blob: 632e76b5947a770440b2f92213c3756a863229e2 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
|
package contentenc
// intraBlock identifies a part of a file block
type intraBlock struct {
// Block number in the file
BlockNo uint64
// Offset into block payload
// In forwared mode: block plaintext
// In reverse mode: offset into block ciphertext. Takes the header into
// account.
Skip uint64
// Length of payload data in this block
// In forwared mode: length of the plaintext
// In reverse mode: length of the ciphertext. Takes header and trailer into
// account.
Length uint64
fs *ContentEnc
}
// isPartial - is the block partial? This means we have to do read-modify-write.
func (ib *intraBlock) IsPartial() bool {
if ib.Skip > 0 || ib.Length < ib.fs.plainBS {
return true
}
return false
}
// BlockCipherOff returns the ciphertext offset corresponding to BlockNo
func (ib *intraBlock) BlockCipherOff() (offset uint64) {
return ib.fs.BlockNoToCipherOff(ib.BlockNo)
}
// BlockPlainOff returns the plaintext offset corresponding to BlockNo
func (ib *intraBlock) BlockPlainOff() (offset uint64) {
return ib.fs.BlockNoToPlainOff(ib.BlockNo)
}
// CropBlock - crop a potentially larger plaintext block down to the relevant part
func (ib *intraBlock) CropBlock(d []byte) []byte {
lenHave := len(d)
lenWant := int(ib.Skip + ib.Length)
if lenHave < lenWant {
return d[ib.Skip:lenHave]
}
return d[ib.Skip:lenWant]
}
// Ciphertext range corresponding to the sum of all "blocks" (complete blocks)
func (ib *intraBlock) JointCiphertextRange(blocks []intraBlock) (offset uint64, length uint64) {
firstBlock := blocks[0]
lastBlock := blocks[len(blocks)-1]
offset = ib.fs.BlockNoToCipherOff(firstBlock.BlockNo)
offsetLast := ib.fs.BlockNoToCipherOff(lastBlock.BlockNo)
length = offsetLast + ib.fs.cipherBS - offset
return offset, length
}
// Plaintext range corresponding to the sum of all "blocks" (complete blocks)
func JointPlaintextRange(blocks []intraBlock) (offset uint64, length uint64) {
firstBlock := blocks[0]
lastBlock := blocks[len(blocks)-1]
offset = firstBlock.BlockPlainOff()
length = lastBlock.BlockPlainOff() + lastBlock.fs.PlainBS() - offset
return offset, length
}
|
