[pbs-devel] [PATCH v2 backup 1/5] add and implement chunk_from_offset for IndexFile
Thomas Lamprecht
t.lamprecht at proxmox.com
Wed Jul 22 16:16:20 CEST 2020
On 22.07.20 15:56, Stefan Reiter wrote:
> Necessary for byte-wise seeking through chunks in an index.
>
> Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
> ---
> src/backup/dynamic_index.rs | 18 ++++++++++++++++++
> src/backup/fixed_index.rs | 11 +++++++++++
> src/backup/index.rs | 3 +++
> 3 files changed, 32 insertions(+)
>
> diff --git a/src/backup/dynamic_index.rs b/src/backup/dynamic_index.rs
> index 4907fe1f..887b7cf3 100644
> --- a/src/backup/dynamic_index.rs
> +++ b/src/backup/dynamic_index.rs
> @@ -216,6 +216,24 @@ impl IndexFile for DynamicIndexReader {
> digest: self.index[pos].digest.clone(),
> })
> }
> +
> + fn chunk_from_offset(&self, offset: u64) -> Option<(usize, u64)> {
> + let end_idx = self.index.len() - 1;
> + let end = self.chunk_end(end_idx);
> + let found_idx = self.binary_search(0, 0, end_idx, end, offset);
> + let found_idx = match found_idx {
> + Ok(i) => i,
> + Err(_) => return None
> + };
> +
> + let found_start = if found_idx == 0 {
> + 0
> + } else {
> + self.chunk_end(found_idx - 1)
> + };
> +
> + Some((found_idx, offset - found_start))
> + }
> }
>
> struct CachedChunk {
> diff --git a/src/backup/fixed_index.rs b/src/backup/fixed_index.rs
> index 73d0dad0..b7e785d6 100644
> --- a/src/backup/fixed_index.rs
> +++ b/src/backup/fixed_index.rs
> @@ -219,6 +219,17 @@ impl IndexFile for FixedIndexReader {
>
> (csum, chunk_end)
> }
> +
> + fn chunk_from_offset(&self, offset: u64) -> Option<(usize, u64)> {
> + if offset >= self.size {
> + return None;
> + }
> +
> + Some((
> + (offset / self.chunk_size as u64) as usize,
> + offset % self.chunk_size as u64
modulo is really slow, but isn't chunk_size always a 2^x and thus we can
do the same here as we do in other places:
offset & (self.chunk_size - 1)
> + ))
> + }
> }
>
> pub struct FixedIndexWriter {
> diff --git a/src/backup/index.rs b/src/backup/index.rs
> index efdf3b54..2eab8524 100644
> --- a/src/backup/index.rs
> +++ b/src/backup/index.rs
> @@ -22,6 +22,9 @@ pub trait IndexFile {
> fn index_bytes(&self) -> u64;
> fn chunk_info(&self, pos: usize) -> Option<ChunkReadInfo>;
>
> + /// Get the chunk index and the relative offset within it for a byte offset
> + fn chunk_from_offset(&self, offset: u64) -> Option<(usize, u64)>;
> +
> /// Compute index checksum and size
> fn compute_csum(&self) -> ([u8; 32], u64);
>
>
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