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@NickCraver

NickCraver/StringSplits.cs

Last active Jun 19, 2019
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StringSplits is a helper class thought up by Marc Gravell we use in the Stack Overflow/Stack Exchange code base to save on string allocations and relieve the garbage collector on gen 0.
/// <summary>
/// Using a single instance of these arrays prevents an allocation of a new array on every call to something like
/// string.Split(';') which is really calling string string.Split(params char[] separator), causing an allocation
/// of an additional array behind the scenes.
/// </summary>
/// <remarks>
/// For most applications this is a micro-optimization that doesn't matter. However, for very high traffic code paths
/// this can generate a significant amount of items that the gen 0 garbage collector needs to collect, causing micro-stalls
/// in the app domain when it runs, or runs more often.
/// </remarks>
public static class StringSplits
{
public static readonly char[] Space = { ' ' },
Comma = { ',' },
Period = { '.' },
Minus = { '-' },
Plus = { '+' },
Asterisk = { '*' },
Percent = { '%' },
Ampersand = { '&' },
Equal = { '=' },
Underscore = { '_' },
NewLine = { '\n' },
SemiColon = { ';' },
Colon = { ':' },
VerticalBar = { '|' },
ForwardSlash = { '/' },
DoubleQuote = { '"' },
NewLine_CarriageReturn = { '\n', '\r' },
Comma_Space = { ',', ' ' },
Comma_SemiColon = { ',', ';' },
Comma_SemiColon_Space = { ',', ';', ' ' },
BackSlash_Slash_Period = { '\\', '/', '.' },
DoubleRightArrow = { '»' };
public static readonly string[] CarriageReturnNewLineString = { "\r\n" };
/// <summary>
/// Returns a list of ints (usually representing models' ids) from a semi-colon delimited string, e.g. "15145651;15145707;15145703"
/// </summary>
public static List<int> SplitVectorizedIds(this string semiColonDelimitedIds)
{
var result = new List<int>();
if (!string.IsNullOrEmpty(semiColonDelimitedIds))
{
foreach (var idStr in semiColonDelimitedIds.Split(StringSplits.SemiColon))
{
int id;
if (int.TryParse(idStr, out id))
{
result.Add(id);
}
}
}
return result;
}
/// <summary>
/// For seeing if a token is in a delimited string without splitting it out into individual string components first.
/// Calling .Split('<delim>') causes an allocation of additional strings which are also not interned and use duplicate
/// memory to store the same thing. If you're splitting a setting or something else often, splitting would put a lot
/// of copies of the same string that then need to be garbage collected.
/// This helps on 3 points: lookup faster, allocate less, cleanup less.
/// <summary>
public static bool ContainsToken(string value, string token, char delimiter = ';')
{
if (string.IsNullOrEmpty(token)) return false;
if (string.IsNullOrEmpty(value)) return false;
int lastIndex = -1, idx, endIndex = value.Length - token.Length, tokenLength = token.Length;
while ((idx = value.IndexOf(token, lastIndex + 1)) > lastIndex)
{
lastIndex = idx;
if ((idx == 0 || (value[idx - 1] == delimiter))
&& (idx == endIndex || (value[idx + tokenLength] == delimiter)))
{
return true;
}
}
return false;
}
}
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