fixed tests for libsais with bitpacking

libsais64-rs/src/lib.rs

@@ -13,10 +13,16 @@ include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
 ///
 /// Returns Some with the suffix array build over the text if construction succeeds
 /// Returns None if construction of the suffix array failed
-pub fn sais64_long(text: &mut Vec<i64>, alphabet_size: i64) -> Option<Vec<i64>> {
+pub fn sais64_long(text: &mut Vec<i64>, alphabet_size: i64, sparseness_factor: u8) -> Option<Vec<i64>> {
     let mut sa = vec![0; text.len()];
     let exit_code = unsafe { libsais64_long(text.as_mut_ptr(), sa.as_mut_ptr(), text.len() as i64, alphabet_size, 0) };
-    if exit_code == 0 { Some(sa) } else { None }
+    if exit_code == 0 {
+        let sparseness_factor = sparseness_factor as i64;
+        for elem in sa.iter_mut() {
+            *elem *= sparseness_factor;
+        }
+        Some(sa) 
+    } else { None }
 }
 
 #[cfg(test)]
@@ -25,8 +31,14 @@ mod tests {
 
     #[test]
     fn check_build_sa_with_libsais64() {
-        let text = "banana$";
-        let sa = sais64(text.as_bytes());
-        assert_eq!(sa, Some(vec![6, 5, 3, 1, 0, 4, 2]));
+        let bits_per_char = 5;
+        let sparseness_factor = 4;
+        let mut text = [100834,   // BANA
+            493603,                     // NA-B
+            80975,                      // ANAN
+            65536                       // A$
+        ].to_vec();
+        let sa = sais64_long(&mut text, 1 << (bits_per_char * sparseness_factor), sparseness_factor);
+        assert_eq!(sa, Some(vec![12, 8, 0, 4]));
     }
 }

sa-builder/src/bitpacking.rs

@@ -15,6 +15,10 @@ pub fn bitpack_text(text: &Vec<u8>, sparseness_factor: u8) -> Vec<i64> {
     let num_ints = (text.len() + (sparseness_factor-1)) / sparseness_factor;
     let mut text_packed = vec![0; num_ints];
 
+    if text.len() == 0 {
+        return text_packed;
+    }
+
     for i in 0..(num_ints-1) {
         let ti = i * sparseness_factor;
         let mut element = 0i64;

sa-builder/src/lib.rs

@@ -60,7 +60,8 @@ pub fn build_ssa(
     let mut sa = match construction_algorithm {
         SAConstructionAlgorithm::LibSais => {
             let mut packed_text = bitpack_text(text, sparseness_factor);
-            libsais64_rs::sais64_long(&mut packed_text, 1 << (BITS_PER_CHAR * sparseness_factor as usize))
+
+            libsais64_rs::sais64_long(&mut packed_text, 1 << (BITS_PER_CHAR * sparseness_factor as usize), sparseness_factor)
         },
         SAConstructionAlgorithm::LibDivSufSort => libdivsufsort_rs::divsufsort64(text)
     }