7 class QcowHeaderExtension:
9 def __init__(self, magic, length, data):
11 padding = 8 - (length % 8)
12 data += "\0" * padding
19 def create(cls, magic, data):
20 return QcowHeaderExtension(magic, len(data), data)
28 # Version 2 header fields
29 [ uint32_t, '%#x', 'magic' ],
30 [ uint32_t, '%d', 'version' ],
31 [ uint64_t, '%#x', 'backing_file_offset' ],
32 [ uint32_t, '%#x', 'backing_file_size' ],
33 [ uint32_t, '%d', 'cluster_bits' ],
34 [ uint64_t, '%d', 'size' ],
35 [ uint32_t, '%d', 'crypt_method' ],
36 [ uint32_t, '%d', 'l1_size' ],
37 [ uint64_t, '%#x', 'l1_table_offset' ],
38 [ uint64_t, '%#x', 'refcount_table_offset' ],
39 [ uint32_t, '%d', 'refcount_table_clusters' ],
40 [ uint32_t, '%d', 'nb_snapshots' ],
41 [ uint64_t, '%#x', 'snapshot_offset' ],
43 # Version 3 header fields
44 [ uint64_t, '%#x', 'incompatible_features' ],
45 [ uint64_t, '%#x', 'compatible_features' ],
46 [ uint64_t, '%#x', 'autoclear_features' ],
47 [ uint32_t, '%d', 'refcount_order' ],
48 [ uint32_t, '%d', 'header_length' ],
51 fmt = '>' + ''.join(field[0] for field in fields)
53 def __init__(self, fd):
55 buf_size = struct.calcsize(QcowHeader.fmt)
58 buf = fd.read(buf_size)
60 header = struct.unpack(QcowHeader.fmt, buf)
61 self.__dict__ = dict((field[2], header[i])
62 for i, field in enumerate(QcowHeader.fields))
65 self.cluster_size = 1 << self.cluster_bits
67 fd.seek(self.header_length)
68 self.load_extensions(fd)
70 if self.backing_file_offset:
71 fd.seek(self.backing_file_offset)
72 self.backing_file = fd.read(self.backing_file_size)
74 self.backing_file = None
76 def set_defaults(self):
78 self.incompatible_features = 0
79 self.compatible_features = 0
80 self.autoclear_features = 0
81 self.refcount_order = 4
82 self.header_length = 72
84 def load_extensions(self, fd):
87 if self.backing_file_offset != 0:
88 end = min(self.cluster_size, self.backing_file_offset)
90 end = self.cluster_size
92 while fd.tell() < end:
93 (magic, length) = struct.unpack('>II', fd.read(8))
97 padded = (length + 7) & ~7
98 data = fd.read(padded)
99 self.extensions.append(QcowHeaderExtension(magic, length, data))
101 def update_extensions(self, fd):
103 fd.seek(self.header_length)
104 extensions = self.extensions
105 extensions.append(QcowHeaderExtension(0, 0, ""))
106 for ex in extensions:
107 buf = struct.pack('>II', ex.magic, ex.length)
111 if self.backing_file != None:
112 self.backing_file_offset = fd.tell()
113 fd.write(self.backing_file)
115 if fd.tell() > self.cluster_size:
116 raise Exception("I think I just broke the image...")
119 def update(self, fd):
120 header_bytes = self.header_length
122 self.update_extensions(fd)
125 header = tuple(self.__dict__[f] for t, p, f in QcowHeader.fields)
126 buf = struct.pack(QcowHeader.fmt, *header)
127 buf = buf[0:header_bytes-1]
131 for f in QcowHeader.fields:
132 print "%-25s" % f[2], f[1] % self.__dict__[f[2]]
135 def dump_extensions(self):
136 for ex in self.extensions:
138 data = ex.data[:ex.length]
139 if all(c in string.printable for c in data):
144 print "Header extension:"
145 print "%-25s %#x" % ("magic", ex.magic)
146 print "%-25s %d" % ("length", ex.length)
147 print "%-25s %s" % ("data", data)
151 def cmd_dump_header(fd):
156 def cmd_set_header(fd, name, value):
158 value = int(value, 0)
160 print "'%s' is not a valid number" % value
163 fields = (field[2] for field in QcowHeader.fields)
164 if not name in fields:
165 print "'%s' is not a known header field" % name
169 h.__dict__[name] = value
172 def cmd_add_header_ext(fd, magic, data):
174 magic = int(magic, 0)
176 print "'%s' is not a valid magic number" % magic
180 h.extensions.append(QcowHeaderExtension.create(magic, data))
183 def cmd_add_header_ext_stdio(fd, magic):
184 data = sys.stdin.read()
185 cmd_add_header_ext(fd, magic, data)
187 def cmd_del_header_ext(fd, magic):
189 magic = int(magic, 0)
191 print "'%s' is not a valid magic number" % magic
197 for ex in h.extensions:
198 if ex.magic == magic:
200 h.extensions.remove(ex)
203 print "No such header extension"
208 def cmd_set_feature_bit(fd, group, bit):
211 if bit < 0 or bit >= 64:
214 print "'%s' is not a valid bit number in range [0, 64)" % bit
218 if group == 'incompatible':
219 h.incompatible_features |= 1 << bit
220 elif group == 'compatible':
221 h.compatible_features |= 1 << bit
222 elif group == 'autoclear':
223 h.autoclear_features |= 1 << bit
225 print "'%s' is not a valid group, try 'incompatible', 'compatible', or 'autoclear'" % group
231 [ 'dump-header', cmd_dump_header, 0, 'Dump image header and header extensions' ],
232 [ 'set-header', cmd_set_header, 2, 'Set a field in the header'],
233 [ 'add-header-ext', cmd_add_header_ext, 2, 'Add a header extension' ],
234 [ 'add-header-ext-stdio', cmd_add_header_ext_stdio, 1, 'Add a header extension, data from stdin' ],
235 [ 'del-header-ext', cmd_del_header_ext, 1, 'Delete a header extension' ],
236 [ 'set-feature-bit', cmd_set_feature_bit, 2, 'Set a feature bit'],
239 def main(filename, cmd, args):
240 fd = open(filename, "r+b")
242 for name, handler, num_args, desc in cmds:
245 elif len(args) != num_args:
251 print "Unknown command '%s'" % cmd
256 print "Usage: %s <file> <cmd> [<arg>, ...]" % sys.argv[0]
258 print "Supported commands:"
259 for name, handler, num_args, desc in cmds:
260 print " %-20s - %s" % (name, desc)
262 if __name__ == '__main__':
263 if len(sys.argv) < 3:
267 main(sys.argv[1], sys.argv[2], sys.argv[3:])