add: test cases for chunking

tests/chunking.rs

+extern crate seahash;
+use seahash::SeaHasher as H;
+
+use std::hash::Hasher;
+
+#[test]
+fn hash_chunking_vs_not() {
+    // originally from https://gitlab.redox-os.org/redox-os/seahash/issues/5
+    let c1: &[u8] = b"This hashing algorithm was extracted from the Rustc compiler.";
+    let c2: &[u8] = b" This is the same hashing algoirthm used for some internal operations in FireFox.";
+    let c3: &[u8] = b" The strength of this algorithm is in hashing 8 bytes at a time on 64-bit platforms, where the FNV algorithm works on one byte at a time.";
+
+    let mut h1 = H::default();
+    h1.write(c1);
+    h1.write(c2);
+    h1.write(c3);
+    let hash1 = h1.finish();
+
+    let mut c4 = Vec::<u8>::new();
+    c4.extend_from_slice(c1);
+    c4.extend_from_slice(c2);
+    c4.extend_from_slice(c3);
+
+    let mut h2 = H::default();
+    h2.write(&c4);
+    let hash2 = h2.finish();
+
+    let reference = seahash::reference::hash(&c4);
+    let buffer = seahash::hash(&c4);
+
+    println!("hash1: {:016x}", hash1);
+    println!("hash2: {:016x}", hash2);
+    println!("ref  : {:016x}", reference);
+    println!("buf  : {:016x}", buffer);
+
+    assert_eq!(hash1, hash2);
+    assert_eq!(hash1, reference);
+    assert_eq!(hash1, buffer);
+}
+
+#[test]
+fn test_different_chunk_sizes() {
+    let v = {
+        let c1: &[u8] = b"This hashing algorithm was extracted from the Rustc compiler.";
+        let c2: &[u8] = b" This is the same hashing algoirthm used for some internal operations in FireFox.";
+        let c3: &[u8] = b" The strength of this algorithm is in hashing 8 bytes at a time on 64-bit platforms, where the FNV algorithm works on one byte at a time.";
+
+        [c1, c2, c3].concat()
+    };
+
+    let mut h1 = H::default();
+    h1.write(&v);
+    let h1 = h1.finish();
+
+    for chunk_len in 1..v.len() {
+        let mut h2 = H::default();
+        for w in v.chunks(chunk_len) {
+            h2.write(w);
+        }
+        let h2 = h2.finish();
+
+        assert_eq!(h1, h2, "failed with chunk_len={}", chunk_len);
+
+        println!("ok: {}", chunk_len);
+    }
+}