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Devious C# class that makes .NET strings mutable without requiring the /unsafe compiler switch
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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