From: Kostya Shishkov <kostya.shishkov@gmail.com>
Date: Thu, 20 May 2021 15:33:45 +0000 (+0200)
Subject: deflate: better check for zlib header
X-Git-Url: https://git.nihav.org/?p=nihav.git;a=commitdiff_plain;h=0c9b706ab86de253938471cde127abde866210dd

deflate: better check for zlib header
---

diff --git a/nihav-core/src/compr/deflate.rs b/nihav-core/src/compr/deflate.rs
index e917519..89e0fde 100644
--- a/nihav-core/src/compr/deflate.rs
+++ b/nihav-core/src/compr/deflate.rs
@@ -386,6 +386,15 @@ impl Inflate {
                 self.output_idx = 0;
                 CurrentSource::reinit(src, self.br)
             };
+        // check for zlib stream header
+        if let (&InflateState::Start, true) = (&self.state, src.len() > 2) {
+            let cm    = src[0] & 0xF;
+            let cinfo = src[0] >> 4;
+            let hdr   = (u16::from(src[0]) << 8) | u16::from(src[1]);
+            if cm == 8 && cinfo <= 7 && (hdr % 31) == 0 {
+                csrc.skip(16).unwrap();
+            }
+        }
         'main: loop {
             match self.state {
                 InflateState::Start | InflateState::BlockStart => {
@@ -737,8 +746,7 @@ impl Inflate {
     ///! Decompresses input data into output returning the uncompressed data length.
     pub fn uncompress(src: &[u8], dst: &mut [u8]) -> DecompressResult<usize> {
         let mut inflate = Self::new();
-        let off = if src.len() > 2 && src[0] == 0x78 && (src[1] != 0 && ((src[1] - 1) % 31) == 0) { 2 } else { 0 };
-        inflate.decompress_data(&src[off..], dst, false)
+        inflate.decompress_data(src, dst, false)
     }
 }