strutil.cs

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using System;

namespace Mf.Util
{
	/// <summary>
	/// Summary description for StrUtil.
	/// </summary>
	public class StrUtil
	{
      /// <summary> Class cannot be instantiated</summary>
      private StrUtil()
		{
		}

      #region Left
      /// <summary>
      /// Gets the leftmost n characters of a String. If n characters are not
      /// available, or the String is <code>null</code>, the String will be
      /// returned without an exception.
      /// </summary>
      /// <param name="str">The String to get the leftmost characters from</param>
      /// <param name="int">The length of the required String</param>
      /// <returns>The leftmost characters</returns>
      public static string Left(string str, int len) 
      {
         if (len < 0 || str == null || str.Length <= len ) 
         {
            return str;
         } 
         else 
         {
            return str.Substring(0, len);
         }
      }
      #endregion

      #region LeftIndexOf
      /// <summary>
      /// Gets the left most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the left most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <returns>The left most characters</returns>
      public static string LeftIndexOf( string str, string search )
      {
         return LeftIndexOf( str, search, 0, false );
      }

      /// <summary>
      /// Gets the left most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the left most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="includeSearchString">If true will include the search string in the result, if false then the search string is excluded</param>
      /// <returns>The left most characters</returns>
      public static string LeftIndexOf( string str, string search, bool includeSearchString )
      {
         return LeftIndexOf( str, search, 0, includeSearchString );
      }

      /// <summary>
      /// Gets the left most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the left most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="fromIndex">The index to start the search from</param>
      /// <returns>The left most characters</returns>
      public static string LeftIndexOf( string str, string search, int fromIndex )
      {
         return LeftIndexOf( str, search, fromIndex, false );
      }

      /// <summary>
      /// Gets the left most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the left most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="fromIndex">The index to start the search from</param>
      /// <param name="includeSearchString">If true will include the search string in the result, if false then the search string is excluded</param>
      /// <returns>The left most characters</returns>
      public static string LeftIndexOf( string str, string search, int fromIndex, bool includeSearchString )
      {
         if ( Is.EmptyString( str ) || Is.EmptyString( search ) )
         {
            return str;
         }
         else
         {
            if ( fromIndex > str.Length )
            {
               return str;
            }

            int pos = str.IndexOf( search, fromIndex );

            if ( pos == -1 )
            {
               return str;
            }
            else
            {
               return str.Substring( 0, pos + ( includeSearchString ? search.Length : 0 ) );
            }
         }
      }
#endregion

      #region LeftOf
      /// <summary>
      /// Gets the characters to the left of <var>pos</var>.
      /// </summary>
      /// <param name="string">The String to get the left most characters from</param>
      /// <param name="int">The position to cut from</param>
      /// <returns>The left most characters</returns>
      public static string LeftOf(string str, int pos) 
      {
         if ( str == null )
         {
            return null;
         }
         else
         {
            if ( pos == -1          ) return "";
            if ( pos  > str.Length  ) return str;

            return Substring( str, 0, pos );
         }
      }
      #endregion

      #region Right
      /// <summary>
      /// Gets the right most n characters of a String. If n characters are not
      /// available, or the String is <code>null</code>, the String will be
      /// returned without an exception.
      /// </summary>
      /// <param name="str">The String to get the right most characters from</param>
      /// <param name="int">The length of the required String</param>
      /// <returns>The right most characters</returns>
      public static string Right(string str, int len) 
      {
         if (len < 0 || str == null || str.Length <= len ) 
         {
            return str;
         } 
         else 
         {
            return str.Substring( str.Length - len);
         }
      }
      #endregion
 
      #region RightIndexOf
      /// <summary>
      /// Gets the right most characters starting from the index of <var>search</var>.
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the right most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <returns>The right most characters</returns>
      public static string RightIndexOf( string str, string search )
      {
         return RightIndexOf( str, search, 0, false );
      }

      /// <summary>
      /// Gets the right most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the right most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="includeSearchString">If true will include the search string in the result, if false then the search string is excluded</param>
      /// <returns>The right most characters</returns>
      public static string RightIndexOf( string str, string search, bool includeSearchString )
      {
         return RightIndexOf( str, search, 0, includeSearchString );
      }

      /// <summary>
      /// Gets the right most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the right most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="fromIndex">The index to start the search from</param>
      /// <returns>The right most characters</returns>
      public static string RightIndexOf( string str, string search, int fromIndex )
      {
         return RightIndexOf( str, search, fromIndex, false );
      }

      /// <summary>
      /// Gets the right most characters starting from the index of <var>search</var>
      /// <br/>
      /// If <var>str</var> is <code>null</code>, then <var>str</var> will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the right most characters off</param>
      /// <param name="search">The string to search for</param>
      /// <param name="fromIndex">The index to start the search from</param>
      /// <param name="includeSearchString">If true will include the search string in the result, if false then the search string is excluded</param>
      /// <returns>The right most characters</returns>
      public static string RightIndexOf( string str, string search, int fromIndex, bool includeSearchString )
      {
         if ( Is.EmptyString( str ) || Is.EmptyString( search ) || fromIndex > str.Length )
         {
            return str;
         }
         else
         {
            int pos = str.IndexOf( search, fromIndex );

            if ( pos == -1 )
            {
               return str;
            }
            else
            {
               return str.Substring( pos + ( includeSearchString ? 0 : search.Length ) );
            }
         }
      }
      #endregion

      #region RightLastIndexOf
      /// <summary>
      /// Gets the right most characters starting from the last index of <var>search</var>.
      /// <br/>
      /// If the String is <code>null</code>, the String will be returned without an exception.
      /// <br/><br/>
      /// If <var>search</var> is not found then <var>str</var> will be returned without an exception.
      /// </summary>
      /// <param name="str">The string to get the right most characters off</param>
      /// <param name="search">The last occurence of search to start from</param>
      /// <returns>The right most characters</returns>
      public static string RightLastIndexOf( string str, string search )
      {
         if ( ( str == null ) || (search == null ) )
         {
            return str;
         }
         else
         {
            int pos = str.LastIndexOf( search );

            if ( pos == -1 )
            {
               return str;
            }
            else
            {
               return str.Substring( pos + search.Length );
            }
         }

      }
      #endregion

      #region RightOf
      /// <summary>
      /// Gets the characters to the right of <var>pos</var>.
      /// </summary>
      /// <param name="string">The String to get the right most characters from</param>
      /// <param name="int">The position to cut from</param>
      /// <returns>The right most characters</returns>
      public static string RightOf(string str, int pos) 
      {
         if ( str == null )
         {
            return null;
         }
         else
         {
            if ( pos == -1 )
            {
               return str;
            }
            return Substring( str, pos+1 );
         }
      }
      #endregion

      #region Substring
      /// <summary>
      /// Gets a substring from the specified string avoiding exceptions from invalid start indexes or null strings.
      /// </summary>
      /// <param name="str">The String to get the substring from</param>
      /// <param name="int">The index of the start of the substring</param>
      /// <returns>substring from start position</returns>
      public static string Substring(string str, int start) 
      {
         if ( str == null ) return null;

         if ( start < 0) start = 0;                   // Start must be 0 or greater
         if ( start > str.Length ) return "";         // Start to big

         return str.Substring( start );
      }

      /// <summary>
      /// Gets a substring from the specified string avoiding exceptions from invalid start indexes, lengths or null strings.
      /// </summary>
      /// <param name="string">The String to get the substring from</param>
      /// <param name="int">The index of the start of the substring</param>
      /// <param name="int">The number of characters in the substring. </param>
      /// <returns>substring from start position for <var>length</var> characters</returns>
      public static string Substring(string str, int start, int length ) 
      {
         if ( str == null ) return null;

         if ( start < 0 ) 
         {
            start = 0;                     // Start must be 0 or greater
         }
         if ( length > str.Length-start )
         {
            length = str.Length-start;
         }

         return str.Substring( start, length );
      }
      #endregion

      #region StartsWith
      /// <summary>
      /// Similer to String.StartsWith except that it is case-insensitive.
      /// </summary>
      /// <param name="str">The string to test</param>
      /// <param name="startsWith">The string to seek</param>
      /// <returns><b>true</b> if value matches the beginning of this string or is Empty; otherwise <b>false</b></returns>
      public static bool StartsWith( string str, string startsWith )
      {
         if ( str == null || startsWith == null || startsWith.Length > str.Length )
         {
            return false;
         }
         
         // REFACTOR: Would be quicker to test each character in a loop
         return str.ToLower( ).StartsWith( startsWith.ToLower( ) );
      }
      #endregion

   }
}