mcs/class/System.Data/Mono.Data.SqlExpressions/StringFunctions.cs

   1 //
   2 // StringFunctions.cs
   3 //
   4 // Author:
   5 //   Juraj Skripsky (juraj@hotfeet.ch)
   6 //
   7 // (C) 2004 HotFeet GmbH (http://www.hotfeet.ch)
   8 //
   9
  10 //
  11 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32
  33 using System;
  34 using System.Collections;
  35 using System.Data;
  36
  37 namespace Mono.Data.SqlExpressions {
  38         internal abstract class StringFunction : UnaryExpression {
  39                 protected StringFunction (IExpression e) : base (e) {}
  40
  41                 override public object Eval (DataRow row)
  42                 {
  43                         object val = expr.Eval (row);
  44                         if(val == null)
  45                                 return null;
  46
  47                         if (!(val is string)) {
  48                                 string fnct = this.GetType ().ToString ();
  49                                 int start = fnct.LastIndexOf('.') + 1;
  50                                 fnct = fnct.Substring (start, fnct.Length - start - "Function".Length);
  51                                 throw new EvaluateException (String.Format ("'{0}' can be applied only to strings.", fnct));
  52                         }
  53
  54                         return val;
  55                 }
  56         }
  57
  58         internal class SubstringFunction : StringFunction {
  59                 int start, len;
  60                 public SubstringFunction (IExpression e, int start, int len) : base (e)
  61                 {
  62                         this.start = start;
  63                         this.len = len;
  64                 }
  65
  66                 override public object Eval (DataRow row)
  67                 {
  68                         string str = (string)base.Eval (row);
  69                         if(str == null)
  70                                 return null;
  71
  72                         if (start > str.Length)
  73                                 return String.Empty;
  74
  75                         return str.Substring (start - 1, System.Math.Min (len, str.Length - (start - 1)));
  76                 }
  77         }
  78
  79         internal class LenFunction : StringFunction {
  80                 public LenFunction (IExpression e) : base (e) {}
  81
  82                 override public object Eval (DataRow row)
  83                 {
  84                         string str = (string)base.Eval (row);
  85                         if(str == null)
  86                                 return 0;
  87
  88                         return str.Length;
  89                 }
  90         }
  91
  92         internal class TrimFunction : StringFunction {
  93                 public TrimFunction (IExpression e) : base (e) {}
  94
  95                 override public object Eval (DataRow row)
  96                 {
  97                         string str = (string)base.Eval (row);
  98                         if(str == null)
  99                                 return null;
 100
 101                         return str.Trim();
 102                 }
 103         }
 104 }