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authorDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-06-28 12:41:26 +0200
committerDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-06-28 15:07:34 +0200
commit4e017928c7b5b590d2c7e04e42cb497eb3a4f8cf (patch)
tree28f649af1074ab74576a9a715991c610b210f1c0 /lib/sqfs/data_writer.c
parentd89d7e3d7f5b21fe53ea0cbf65134bdc3df30950 (diff)
Add support for packing sparse files
This commit adds support for packing sparse files into squashfs images as follows: - In the data writer: simply detect zero blocks and write a zero to the block size field and don't emit any data. Record the number of bytes saved this way. For fragments, set the fragment offset to invalid. - In the inode writer: write out the number of bytes saved for sparse files. If there should be a fragment but there is none, append a block count of 0. - In the data reader: if the block size is 0, read nothing from disk and emit an empty block. Do the same if the fragment is missing. - In the inode reader: restore the number of bytes saved for sparse files. The sparse files can be packed and unpacked, but the unpacking will not create sparse files for now. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Diffstat (limited to 'lib/sqfs/data_writer.c')
-rw-r--r--lib/sqfs/data_writer.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/sqfs/data_writer.c b/lib/sqfs/data_writer.c
index 753e5d4..70fe884 100644
--- a/lib/sqfs/data_writer.c
+++ b/lib/sqfs/data_writer.c
@@ -78,6 +78,11 @@ static int grow_fragment_table(data_writer_t *data)
return 0;
}
+static bool is_zero_block(unsigned char *ptr, size_t size)
+{
+ return ptr[0] == 0 && memcmp(ptr, ptr + 1, size - 1) == 0;
+}
+
int data_writer_flush_fragments(data_writer_t *data)
{
uint64_t offset;
@@ -115,6 +120,7 @@ int write_data_from_fd(data_writer_t *data, file_info_t *fi, int infd)
size_t diff;
fi->startblock = data->super->bytes_used;
+ fi->sparse = 0;
while (count != 0) {
diff = count > (uint64_t)data->super->block_size ?
@@ -126,6 +132,18 @@ int write_data_from_fd(data_writer_t *data, file_info_t *fi, int infd)
if ((size_t)ret < diff)
goto fail_trunc;
+ if (is_zero_block(data->block, diff)) {
+ if (diff < data->super->block_size) {
+ fi->fragment_offset = 0xFFFFFFFF;
+ fi->fragment = 0xFFFFFFFF;
+ } else {
+ fi->blocksizes[blk_idx++] = 0;
+ }
+ fi->sparse += diff;
+ count -= diff;
+ continue;
+ }
+
if (diff < data->super->block_size) {
if (data->frag_offset + diff > data->super->block_size) {
if (data_writer_flush_fragments(data))