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authorJakob Unterwurzacher2016-08-30 00:20:31 +0200
committerJakob Unterwurzacher2016-09-25 16:43:17 +0200
commit5931eea3877ae34cdb18ac36e5cf5fba3f74b82b (patch)
treef6cd8dd41c213013741ae893e67ec1adf3ff5b4c /internal/contentenc/intrablock.go
parent1d4c6288f29d74efce83ada1ea2a7b3819178bde (diff)
contentenc: add helpers for reverse mode
Add the reverse variant of DecryptBlocks etc: * EncryptBlocks * JointPlaintextRange * ExplodeCipherRange
Diffstat (limited to 'internal/contentenc/intrablock.go')
-rw-r--r--internal/contentenc/intrablock.go28
1 files changed, 24 insertions, 4 deletions
diff --git a/internal/contentenc/intrablock.go b/internal/contentenc/intrablock.go
index 9a22ea2..632e76b 100644
--- a/internal/contentenc/intrablock.go
+++ b/internal/contentenc/intrablock.go
@@ -2,10 +2,19 @@ package contentenc
// intraBlock identifies a part of a file block
type intraBlock struct {
- BlockNo uint64 // Block number in file
- Skip uint64 // Offset into block plaintext
- Length uint64 // Length of plaintext data in this block
- fs *ContentEnc
+ // 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.
@@ -47,3 +56,14 @@ func (ib *intraBlock) JointCiphertextRange(blocks []intraBlock) (offset uint64,
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
+}