aalekseyev created this revision. Herald added a reviewer: hg-reviewers. Herald added a subscriber: mercurial-patches.
REVISION SUMMARY Centralize index header parsing, parse the generaldelta flag, and leave breadcrumbs to relate the code to python. REPOSITORY rHG Mercurial BRANCH stable REVISION DETAIL https://phab.mercurial-scm.org/D11881 AFFECTED FILES rust/hg-core/src/revlog/index.rs rust/hg-core/src/revlog/revlog.rs CHANGE DETAILS diff --git a/rust/hg-core/src/revlog/revlog.rs b/rust/hg-core/src/revlog/revlog.rs --- a/rust/hg-core/src/revlog/revlog.rs +++ b/rust/hg-core/src/revlog/revlog.rs @@ -3,7 +3,6 @@ use std::ops::Deref; use std::path::Path; -use byteorder::{BigEndian, ByteOrder}; use flate2::read::ZlibDecoder; use micro_timer::timed; use sha1::{Digest, Sha1}; @@ -74,13 +73,6 @@ match repo.store_vfs().mmap_open_opt(&index_path)? { None => Index::new(Box::new(vec![])), Some(index_mmap) => { - let version = get_version(&index_mmap)?; - if version != 1 { - // A proper new version should have had a repo/store - // requirement. - return Err(HgError::corrupted("corrupted revlog")); - } - let index = Index::new(Box::new(index_mmap))?; Ok(index) } @@ -387,19 +379,6 @@ } } -/// Format version of the revlog. -pub fn get_version(index_bytes: &[u8]) -> Result<u16, HgError> { - if index_bytes.len() == 0 { - return Ok(1); - }; - if index_bytes.len() < 4 { - return Err(HgError::corrupted( - "corrupted revlog: can't read the index format header", - )); - }; - Ok(BigEndian::read_u16(&index_bytes[2..=3])) -} - /// Calculate the hash of a revision given its data and its parents. fn hash( data: &[u8], diff --git a/rust/hg-core/src/revlog/index.rs b/rust/hg-core/src/revlog/index.rs --- a/rust/hg-core/src/revlog/index.rs +++ b/rust/hg-core/src/revlog/index.rs @@ -9,6 +9,76 @@ pub const INDEX_ENTRY_SIZE: usize = 64; +pub struct IndexHeader { + header_bytes: [u8; 4], +} + +#[derive(Copy, Clone)] +pub struct IndexHeaderFlags { + flags: u16, +} + +// Corresponds to the high bits of `_format_flags` in python +impl IndexHeaderFlags { + // Corresponds to FLAG_INLINE_DATA in python + pub fn is_inline(self) -> bool { + return self.flags & 1 != 0; + } + // Corresponds to FLAG_GENERALDELTA in python + pub fn uses_generaldelta(self) -> bool { + return self.flags & 2 != 0; + } +} + +// Corresponds to the INDEX_HEADER structure, +// which is parsed as a `header` variable in `_loadindex` in `revlog.py` +impl IndexHeader { + fn format_flags(&self) -> IndexHeaderFlags { + // No "unknown flags" check here, unlike in python. Maybe there should + // be. + return IndexHeaderFlags { + flags: BigEndian::read_u16(&self.header_bytes[0..2]), + }; + } + + // The only revlog version currently supported by rhg. + const REVLOGV1: u16 = 1; + + // Corresponds to `_format_version` in Python. + // The only curently supported version is + fn format_version(&self) -> u16 { + return BigEndian::read_u16(&self.header_bytes[2..4]); + } + + const EMPTY_INDEX_HEADER: IndexHeader = IndexHeader { + // We treat an empty file as a valid index with no entries. + // Here we make an arbitrary choice of what we assume the format of the + // index to be (V1, using generaldelta). + // This doesn't matter too much, since we're only doing read-only + // access. but the value corresponds to the `new_header` variable in + // `revlog.py`, `_loadindex` + header_bytes: [0, 3, 0, 1], + }; + + fn parse(index_bytes: &[u8]) -> Result<IndexHeader, HgError> { + if index_bytes.len() == 0 { + return Ok(IndexHeader::EMPTY_INDEX_HEADER); + } + if index_bytes.len() < 4 { + return Err(HgError::corrupted( + "corrupted revlog: can't read the index format header", + )); + } + return Ok(IndexHeader { + header_bytes: { + let bytes: [u8; 4] = + index_bytes[0..4].try_into().expect("impossible"); + bytes + }, + }); + } +} + /// A Revlog index pub struct Index { bytes: Box<dyn Deref<Target = [u8]> + Send>, @@ -23,7 +93,15 @@ pub fn new( bytes: Box<dyn Deref<Target = [u8]> + Send>, ) -> Result<Self, HgError> { - if is_inline(&bytes) { + let header = IndexHeader::parse(bytes.as_ref())?; + + if header.format_version() != IndexHeader::REVLOGV1 { + // A proper new version should have had a repo/store + // requirement. + return Err(HgError::corrupted("unsupported revlog version")); + } + + if header.format_flags().is_inline() { let mut offset: usize = 0; let mut offsets = Vec::new(); @@ -206,17 +284,6 @@ } } -/// Value of the inline flag. -pub fn is_inline(index_bytes: &[u8]) -> bool { - if index_bytes.len() < 4 { - return true; - } - match &index_bytes[0..=1] { - [0, 0] | [0, 2] => false, - _ => true, - } -} - #[cfg(test)] mod tests { use super::*; To: aalekseyev, #hg-reviewers Cc: mercurial-patches, mercurial-devel _______________________________________________ Mercurial-devel mailing list Mercurial-devel@mercurial-scm.org https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
