static int is_vfat(int fd)
{
unsigned char buf[2];
/* No consistent 'magic' in FAT32, but some fields
* have fixed values (always little-endian) in all but
* very obscure cases */
/* Check signature */
if (seek_and_read(fd, 0x1FE, buf, 2))
return 0;
if (buf[0] != 0x55 || buf[1] != 0xAA)
return 0;
/* Check number of FATs, should be 2 */
if (seek_and_read(fd, 0x10, buf, 1))
return 0;
if (buf[0] != 2)
return 0;
/* Check bytes per sector, should be 512 */
if (seek_and_read(fd, 0x0B, buf, 2))
return 0;
if (buf[0] != 0x00 || buf[1] != 0x02)
return 0;
return 1;
}
static int is_iso9660(int fd)
{
unsigned char buf[5];
/* Check for ISO9660 magic value */
if (seek_and_read(fd, 16 * 2048 + 1, buf, 5))
return 0;
if (!memcmp(buf, "CD001", 5))
return 1;
return 0;
}
/*--------------------------------------------------------------------------
* read_chunk
* reads a chunk from the input files into a_chunk, the position of the
* chunk is specified by chunk_no
*--------------------------------------------------------------------------
*/
static void
read_chunk(int chunk_no[],
int C[],
char a_chunk[],
int srcfd,
int n,
int baseSize,
int PX[],
int dist[])
{
int i, j, cp, unit_transfer;
int start_pos, pos[MAXDIM];
int indx[MAXDIM];
int fpOff;
for ( i = start_pos = 0; i < n; i++) {
pos[i] = chunk_no[i] * C[i];
start_pos += pos[i]*PX[i];
}
start_pos *= baseSize;
/* Read a block of dimesion C starting at co-ordinates pos */
unit_transfer = C[n-1] * baseSize;
for (i = 0; i < n; indx[i++] = 0)
;
fpOff = start_pos;
seek_and_read(fpOff, unit_transfer, a_chunk, srcfd, SEEK_SET);
fpOff += unit_transfer;
cp = unit_transfer;
while ((j = next_tuple(n-1, indx, C)) != -1) {
fpOff += dist[j];
seek_and_read(fpOff, unit_transfer, &(a_chunk[cp]), srcfd, SEEK_SET);
cp += unit_transfer;
fpOff += unit_transfer;
}
}
static const char *is_extN(int fd)
{
struct ext2_super_block sb;
if (seek_and_read(fd, 1024, &sb, sizeof(sb)))
return 0;
if (sb.s_magic != EXT2_SUPER_MAGIC)
return 0;
/* no journal? */
if (!(sb.s_feature_compat & EXT3_FEATURE_COMPAT_HAS_JOURNAL))
return "ext2";
/* small INCOMPAT? */
if (sb.s_feature_incompat < EXT3_FEATURE_INCOMPAT_EXTENTS &&
/* and small RO_COMPAT? */
sb.s_feature_ro_compat < EXT4_FEATURE_RO_COMPAT_HUGE_FILE)
return "ext3";
return "ext4";
}
void in_place_stream::_calc_send ()
{
//
// refer to <<In-Place Rsync: File Synchronization for Mobile and Wireless Devices>>
// to get the algorithm details.
//
typedef std::list<equal_node*>::iterator it_t;
std::list<equal_node*> result;
std::set<equal_node *> enode_set;
std::copy (equal_nodes_.begin (), equal_nodes_.end ()
, std::inserter (enode_set, enode_set.end ()));
for (it_t pos = equal_nodes_.begin (); pos != equal_nodes_.end (); ++pos)
_handle_node (enode_set, *pos, result);
for (it_t pos = result.begin (); pos != result.end (); ++pos) {
equal_node * node = *pos;
assert (node->tpos.t_offset == 0);
//
// 对于没有移动的块，不需要发送，可以节省一些传输成本，对于只更改不插入的文件
// 这会带来直接的优势。并且在重新构造文件时，因为移动更少的数据，因此会有直接的性能提升。
//
if (node->tpos.index * node->blength != node->s_offset)
output_.add_block (node->tpos, node->blength, node->s_offset);
}
reader_.open_file ();
for (std::list<diff_node>::iterator pos = diff_nodes_.begin ()
; pos != diff_nodes_.end (); ++pos) {
const diff_node & node = *pos;
seek_and_read (reader_, node.s_offset, node.blength, buff_.begin ());
output_.add_block (buff_.begin (), node.blength, node.s_offset);
}
reader_.close_file ();
return;
}
