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use byteorder::{BigEndian, ByteOrder};
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use crate::revlog::{Revision, NULL_REVISION};
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pub const INDEX_ENTRY_SIZE: usize = 64;
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/// A Revlog index
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#[derive(Debug)]
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pub struct Index<'a> {
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bytes: &'a [u8],
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/// Offsets of starts of index blocks.
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/// Only needed when the index is interleaved with data.
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offsets: Option<Vec<usize>>,
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}
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impl<'a> Index<'a> {
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/// Create an index from bytes.
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/// Calculate the start of each entry when is_inline is true.
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pub fn new(bytes: &'a [u8], is_inline: bool) -> Self {
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if is_inline {
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let mut offset: usize = 0;
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let mut offsets = Vec::new();
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while (bytes.len() - offset) >= INDEX_ENTRY_SIZE {
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offsets.push(offset);
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let end = offset + INDEX_ENTRY_SIZE;
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let entry = IndexEntry {
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bytes: &bytes[offset..end],
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offset_override: None,
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};
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offset += INDEX_ENTRY_SIZE + entry.compressed_len();
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}
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Self {
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bytes,
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offsets: Some(offsets),
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}
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} else {
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Self {
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bytes,
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offsets: None,
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}
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}
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}
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/// Return the index entry corresponding to the given revision if it
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/// exists.
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pub fn get_entry(&self, rev: Revision) -> Option<IndexEntry> {
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if rev == NULL_REVISION {
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return None;
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}
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if let Some(offsets) = &self.offsets {
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self.get_entry_inline(rev, offsets)
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} else {
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self.get_entry_separated(rev)
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}
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}
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fn get_entry_inline(
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&self,
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rev: Revision,
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offsets: &[usize],
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) -> Option<IndexEntry> {
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let start = *offsets.get(rev as usize)?;
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let end = start.checked_add(INDEX_ENTRY_SIZE)?;
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let bytes = &self.bytes[start..end];
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// See IndexEntry for an explanation of this override.
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let offset_override = Some(end);
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Some(IndexEntry {
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bytes,
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offset_override,
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})
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}
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fn get_entry_separated(&self, rev: Revision) -> Option<IndexEntry> {
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let max_rev = self.bytes.len() / INDEX_ENTRY_SIZE;
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if rev as usize >= max_rev {
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return None;
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}
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let start = rev as usize * INDEX_ENTRY_SIZE;
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let end = start + INDEX_ENTRY_SIZE;
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let bytes = &self.bytes[start..end];
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// See IndexEntry for an explanation of this override.
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let offset_override = match rev {
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0 => Some(0),
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_ => None,
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};
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Some(IndexEntry {
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bytes,
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offset_override,
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})
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}
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}
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#[derive(Debug)]
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pub struct IndexEntry<'a> {
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bytes: &'a [u8],
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/// Allows to override the offset value of the entry.
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///
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/// For interleaved index and data, the offset stored in the index
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/// corresponds to the separated data offset.
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/// It has to be overridden with the actual offset in the interleaved
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/// index which is just after the index block.
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///
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/// For separated index and data, the offset stored in the first index
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/// entry is mixed with the index headers.
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/// It has to be overridden with 0.
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offset_override: Option<usize>,
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}
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impl<'a> IndexEntry<'a> {
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/// Return the offset of the data if not overridden by offset_override.
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pub fn offset(&self) -> usize {
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if let Some(offset_override) = self.offset_override {
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offset_override
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} else {
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let mut bytes = [0; 8];
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bytes[2..8].copy_from_slice(&self.bytes[0..=5]);
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BigEndian::read_u64(&bytes[..]) as usize
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}
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}
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/// Return the compressed length of the data.
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pub fn compressed_len(&self) -> usize {
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BigEndian::read_u32(&self.bytes[8..=11]) as usize
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}
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/// Return the uncompressed length of the data.
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pub fn uncompressed_len(&self) -> usize {
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BigEndian::read_u32(&self.bytes[12..=15]) as usize
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}
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/// Return the revision upon which the data has been derived.
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pub fn base_revision(&self) -> Revision {
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// TODO Maybe return an Option when base_revision == rev?
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// Requires to add rev to IndexEntry
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BigEndian::read_i32(&self.bytes[16..])
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}
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pub fn p1(&self) -> Revision {
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BigEndian::read_i32(&self.bytes[24..])
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}
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pub fn p2(&self) -> Revision {
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BigEndian::read_i32(&self.bytes[28..])
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}
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/// Return the hash of revision's full text.
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///
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/// Currently, SHA-1 is used and only the first 20 bytes of this field
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/// are used.
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pub fn hash(&self) -> &[u8] {
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&self.bytes[32..52]
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[cfg(test)]
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#[derive(Debug, Copy, Clone)]
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pub struct IndexEntryBuilder {
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is_first: bool,
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is_inline: bool,
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is_general_delta: bool,
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version: u16,
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offset: usize,
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compressed_len: usize,
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uncompressed_len: usize,
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base_revision: Revision,
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}
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#[cfg(test)]
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impl IndexEntryBuilder {
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pub fn new() -> Self {
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Self {
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is_first: false,
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is_inline: false,
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is_general_delta: true,
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version: 2,
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offset: 0,
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compressed_len: 0,
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uncompressed_len: 0,
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base_revision: 0,
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}
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}
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pub fn is_first(&mut self, value: bool) -> &mut Self {
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self.is_first = value;
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self
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}
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pub fn with_inline(&mut self, value: bool) -> &mut Self {
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self.is_inline = value;
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self
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}
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pub fn with_general_delta(&mut self, value: bool) -> &mut Self {
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self.is_general_delta = value;
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self
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}
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pub fn with_version(&mut self, value: u16) -> &mut Self {
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self.version = value;
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self
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}
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pub fn with_offset(&mut self, value: usize) -> &mut Self {
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self.offset = value;
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self
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}
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pub fn with_compressed_len(&mut self, value: usize) -> &mut Self {
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self.compressed_len = value;
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self
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}
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pub fn with_uncompressed_len(&mut self, value: usize) -> &mut Self {
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self.uncompressed_len = value;
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self
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}
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pub fn with_base_revision(&mut self, value: Revision) -> &mut Self {
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self.base_revision = value;
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self
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}
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pub fn build(&self) -> Vec<u8> {
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let mut bytes = Vec::with_capacity(INDEX_ENTRY_SIZE);
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if self.is_first {
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bytes.extend(&match (self.is_general_delta, self.is_inline) {
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(false, false) => [0u8, 0],
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(false, true) => [0u8, 1],
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(true, false) => [0u8, 2],
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(true, true) => [0u8, 3],
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});
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bytes.extend(&self.version.to_be_bytes());
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// Remaining offset bytes.
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bytes.extend(&[0u8; 2]);
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} else {
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// Offset is only 6 bytes will usize is 8.
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bytes.extend(&self.offset.to_be_bytes()[2..]);
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}
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bytes.extend(&[0u8; 2]); // Revision flags.
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bytes.extend(&self.compressed_len.to_be_bytes()[4..]);
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bytes.extend(&self.uncompressed_len.to_be_bytes()[4..]);
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bytes.extend(&self.base_revision.to_be_bytes());
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bytes
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}
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}
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#[test]
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fn test_offset() {
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let bytes = IndexEntryBuilder::new().with_offset(1).build();
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let entry = IndexEntry {
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bytes: &bytes,
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offset_override: None,
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};
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assert_eq!(entry.offset(), 1)
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}
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#[test]
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fn test_with_overridden_offset() {
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let bytes = IndexEntryBuilder::new().with_offset(1).build();
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let entry = IndexEntry {
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bytes: &bytes,
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offset_override: Some(2),
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};
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assert_eq!(entry.offset(), 2)
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}
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#[test]
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fn test_compressed_len() {
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let bytes = IndexEntryBuilder::new().with_compressed_len(1).build();
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let entry = IndexEntry {
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bytes: &bytes,
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offset_override: None,
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};
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assert_eq!(entry.compressed_len(), 1)
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}
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#[test]
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fn test_uncompressed_len() {
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let bytes = IndexEntryBuilder::new().with_uncompressed_len(1).build();
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let entry = IndexEntry {
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bytes: &bytes,
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offset_override: None,
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};
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assert_eq!(entry.uncompressed_len(), 1)
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}
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#[test]
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fn test_base_revision() {
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let bytes = IndexEntryBuilder::new().with_base_revision(1).build();
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let entry = IndexEntry {
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bytes: &bytes,
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offset_override: None,
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};
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assert_eq!(entry.base_revision(), 1)
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}
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}
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#[cfg(test)]
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pub use tests::IndexEntryBuilder;
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