/// <summary>
/// 检查指定的异常句柄。如果存在异常则抛出异常。
/// </summary>
/// <param name="error">异常句柄。</param>
internal static void Check(IntPtr error)
{
if (error != IntPtr.Zero)
{
try
{
var message = Marshal.PtrToStringAnsi(error);
throw new LevelDBException(message);
}
finally
{
LevelDBInterop.leveldb_free(error);
}
}
}
// <summary>
// DB implementations can export properties about their state
// via this method. If "property" is a valid property understood by this
// DB implementation, fills "*value" with its current value and returns
// true. Otherwise returns false.
//
// Valid property names include:
//
// "leveldb.num-files-at-level<N>" - return the number of files at level <N>,
// where <N> is an ASCII representation of a level number (e.g. "0").
// "leveldb.stats" - returns a multi-line string that describes statistics
// about the internal operation of the DB.
// </summary>
/// <summary>
/// 获取数据库属性。
/// </summary>
/// <param name="name">属性名称。</param>
/// <returns>一个属性的值。</returns>
public string PropertyValue(string name)
{
var ptr = LevelDBInterop.leveldb_property_value(this._handle, name);
if (ptr == IntPtr.Zero)
{
return(null);
}
try
{
return(Marshal.PtrToStringAnsi(ptr));
}
finally
{
LevelDBInterop.leveldb_free(ptr);
GC.KeepAlive(this);
}
}
private string InnerGet(IntPtr readOptions, string key)
{
var keyData = Encoding.UTF8.GetBytes(key);
IntPtr error;
IntPtr lengthPtr;
var valuePtr = LevelDBInterop.leveldb_get(this.Database, readOptions, keyData, (IntPtr)keyData.Length, out lengthPtr, out error);
LevelDBException.Check(error);
if (valuePtr == IntPtr.Zero)
{
return(null);
}
try
{
return(GetValue(valuePtr, lengthPtr));
}
finally
{
LevelDBInterop.leveldb_free(valuePtr);
GC.KeepAlive(readOptions);
GC.KeepAlive(this);
}
}
/// <summary>
/// 获取指定键的值。
/// </summary>
/// <param name="key">键。</param>
/// <param name="options">读的选项。</param>
/// <returns>返回一个值，如果值不存在则返回 null 值。</returns>
public unsafe BinaryValue Get(BinaryValue key, ReadOptions options = null)
{
this.ThrowWhenDisposed();
if (options == null)
{
options = new ReadOptions();
}
var keyData = key.ByteArray;
IntPtr error;
IntPtr lengthPtr;
var valuePtr = LevelDBInterop.leveldb_get(this._handle, options._handle, keyData, (IntPtr)keyData.LongLength, out lengthPtr, out error);
LevelDBException.Check(error);
if (valuePtr == IntPtr.Zero)
{
return(null);
}
try
{
var length = (long)lengthPtr;
var value = new byte[length];
var valueNative = (byte *)valuePtr.ToPointer();
for (long i = 0; i < length; ++i)
{
value[i] = valueNative[i];
}
return(new BinaryValue(value));
}
finally
{
LevelDBInterop.leveldb_free(valuePtr);
GC.KeepAlive(options);
GC.KeepAlive(this);
}
}
