![]() NET 7, both the source generator and RegexCompiler were almost entirely rewritten, fundamentally changing the structure of the generated code. The generator even generates triple-slash (XML) comments to help make the expression understandable at a glance and where it's used. You can set breakpoints in it, you can step through it, and you can use it as a learning tool to understand exactly how the regex engine is processing your pattern with your input. ![]() Or, alternatively, select the project node in Solution Explorer, then expand Dependencies > Analyzers > .RegexGenerator > RegexGenerator.g.cs to see the generated C# code from this regex generator. In Visual Studio, right-click on your partial method declaration and select Go To Definition. The generated implementation of AbcOrDefGeneratedRegex() similarly caches a singleton Regex instance, so no additional caching is needed to consume code. If (AbcOrDefGeneratedRegex().IsMatch(text)) Private static partial Regex AbcOrDefGeneratedRegex() You can now rewrite the previous code as follows: If (s_abcOrDefGeneratedRegex.IsMatch(text)) Private static void EvaluateText(string text) Options: RegexOptions.Compiled | RegexOptions.IgnoreCase) For example, you might have written code like this: private static readonly Regex s_abcOrDefGeneratedRegex = The source generator provides an implementation of that method that implements all the logic for the Regex. NET 7 SDK includes a new source generator that recognizes the new GeneratedRegexAttribute on a partial method that returns Regex. Just like an analyzer, a source generator is a component that plugs into the compiler and is handed all of the same information as an analyzer, but in addition to being able to emit diagnostics, it can also augment the compilation unit with additional source code. More recently, Roslyn enabled source generators. When the C# compiler was rewritten as the "Roslyn" C# compiler, it exposed object models for the entire compilation pipeline, as well as analyzers. NET 7 introduces a new RegexGenerator source generator. The use of also inhibits the use of RegexOptions.Compiled in certain environments some operating systems don't permit dynamically generated code to be executed, and on such systems, Compiled will become a no-op. RegexOptions.Compiled represents a fundamental tradeoff between overheads on the first use and overheads on every subsequent use. The generated IL further needs to be JIT-compiled on first use leading to even more expense at startup. Not only are all of the same costs paid as for the interpreter, but it then needs to compile that resulting RegexNode tree and generated opcodes/operands into IL, which adds non-trivial expense. The most impactful is that it incurs much more construction cost than using the interpreter. There are several downsides to RegexOptions.Compiled. This special casing and the ability to perform optimizations based on knowledge of the pattern are some of the main reasons for specifying RegexOptions.Compiled yields much faster-matching throughput than does the interpreter. For example, if the pattern contained, the interpreter would see an opcode that said "match the input character at the current position against the set specified in this set description" whereas the compiled IL would contain code that effectively said, "match the input character at the current position against 'a' or 'c'". This IL would essentially do exactly what the interpreter would do, except specialized for the exact pattern being processed. When a match was performed, those DynamicMethods would be invoked. The resulting instructions would be transformed further by the reflection-emit-based compiler into IL instructions that would be written to a few DynamicMethods. When you specify RegexOptions.Compiled, all of the same construction-time work would be performed. When instantiating a new Regex instance or calling one of the static methods on Regex, the interpreter is the default engine employed. ![]() When a match is performed, the interpreter simply walks through those instructions, processing them against the input text. The tree is written into a form that can be interpreted as a series of opcodes and operands that provide instructions to the regex interpreter engine on how to match. The tree is then optimized in various ways, transforming the pattern into a functionally equivalent variation that can be more efficiently executed. The specified pattern is parsed, both to ensure the validity of the pattern and to transform it into an internal tree that represents the parsed regex. When you write new Regex("somepattern"), a few things happen. To learn when source generation is possible, see When to use it. ![]() Source generation can help your app start faster, run more quickly and be more trimmable. Where possible, use source generated regular expressions instead of compiling regular expressions using the RegexOptions.Compiled option. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |