StringSpan.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.Runtime.InteropServices;

namespace SiliconStudio.Core
{
    /// <summary>
    /// A region of character in a string.
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
    public struct StringSpan : IEquatable<StringSpan>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="StringSpan"/> struct.
        /// </summary>
        /// <param name="start">The start.</param>
        /// <param name="length">The length.</param>
        public StringSpan(int start, int length)
        {
            Start = start;
            Length = length;
        }

        /// <summary>
        /// The start of the span.
        /// </summary>
        public int Start;

        /// <summary>
        /// The length of the span
        /// </summary>
        public int Length;

        /// <summary>
        /// Gets a value indicating whether this instance is valid (Start greater or equal to 0, and Length greater than 0)
        /// </summary>
        /// <value><c>true</c> if this instance is valid; otherwise, <c>false</c>.</value>
        public bool IsValid
        {
            get
            {
                return Start >= 0 && Length > 0;
            }
        }

        /// <summary>
        /// Gets the next position = Start + Length.
        /// </summary>
        /// <value>The next.</value>
        public int Next
        {
            get
            {
                return Start + Length;
            }
        }

        public bool Equals(StringSpan other)
        {
            return Start == other.Start && Length == other.Length;
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            return obj is StringSpan && Equals((StringSpan)obj);
        }

        public override int GetHashCode()
        {
            unchecked
            {
                return (Start*397) ^ Length;
            }
        }

        public static bool operator ==(StringSpan left, StringSpan right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(StringSpan left, StringSpan right)
        {
            return !left.Equals(right);
        }

        public override string ToString()
        {
            return IsValid ? string.Format("[{0}-{1}]", Start, Next - 1) : "[N/A]";
        }
    }
}