Add test

Author: StanFromIreland

Lib/test/test_tools/test_msgfmt.py

@@ -9,7 +9,7 @@
 
 from test.support.os_helper import temp_cwd
 from test.support.script_helper import assert_python_failure, assert_python_ok
-from test.test_tools import skip_if_missing, toolsdir
+from test.test_tools import imports_under_tool, skip_if_missing, toolsdir
 
 
 skip_if_missing('i18n')
@@ -18,6 +18,9 @@
 script_dir = Path(toolsdir) / 'i18n'
 msgfmt = script_dir / 'msgfmt.py'
 
+with imports_under_tool("i18n"):
+    from msgfmt import _hashpjw
+
 
 def compile_messages(po_file, mo_file):
     assert_python_ok(msgfmt, '-o', mo_file, po_file)
@@ -42,7 +45,25 @@ def test_compilation(self):
                     self.assertDictEqual(actual._catalog, expected._catalog)
 
     def test_hash_table(self):
-        pass
+        # Check _hashpjw generates correct hash values
+        self.assertEqual(_hashpjw(b"stan"), 502398)
+        self.assertEqual(_hashpjw(b"foo"), 27999)
+
+        # Check hash table is generated correctly for general.po
+        with temp_cwd():
+            tmp_mo_file = "messages.mo"
+            compile_messages(data_dir / "general.po", tmp_mo_file)
+            with open(tmp_mo_file, "rb") as f:
+                mo_data = f.read()
+
+            header = struct.unpack("=7I", mo_data[:28])
+            hash_table_size, hash_table_offset = header[5:7]
+
+            hash_tab = struct.unpack(f"={hash_table_size}I",
+                                       mo_data[hash_table_offset : hash_table_offset + (hash_table_size * 4)])
+
+            self.assertEqual(hash_tab, (1, 3, 0, 8, 9, 7, 2, 0, 4, 5, 0, 6, 0))
+
 
     def test_binary_header(self):
         with temp_cwd():

Tools/i18n/msgfmt.py

@@ -62,7 +62,7 @@ def generate():
     global MESSAGES
 
     def hash_insert_entry(string, i):
-        hash_val = hashpjw(string)
+        hash_val = _hashpjw(string)
         hash_cursor = hash_val % hash_tab_size
         inc = 1 + (hash_val % (hash_tab_size - 2))
         while hash_table[hash_cursor]:
@@ -90,7 +90,7 @@ def hash_insert_entry(string, i):
     #  Because unsuccessful searches are unlikely this is a good value.
     #  Formulas: [Knuth, The Art of Computer Programming, Volume 3,
     #                 766 Sorting and Searching, 1973, Addison Wesley]
-    hash_tab_size = next_prime((len(MESSAGES) * 4) // 3)
+    hash_tab_size = _next_prime((len(MESSAGES) * 4) // 3)
     if hash_tab_size <= 2:
         hash_tab_size = 3
     hash_table = array.array("I", [0] * hash_tab_size)
@@ -294,7 +294,7 @@ def main():
 
 # Peter J. Weinberger hash function
 # See: https://www.drdobbs.com/database/hashing-rehashed/184409859
-def hashpjw(strs):
+def _hashpjw(strs):
     hval = 0
     for s in strs:
         if not s:
@@ -308,7 +308,7 @@ def hashpjw(strs):
     return hval
 
 
-def next_prime(start):
+def _next_prime(start):
     def is_prime(num):
         divn = 3
         sq = divn * divn