Add deserialize fuzzer

fuzz/Cargo.toml

@@ -32,3 +32,9 @@ name = "against_bitvec"
 path = "fuzz_targets/against_bitvec.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "deserialize"
+path = "fuzz_targets/deserialize.rs"
+test = false
+doc = false

fuzz/fuzz_targets/deserialize.rs

@@ -0,0 +1,29 @@
+#![no_main]
+
+use croaring::{Bitmap, Native, Portable};
+use libfuzzer_sys::fuzz_target;
+
+fn check_bitmap<D: croaring::bitmap::Deserializer>(input: &[u8]) {
+    let bitmap = Bitmap::try_deserialize::<D>(input);
+    if let Some(mut bitmap) = bitmap {
+        bitmap.internal_validate().unwrap();
+
+        let start_cardinality = bitmap.cardinality();
+        let mut new_cardinality = start_cardinality;
+        for i in 100..1000 {
+            if !bitmap.contains(i) {
+                bitmap.add(i);
+                new_cardinality += 1;
+            }
+        }
+        assert_eq!(new_cardinality, bitmap.cardinality());
+
+        let unsafe_version = unsafe { D::try_deserialize_unchecked(input) };
+        assert_eq!(bitmap, unsafe_version);
+    }
+}
+
+fuzz_target!(|input: &[u8]| {
+    check_bitmap::<Portable>(input);
+    check_bitmap::<Native>(input);
+});