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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 data from this block
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
}
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