// _VerifyHashFunction
bool
Volume::_VerifyHashFunction(hash_function_t function)
{
bool result = true;
// iterate over the entries in the root dir until we find an entry, that
// doesn't falsify the hash function
DirEntryIterator iterator(fTree, fRootVNode->GetDirID(),
fRootVNode->GetObjectID(), DOT_DOT_OFFSET + 1);
DirItem item;
int32 index = 0;
while (iterator.GetNext(&item, &index) == B_OK) {
DirEntry *entry = item.EntryAt(index);
uint64 offset = entry->GetOffset();
// try the hash function
size_t nameLen = 0;
if (const char *name = item.EntryNameAt(index, &nameLen)) {
uint64 testOffset = key_offset_for_name(function, name, nameLen);
if (offset_hash_value(offset) != offset_hash_value(testOffset)) {
result = false;
break;
}
} // else: bad data
}
return result;
}
/*! \brief Returns the next entry belonging to the directory.
\param foundItem Pointer to a pre-allocated Item that shall be set
to the found item.
\param entryIndex Pointer to a pre-allocated int32 that shall be set
to the found entry index.
\param _entry Pointer to a pre-allocated DirEntry pointer that shall be set
to the found entry. May be \c NULL.
\return \c B_OK, if everything went fine, \c B_ENTRY_NOT_FOUND, if we're
through.
*/
status_t
DirEntryIterator::GetNext(DirItem *foundItem, int32 *entryIndex,
DirEntry **_entry)
{
status_t error = (foundItem && entryIndex ? InitCheck() : B_BAD_VALUE);
// get the next DirItem, if necessary
// the loop skips empty DirItems gracefully
while (error == B_OK
&& (fIndex < 0 || fIndex >= fDirItem.GetEntryCount())) {
error = fItemIterator.GetNext(&fDirItem, TYPE_DIRENTRY);
if (error == B_OK) {
if (fDirItem.Check() == B_OK)
fIndex = 0;
else // bad data: skip the item
fIndex = -1;
}
}
// get the next entry and check whether it has the correct offset
if (error == B_OK) {
DirEntry *entry = fDirItem.EntryAt(fIndex);
if (!fFixedHash
|| offset_hash_value(entry->GetOffset())
== offset_hash_value(GetOffset())) {
*foundItem = fDirItem;
*entryIndex = fIndex;
if (_entry)
*_entry = entry;
fIndex++;
} else
error = B_ENTRY_NOT_FOUND;
}
return error;
}
/*! \brief Returns the previous entry belonging to the directory.
\param foundItem Pointer to a pre-allocated Item that shall be set
to the found item.
\param entryIndex Pointer to a pre-allocated int32 that shall be set
to the found entry index.
\param _entry Pointer to a pre-allocated DirEntry pointer that shall be set
to the found entry. May be \c NULL.
\return \c B_OK, if everything went fine, \c B_ENTRY_NOT_FOUND, if we're
through.
*/
status_t
DirEntryIterator::GetPrevious(DirItem *foundItem, int32 *entryIndex,
DirEntry **_entry)
{
//printf("DirEntryIterator::GetPrevious()\n");
status_t error = (foundItem && entryIndex ? InitCheck() : B_BAD_VALUE);
if (error == B_OK && fDone)
error = B_ENTRY_NOT_FOUND;
// get the next DirItem, if necessary
// the loop skips empty DirItems gracefully
while (error == B_OK
&& (fIndex < 0 || fIndex >= fDirItem.GetEntryCount())) {
error = fItemIterator.GetPrevious(&fDirItem, TYPE_DIRENTRY);
if (error == B_OK) {
if (fDirItem.Check() == B_OK)
fIndex = fDirItem.GetEntryCount() - 1;
else // bad data: skip the item
fIndex = -1;
}
}
//printf(" found dir item: %s\n", strerror(error));
// skip entries with a greater offset
while (error == B_OK && fIndex >= 0
&& fDirItem.EntryAt(fIndex)->GetOffset() > GetOffset()) {
//printf(" skipping entry %ld: offset %lu\n", fIndex, fDirItem.EntryAt(fIndex)->GetOffset());
fIndex--;
}
// get the entry and check whether it has the correct offset
if (error == B_OK) {
//printf(" entries with greater offsets skipped: index: %ld\n", fIndex);
if (fIndex >= 0
//&& (printf(" entry index %ld: offset %lu\n", fIndex, fDirItem.EntryAt(fIndex)->GetOffset()), true)
&& (!fFixedHash
|| offset_hash_value(fDirItem.EntryAt(fIndex)->GetOffset())
== offset_hash_value(GetOffset()))) {
//printf(" entry found\n");
DirEntry *entry = fDirItem.EntryAt(fIndex);
*foundItem = fDirItem;
*entryIndex = fIndex;
fDone = (fFixedHash
&& offset_generation_number(entry->GetOffset()) == 0);
if (_entry)
*_entry = entry;
fIndex--;
} else
error = B_ENTRY_NOT_FOUND;
}
//printf("DirEntryIterator::GetPrevious() done: %s\n", strerror(error));
return error;
}
// _DetectHashFunction
uint32
Volume::_DetectHashFunction()
{
// iterate over the entries in the root dir until we find an entry, that
// let us draw an unambiguous conclusion
DirEntryIterator iterator(fTree, fRootVNode->GetDirID(),
fRootVNode->GetObjectID(), DOT_DOT_OFFSET + 1);
uint32 foundCode = UNSET_HASH;
DirItem item;
int32 index = 0;
while (foundCode == UNSET_HASH
&& iterator.GetNext(&item, &index) == B_OK) {
DirEntry *entry = item.EntryAt(index);
uint64 offset = entry->GetOffset();
uint32 hashCodes[] = { TEA_HASH, YURA_HASH, R5_HASH };
int32 hashCodeCount = sizeof(hashCodes) / sizeof(uint32);
size_t nameLen = 0;
const char *name = item.EntryNameAt(index, &nameLen);
if (!name) // bad data!
continue;
// try each hash function -- if there's a single winner, we're done,
// otherwise the next entry must help
for (int32 i = 0; i < hashCodeCount; i++) {
hash_function_t function = hash_function_for_code(hashCodes[i]);
uint64 testOffset = key_offset_for_name(function, name, nameLen);
if (offset_hash_value(offset) == offset_hash_value(testOffset)) {
if (foundCode != UNSET_HASH) {
// ambiguous
foundCode = UNSET_HASH;
break;
} else
foundCode = hashCodes[i];
}
}
}
return foundCode;
}
