--- /dev/null
+/*
+ Bitmask 1.7 - A pixel-perfect collision detection library.
+
+ Copyright (C) 2002-2005 Ulf Ekstrom except for the bitcount
+ function which is copyright (C) Donald W. Gillies, 1992.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public
+ License as published by the Free Software Foundation; either
+ version 2 of the License, or (at your option) any later version.
+
+ This library 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
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with this library; if not, write to the Free
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#ifndef BITMASK_H
+#define BITMASK_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <limits.h>
+/* Define INLINE for different compilers. If your compiler does not
+ support inlining then there might be a performance hit in
+ bitmask_overlap_area().
+*/
+#ifndef INLINE
+# ifdef __GNUC__
+# define INLINE inline
+# else
+# ifdef _MSC_VER
+# define INLINE __inline
+# else
+# define INLINE
+# endif
+# endif
+#endif
+
+#define BITMASK_W unsigned long int
+#define BITMASK_W_LEN (sizeof(BITMASK_W)*CHAR_BIT)
+#define BITMASK_W_MASK (BITMASK_W_LEN - 1)
+#define BITMASK_N(n) ((BITMASK_W)1 << (n))
+
+typedef struct bitmask
+{
+ int w,h;
+ BITMASK_W bits[1];
+} bitmask_t;
+
+/* Creates a bitmask of width w and height h, where
+ w and h must both be greater than or equal to 0.
+ The mask is automatically cleared when created.
+ */
+bitmask_t *bitmask_create(int w, int h);
+
+/* Frees all the memory allocated by bitmask_create for m. */
+void bitmask_free(bitmask_t *m);
+
+/* Create a copy of the given bitmask. */
+bitmask_t *bitmask_copy(bitmask_t *m);
+
+/* Clears all bits in the mask */
+void bitmask_clear(bitmask_t *m);
+
+/* Sets all bits in the mask */
+void bitmask_fill(bitmask_t *m);
+
+/* Flips all bits in the mask */
+void bitmask_invert(bitmask_t *m);
+
+/* Counts the bits in the mask */
+unsigned int bitmask_count(bitmask_t *m);
+
+/* Returns nonzero if the bit at (x,y) is set. Coordinates start at
+ (0,0) */
+static INLINE int bitmask_getbit(const bitmask_t *m, int x, int y)
+{
+ return (m->bits[x/BITMASK_W_LEN*m->h + y] & BITMASK_N(x & BITMASK_W_MASK)) != 0;
+}
+
+/* Sets the bit at (x,y) */
+static INLINE void bitmask_setbit(bitmask_t *m, int x, int y)
+{
+ m->bits[x/BITMASK_W_LEN*m->h + y] |= BITMASK_N(x & BITMASK_W_MASK);
+}
+
+/* Clears the bit at (x,y) */
+static INLINE void bitmask_clearbit(bitmask_t *m, int x, int y)
+{
+ m->bits[x/BITMASK_W_LEN*m->h + y] &= ~BITMASK_N(x & BITMASK_W_MASK);
+}
+
+/* Returns nonzero if the masks overlap with the given offset.
+ The overlap tests uses the following offsets (which may be negative):
+
+ +----+----------..
+ |A | yoffset
+ | +-+----------..
+ +--|B
+ |xoffset
+ | |
+ : :
+*/
+int bitmask_overlap(const bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
+
+/* Like bitmask_overlap(), but will also give a point of intersection.
+ x and y are given in the coordinates of mask a, and are untouched
+ if there is no overlap. */
+int bitmask_overlap_pos(const bitmask_t *a, const bitmask_t *b,
+ int xoffset, int yoffset, int *x, int *y);
+
+/* Returns the number of overlapping 'pixels' */
+int bitmask_overlap_area(const bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
+
+/* Fills a mask with the overlap of two other masks. A bitwise AND. */
+void bitmask_overlap_mask (const bitmask_t *a, const bitmask_t *b, bitmask_t *c, int xoffset, int yoffset);
+
+/* Draws mask b onto mask a (bitwise OR). Can be used to compose large
+ (game background?) mask from several submasks, which may speed up
+ the testing. */
+
+void bitmask_draw(bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
+
+void bitmask_erase(bitmask_t *a, const bitmask_t *b, int xoffset, int yoffset);
+
+/* Return a new scaled bitmask, with dimensions w*h. The quality of the
+ scaling may not be perfect for all circumstances, but it should
+ be reasonable. If either w or h is 0 a clear 1x1 mask is returned. */
+bitmask_t *bitmask_scale(const bitmask_t *m, int w, int h);
+
+/* Convolve b into a, drawing the output into o, shifted by offset. If offset
+ * is 0, then the (x,y) bit will be set if and only if
+ * bitmask_overlap(a, b, x - b->w - 1, y - b->h - 1) returns true.
+ *
+ * Modifies bits o[xoffset ... xoffset + a->w + b->w - 1)
+ * [yoffset ... yoffset + a->h + b->h - 1). */
+void bitmask_convolve(const bitmask_t *a, const bitmask_t *b, bitmask_t *o, int xoffset, int yoffset);
+
+#ifdef __cplusplus
+} /* End of extern "C" { */
+#endif
+
+#endif
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