Mercurial > public > mercurial-scm > hg-stable
view rust/hg-core/src/revlog.rs @ 44228:7f86426fdd2c
rust-node: binary Node ID and conversion utilities
The choice of type makes sure that a `Node` has the exact
wanted size. We'll use a different type for prefixes.
Added dependency: hexadecimal conversion relies on the
`hex` crate.
The fact that sooner or later Mercurial is going to need
to change its hash sizes has been taken strongly in
consideration:
- the hash length is a constant, but that is not directly
exposed to callers. Changing the value of that constant
is the only thing to do to change the hash length (even
in unit tests)
- the code could be adapted to support several sizes of hashes,
if that turned out to be useful. To that effect, only the
size of a given `Node` is exposed in the public API.
- callers not involved in initial computation, I/O and FFI
are able to operate without a priori assumptions on the hash
size. The traits `FromHex` and `ToHex` have not been directly
implemented, so that the doc-comments explaining these
restrictions would stay really visible in `cargo doc`
Differential Revision: https://phab.mercurial-scm.org/D7788
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Wed, 22 Jan 2020 16:37:05 +0100 |
parents | 63db6657d280 |
children | 3fb39dc2e356 |
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// Copyright 2018-2020 Georges Racinet <georges.racinet@octobus.net> // and Mercurial contributors // // This software may be used and distributed according to the terms of the // GNU General Public License version 2 or any later version. //! Mercurial concepts for handling revision history pub mod node; pub mod nodemap; pub use node::{Node, NodeError}; /// Mercurial revision numbers /// /// As noted in revlog.c, revision numbers are actually encoded in /// 4 bytes, and are liberally converted to ints, whence the i32 pub type Revision = i32; /// Marker expressing the absence of a parent /// /// Independently of the actual representation, `NULL_REVISION` is guaranteed /// to be smaller than all existing revisions. pub const NULL_REVISION: Revision = -1; /// Same as `mercurial.node.wdirrev` /// /// This is also equal to `i32::max_value()`, but it's better to spell /// it out explicitely, same as in `mercurial.node` pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff; /// The simplest expression of what we need of Mercurial DAGs. pub trait Graph { /// Return the two parents of the given `Revision`. /// /// Each of the parents can be independently `NULL_REVISION` fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError>; } #[derive(Clone, Debug, PartialEq)] pub enum GraphError { ParentOutOfRange(Revision), WorkingDirectoryUnsupported, }