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// Copyright 2018-2020 Georges Racinet <georges.racinet@octobus.net>
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// and Mercurial contributors
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//
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// This software may be used and distributed according to the terms of the
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// GNU General Public License version 2 or any later version.
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//! Mercurial concepts for handling revision history
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pub mod node;
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pub mod nodemap;
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pub use node::{Node, NodeError};
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/// Mercurial revision numbers
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///
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/// As noted in revlog.c, revision numbers are actually encoded in
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/// 4 bytes, and are liberally converted to ints, whence the i32
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pub type Revision = i32;
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/// Marker expressing the absence of a parent
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///
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/// Independently of the actual representation, `NULL_REVISION` is guaranteed
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/// to be smaller than all existing revisions.
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pub const NULL_REVISION: Revision = -1;
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/// Same as `mercurial.node.wdirrev`
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///
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/// This is also equal to `i32::max_value()`, but it's better to spell
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/// it out explicitely, same as in `mercurial.node`
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pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;
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/// The simplest expression of what we need of Mercurial DAGs.
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pub trait Graph {
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/// Return the two parents of the given `Revision`.
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///
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/// Each of the parents can be independently `NULL_REVISION`
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fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError>;
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}
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#[derive(Clone, Debug, PartialEq)]
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pub enum GraphError {
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ParentOutOfRange(Revision),
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WorkingDirectoryUnsupported,
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}
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/// The Mercurial Revlog Index
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///
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/// This is currently limited to the minimal interface that is needed for
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/// the [`nodemap`](nodemap/index.html) module
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pub trait RevlogIndex {
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/// Total number of Revisions referenced in this index
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fn len(&self) -> usize;
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/// Return a reference to the Node or `None` if rev is out of bounds
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///
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/// `NULL_REVISION` is not considered to be out of bounds.
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fn node(&self, rev: Revision) -> Option<&Node>;
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}
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