Mask checksums to lower 32bits

Upper bits affect the result of `crc32` in zlib 1.2.12.

Author: nobu

ext/zlib/zlib.c

@@ -374,18 +374,24 @@ rb_zlib_version(VALUE klass)
     return rb_str_new2(zlibVersion());
 }
 
+#if SIZEOF_LONG * CHAR_BIT > 32
+# define mask32(x) ((x) & 0xffffffff)
+#else
+# define mask32(x) (x)
+#endif
+
 #if SIZEOF_LONG > SIZEOF_INT
 static uLong
 checksum_long(uLong (*func)(uLong, const Bytef*, uInt), uLong sum, const Bytef *ptr, long len)
 {
     if (len > UINT_MAX) {
 	do {
-	    sum = func(sum, ptr, UINT_MAX);
+	    sum = func(mask32(sum), ptr, UINT_MAX);
 	    ptr += UINT_MAX;
 	    len -= UINT_MAX;
 	} while (len >= UINT_MAX);
     }
-    if (len > 0) sum = func(sum, ptr, (uInt)len);
+    if (len > 0) sum = func(mask32(sum), ptr, (uInt)len);
     return sum;
 }
 #else
@@ -411,7 +417,7 @@ do_checksum(int argc, VALUE *argv, uLong (*func)(uLong, const Bytef*, uInt))
     }
 
     if (NIL_P(str)) {
-	sum = func(sum, Z_NULL, 0);
+	sum = func(mask32(sum), Z_NULL, 0);
     }
     else if (rb_obj_is_kind_of(str, rb_cIO)) {
         VALUE buf;

test/zlib/test_zlib.rb

@@ -1303,6 +1303,7 @@ def test_adler32
       assert_equal(0x02820145, Zlib.adler32("foo"))
       assert_equal(0x02820145, Zlib.adler32("o", Zlib.adler32("fo")))
       assert_equal(0x8a62c964, Zlib.adler32("abc\x01\x02\x03" * 10000))
+      assert_equal(0x97d1a9f7, Zlib.adler32("p", -305419897))
       Tempfile.create("test_zlib_gzip_file_to_io") {|t|
         File.binwrite(t.path, "foo")
         t.rewind
@@ -1338,6 +1339,7 @@ def test_crc32
       assert_equal(0x8c736521, Zlib.crc32("foo"))
       assert_equal(0x8c736521, Zlib.crc32("o", Zlib.crc32("fo")))
       assert_equal(0x07f0d68f, Zlib.crc32("abc\x01\x02\x03" * 10000))
+      assert_equal(0xf136439b, Zlib.crc32("p", -305419897))
       Tempfile.create("test_zlib_gzip_file_to_io") {|t|
         File.binwrite(t.path, "foo")
         t.rewind