rust-bitcoin / rust-bitcoin / 15002737639

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Merge rust-bitcoin/rust-bitcoin#4485: Add `Builder::with_capacity()`

<a class=hub.com/rust-bitcoin/rust-bitcoin/commit/<a class="double-link" href="https://git"><a class=hub.com/rust-bitcoin/rust-bitcoin/commit/d003d4859251abb01929ccab6009a02e0c96b0cd">d003d4859<a href="https://github.com/rust-bitcoin/rust-bitcoin/commit/bc93498b3e2a8bbd912afbbdfaa10d572c015ab8"> Add `Builder::with_capacity()` (Daniel Roberts)
<a class="double-link" href="https://github.com/rust-bitcoin/rust-bitcoin/commit/e492f94289887b50d0c10f976830d4fbf48d5866">e492f9428</a> Update `ScriptBuf::with_capacity` docs (Daniel Roberts)

Pull request description:

  Enable the creation of `bitcoin::script::Builder` with a preallocated capacity.

  This is pretty minor, but it provides a small speedup if used correctly. I've observed a 0.4% speedup and a 0.7% speedup in two code bases that create lots of outputs (on the order of tens to hundreds of thousands). It provided a much larger speedup (5% or so) in the latter code base before some other optimizations dwarfed it.

  I have a branch that also uses it for `ScriptBufExt::new_*()` but while it provides a small performance improvement for all script types except one, `ScriptBufExt::new_p2tr()` actually causes a small performance regression. Since the only use case I have for creating lots and lots of scripts is in taproot with CHECKTEMPLATEVERIFY, I'm holding back that change if/until I figure out what's going on exactly (and hopefully resolve it).

ACKs for top commit:
  tcharding:
    ACK d003d4859251abb01929ccab6009a02e0c96b0cd
  apoelstra:
    ACK d003d4859251abb01929ccab6009a02e0c96b0cd; successfully ran local tests

Tree-SHA512: 51137574c093a5636afc7d28fee343f8e9a

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