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Copy pathNpgsqlLogSequenceNumber.cs
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335 lines (307 loc) · 17.5 KB
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using System;
using System.Globalization;
// ReSharper disable once CheckNamespace
namespace NpgsqlTypes;
/// <summary>
/// Wraps a PostgreSQL Write-Ahead Log Sequence Number (see: https://www.postgresql.org/docs/current/datatype-pg-lsn.html)
/// </summary>
/// <remarks>
/// Log Sequence Numbers are a fundamental concept of the PostgreSQL Write-Ahead Log and by that of
/// PostgreSQL replication. See https://www.postgresql.org/docs/current/wal-internals.html for what they represent.
///
/// This struct provides conversions from/to <see cref="string"/> and <see cref="ulong"/> and beyond that tries to port
/// the methods and operators in https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/adt/pg_lsn.c
/// but nothing more.
/// </remarks>
public readonly struct NpgsqlLogSequenceNumber : IEquatable<NpgsqlLogSequenceNumber>, IComparable<NpgsqlLogSequenceNumber>
{
/// <summary>
/// Zero is used indicate an invalid Log Sequence Number. No XLOG record can begin at zero.
/// </summary>
public static readonly NpgsqlLogSequenceNumber Invalid = default;
readonly ulong _value;
/// <summary>
/// Initializes a new instance of <see cref="NpgsqlLogSequenceNumber"/>.
/// </summary>
/// <param name="value">The value to wrap.</param>
public NpgsqlLogSequenceNumber(ulong value)
=> _value = value;
/// <summary>
/// Returns a value indicating whether this instance is equal to a specified <see cref="NpgsqlLogSequenceNumber"/>
/// instance.
/// </summary>
/// <param name="other">A <see cref="NpgsqlLogSequenceNumber"/> instance to compare to this instance.</param>
/// <returns><see langword="true" /> if the current instance is equal to the value parameter;
/// otherwise, <see langword="false" />.</returns>
public bool Equals(NpgsqlLogSequenceNumber other)
=> _value == other._value;
/// <summary>
/// Compares this instance to a specified <see cref="NpgsqlLogSequenceNumber"/> and returns an indication of their
/// relative values.
/// </summary>
/// <param name="value">A <see cref="NpgsqlLogSequenceNumber"/> instance to compare to this instance.</param>
/// <returns>A signed number indicating the relative values of this instance and <paramref name="value" />.</returns>
public int CompareTo(NpgsqlLogSequenceNumber value)
=> _value.CompareTo(value._value);
/// <summary>
/// Returns a value indicating whether this instance is equal to a specified object.
/// </summary>
/// <param name="obj">An object to compare to this instance</param>
/// <returns><see langword="true" /> if the current instance is equal to the value parameter;
/// otherwise, <see langword="false" />.</returns>
public override bool Equals(object? obj)
=> obj is NpgsqlLogSequenceNumber lsn && lsn._value == _value;
/// <summary>
/// Returns the hash code for this instance.
/// </summary>
/// <returns>A 32-bit signed integer hash code.</returns>
public override int GetHashCode()
=> _value.GetHashCode();
/// <summary>
/// Converts the numeric value of this instance to its equivalent string representation.
/// </summary>
/// <returns>The string representation of the value of this instance, consisting of two hexadecimal numbers of
/// up to 8 digits each, separated by a slash</returns>
public override string ToString()
=> unchecked($"{(uint)(_value >> 32):X}/{(uint)_value:X}");
/// <summary>
/// Converts the string representation of a Log Sequence Number to a <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="s">A string that represents the Log Sequence Number to convert.</param>
/// <returns>
/// A <see cref="NpgsqlLogSequenceNumber"/> equivalent to the Log Sequence Number specified in <paramref name="s" />.
/// </returns>
/// <exception cref="ArgumentNullException">The <paramref name="s" /> parameter is <see langword="null"/>.</exception>
/// <exception cref="OverflowException">
/// The <paramref name="s" /> parameter represents a number less than <see cref="ulong.MinValue"/> or greater than
/// <see cref="ulong.MaxValue"/>.
/// </exception>
/// <exception cref="FormatException">The <paramref name="s" /> parameter is not in the right format.</exception>
public static NpgsqlLogSequenceNumber Parse(string s)
// ReSharper disable once ConditionIsAlwaysTrueOrFalse
=> s is null
? throw new ArgumentNullException(nameof(s))
: Parse(s.AsSpan());
/// <summary>
/// Converts the span representation of a Log Sequence Number to a <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="s">A span containing the characters that represent the Log Sequence Number to convert.</param>
/// <returns>
/// A <see cref="NpgsqlLogSequenceNumber"/> equivalent to the Log Sequence Number specified in <paramref name="s" />.
/// </returns>
/// <exception cref="OverflowException">
/// The <paramref name="s" /> parameter represents a number less than <see cref="ulong.MinValue"/> or greater than
/// <see cref="ulong.MaxValue"/>.
/// </exception>
/// <exception cref="FormatException">The <paramref name="s" /> parameter is not in the right format.</exception>
public static NpgsqlLogSequenceNumber Parse(ReadOnlySpan<char> s)
=> TryParse(s, out var parsed)
? parsed
: throw new FormatException($"Invalid Log Sequence Number: '{s.ToString()}'.");
/// <summary>
/// Tries to convert the string representation of a Log Sequence Number to an <see cref="NpgsqlLogSequenceNumber"/>
/// instance. A return value indicates whether the conversion succeeded or failed.
/// </summary>
/// <param name="s">A string that represents the Log Sequence Number to convert.</param>
/// <param name="result">
/// When this method returns, contains a <see cref="NpgsqlLogSequenceNumber"/> instance equivalent to the Log Sequence
/// Number contained in <paramref name="s"/>, if the conversion succeeded, or the default value for
/// <see cref="NpgsqlLogSequenceNumber"/> (<c>0</c>) if the conversion failed. The conversion fails if the <paramref name="s" />
/// parameter is <see langword="null"/> or <see cref="string.Empty"/>, is not in the right format, or represents a number
/// less than <see cref="ulong.MinValue"/> or greater than <see cref="ulong.MaxValue"/>. This parameter is
/// passed uninitialized; any value originally supplied in result will be overwritten.
/// </param>
/// <returns>
/// <see langword="true" /> if <paramref name="s"/>c> was converted successfully; otherwise, <see langword="false" />.
/// </returns>
public static bool TryParse(string s, out NpgsqlLogSequenceNumber result)
=> TryParse(s.AsSpan(), out result);
/// <summary>
/// Tries to convert the span representation of a Log Sequence Number to an <see cref="NpgsqlLogSequenceNumber"/>
/// instance. A return value indicates whether the conversion succeeded or failed.
/// </summary>
/// <param name="s">A span containing the characters that represent the Log Sequence Number to convert.</param>
/// <param name="result">
/// When this method returns, contains a <see cref="NpgsqlLogSequenceNumber"/> instance equivalent to the Log Sequence
/// Number contained in <paramref name="s"/>, if the conversion succeeded, or the default value for
/// <see cref="NpgsqlLogSequenceNumber"/> (<c>0</c>) if the conversion failed. The conversion fails if the <paramref name="s" />
/// parameter is empty, is not in the right format, or represents a number less than
/// <see cref="ulong.MinValue"/> or greater than <see cref="ulong.MaxValue"/>. This parameter is passed
/// uninitialized; any value originally supplied in result will be overwritten.
/// </param>
/// <returns>
/// <see langword="true" /> if <paramref name="s"/> was converted successfully; otherwise, <see langword="false" />.</returns>
public static bool TryParse(ReadOnlySpan<char> s, out NpgsqlLogSequenceNumber result)
{
for (var i = 0; i < s.Length; i++)
{
if (s[i] != '/') continue;
var firstPart = s.Slice(0, i);
var secondPart = s.Slice(++i);
if (!uint.TryParse(firstPart, NumberStyles.AllowHexSpecifier, null, out var first))
{
result = default;
return false;
}
if (!uint.TryParse(secondPart, NumberStyles.AllowHexSpecifier, null, out var second))
{
result = default;
return false;
}
result = new NpgsqlLogSequenceNumber(((ulong)first << 32) + second);
return true;
}
result = default;
return false;
}
/// <summary>
/// Converts the value of a 64-bit unsigned integer to a <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="value">A 64-bit unsigned integer.</param>
/// <returns>A new instance of <see cref="NpgsqlLogSequenceNumber"/> initialized to <paramref name="value" />.</returns>
public static explicit operator NpgsqlLogSequenceNumber(ulong value)
=> new(value);
/// <summary>
/// Converts the value of a <see cref="NpgsqlLogSequenceNumber"/> instance to a 64-bit unsigned integer value.
/// </summary>
/// <param name="value">A <see cref="NpgsqlLogSequenceNumber"/> instance</param>
/// <returns>The contents of <paramref name="value" /> as 64-bit unsigned integer.</returns>
public static explicit operator ulong(NpgsqlLogSequenceNumber value)
=> value._value;
/// <summary>
/// Returns a value that indicates whether two specified instances of <see cref="NpgsqlLogSequenceNumber"/> are equal.
/// </summary>
/// <param name="value1">The first Log Sequence Number to compare.</param>
/// <param name="value2">The second Log Sequence Number to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> equals <paramref name="value2" />; otherwise, <see langword="false" />.
/// </returns>
public static bool operator ==(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value == value2._value;
/// <summary>
/// Returns a value that indicates whether two specified instances of <see cref="NpgsqlLogSequenceNumber"/> are not
/// equal.
/// </summary>
/// <param name="value1">The first Log Sequence Number to compare.</param>
/// <param name="value2">The second Log Sequence Number to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> does not equal <paramref name="value2" />; otherwise,
/// <see langword="false" />.
/// </returns>
public static bool operator !=(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value != value2._value;
/// <summary>
/// Returns a value indicating whether a specified <see cref="NpgsqlLogSequenceNumber"/> instance is greater than
/// another specified <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> is greater than <paramref name="value2" />; otherwise,
/// <see langword="false" />.
/// </returns>
public static bool operator >(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value > value2._value;
/// <summary>
/// Returns a value indicating whether a specified <see cref="NpgsqlLogSequenceNumber"/> instance is less than
/// another specified <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> is less than <paramref name="value2" />; otherwise,
/// <see langword="false" />.
/// </returns>
public static bool operator <(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value < value2._value;
/// <summary>
/// Returns a value indicating whether a specified <see cref="NpgsqlLogSequenceNumber"/> instance is greater than or
/// equal to another specified <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> is greater than or equal to <paramref name="value2" />;
/// otherwise, <see langword="false" />.
/// </returns>
public static bool operator >=(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value >= value2._value;
/// <summary>
/// Returns the larger of two <see cref="NpgsqlLogSequenceNumber"/> values.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// The larger of the two <see cref="NpgsqlLogSequenceNumber"/> values.
/// </returns>
public static NpgsqlLogSequenceNumber Larger(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value > value2._value ? value1 : value2;
/// <summary>
/// Returns the smaller of two <see cref="NpgsqlLogSequenceNumber"/> values.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// The smaller of the two <see cref="NpgsqlLogSequenceNumber"/> values.
/// </returns>
public static NpgsqlLogSequenceNumber Smaller(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value < value2._value ? value1 : value2;
/// <summary>
/// Returns a value indicating whether a specified <see cref="NpgsqlLogSequenceNumber"/> instance is less than or
/// equal to another specified <see cref="NpgsqlLogSequenceNumber"/> instance.
/// </summary>
/// <param name="value1">The first value to compare.</param>
/// <param name="value2">The second value to compare.</param>
/// <returns>
/// <see langword="true" /> if <paramref name="value1" /> is less than or equal to <paramref name="value2" />;
/// otherwise, <see langword="false" />.
/// </returns>
public static bool operator <=(NpgsqlLogSequenceNumber value1, NpgsqlLogSequenceNumber value2)
=> value1._value <= value2._value;
/// <summary>
/// Subtracts two specified <see cref="NpgsqlLogSequenceNumber"/> values.
/// </summary>
/// <param name="first">The first <see cref="NpgsqlLogSequenceNumber"/> value.</param>
/// <param name="second">The second <see cref="NpgsqlLogSequenceNumber"/> value.</param>
/// <returns>The number of bytes separating those write-ahead log locations.</returns>
public static ulong operator -(NpgsqlLogSequenceNumber first, NpgsqlLogSequenceNumber second)
=> first._value < second._value
? second._value - first._value
: first._value - second._value;
/// <summary>
/// Subtract the number of bytes from a <see cref="NpgsqlLogSequenceNumber"/> instance, giving a new
/// <see cref="NpgsqlLogSequenceNumber"/> instance.
/// Handles both positive and negative numbers of bytes.
/// </summary>
/// <param name="lsn">
/// The <see cref="NpgsqlLogSequenceNumber"/> instance representing a write-ahead log location.
/// </param>
/// <param name="nbytes">The number of bytes to subtract.</param>
/// <returns>A new <see cref="NpgsqlLogSequenceNumber"/> instance.</returns>
/// <exception cref="OverflowException">
/// The resulting <see cref="NpgsqlLogSequenceNumber"/> instance would represent a number less than
/// <see cref="ulong.MinValue"/>.
/// </exception>
public static NpgsqlLogSequenceNumber operator -(NpgsqlLogSequenceNumber lsn, double nbytes)
=> double.IsNaN(nbytes) || double.IsInfinity(nbytes)
? throw new NotFiniteNumberException($"Cannot subtract {nbytes} from {nameof(NpgsqlLogSequenceNumber)}", nbytes)
: new NpgsqlLogSequenceNumber(checked((ulong)(lsn._value - nbytes)));
/// <summary>
/// Add the number of bytes to a <see cref="NpgsqlLogSequenceNumber"/> instance, giving a new
/// <see cref="NpgsqlLogSequenceNumber"/> instance.
/// Handles both positive and negative numbers of bytes.
/// </summary>
/// <param name="lsn">
/// The <see cref="NpgsqlLogSequenceNumber"/> instance representing a write-ahead log location.
/// </param>
/// <param name="nbytes">The number of bytes to add.</param>
/// <returns>A new <see cref="NpgsqlLogSequenceNumber"/> instance.</returns>
/// <exception cref="OverflowException">
/// The resulting <see cref="NpgsqlLogSequenceNumber"/> instance would represent a number greater than
/// <see cref="ulong.MaxValue"/>.
/// </exception>
public static NpgsqlLogSequenceNumber operator +(NpgsqlLogSequenceNumber lsn, double nbytes)
=> double.IsNaN(nbytes) || double.IsInfinity(nbytes)
? throw new NotFiniteNumberException($"Cannot add {nbytes} to {nameof(NpgsqlLogSequenceNumber)}", nbytes)
: new NpgsqlLogSequenceNumber(checked((ulong)(lsn._value + nbytes)));
}
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