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diff --git a/source/blender/blenlib/intern/BLI_memiter.c b/source/blender/blenlib/intern/BLI_memiter.c
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+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program 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; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/blenlib/intern/BLI_memiter.c
+ *  \ingroup bli
+ *
+ * Simple, fast memory allocator for allocating many small elements of different sizes
+ * in fixed size memory chunks,
+ * although allocations bigger than the chunk size are supported.
+ * They will reduce the efficiency of this data-structure.
+ * Elements are pointer aligned.
+ *
+ * Supports:
+ *
+ * - Allocation of mixed sizes.
+ * - Iterating over allocations in-order.
+ * - Clearing for re-use.
+ *
+ * Unsupported:
+ *
+ * - Freeing individual elements.
+ *
+ * \note We could inline iteration stepping,
+ * but tests show this doesn't give noticeable speedup.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "BLI_utildefines.h"
+
+#include "BLI_memiter.h" /* own include */
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_strict_flags.h" /* keep last */
+
+typedef uintptr_t data_t;
+typedef intptr_t offset_t;
+
+/* Write the chunk terminator on adding each element.
+ * typically we rely on the 'count' to avoid iterating past the end. */
+// #define USE_TERMINATE_PARANOID
+
+/* Currently totalloc isnt used. */
+ // #define USE_TOTALLOC
+
+/* pad must be power of two */
+#define PADUP(num, pad) (((num) + ((pad) - 1)) & ~((pad) - 1))
+
+typedef struct BLI_memiter_elem {
+	offset_t size;
+	data_t data[0];
+} BLI_memiter_elem;
+
+typedef struct BLI_memiter_chunk {
+	struct BLI_memiter_chunk *next;
+	/**
+	 * internal format is:
+	 * ``[next_pointer, size:data, size:data, ..., negative_offset]``
+	 *
+	 * Where negative offset rewinds to the start.
+	 */
+	data_t data[0];
+} BLI_memiter_chunk;
+
+typedef struct BLI_memiter {
+	/* A pointer to 'head' is needed so we can iterate in the order allocated. */
+	struct BLI_memiter_chunk *head, *tail;
+	data_t *data_curr;
+	data_t *data_last;
+	/* Used unless a large element is requested.
+	 * (which should be very rare!). */
+	uint chunk_size_in_bytes_min;
+	uint count;
+#ifdef USE_TOTALLOC
+	uint totalloc;
+#endif
+} BLI_memiter;
+
+
+BLI_INLINE uint data_offset_from_size(uint size)
+{
+	return (PADUP(size, (uint)sizeof(data_t))) / (uint)sizeof(data_t);
+}
+
+static void memiter_set_rewind_offset(BLI_memiter *mi)
+{
+	BLI_memiter_elem *elem = (BLI_memiter_elem *)mi->data_curr;
+	elem->size = (offset_t)(((data_t *)mi->tail) - mi->data_curr);
+	BLI_assert(elem->size < 0);
+}
+
+static void memiter_init(BLI_memiter *mi)
+{
+	mi->head = NULL;
+	mi->tail = NULL;
+	mi->data_curr = NULL;
+	mi->data_last = NULL;
+	mi->count = 0;
+#ifdef USE_TOTALLOC
+	mi->totalloc = 0;
+#endif
+}
+
+/* -------------------------------------------------------------------- */
+
+/** \name Public API's
+ * \{ */
+
+/**
+ * \param chunk_size_min: Should be a power of two and
+ * significantly larger than the average element size used.
+ *
+ * While allocations of any size are supported, they won't be efficient
+ * (effectively becoming a single-linked list).
+ *
+ * Its intended that many elements can be stored per chunk.
+ */
+BLI_memiter *BLI_memiter_create(uint chunk_size_min)
+{
+	BLI_memiter *mi = MEM_mallocN(sizeof(BLI_memiter), "BLI_memiter");
+	memiter_init(mi);
+
+	/* Small values are used for tests to check for correctness,
+	 * but otherwise not that useful. */
+	const uint slop_space = (sizeof(BLI_memiter_chunk) + MEM_SIZE_OVERHEAD);
+	if (chunk_size_min >= 1024) {
+		/* As long as the input is a power of 2, this will give efficient sizes. */
+		chunk_size_min -= slop_space;
+	}
+
+	mi->chunk_size_in_bytes_min = chunk_size_min;
+	return mi;
+}
+
+void *BLI_memiter_alloc(BLI_memiter *mi, uint elem_size)
+{
+	const uint data_offset = data_offset_from_size(elem_size);
+	data_t *data_curr_next = mi->data_curr + (1 + data_offset);
+
+	if (UNLIKELY(mi->data_curr == NULL) || (data_curr_next > mi->data_last)) {
+
+#ifndef USE_TERMINATE_PARANOID
+		if (mi->data_curr != NULL) {
+			memiter_set_rewind_offset(mi);
+		}
+#endif
+
+		uint chunk_size_in_bytes = mi->chunk_size_in_bytes_min;
+		if (UNLIKELY(chunk_size_in_bytes < elem_size + (uint)sizeof(data_t[2]))) {
+			chunk_size_in_bytes = elem_size + (uint)sizeof(data_t[2]);
+		}
+		uint chunk_size = data_offset_from_size(chunk_size_in_bytes);
+		BLI_memiter_chunk *chunk = MEM_mallocN(
+		        sizeof(BLI_memiter_chunk) +
+		        (chunk_size * sizeof(data_t)),
+		        "BLI_memiter_chunk");
+
+		if (mi->head == NULL) {
+			BLI_assert(mi->tail == NULL);
+			mi->head = chunk;
+		}
+		else {
+			mi->tail->next = chunk;
+		}
+		mi->tail = chunk;
+		chunk->next = NULL;
+
+		mi->data_curr = chunk->data;
+		mi->data_last = chunk->data + (chunk_size - 1);
+		data_curr_next = mi->data_curr + (1 + data_offset);
+	}
+
+	BLI_assert(data_curr_next <= mi->data_last);
+
+	BLI_memiter_elem *elem      = (BLI_memiter_elem *)mi->data_curr;
+	elem->size = (offset_t)elem_size;
+	mi->data_curr = data_curr_next;
+
+#ifdef USE_TERMINATE_PARANOID
+	memiter_set_rewind_offset(mi);
+#endif
+
+	mi->count += 1;
+
+#ifdef USE_TOTALLOC
+	mi->totalloc += elem_size;
+#endif
+
+	return elem->data;
+}
+
+void *BLI_memiter_calloc(BLI_memiter *mi, uint elem_size)
+{
+	void *data = BLI_memiter_alloc(mi, elem_size);
+	memset(data, 0, elem_size);
+	return data;
+}
+
+void BLI_memiter_alloc_from(BLI_memiter *mi, uint elem_size, const void *data_from)
+{
+	void *data = BLI_memiter_alloc(mi, elem_size);
+	memcpy(data, data_from, elem_size);
+}
+
+static void memiter_free_data(BLI_memiter *mi)
+{
+	BLI_memiter_chunk *chunk = mi->head;
+	while (chunk) {
+		BLI_memiter_chunk *chunk_next = chunk->next;
+		MEM_freeN(chunk);
+		chunk = chunk_next;
+	}
+}
+
+void BLI_memiter_destroy(BLI_memiter *mi)
+{
+	memiter_free_data(mi);
+	MEM_freeN(mi);
+}
+
+void BLI_memiter_clear(BLI_memiter *mi)
+{
+	memiter_free_data(mi);
+	memiter_init(mi);
+}
+
+uint BLI_memiter_count(const BLI_memiter *mi)
+{
+	return mi->count;
+}
+
+/** \} */
+
+
+/* -------------------------------------------------------------------- */
+
+/** \name Helper API's
+ * \{ */
+
+/* Support direct lookup for first. */
+void *BLI_memiter_elem_first(BLI_memiter *mi)
+{
+	if (mi->head != NULL) {
+		BLI_memiter_chunk *chunk = mi->head;
+		BLI_memiter_elem *elem = (BLI_memiter_elem *)chunk->data;
+		return elem->data;
+	}
+	else {
+		return NULL;
+	}
+}
+
+void *BLI_memiter_elem_first_size(BLI_memiter *mi, uint *r_size)
+{
+	if (mi->head != NULL) {
+		BLI_memiter_chunk *chunk = mi->head;
+		BLI_memiter_elem *elem = (BLI_memiter_elem *)chunk->data;
+		*r_size = (uint)elem->size;
+		return elem->data;
+	}
+	else {
+		return NULL;
+	}
+}
+
+/** \} */
+
+
+/* -------------------------------------------------------------------- */
+
+/** \name Iterator API's
+ *
+ * \note We could loop over elements until a NULL chunk is found,
+ * however this means every allocation needs to preemptively run
+ * #memiter_set_rewind_offset (see #USE_TERMINATE_PARANOID).
+ * Unless we have a call to finalize allocation (which complicates usage).
+ * So use a counter instead.
+ *
+ * \{ */
+
+void BLI_memiter_iter_init(BLI_memiter *mi, BLI_memiter_handle *iter)
+{
+	iter->elem = mi->head ? (BLI_memiter_elem *)mi->head->data : NULL;
+	iter->elem_left = mi->count;
+}
+
+bool BLI_memiter_iter_done(const BLI_memiter_handle *iter)
+{
+	return iter->elem_left != 0;
+}
+
+BLI_INLINE void memiter_chunk_step(BLI_memiter_handle *iter)
+{
+	BLI_assert(iter->elem->size < 0);
+	BLI_memiter_chunk *chunk = (BLI_memiter_chunk *)(((data_t *)iter->elem) + iter->elem->size);
+	chunk = chunk->next;
+	iter->elem = chunk ? (BLI_memiter_elem *)chunk->data : NULL;
+	BLI_assert(iter->elem == NULL || iter->elem->size >= 0);
+}
+
+void *BLI_memiter_iter_step_size(BLI_memiter_handle *iter, uint *r_size)
+{
+	if (iter->elem_left != 0) {
+		iter->elem_left -= 1;
+		if (UNLIKELY(iter->elem->size < 0)) {
+			memiter_chunk_step(iter);
+		}
+		BLI_assert(iter->elem->size >= 0);
+		uint size = (uint)iter->elem->size;
+		*r_size = size;  /* <-- only difference */
+		data_t *data = iter->elem->data;
+		iter->elem = (BLI_memiter_elem *)&data[data_offset_from_size(size)];
+		return (void *)data;
+	}
+	else {
+		return NULL;
+	}
+}
+
+void *BLI_memiter_iter_step(BLI_memiter_handle *iter)
+{
+	if (iter->elem_left != 0) {
+		iter->elem_left -= 1;
+		if (UNLIKELY(iter->elem->size < 0)) {
+			memiter_chunk_step(iter);
+		}
+		BLI_assert(iter->elem->size >= 0);
+		uint size = (uint)iter->elem->size;
+		data_t *data = iter->elem->data;
+		iter->elem = (BLI_memiter_elem *)&data[data_offset_from_size(size)];
+		return (void *)data;
+	}
+	else {
+		return NULL;
+	}
+}
+
+/** \} */