
+
+out:
+ backed_block_list_move(from->backed_block_list,
+ to->backed_block_list, start, last_bb);
+
+ close_output_file(out_counter);
+
+ return bb;
+}
+
+int sparse_file_resparse(struct sparse_file *in_s, unsigned int max_len,
+ struct sparse_file **out_s, int out_s_count)
+{
+ struct backed_block *bb;
+ unsigned int overhead;
+ struct sparse_file *s;
+ struct sparse_file *tmp;
+ int c = 0;
+
+ tmp = sparse_file_new(in_s->block_size, in_s->len);
+ if (!tmp) {
+ return -ENOMEM;
+ }
+
+ do {
+ s = sparse_file_new(in_s->block_size, in_s->len);
+
+ bb = move_chunks_up_to_len(in_s, s, max_len);
+
+ if (c < out_s_count) {
+ out_s[c] = s;
+ } else {
+ backed_block_list_move(s->backed_block_list, tmp->backed_block_list,
+ NULL, NULL);
+ sparse_file_destroy(s);
+ }
+ c++;
+ } while (bb);
+
+ backed_block_list_move(tmp->backed_block_list, in_s->backed_block_list,
+ NULL, NULL);
+
+ sparse_file_destroy(tmp);
+
+ return c;
+}
+
void sparse_file_verbose(struct sparse_file *s)
{
s->verbose = true;