zcash_script

Rust bindings to the ECC's zcash_script C++ library.

Developing

This crate works by manually including the zcash_script .h and .cpp files, using bindgen to generate Rust bindings, and compiling everything together into a single library. Due to the way the zcash_script is written we unfortunately need to include a lot of other stuff e.g. the orchard library.

Updating this crate

1. Update depend/zcash with the latest tagged version of zcashd
2. Update Cargo.toml versions to match the versions used by the latest tagged version of zcashd, and its dependencies
3. Publish a new release

Updating depend/zcash

We keep a copy of the zcash source in depend/zcash with the help of git subtree. It has one single difference that must be enforced every time it's updated: the root Cargo.toml must be deleted, since otherwise cargo will ignore the entire folder when publishing the crate (see rust-lang/cargo#8597).

However, git subtree requires merge commits in order to make further updates work correctly. Since we don't allow those in our repository, we start over every time, basically using it as a glorified git clone. This issue is being tracked in #35.

If you need to update the zcash source, run:

git rm -r depend/zcash
(commit changes)
git subtree add -P depend/zcash https://github.com/zcash/zcash.git <ref> --squash
git rm depend/zcash/Cargo.toml
(commit changes)

where <ref> is a reference to a branch, tag or commit (it should be a tag when preparing a release, but it will be likely a branch or commit when testing).

Updating Cargo.toml

Note that zcash_script (the C++ library/folder inside zcash) uses some Rust FFI functions from zcash; and it also links to librustzcash which is written in Rust. Therefore, when updating zcash_script (this crate), we need to make sure that shared dependencies between all of those are the same versions (and are patched to the same revisions, if applicable). To do that, check for versions in:

• zcash/Cargo.toml in the revision pointed to by this crate (also check for patches)
• librustzcash/Cargo.toml in the revision pointed to by zcash (also check for patches)
• librustzcash/<crate>/Cargo.toml in the revision pointed to by zcash
• orchard/Cargo.toml in the revision pointed to by zcash (also check for patches)

To double-check, you can use cargo tree or cargo deny check bans on Zebra, once the zcash_script, librustzcash, and orchard versions have all been updated.

Publishing New Releases

Releases for zcash-script are made with the help of cargo release.

Checklist:

• create a new branch batch the release commits into a PR
• update CHANGELOG.md to document any major changes since the last release rust-lang/cargo#8597)
• open a PR to merge your branch into master
• locally run cargo release -- <level> where level can be patch, minor, or major (source)

NOTE: It's important to specify the level when using cargo release because of the way it implements the substitutions. We specify a number of automatic substitutions in Cargo.toml but they will only be applied if cargo release also handles incrementing the version itself, do not increment the version by hand and then run cargo release or cargo release -- release, or it will not correctly update all version references in the codebase.