compress: prevent divide-by-zero when no data is read (#37706)

If the first call to `loop_read()` returns 0 (no input), `total_in`
remains 0, causing `total_out/total_in` to potential divide by zero.

We add a check before logging the compression ratio to skip the
percentage calculation when total_in is zero.

Co-authored-by: jinyaoguo <[email protected]>
(cherry picked from commit 2584f74)
(cherry picked from commit 18a42e321d699e7f3ae46930fa070228d02774ed)
(cherry picked from commit eaffe6679b6bcf6d5ba4d468332079a9ac82da43)
(cherry picked from commit 93f677f)
(cherry picked from commit cb57cbc)

Author: 2 people

src/basic/compress.c

@@ -703,9 +703,12 @@ int compress_stream_lz4(int fdf, int fdt, uint64_t max_bytes, uint64_t *ret_unco
         if (ret_uncompressed_size)
                 *ret_uncompressed_size = total_in;
 
-        log_debug("LZ4 compression finished (%" PRIu64 " -> %" PRIu64 " bytes, %.1f%%)",
-                  total_in, total_out,
-                  (double) total_out / total_in * 100);
+        if (total_in == 0)
+                log_debug("LZ4 compression finished (no input data)");
+        else
+                log_debug("LZ4 compression finished (%" PRIu64 " -> %" PRIu64 " bytes, %.1f%%)",
+                        total_in, total_out,
+                        (double) total_out / total_in * 100);
 
         return COMPRESSION_LZ4;
 #else