private int CalculateBucketOffset(QdbmKey key, out int bucketId)
{
bucketId = (int)(key.GetHashCode() % _qdbmHeader.BucketNumber);
var bucketOffset = Constants.OffsetBuckets + bucketId * sizeof(int);
return(bucketOffset);
}
public void Put(QdbmKey key, byte[] value)
{
if (key == null || key.KeyBytes.Length == 0)
{
throw new ArgumentException("key must be specified", nameof(key));
}
if (value == null || value.Length == 0)
{
throw new ArgumentException("value must be specified", nameof(value));
}
_databaseStream.Seek(Constants.OffsetHeaderRecordCount, SeekOrigin.Begin);
var existingRecordHeader = GetRecordHeader(key);
var keySize = key.KeyBytes.Length;
var valueSize = value.Length;
var recordHeader = new QdbmRecordHeader
{
KeySize = keySize,
ValueSize = valueSize
};
var record = new QdbmRecord(key, recordHeader, value);
if (existingRecordHeader?.Size >= recordHeader.Size)
{
record.Header.Offset = existingRecordHeader.Offset;
WriteRecordToDbStream(record);
}
else
{
AppendRecordToDbStream(record);
}
var recordOffset = record.Header.Offset;
var bucketOffset = CalculateBucketOffset(record.Key, out var bucketId);
_databaseStream.Seek(bucketOffset, SeekOrigin.Begin);
var existingRecordOffset = _databaseBinaryReader.ReadInt32();
if (existingRecordOffset == 0)
{
_databaseStream.Seek(bucketOffset, SeekOrigin.Begin);
_databaseBinaryWriter.Write(recordOffset);
_buckets[bucketId] = bucketOffset;
}
else
{
SetChildOffset(record.Key.SecondaryHashCode, existingRecordOffset, recordOffset);
}
}
private QdbmRecord ReadRecord(QdbmRecordHeader recordHeader)
{
_databaseStream.Seek(recordHeader.Offset + Constants.OffsetRecordKeyOffset, SeekOrigin.Begin);
var key = _databaseBinaryReader.ReadBytes(recordHeader.KeySize);
var value = _databaseBinaryReader.ReadBytes(recordHeader.ValueSize);
var qdbmKey = new QdbmKey(key);
if (qdbmKey.SecondaryHashCode != recordHeader.SecondHashValue)
{
throw new InvalidOperationException("Database is corrupt.");
}
var qdbmRecord = new QdbmRecord(qdbmKey, recordHeader, value);
return(qdbmRecord);
}
public byte[] Get(QdbmKey key)
{
var header = GetRecordHeader(key);
if (header == null)
{
return(null);
}
var record = ReadRecord(header);
if (record.Key.KeyBytes.Length == key.KeyBytes.Length &&
record.Key.KeyBytes.SequenceEqual(key.KeyBytes))
{
return(record.Value);
}
return(null);
}
private QdbmRecordHeader GetRecordHeader(QdbmKey key)
{
var bucketOffset = CalculateBucketOffset(key, out _);
_databaseStream.Seek(bucketOffset, SeekOrigin.Begin);
var recordOffset = _databaseBinaryReader.ReadInt32();
if (recordOffset == 0)
{
return(null);
}
var header = ReadRecordHeader(recordOffset);
while (true)
{
if (header.LeftChildOffset != 0 && key.SecondaryHashCode > header.SecondHashValue)
{
header = ReadRecordHeader(header.LeftChildOffset);
continue;
}
if (header.RightChildOffset != 0 && key.SecondaryHashCode < header.SecondHashValue)
{
header = ReadRecordHeader(header.RightChildOffset);
continue;
}
break;
}
if (header.SecondHashValue != key.SecondaryHashCode)
{
return(null);
}
return(header);
}
public QdbmRecord(QdbmKey key, QdbmRecordHeader header, byte[] value)
{
Key = key;
Header = header;
Value = value;
}