fix a bug in the value of the FTEXT field of the gz header

test-libz-rs-sys/src/deflate.rs

@@ -671,6 +671,75 @@ fn deflate_bound_gzip_header_help(
     true
 }
 
+#[test]
+fn gz_header_text_and_hcrc_check() {
+    // when constructing the gz header flags, zlib-rs performed a check
+    // for `text > 0` that should have been `text != 0`, similarly for hcrc.
+    let config = DeflateConfig {
+        level: 9,
+        method: Method::Deflated,
+        window_bits: 31,
+        mem_level: 3,
+        strategy: Strategy::Fixed,
+    };
+
+    assert_eq_rs_ng!({
+        let mut strm = MaybeUninit::zeroed();
+
+        // first validate the config
+        let err = deflateInit2_(
+            strm.as_mut_ptr(),
+            config.level,
+            config.method as i32,
+            config.window_bits,
+            config.mem_level,
+            config.strategy as i32,
+            zlibVersion(),
+            core::mem::size_of::<z_stream>() as _,
+        );
+
+        assert_eq!(err, 0);
+
+        let strm = strm.assume_init_mut();
+
+        let mut header = gz_header {
+            text: -42,
+            time: 0,
+            os: 0,
+            extra: core::ptr::null_mut(),
+            extra_len: 0,
+            name: [0u8].as_mut_ptr(),
+            comment: [0u8].as_mut_ptr(),
+            hcrc: -42,
+            //
+            xflags: 0,
+            extra_max: 0,
+            name_max: 0,
+            comm_max: 0,
+            done: 0,
+        };
+
+        // this may fail if the config is not set up for gzip
+        let _ = deflateSetHeader(strm, &mut header);
+
+        let input = "\0\u{2}\0\0\0\0\0\0\0\u{10}";
+        let mut output = [0u8; 32];
+
+        strm.avail_in = input.len() as _;
+        strm.avail_out = output.len() as _;
+
+        strm.next_in = input.as_ptr().cast_mut();
+        strm.next_out = output.as_mut_ptr();
+
+        let err = deflate(strm, DeflateFlush::NoFlush as i32);
+        assert_eq!(err, 0);
+
+        deflateEnd(strm);
+
+        output
+    });
+}
+
 #[test]
 #[cfg_attr(miri, ignore = "slow")]
 fn deflate_bound_gzip_header() {

zlib-rs/src/c_api.rs

@@ -252,8 +252,8 @@ impl gz_header {
     };
 
     pub(crate) fn flags(&self) -> u8 {
-        (if self.text > 0 { 1 } else { 0 })
-            + (if self.hcrc > 0 { 2 } else { 0 })
+        (if self.text != 0 { 1 } else { 0 })
+            + (if self.hcrc != 0 { 2 } else { 0 })
             + (if self.extra.is_null() { 0 } else { 4 })
             + (if self.name.is_null() { 0 } else { 8 })
             + (if self.comment.is_null() { 0 } else { 16 })

zlib-rs/src/deflate.rs

@@ -2603,7 +2603,7 @@ pub fn deflate(stream: &mut DeflateStream, flush: DeflateFlush) -> ReturnCode {
                     stream.state.bit_writer.pending.extend(&bytes);
                 }
 
-                if gzhead.hcrc > 0 {
+                if gzhead.hcrc != 0 {
                     stream.adler = crc32(
                         stream.adler as u32,
                         stream.state.bit_writer.pending.pending(),