Add Pattern.programSize() and Matcher.programSize()
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This PR exposes `Pattern.programSize()` and `Matcher.programSize()` public API. The program size represents a very approximate measure of a regexp's "cost". Larger numbers are more expensive than smaller numbers. Similar to the canonical C++ implementation, re2j will return the program size as the number of instructions of the regex program without making any promises or claims except "larger is more expensive". Context: The need for this change arose from cross-language projects, such as gRPC and CEL. gRPC needs to configure the maximum size of regex programs in CEL to the same number across all languages. While it's possible in CEL-Cpp and gRPC-Cpp, CEL-Java doesn't provide the same configuration option simply because the program size is not available in re2j. In Go, the number of instruction is available in Go via the length of https://pkg.go.dev/regexp/syntax#Prog.Inst.
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This PR exposes
Pattern.programSize()andMatcher.programSize()public API.The program size represents a very approximate measure of a regexp's "cost". Larger numbers are more expensive than smaller numbers.
Similar to the canonical C++ implementation (see
RE2.ProgramSize()), re2j will return the program size as the number of instructions of the regex program without making any promises or claims except "larger is more expensive".Context: The need for this change arose from cross-language projects, such as gRPC and CEL. gRPC needs to configure the maximum size of regex programs in CEL to the same number across all languages. While it's possible in gRPC-Cpp via CEL-Cpp
options.regex_max_program_sizethat uses re2's ProgramSize, CEL-Java doesn't provide the same configuration option simply because the program size is not available in re2j. In Go, the number of instruction is available in Golen(syntax.Prog.Inst).Internal ref: go/grpc-cel-integration
CCs:
@ejona86 (grpc-java), @markdroth (grpc)
@l46kok (cel-java), @TristonianJones (cel)