libsparse: add sparse_file_len

Add sparse_file_len, which will compute the size of data that would
be produced if sparse_file_write was called.  Useful combined with
sparse_file_callback.

Change-Id: I1a156d1071760f5559483954a5c62ffc20298703

2 files changed, 38 insertions, 0 deletions

diff --git a/libsparse/include/sparse/sparse.h b/libsparse/include/sparse/sparse.h
index fe003f6..17d085c 100644
--- a/libsparse/include/sparse/sparse.h
+++ b/libsparse/include/sparse/sparse.h
@@ -158,6 +158,20 @@ int sparse_file_write(struct sparse_file *s, int fd, bool gz, bool sparse,
 		bool crc);
 
 /**
+ * sparse_file_len - return the length of a sparse file if written to disk
+ *
+ * @s - sparse file cookie
+ * @sparse - write in the Android sparse file format
+ * @crc - append a crc chunk
+ *
+ * Returns the size a sparse file would be on disk if it were written in the
+ * specified format.  If sparse is true, this is the size of the data in the
+ * sparse format.  If sparse is false, this is the size of the normal
+ * non-sparse file.
+ */
+int64_t sparse_file_len(struct sparse_file *s, bool sparse, bool crc);
+
+/**
  * sparse_file_callback - call a callback for blocks in sparse file
  *
  * @s - sparse file cookie
diff --git a/libsparse/sparse.c b/libsparse/sparse.c
index 77f02fc..f04f687 100644
--- a/libsparse/sparse.c
+++ b/libsparse/sparse.c
@@ -196,6 +196,30 @@ static int out_counter_write(void *priv, const void *data, int len)
 	return 0;
 }
 
+int64_t sparse_file_len(struct sparse_file *s, bool sparse, bool crc)
+{
+	int ret;
+	int chunks = sparse_count_chunks(s);
+	int64_t count = 0;
+	struct output_file *out;
+
+	out = open_output_callback(out_counter_write, &count,
+			s->block_size, s->len, false, sparse, chunks, crc);
+	if (!out) {
+		return -1;
+	}
+
+	ret = write_all_blocks(s, out);
+
+	close_output_file(out);
+
+	if (ret < 0) {
+		return -1;
+	}
+
+	return count;
+}
+
 static struct backed_block *move_chunks_up_to_len(struct sparse_file *from,
 		struct sparse_file *to, unsigned int len)
 {