hardcoresushi/libgocryptfs
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fusefrontend: rename "createsHole" to clearer "createsCiphertextHole"

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...and add comments for what is happening.
This commit is contained in:
Jakob Unterwurzacher 2016-10-25 21:19:37 +02:00
parent f41d2e0676
commit 6538dc15af
2 changed files with 9 additions and 3 deletions
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2
internal/fusefrontend/file.go
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@ -306,7 +306,7 @@ func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) {
return 0, fuse.ToStatus(err)
}
plainSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size()))
if f.createsHole(plainSize, off) {
if f.createsCiphertextHole(plainSize, off) {
status := f.zeroPad(plainSize)
if status != fuse.OK {
tlog.Warn.Printf("zeroPad returned error %v", status)

10
internal/fusefrontend/file_holes.go
View File

@ -8,10 +8,16 @@ import (
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// Will a write to offset "off" create a file hole?
func (f *file) createsHole(plainSize uint64, off int64) bool {
// Will a write to plaintext offset "off" create a file hole in the ciphertext?
func (f *file) createsCiphertextHole(plainSize uint64, off int64) bool {
// Appending a single byte to the file (equivalent to writing to
// offset=plainSize) would write to "nextBlock".
nextBlock := f.contentEnc.PlainOffToBlockNo(plainSize)
// targetBlock is the block the user wants to write to.
targetBlock := f.contentEnc.PlainOffToBlockNo(uint64(off))
// If the write goes past the next block, nextBlock will have
// to be zero-padded to the block boundary and at least nextBlock+1
// becomes a file hole in the ciphertext.
return targetBlock > nextBlock
}