## demonstrates using BackupSeek to enumerate data streams for a file
import win32file, win32api, win32con
from win32com import storagecon
import pythoncom, pywintypes
import struct, traceback

stream_types={
    win32con.BACKUP_DATA:"Standard data", 
    win32con.BACKUP_EA_DATA:"Extended attribute data", 
    win32con.BACKUP_SECURITY_DATA:"Security descriptor data", 
    win32con.BACKUP_ALTERNATE_DATA:"Alternative data streams", 
    win32con.BACKUP_LINK:"Hard link information",
    win32con.BACKUP_PROPERTY_DATA:"Property data",
    win32con.BACKUP_OBJECT_ID:"Objects identifiers",
    win32con.BACKUP_REPARSE_DATA:"Reparse points",
    win32con.BACKUP_SPARSE_BLOCK:"Sparse file"
}

tempdir=win32api.GetTempPath()
tempfile=win32api.GetTempFileName(tempdir,'bkr')[0]
print('Filename:',tempfile)

f=open(tempfile,'w')
f.write('some random junk'+'x'*100)
f.close()

f=open(tempfile+':streamdata','w')
f.write('data written to alternate stream'+'y'*100)
f.close()

f=open(tempfile+':anotherstream','w')
f.write('z'*200)
f.close()

## add Summary Information, which is stored as a separate stream
m=storagecon.STGM_READWRITE | storagecon.STGM_SHARE_EXCLUSIVE |storagecon.STGM_DIRECT
pss=pythoncom.StgOpenStorageEx(tempfile, m, storagecon.STGFMT_FILE, 0 , pythoncom.IID_IPropertySetStorage,None)
ps=pss.Create(pythoncom.FMTID_SummaryInformation,pythoncom.IID_IPropertyStorage,0,storagecon.STGM_READWRITE|storagecon.STGM_SHARE_EXCLUSIVE)
ps.WriteMultiple((storagecon.PIDSI_KEYWORDS,storagecon.PIDSI_COMMENTS),('keywords','comments'))
ps=None
pss=None

sa=pywintypes.SECURITY_ATTRIBUTES()
sa.bInheritHandle=False
h=win32file.CreateFile(tempfile, win32con.GENERIC_ALL ,win32con.FILE_SHARE_READ,
    sa, win32con.OPEN_EXISTING, win32file.FILE_FLAG_BACKUP_SEMANTICS , None)


""" stream header:
typedef struct _WIN32_STREAM_ID {
    DWORD dwStreamId;  DWORD dwStreamAttributes;  LARGE_INTEGER Size;
    DWORD dwStreamNameSize;  WCHAR cStreamName[ANYSIZE_ARRAY];
}
"""

win32_stream_id_format="LLQL"
win32_stream_id_size=struct.calcsize(win32_stream_id_format)

def parse_stream_header(h,ctxt,data):
    stream_type, stream_attributes, stream_size, stream_name_size=struct.unpack(win32_stream_id_format,data)
    print('\nType:',stream_type,stream_types[stream_type], 'Attributes:', stream_attributes, 'Size:', stream_size, 'Name len:',stream_name_size)
    if stream_name_size>0:
        ## ??? sdk says this size is in characters, but it appears to be number of bytes ???
        bytes_read, stream_name_buf, ctxt=win32file.BackupRead(h, stream_name_size, None, False, True, ctxt)
        stream_name=pywintypes.UnicodeFromRaw(stream_name_buf[:])
    else:
        stream_name='Unnamed'
    print('Name:'+stream_name)
    return ctxt, stream_type, stream_attributes, stream_size, stream_name_size, stream_name

ctxt=0
win32_stream_id_buf=None  ## gets rebound to a writable buffer on first call and reused
while 1:
    bytes_read, win32_stream_id_buf, ctxt=win32file.BackupRead(h, win32_stream_id_size, win32_stream_id_buf, False, True, ctxt)
    if bytes_read==0:
        break
    ctxt, stream_type, stream_attributes, stream_size, stream_name_size, stream_name=\
        parse_stream_header(h, ctxt, win32_stream_id_buf[:])
    if stream_size>0:
        bytes_moved=win32file.BackupSeek(h, stream_size, ctxt)
        print('Moved: ',bytes_moved)

win32file.BackupRead(h, win32_stream_id_size, win32_stream_id_buf, True, True, ctxt)
win32file.CloseHandle(h)

