Fast and memory efficient ASCII string class for .NET

Question

This might have been asked before, but I can't find any such posts. Is there a class to work with ASCII Strings? The benefits are numerous:

1. Comparison should be faster since its just byte-for-byte (instead of UTF-8 with variable encoding)
2. Memory efficient, should use about half the memory in large strings
3. Faster versions of ToUpper()/ToLower() which use a Look-Up-Table that is language invariant

Jon Skeet wrote a basic AsciiString implementation and proved #2, but I'm wondering if anyone took this further and completed such a class. I'm sure there would be uses, although no one would typically take such a route since all the existing String functions would have to be re-implemented by hand. And conversions between String <> AsciiString would be scattered everywhere complicating an otherwise simple program.

Is there such a class? Where?

Answer 1

I thought I would post the outcome of my efforts to implement a system as described with as much string support and compatibility as I could. It's possibly not perfect but it should give you a decent base to improve on if needed.

The ASCIIChar struct and ASCIIString string implicitly convert to their native counterparts for ease of use.

The OP's suggestion for replacements of ToUpper/Lower etc have been implemented in a much quicker way than a lookup list and all the operations are as quick and memory friendly as I could make them.

Sorry couldn't post source, it was too long. See links below.

• ASCIIChar - Replaces char, stores the value in a byte instead of int and provides support methods and compatibility for the string class. Implements virtual all methods and properties available for char.

• ASCIIChars - Provides static properties for each of the valid ASCII characters for ease of use.

• ASCIIString - Replaces string, stores characters in a byte array and implements virtually all methods and properties available for string.

Answer 2

Dotnet has no ASCII string support directly. Strings are UTF16 because Windows API works with ASCII (onr char - one byte) or UTF16 only. Utf8 will be the best solution (java uses it), but .NET does not support it because Windows doesn't.

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Windows API can convert between charsets, but windows api only works with 1 byte chars or 2 byte chars, so if you use UTF8 strings in .NET you must convert them everytime which has impact in performace. Dotnet can use UTF8 and other encondings via BinaryWriter/BinaryReader or a simple StreamWriter/StreamReader.