Merge pull request #134 from grlee77/max_level_fix

dwt_max_level: avoid taking uint_log2 of values<1
PyWavelets · Dec 9, 2015 · a5058b8 · a5058b8
2 parents 935c55b + 9f9bb36
commit a5058b8
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Showing 2 changed files with 18 additions and 8 deletions.
diff --git a/pywt/src/common.c b/pywt/src/common.c
@@ -14,21 +14,23 @@ void *wtcalloc(size_t len, size_t size){
 
 /* Returns the floor of the base-2 log of it's input
  *
- * x = 0
- *    MSVC: returns 0
- *    Undefined on GCC/clang
+ * Undefined for x = 0
  */
-unsigned char uint_log2(unsigned long x){
+unsigned char size_log2(size_t x){
 #if defined(_MSC_VER)
     unsigned long i;
+#if defined (_WIN64)
+    _BitScanReverse64(&i, x);
+#else
     _BitScanReverse(&i, x);
+#endif /* _WIN64 */
     return i;
 #else
     // GCC and clang
     // Safe cast: 0 <= clzl < arch_bits (64) where result is defined
     unsigned char leading_zeros = (unsigned char) __builtin_clzl(x);
-    return sizeof(unsigned long) * 8 - leading_zeros - 1;
-#endif
+    return sizeof(size_t) * 8 - leading_zeros - 1;
+#endif /* _MSC_VER */
 }
 
 /* buffers and max levels params */
@@ -66,10 +68,10 @@ size_t swt_buffer_length(size_t input_len){
 }
 
 unsigned char dwt_max_level(size_t input_len, size_t filter_len){
-    if(input_len < 1 || filter_len < 2)
+    if(filter_len <= 1 || input_len < (filter_len-1))
         return 0;
 
-    return uint_log2(input_len/(filter_len-1));
+    return size_log2(input_len/(filter_len-1));
 }
 
 unsigned char swt_max_level(size_t input_len){

diff --git a/pywt/tests/test__pywt.py b/pywt/tests/test__pywt.py
@@ -79,5 +79,13 @@ def test_wavelet_repr():
     assert_(wavelet.__repr__() == repr_wavelet.__repr__())
 
 
+def test_dwt_max_level():
+    assert_(pywt.dwt_max_level(16, 2) == 4)
+    assert_(pywt.dwt_max_level(16, 8) == 1)
+    assert_(pywt.dwt_max_level(16, 9) == 1)
+    assert_(pywt.dwt_max_level(16, 10) == 0)
+    assert_(pywt.dwt_max_level(16, 18) == 0)
+
+
 if __name__ == '__main__':
     run_module_suite()