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diff --git a/3d_accel_svgadb.h b/3d_accel_svgadb.h
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+/*****************************************************************************
+
+Copyright (c) 2026 Jaroslav Hensl <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+*****************************************************************************/
+#ifndef __3D_ACCEL_SVGADB_H__INCLUDED__
+#define __3D_ACCEL_SVGADB_H__INCLUDED__
+
+#define BSTEP (sizeof(DWORD)*8)
+
+static inline DWORD map_lookup_and_set(DWORD *bitmap, DWORD start, DWORD max)
+{
+	DWORD i = start / BSTEP;
+	DWORD ii = start % BSTEP;
+	
+	bitmap += i;
+	
+	for(; i < max; i += BSTEP)
+	{
+		DWORD tmp = *bitmap;
+		if(tmp != 0) /* skip all-occupied double words */
+		{
+			for(; ii < BSTEP; ii++)
+			{
+				if(((tmp >> ii) & 0x1) != 0)
+				{
+					*bitmap &= ~((DWORD)1 << ii); /* set the bit in bitmap (to zero) */
+					return i+ii;
+				}
+			}
+			ii = 0;
+		}
+		bitmap++;
+	}
+	
+	return max;
+}
+
+static inline void map_reset(DWORD *bitmap, DWORD id)
+{
+	DWORD i = id / BSTEP;
+	DWORD ii = id % BSTEP;
+	
+	bitmap += i;
+	*bitmap |= ((DWORD)1 << ii);
+}
+
+#endif /* __3D_ACCEL_SVGADB_H__INCLUDED__ */