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annotate rust/hg-core/src/re2/mod.rs @ 44305:d8d4fa9a7f18

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rust-re2: add wrapper for calling Re2 from Rust This assumes that Re2 is installed following Google's guide. I am not sure how we want to integrate it in the project, but I think a follow-up patch would be more appropriate for such work. As it stands, *not* having Re2 installed results in a compilation error, which is a problem as it breaks install compatibility. Hence, this is gated behind a non-default `with-re2` compilation feature. Differential Revision: https://phab.mercurial-scm.org/D7910
author Rapha?l Gom?s <rgomes@octobus.net>
date Thu, 16 Jan 2020 13:34:04 +0100
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d8d4fa9a7f18 rust-re2: add wrapper for calling Re2 from Rust
Rapha?l Gom?s <rgomes@octobus.net>
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1 /// re2 module
d8d4fa9a7f18 rust-re2: add wrapper for calling Re2 from Rust
Rapha?l Gom?s <rgomes@octobus.net>
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2 ///
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Rapha?l Gom?s <rgomes@octobus.net>
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3 /// The Python implementation of Mercurial uses the Re2 regex engine when
d8d4fa9a7f18 rust-re2: add wrapper for calling Re2 from Rust
Rapha?l Gom?s <rgomes@octobus.net>
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4 /// possible and if the bindings are installed, falling back to Python's `re`
d8d4fa9a7f18 rust-re2: add wrapper for calling Re2 from Rust
Rapha?l Gom?s <rgomes@octobus.net>
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5 /// in case of unsupported syntax (Re2 is a non-backtracking engine).
d8d4fa9a7f18 rust-re2: add wrapper for calling Re2 from Rust
Rapha?l Gom?s <rgomes@octobus.net>
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6 ///
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Rapha?l Gom?s <rgomes@octobus.net>
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7 /// Using it from Rust is not ideal. We need C++ bindings, a C++ compiler,
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Rapha?l Gom?s <rgomes@octobus.net>
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8 /// Re2 needs to be installed... why not just use the `regex` crate?
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Rapha?l Gom?s <rgomes@octobus.net>
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9 ///
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Rapha?l Gom?s <rgomes@octobus.net>
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10 /// Using Re2 from the Rust implementation guarantees backwards compatibility.
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Rapha?l Gom?s <rgomes@octobus.net>
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11 /// We know it will work out of the box without needing to figure out the
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Rapha?l Gom?s <rgomes@octobus.net>
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12 /// subtle differences in syntax. For example, `regex` currently does not
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Rapha?l Gom?s <rgomes@octobus.net>
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13 /// support empty alternations (regex like `a||b`) which happens more often
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Rapha?l Gom?s <rgomes@octobus.net>
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14 /// than we might think. Old benchmarks also showed worse performance from
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Rapha?l Gom?s <rgomes@octobus.net>
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15 /// regex than with Re2, but the methodology and results were lost, so take
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Rapha?l Gom?s <rgomes@octobus.net>
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16 /// this with a grain of salt.
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Rapha?l Gom?s <rgomes@octobus.net>
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17 ///
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18 /// The idea is to use Re2 for now as a temporary phase and then investigate
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Rapha?l Gom?s <rgomes@octobus.net>
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19 /// how much work would be needed to use `regex`.
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Rapha?l Gom?s <rgomes@octobus.net>
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20 mod re2;
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21 pub use re2::Re2;