using System;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
namespace NewLife.Queue.Utilities
{
/// <summary>Represents an ObjectId
/// </summary>
[Serializable]
public struct ObjectId : IComparable<ObjectId>, IEquatable<ObjectId>
{
// private static fields
private static readonly DateTime __unixEpoch;
private static readonly long __dateTimeMaxValueMillisecondsSinceEpoch;
private static readonly long __dateTimeMinValueMillisecondsSinceEpoch;
private static ObjectId __emptyInstance = default(ObjectId);
private static int __staticMachine;
private static short __staticPid;
private static int __staticIncrement; // high byte will be masked out when generating new ObjectId
private static uint[] _lookup32 = Enumerable.Range(0, 256).Select(i =>
{
string s = i.ToString("x2");
return ((uint)s[0]) + ((uint)s[1] << 16);
}).ToArray();
// we're using 14 bytes instead of 12 to hold the ObjectId in memory but unlike a byte[] there is no additional object on the heap
// the extra two bytes are not visible to anyone outside of this class and they buy us considerable simplification
// an additional advantage of this representation is that it will serialize to JSON without any 64 bit overflow problems
private int _timestamp;
private int _machine;
private short _pid;
private int _increment;
// static constructor
static ObjectId()
{
__unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
__dateTimeMaxValueMillisecondsSinceEpoch = (DateTime.MaxValue - __unixEpoch).Ticks / 10000;
__dateTimeMinValueMillisecondsSinceEpoch = (DateTime.MinValue - __unixEpoch).Ticks / 10000;
__staticMachine = GetMachineHash();
__staticIncrement = (new Random()).Next();
__staticPid = (short)GetCurrentProcessId();
}
// constructors
/// <summary>
/// Initializes a new instance of the ObjectId class.
/// </summary>
/// <param name="bytes">The bytes.</param>
public ObjectId(byte[] bytes)
{
if (bytes == null)
{
throw new ArgumentNullException("bytes");
}
Unpack(bytes, out _timestamp, out _machine, out _pid, out _increment);
}
/// <summary>
/// Initializes a new instance of the ObjectId class.
/// </summary>
/// <param name="timestamp">The timestamp (expressed as a DateTime).</param>
/// <param name="machine">The machine hash.</param>
/// <param name="pid">The PID.</param>
/// <param name="increment">The increment.</param>
public ObjectId(DateTime timestamp, int machine, short pid, int increment)
: this(GetTimestampFromDateTime(timestamp), machine, pid, increment)
{
}
/// <summary>
/// Initializes a new instance of the ObjectId class.
/// </summary>
/// <param name="timestamp">The timestamp.</param>
/// <param name="machine">The machine hash.</param>
/// <param name="pid">The PID.</param>
/// <param name="increment">The increment.</param>
public ObjectId(int timestamp, int machine, short pid, int increment)
{
if ((machine & 0xff000000) != 0)
{
throw new ArgumentOutOfRangeException("machine", "The machine value must be between 0 and 16777215 (it must fit in 3 bytes).");
}
if ((increment & 0xff000000) != 0)
{
throw new ArgumentOutOfRangeException("increment", "The increment value must be between 0 and 16777215 (it must fit in 3 bytes).");
}
_timestamp = timestamp;
_machine = machine;
_pid = pid;
_increment = increment;
}
/// <summary>
/// Initializes a new instance of the ObjectId class.
/// </summary>
/// <param name="value">The value.</param>
public ObjectId(string value)
{
if (value == null)
{
throw new ArgumentNullException("value");
}
Unpack(ParseHexString(value), out _timestamp, out _machine, out _pid, out _increment);
}
// public static properties
/// <summary>
/// Gets an instance of ObjectId where the value is empty.
/// </summary>
public static ObjectId Empty
{
get { return __emptyInstance; }
}
// public properties
/// <summary>
/// Gets the timestamp.
/// </summary>
public int Timestamp
{
get { return _timestamp; }
}
/// <summary>
/// Gets the machine.
/// </summary>
public int Machine
{
get { return _machine; }
}
/// <summary>
/// Gets the PID.
/// </summary>
public short Pid
{
get { return _pid; }
}
/// <summary>
/// Gets the increment.
/// </summary>
public int Increment
{
get { return _increment; }
}
/// <summary>
/// Gets the creation time (derived from the timestamp).
/// </summary>
public DateTime CreationTime
{
get { return __unixEpoch.AddSeconds(_timestamp); }
}
// public operators
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId</param>
/// <returns>True if the first ObjectId is less than the second ObjectId.</returns>
public static bool operator <(ObjectId lhs, ObjectId rhs)
{
return lhs.CompareTo(rhs) < 0;
}
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId</param>
/// <returns>True if the first ObjectId is less than or equal to the second ObjectId.</returns>
public static bool operator <=(ObjectId lhs, ObjectId rhs)
{
return lhs.CompareTo(rhs) <= 0;
}
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId.</param>
/// <returns>True if the two ObjectIds are equal.</returns>
public static bool operator ==(ObjectId lhs, ObjectId rhs)
{
return lhs.Equals(rhs);
}
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId.</param>
/// <returns>True if the two ObjectIds are not equal.</returns>
public static bool operator !=(ObjectId lhs, ObjectId rhs)
{
return !(lhs == rhs);
}
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId</param>
/// <returns>True if the first ObjectId is greather than or equal to the second ObjectId.</returns>
public static bool operator >=(ObjectId lhs, ObjectId rhs)
{
return lhs.CompareTo(rhs) >= 0;
}
/// <summary>
/// Compares two ObjectIds.
/// </summary>
/// <param name="lhs">The first ObjectId.</param>
/// <param name="rhs">The other ObjectId</param>
/// <returns>True if the first ObjectId is greather than the second ObjectId.</returns>
public static bool operator >(ObjectId lhs, ObjectId rhs)
{
return lhs.CompareTo(rhs) > 0;
}
// public static methods
/// <summary>
/// Generates a new ObjectId with a unique value.
/// </summary>
/// <returns>An ObjectId.</returns>
public static ObjectId GenerateNewId()
{
return GenerateNewId(GetTimestampFromDateTime(DateTime.UtcNow));
}
/// <summary>
/// Generates a new ObjectId with a unique value (with the timestamp component based on a given DateTime).
/// </summary>
/// <param name="timestamp">The timestamp component (expressed as a DateTime).</param>
/// <returns>An ObjectId.</returns>
public static ObjectId GenerateNewId(DateTime timestamp)
{
return GenerateNewId(GetTimestampFromDateTime(timestamp));
}
/// <summary>
/// Generates a new ObjectId with a unique value (with the given timestamp).
/// </summary>
/// <param name="timestamp">The timestamp component.</param>
/// <returns>An ObjectId.</returns>
public static ObjectId GenerateNewId(int timestamp)
{
int increment = Interlocked.Increment(ref __staticIncrement) & 0x00ffffff; // only use low order 3 bytes
return new ObjectId(timestamp, __staticMachine, __staticPid, increment);
}
/// <summary>
/// Generates a new ObjectId string with a unique value.
/// </summary>
/// <returns>The string value of the new generated ObjectId.</returns>
public static string GenerateNewStringId()
{
return GenerateNewId().ToString();
}
/// <summary>
/// Packs the components of an ObjectId into a byte array.
/// </summary>
/// <param name="timestamp">The timestamp.</param>
/// <param name="machine">The machine hash.</param>
/// <param name="pid">The PID.</param>
/// <param name="increment">The increment.</param>
/// <returns>A byte array.</returns>
public static byte[] Pack(int timestamp, int machine, short pid, int increment)
{
if ((machine & 0xff000000) != 0)
{
throw new ArgumentOutOfRangeException("machine", "The machine value must be between 0 and 16777215 (it must fit in 3 bytes).");
}
if ((increment & 0xff000000) != 0)
{
throw new ArgumentOutOfRangeException("increment", "The increment value must be between 0 and 16777215 (it must fit in 3 bytes).");
}
byte[] bytes = new byte[12];
bytes[0] = (byte)(timestamp >> 24);
bytes[1] = (byte)(timestamp >> 16);
bytes[2] = (byte)(timestamp >> 8);
bytes[3] = (byte)(timestamp);
bytes[4] = (byte)(machine >> 16);
bytes[5] = (byte)(machine >> 8);
bytes[6] = (byte)(machine);
bytes[7] = (byte)(pid >> 8);
bytes[8] = (byte)(pid);
bytes[9] = (byte)(increment >> 16);
bytes[10] = (byte)(increment >> 8);
bytes[11] = (byte)(increment);
return bytes;
}
/// <summary>
/// Parses a string and creates a new ObjectId.
/// </summary>
/// <param name="s">The string value.</param>
/// <returns>A ObjectId.</returns>
public static ObjectId Parse(string s)
{
if (s == null)
{
throw new ArgumentNullException("s");
}
if (s.Length != 24)
{
throw new ArgumentOutOfRangeException("s", "ObjectId string value must be 24 characters.");
}
return new ObjectId(ParseHexString(s));
}
/// <summary>
/// Unpacks a byte array into the components of an ObjectId.
/// </summary>
/// <param name="bytes">A byte array.</param>
/// <param name="timestamp">The timestamp.</param>
/// <param name="machine">The machine hash.</param>
/// <param name="pid">The PID.</param>
/// <param name="increment">The increment.</param>
public static void Unpack(byte[] bytes, out int timestamp, out int machine, out short pid, out int increment)
{
if (bytes == null)
{
throw new ArgumentNullException("bytes");
}
if (bytes.Length != 12)
{
throw new ArgumentOutOfRangeException("bytes", "Byte array must be 12 bytes long.");
}
timestamp = (bytes[0] << 24) + (bytes[1] << 16) + (bytes[2] << 8) + bytes[3];
machine = (bytes[4] << 16) + (bytes[5] << 8) + bytes[6];
pid = (short)((bytes[7] << 8) + bytes[8]);
increment = (bytes[9] << 16) + (bytes[10] << 8) + bytes[11];
}
// private static methods
/// <summary>
/// Gets the current process id. This method exists because of how CAS operates on the call stack, checking
/// for permissions before executing the method. Hence, if we inlined this call, the calling method would not execute
/// before throwing an exception requiring the try/catch at an even higher level that we don't necessarily control.
/// </summary>
[MethodImpl(MethodImplOptions.NoInlining)]
private static int GetCurrentProcessId()
{
return Process.GetCurrentProcess().Id;
}
private static int GetMachineHash()
{
var hostName = Environment.MachineName; // use instead of Dns.HostName so it will work offline
var md5 = MD5.Create();
var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(hostName));
return (hash[0] << 16) + (hash[1] << 8) + hash[2]; // use first 3 bytes of hash
}
private static int GetTimestampFromDateTime(DateTime timestamp)
{
return (int)Math.Floor((ToUniversalTime(timestamp) - __unixEpoch).TotalSeconds);
}
// public methods
/// <summary>
/// Compares this ObjectId to another ObjectId.
/// </summary>
/// <param name="other">The other ObjectId.</param>
/// <returns>A 32-bit signed integer that indicates whether this ObjectId is less than, equal to, or greather than the other.</returns>
public int CompareTo(ObjectId other)
{
int r = _timestamp.CompareTo(other._timestamp);
if (r != 0) { return r; }
r = _machine.CompareTo(other._machine);
if (r != 0) { return r; }
r = _pid.CompareTo(other._pid);
if (r != 0) { return r; }
return _increment.CompareTo(other._increment);
}
/// <summary>
/// Compares this ObjectId to another ObjectId.
/// </summary>
/// <param name="rhs">The other ObjectId.</param>
/// <returns>True if the two ObjectIds are equal.</returns>
public bool Equals(ObjectId rhs)
{
return
_timestamp == rhs._timestamp &&
_machine == rhs._machine &&
_pid == rhs._pid &&
_increment == rhs._increment;
}
/// <summary>
/// Compares this ObjectId to another object.
/// </summary>
/// <param name="obj">The other object.</param>
/// <returns>True if the other object is an ObjectId and equal to this one.</returns>
public override bool Equals(object obj)
{
if (obj is ObjectId)
{
return Equals((ObjectId)obj);
}
else
{
return false;
}
}
/// <summary>
/// Gets the hash code.
/// </summary>
/// <returns>The hash code.</returns>
public override int GetHashCode()
{
int hash = 17;
hash = 37 * hash + _timestamp.GetHashCode();
hash = 37 * hash + _machine.GetHashCode();
hash = 37 * hash + _pid.GetHashCode();
hash = 37 * hash + _increment.GetHashCode();
return hash;
}
/// <summary>
/// Converts the ObjectId to a byte array.
/// </summary>
/// <returns>A byte array.</returns>
public byte[] ToByteArray()
{
return Pack(_timestamp, _machine, _pid, _increment);
}
/// <summary>
/// Returns a string representation of the value.
/// </summary>
/// <returns>A string representation of the value.</returns>
public override string ToString()
{
return ToHexString(ToByteArray());
}
/// <summary>
/// Parses a hex string into its equivalent byte array.
/// </summary>
/// <param name="s">The hex string to parse.</param>
/// <returns>The byte equivalent of the hex string.</returns>
public static byte[] ParseHexString(string s)
{
if (s == null)
{
throw new ArgumentNullException("s");
}
if (s.Length % 2 == 1)
{
throw new Exception("The binary key cannot have an odd number of digits");
}
byte[] arr = new byte[s.Length >> 1];
for (int i = 0; i < s.Length >> 1; ++i)
{
arr[i] = (byte)((GetHexVal(s[i << 1]) << 4) + (GetHexVal(s[(i << 1) + 1])));
}
return arr;
}
/// <summary>
/// Converts a byte array to a hex string.
/// </summary>
/// <param name="bytes">The byte array.</param>
/// <returns>A hex string.</returns>
public static string ToHexString(byte[] bytes)
{
if (bytes == null)
{
throw new ArgumentNullException("bytes");
}
var result = new char[bytes.Length * 2];
for (int i = 0; i < bytes.Length; i++)
{
var val = _lookup32[bytes[i]];
result[2 * i] = (char)val;
result[2 * i + 1] = (char)(val >> 16);
}
return new string(result);
}
/// <summary>
/// Converts a DateTime to number of milliseconds since Unix epoch.
/// </summary>
/// <param name="dateTime">A DateTime.</param>
/// <returns>Number of seconds since Unix epoch.</returns>
public static long ToMillisecondsSinceEpoch(DateTime dateTime)
{
var utcDateTime = ToUniversalTime(dateTime);
return (utcDateTime - __unixEpoch).Ticks / 10000;
}
/// <summary>
/// Converts a DateTime to UTC (with special handling for MinValue and MaxValue).
/// </summary>
/// <param name="dateTime">A DateTime.</param>
/// <returns>The DateTime in UTC.</returns>
public static DateTime ToUniversalTime(DateTime dateTime)
{
if (dateTime == DateTime.MinValue)
{
return DateTime.SpecifyKind(DateTime.MinValue, DateTimeKind.Utc);
}
else if (dateTime == DateTime.MaxValue)
{
return DateTime.SpecifyKind(DateTime.MaxValue, DateTimeKind.Utc);
}
else
{
return dateTime.ToUniversalTime();
}
}
private static int GetHexVal(char hex)
{
int val = (int)hex;
//For uppercase A-F letters:
//return val - (val < 58 ? 48 : 55);
//For lowercase a-f letters:
//return val - (val < 58 ? 48 : 87);
//Or the two combined, but a bit slower:
return val - (val < 58 ? 48 : (val < 97 ? 55 : 87));
}
}
}
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