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include/mupdf/fitz/heap-imp.h

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+// Copyright (C) 2004-2022 Artifex Software, Inc.
+//
+// This file is part of MuPDF.
+//
+// MuPDF is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Affero General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// MuPDF 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 Affero General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with MuPDF. If not, see <https://www.gnu.org/licenses/agpl-3.0.en.html>
+//
+// Alternative licensing terms are available from the licensor.
+// For commercial licensing, see <https://www.artifex.com/> or contact
+// Artifex Software, Inc., 39 Mesa Street, Suite 108A, San Francisco,
+// CA 94129, USA, for further information.
+
+/* This file has preprocessor magic in it to instantiate both
+ * protoypes and implementations for heap sorting structures
+ * of various different types. Effectively, it's templating for
+ * C.
+ *
+ * If you are including this file directly without intending to
+ * be instantiating a new set of heap sort functions, you are
+ * doing the wrong thing.
+ */
+
+#ifndef MUPDF_FITZ_HEAP_I_KNOW_WHAT_IM_DOING
+#error Do not include heap-imp.h unless you know what youre doing
+#endif
+
+#define HEAP_XCAT(A,B) A##B
+#define HEAP_CAT(A,B) HEAP_XCAT(A,B)
+
+#ifndef MUPDF_FITZ_HEAP_IMPLEMENT
+typedef struct
+{
+  int max;
+  int len;
+  HEAP_CONTAINER_TYPE *heap;
+} HEAP_TYPE_NAME;
+#endif
+
+void HEAP_CAT(HEAP_TYPE_NAME,_insert)(fz_context *ctx, HEAP_TYPE_NAME *heap, HEAP_CONTAINER_TYPE v
+#ifndef HEAP_CMP
+				, int (*HEAP_CMP)(HEAP_CONTAINER_TYPE *a, HEAP_CONTAINER_TYPE *b)
+#endif
+				)
+#ifndef MUPDF_FITZ_HEAP_IMPLEMENT
+;
+#else
+{
+	int i;
+	HEAP_CONTAINER_TYPE *h;
+
+	if (heap->max == heap->len)
+	{
+		int m = heap->max * 2;
+
+		if (m == 0)
+			m = 32;
+
+		heap->heap = (HEAP_CONTAINER_TYPE *)fz_realloc(ctx, heap->heap, sizeof(*heap->heap) * m);
+		heap->max = m;
+	}
+	h = heap->heap;
+
+	/* Insert it into the heap. Consider inserting at position i, and
+	 * then 'heapify' back. We can delay the actual insertion to the
+	 * end of the process. */
+	i = heap->len++;
+	while (i != 0)
+	{
+		int parent_idx = (i-1)/2;
+		HEAP_CONTAINER_TYPE *parent_val = &h[parent_idx];
+		if (HEAP_CMP(parent_val, &v) > 0)
+			break;
+		h[i] = h[parent_idx];
+		i = parent_idx;
+	}
+	h[i] = v;
+}
+#endif
+
+void HEAP_CAT(HEAP_TYPE_NAME,_sort)(fz_context *ctx, HEAP_TYPE_NAME *heap
+#ifndef HEAP_CMP
+				, int (*HEAP_CMP)(HEAP_CONTAINER_TYPE *a, HEAP_CONTAINER_TYPE *b)
+#endif
+				)
+#ifndef MUPDF_FITZ_HEAP_IMPLEMENT
+;
+#else
+{
+	int j;
+	HEAP_CONTAINER_TYPE *h = heap->heap;
+
+	/* elements j to len are always sorted. 0 to j are always a valid heap. Gradually move j to 0. */
+	for (j = heap->len-1; j > 0; j--)
+	{
+		int k;
+		HEAP_CONTAINER_TYPE val;
+
+		/* Swap max element with j. Invariant valid for next value to j. */
+		val = h[j];
+		h[j] = h[0];
+		/* Now reform the heap. 0 to k is a valid heap. */
+		k = 0;
+		while (1)
+		{
+			int kid = k*2+1;
+			if (kid >= j)
+				break;
+			if (kid+1 < j && (HEAP_CMP(&h[kid+1], &h[kid])) > 0)
+				kid++;
+			if ((HEAP_CMP(&val, &h[kid])) > 0)
+				break;
+			h[k] = h[kid];
+			k = kid;
+		}
+		h[k] = val;
+	}
+}
+#endif
+
+void HEAP_CAT(HEAP_TYPE_NAME,_uniq)(fz_context *ctx, HEAP_TYPE_NAME *heap
+#ifndef HEAP_CMP
+				, int (*HEAP_CMP)(HEAP_CONTAINER_TYPE *a, HEAP_CONTAINER_TYPE *b)
+#endif
+				)
+#ifndef MUPDF_FITZ_HEAP_IMPLEMENT
+;
+#else
+{
+	int n = heap->len;
+	int i, j = 0;
+	HEAP_CONTAINER_TYPE *h = heap->heap;
+
+	if (n == 0)
+		return;
+
+	j = 0;
+	for (i = 1; i < n; i++)
+	{
+		if (HEAP_CMP(&h[j], &h[i]) == 0)
+			continue;
+		j++;
+		if (i != j)
+			h[j] = h[i];
+	}
+	heap->len = j+1;
+}
+#endif
+
+#undef HEAP_CONTAINER_TYPE
+#undef HEAP_TYPE_NAME
+#undef HEAP_CMP
+#undef HEAP_XCAT
+#undef HEAP_CAT