Handle 0 chunk schunks in get_slice_nchunks

Author: lshaw8317

blosc/schunk.c

@@ -1393,7 +1393,10 @@ int blosc2_schunk_set_slice_buffer(blosc2_schunk *schunk, int64_t start, int64_t
 
 int schunk_get_slice_nchunks(blosc2_schunk *schunk, int64_t start, int64_t stop, int64_t **chunks_idx) {
   BLOSC_ERROR_NULL(schunk, BLOSC2_ERROR_NULL_POINTER);
-
+  if (schunk->nchunks == 0){  
+    *chunks_idx = malloc(0);
+    return 0;
+  }
   int64_t byte_start = start * schunk->typesize;
   int64_t byte_stop = stop * schunk->typesize;
   int64_t nchunk_start = byte_start / schunk->chunksize;

tests/test_get_slice_nchunks.c

@@ -46,6 +46,7 @@ test_ndata tndata[] = {
         {5, 0, CHUNKSIZE * 5 + 200 * 100 + 300, true, 0, 6}, // last chunk shorter
         {2, 10, CHUNKSIZE * 2 + 400, true, 0, 3}, // start != 0, last chunk shorter
         {12,  CHUNKSIZE * 1 + 300, CHUNKSIZE * 4 + 100, false, 1, 5}, // start not in first chunk
+        {0,  0, 100, false, 0, 0}, // shape 0 array
 };
 
 typedef struct {
@@ -84,6 +85,8 @@ static char* test_get_slice_nchunks(void) {
                             .urlpath=tdata.urlpath, .contiguous=tdata.contiguous};
   schunk = blosc2_schunk_new(&storage);
 
+  if (tdata.nchunks == 0){schunk->chunksize = 0;}
+
   // Feed it with data
   if (!tdata.shorter_last_chunk) {
     for (int nchunk = 0; nchunk < tdata.nchunks; nchunk++) {