Win32: Support for Pasting 16bpp DIBs

src/bitcount.h

@@ -0,0 +1,83 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+    Copyright 2018 Thomas Bernard
+    Copyright 1996-2001 Sunset Design (Guillaume Dorme & Karl Maritaud)
+
+    Grafx2 is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; version 2
+    of the License.
+
+    Grafx2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+//////////////////////////////////////////////////////////////////////////////
+///@file bitcount.h
+/// helper functions (or macros) to count bits in machine words
+//////////////////////////////////////////////////////////////////////////////
+
+#ifndef BITCOUNT_H__
+#define BITCOINT_H__
+
+#if defined(__GNUC__) && __GNUC__ > 2
+/* use GCC built in's */
+#define count_set_bits __builtin_popcount
+#define count_trailing_zeros __builtin_ctz
+#else
+
+/**
+ * Count the number of bit sets "Popcount"
+ *
+ * Based on Wikipedia article for Hamming_weight, it's optimized
+ * for cases when zeroes are more frequent.
+ */
+static int count_set_bits(unsigned int value)
+{
+  int count;
+
+  for (count = 0; value != 0; count++)
+    value &= value-1;
+  return count;
+}
+
+#if defined(_MSC_VER)
+
+#include <intrin.h>
+// beware : the MSVC __popcnt intrinsic is not compatible with all CPU's
+// _BitScanForward() is available on all architectures.
+
+static int count_trailing_zeros(unsigned int value)
+{
+  unsigned long count;
+
+  if (_BitScanForward(&count, value))
+    return count;
+  else
+    return -1;
+}
+#else
+/**
+ * Count the number of low order zero's before the first bit set
+ */
+static int count_trailing_zeros(unsigned int value)
+{
+  int count;
+
+  if (value == 0)
+    return -1;
+  for (count = 0; (value & 1) == 0; value >>= 1)
+    count++;
+  return count;
+}
+#endif
+#endif
+
+#endif