Created
August 16, 2012 17:01
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Devious C# class that makes .NET strings mutable without requiring the /unsafe compiler switch
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public static class EvilStringHelper | |
{ | |
private static readonly Action<string, int, char> _setChar; | |
private static readonly Action<string, int> _setLength; | |
static EvilStringHelper() | |
{ | |
if (Environment.Version.Major < 4) | |
{ | |
MethodInfo setCharMethod = typeof(string).GetMethod( | |
"SetChar", | |
BindingFlags.Instance | BindingFlags.NonPublic | |
); | |
_setChar = (Action<string, int, char>)Delegate.CreateDelegate(typeof(Action<string, int, char>), setCharMethod); | |
MethodInfo setLengthMethod = typeof(string).GetMethod( | |
"SetLength", | |
BindingFlags.Instance | BindingFlags.NonPublic | |
); | |
_setLength = (Action<string, int>)Delegate.CreateDelegate(typeof(Action<string, int>), setLengthMethod); | |
} | |
else | |
{ | |
MethodInfo fillStringCheckedMethod = typeof(string).GetMethod( | |
"FillStringChecked", | |
BindingFlags.Static | BindingFlags.NonPublic | |
); | |
Action<string, int, string> fillStringCheckedDelegate = (Action<string, int, string>)Delegate.CreateDelegate( | |
typeof(Action<string, int, string>), fillStringCheckedMethod | |
); | |
_setChar = (str, i, c) => fillStringCheckedDelegate(str, i, c.ToString()); | |
FieldInfo stringLengthField = typeof(string).GetField( | |
"m_stringLength", | |
BindingFlags.Instance | BindingFlags.NonPublic | |
); | |
var input = Expression.Parameter(typeof(string), "input"); | |
var length = Expression.Parameter(typeof(int), "length"); | |
var setLengthLambda = Expression.Lambda<Action<string, int>>( | |
Expression.Assign(Expression.Field(input, stringLengthField), length), | |
input, | |
length | |
); | |
_setLength = setLengthLambda.Compile(); | |
} | |
} | |
public static void ChangeTo(this string text, string value) | |
{ | |
_setLength(text, value.Length); | |
for (int i = 0; i < value.Length; ++i) | |
text.SetChar(i, value[i]); | |
} | |
public static void SetChar(this string text, int index, char value) | |
{ | |
_setChar(text, index, value); | |
} | |
public static void ReverseInPlace(this string text) | |
{ | |
int i = 0; | |
int j = text.Length - 1; | |
while (i < j) | |
{ | |
char temp = text[j]; | |
_setChar(text, j--, text[i]); | |
_setChar(text, i++, temp); | |
} | |
} | |
public static unsafe string ReverseOutOfPlace(this string text) | |
{ | |
int length = text.Length; | |
char* reversed = stackalloc char[length]; | |
int i = 0, j = length - 1; | |
fixed (char* p = text) | |
{ | |
while (i < length) | |
{ | |
reversed[i++] = p[j--]; | |
} | |
} | |
return new string(reversed, 0, length); | |
} | |
} |
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