private long readHeader(int id) throws IOException {
long header = p_alloc(MINIMUM_PAGE_SIZE);
try {
try {
mPageArray.readPage(id, header, 0, MINIMUM_PAGE_SIZE);
} catch (EOFException e) {
throw new CorruptDatabaseException("File is smaller than expected");
}
long magic = p_longGetLE(header, I_MAGIC_NUMBER);
if (magic != MAGIC_NUMBER) {
throw new CorruptDatabaseException("Wrong magic number: " + magic);
}
int checksum = p_intGetLE(header, I_CHECKSUM);
int newChecksum = setHeaderChecksum(header);
if (newChecksum != checksum) {
throw new CorruptDatabaseException(
"Header checksum mismatch: " + newChecksum + " != " + checksum);
}
return header;
} catch (Throwable e) {
p_delete(header);
throw e;
}
}
@Override
public void readPage(long id, long page) throws IOException {
try {
mPageArray.readPage(id, page, 0, pageSize());
} catch (Throwable e) {
throw closeOnFailure(e);
}
}
private void readPartial(long index, int start, byte[] buf, int offset, int length)
throws IOException {
long page = p_alloc(start + length);
try {
mPageArray.readPage(index, page, 0, start + length);
p_copyToArray(page, start, buf, offset, length);
} finally {
p_delete(page);
}
}
/** @see _SnapshotPageArray#beginSnapshot */
Snapshot beginSnapshot(_LocalDatabase db) throws IOException {
mHeaderLatch.acquireShared();
try {
long pageCount, redoPos;
long header = p_alloc(MINIMUM_PAGE_SIZE);
try {
mPageArray.readPage(mCommitNumber & 1, header, 0, MINIMUM_PAGE_SIZE);
pageCount = _PageManager.readTotalPageCount(header, I_MANAGER_HEADER);
redoPos = _LocalDatabase.readRedoPosition(header, I_EXTRA_DATA);
} finally {
p_delete(header);
}
return mPageArray.beginSnapshot(db, pageCount, redoPos);
} finally {
mHeaderLatch.releaseShared();
}
}