annotate rust/hg-core/src/revlog.rs @ 48614:3efc8644dd00

test-http-bad-server: refactor the reading logic to avoid early return

Our ultimate goal is to add another way to define the connection needs to be
closed. To do so, we need the "read" code to be more unified.

Differential Revision: https://phab.mercurial-scm.org/D12045

// Copyright 2018-2020 Georges Racinet <[e-mail]>
//           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;
mod nodemap_docket;
pub mod path_encode;
pub use node::{FromHexError, Node, NodePrefix};
pub mod changelog;
pub mod filelog;
pub mod index;
pub mod manifest;
pub mod patch;
pub mod revlog;

/// 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`
#[allow(clippy::unreadable_literal)]
pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;

pub const WORKING_DIRECTORY_HEX: &str =
    "ffffffffffffffffffffffffffffffffffffffff";

/// 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,
}

/// The Mercurial Revlog Index
///
/// This is currently limited to the minimal interface that is needed for
/// the [`nodemap`](nodemap/index.html) module
pub trait RevlogIndex {
    /// Total number of Revisions referenced in this index
    fn len(&self) -> usize;

    fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Return a reference to the Node or `None` if rev is out of bounds
    ///
    /// `NULL_REVISION` is not considered to be out of bounds.
    fn node(&self, rev: Revision) -> Option<&Node>;
}