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perf: Optimize for the fact that false signatures can't overlap with real ones

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This commit is contained in:
Chris Hennick 2024-05-08 10:59:32 -07:00
parent 50767eb84a
commit eb063ad432
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GPG key ID: DA47AABA4961C509
1 changed files with 16 additions and 5 deletions
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21
src/spec.rs
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@ -1,5 +1,6 @@
use crate::result::{ZipError, ZipResult};
use crate::unstable::{LittleEndianReadExt, LittleEndianWriteExt};
use core::mem::size_of_val;
use std::borrow::Cow;
use std::io;
use std::io::prelude::*;
@ -65,8 +66,10 @@ impl CentralDirectoryEnd {
let mut pos = file_length - HEADER_SIZE;
while pos >= search_upper_bound {
let mut have_signature = false;
reader.seek(io::SeekFrom::Start(pos))?;
if reader.read_u32_le()? == CENTRAL_DIRECTORY_END_SIGNATURE {
have_signature = true;
reader.seek(io::SeekFrom::Current(
BYTES_BETWEEN_MAGIC_AND_COMMENT_SIZE as i64,
))?;
@ -75,7 +78,11 @@ impl CentralDirectoryEnd {
return Ok((end_header, cde_start_pos));
}
}
pos = match pos.checked_sub(1) {
pos = match pos.checked_sub(if have_signature {
size_of_val(&CENTRAL_DIRECTORY_END_SIGNATURE) as u64
} else {
1
}) {
Some(p) => p,
None => break,
};
@ -155,9 +162,10 @@ impl Zip64CentralDirectoryEnd {
let mut pos = search_upper_bound;
while pos >= nominal_offset {
let mut have_signature = false;
reader.seek(io::SeekFrom::Start(pos))?;
if reader.read_u32_le()? == ZIP64_CENTRAL_DIRECTORY_END_SIGNATURE {
have_signature = true;
let archive_offset = pos - nominal_offset;
let _record_size = reader.read_u64_le()?;
@ -186,10 +194,13 @@ impl Zip64CentralDirectoryEnd {
archive_offset,
));
}
if pos > 0 {
pos -= 1;
pos = match pos.checked_sub(if have_signature {
size_of_val(&ZIP64_CENTRAL_DIRECTORY_END_SIGNATURE) as u64
} else {
break;
1
}) {
None => break,
Some(p) => p,
}
}
if results.is_empty() {