refactor: using div_ceil to calculate num of chunks from given file size

src/lib.rs

@@ -572,11 +572,8 @@ fn get_num_chunks(file_size: usize) -> usize {
     if file_size < (3 * MAX_CHUNK_SIZE) {
         return 3;
     }
-    if file_size % MAX_CHUNK_SIZE == 0 {
-        file_size / MAX_CHUNK_SIZE
-    } else {
-        (file_size / MAX_CHUNK_SIZE) + 1
-    }
+
+    usize::div_ceil(file_size, MAX_CHUNK_SIZE)
 }
 
 // Returns the size of a chunk according to file size.

src/tests.rs

@@ -9,7 +9,7 @@
 use crate::{
     decrypt_full_set, decrypt_range, encrypt, get_chunk_size, get_num_chunks, overlapped_chunks,
     seek_info, test_helpers::random_bytes, DataMap, EncryptedChunk, Error, StreamSelfDecryptor,
-    StreamSelfEncryptor, MIN_ENCRYPTABLE_BYTES,
+    StreamSelfEncryptor, MAX_CHUNK_SIZE, MIN_CHUNK_SIZE, MIN_ENCRYPTABLE_BYTES,
 };
 use bytes::Bytes;
 use itertools::Itertools;
@@ -241,6 +241,20 @@ fn get_chunk_sizes() -> Result<(), Error> {
     Ok(())
 }
 
+#[test]
+fn test_get_num_chunks() {
+    for i in 0..3 * MIN_CHUNK_SIZE {
+        assert_eq!(get_num_chunks(i), 0);
+    }
+
+    for i in 3 * MIN_CHUNK_SIZE..3 * MAX_CHUNK_SIZE {
+        assert_eq!(get_num_chunks(i), 3);
+    }
+
+    assert_eq!(get_num_chunks(3 * MAX_CHUNK_SIZE), 3);
+    assert_eq!(get_num_chunks(3 * MAX_CHUNK_SIZE + 1), 4);
+}
+
 #[test]
 fn seek_and_join() -> Result<(), Error> {
     for i in 1..15 {