path: root/source/blender/blenkernel/intern/undo_system.c

/*
 * ***** 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/blenkernel/intern/undo_system.c
 *  \ingroup bke
 *
 * Used by ED_undo.h, internal implementation.
 */

#include <string.h>

#include "CLG_log.h"

#include "BLI_utildefines.h"
#include "BLI_sys_types.h"
#include "BLI_listbase.h"
#include "BLI_string.h"
#include "BLI_sort_utils.h"

#include "DNA_listBase.h"
#include "DNA_windowmanager_types.h"

#include "BKE_context.h"
#include "BKE_global.h"
#include "BKE_library_override.h"
#include "BKE_main.h"
#include "BKE_undo_system.h"

#include "MEM_guardedalloc.h"

#define undo_stack _wm_undo_stack_disallow  /* pass in as a variable always. */

/** Odd requirement of Blender that we always keep a memfile undo in the stack. */
#define WITH_GLOBAL_UNDO_KEEP_ONE

/** Make sure all ID's created at the point we add an undo step that uses ID's. */
#define WITH_GLOBAL_UNDO_ENSURE_UPDATED

/** We only need this locally. */
static CLG_LogRef LOG = {"bke.undosys"};

/* -------------------------------------------------------------------- */
/** \name Internal Nested Undo Checks
 *
 * Make sure we're not running undo operations from 'step_encode', 'step_decode' callbacks.
 * bugs caused by this situation aren't _that_ hard to spot but aren't always so obvious.
 * Best we have a check which shows the problem immediately.
 *
 * \{ */
#define WITH_NESTED_UNDO_CHECK

#ifdef WITH_NESTED_UNDO_CHECK
static bool g_undo_callback_running = false;
#  define UNDO_NESTED_ASSERT(state) BLI_assert(g_undo_callback_running == state)
#  define UNDO_NESTED_CHECK_BEGIN { \
	UNDO_NESTED_ASSERT(false); \
	g_undo_callback_running = true; \
} ((void)0)
#  define UNDO_NESTED_CHECK_END { \
	UNDO_NESTED_ASSERT(true); \
	g_undo_callback_running = false; \
} ((void)0)
#else
#  define UNDO_NESTED_ASSERT(state) ((void)0)
#  define UNDO_NESTED_CHECK_BEGIN ((void)0)
#  define UNDO_NESTED_CHECK_END   ((void)0)
#endif
/** \} */

/* -------------------------------------------------------------------- */
/** \name Public Undo Types
 *
 * Unfortunately we need this for a handful of places.
 */
const UndoType *BKE_UNDOSYS_TYPE_IMAGE = NULL;
const UndoType *BKE_UNDOSYS_TYPE_MEMFILE = NULL;
const UndoType *BKE_UNDOSYS_TYPE_PAINTCURVE = NULL;
const UndoType *BKE_UNDOSYS_TYPE_PARTICLE = NULL;
const UndoType *BKE_UNDOSYS_TYPE_SCULPT = NULL;
const UndoType *BKE_UNDOSYS_TYPE_TEXT = NULL;
/** \} */

/* UndoType */

static ListBase g_undo_types = {NULL, NULL};

static const UndoType *BKE_undosys_type_from_context(bContext *C)
{
	for (const UndoType *ut = g_undo_types.first; ut; ut = ut->next) {
		/* No poll means we don't check context. */
		if (ut->poll && ut->poll(C)) {
			return ut;
		}
	}
	return NULL;
}

/* -------------------------------------------------------------------- */
/** \name Internal Callback Wrappers
 *
 * #UndoRefID is simply a way to avoid inlining name copy and lookups,
 * since it's easy to forget a single case when done inline (crashing in some cases).
 *
 * \{ */

static void undosys_id_ref_store(void *UNUSED(user_data), UndoRefID *id_ref)
{
	BLI_assert(id_ref->name[0] == '\0');
	if (id_ref->ptr) {
		BLI_strncpy(id_ref->name, id_ref->ptr->name, sizeof(id_ref->name));
		/* Not needed, just prevents stale data access. */
		id_ref->ptr = NULL;
	}
}

static void undosys_id_ref_resolve(void *user_data, UndoRefID *id_ref)
{
	/* Note: we could optimize this, for now it's not too bad since it only runs when we access undo! */
	Main *bmain = user_data;
	ListBase *lb = which_libbase(bmain, GS(id_ref->name));
	for (ID *id = lb->first; id; id = id->next) {
		if (STREQ(id_ref->name, id->name) && (id->lib == NULL)) {
			id_ref->ptr = id;
			break;
		}
	}
}

static bool undosys_step_encode(bContext *C, UndoStep *us)
{
	CLOG_INFO(&LOG, 2, "addr=%p, name='%s', type='%s'", us, us->name, us->type->name);
	UNDO_NESTED_CHECK_BEGIN;
	bool ok = us->type->step_encode(C, us);
	UNDO_NESTED_CHECK_END;
	if (ok) {
		if (us->type->step_foreach_ID_ref != NULL) {
			/* Don't use from context yet because sometimes context is fake and not all members are filled in. */
			Main *bmain = G.main;
			us->type->step_foreach_ID_ref(us, undosys_id_ref_store, bmain);
		}
	}
	if (ok == false) {
		CLOG_INFO(&LOG, 2, "encode callback didn't create undo step");
	}
	return ok;
}

static void undosys_step_decode(bContext *C, UndoStep *us, int dir)
{
	CLOG_INFO(&LOG, 2, "addr=%p, name='%s', type='%s'", us, us->name, us->type->name);
	if (us->type->step_foreach_ID_ref) {
		/* Don't use from context yet because sometimes context is fake and not all members are filled in. */
		Main *bmain = G.main;
		us->type->step_foreach_ID_ref(us, undosys_id_ref_resolve, bmain);
	}

	UNDO_NESTED_CHECK_BEGIN;
	us->type->step_decode(C, us, dir);
	UNDO_NESTED_CHECK_END;
}

static void undosys_step_free_and_unlink(UndoStack *ustack, UndoStep *us)
{
	CLOG_INFO(&LOG, 2, "addr=%p, name='%s', type='%s'", us, us->name, us->type->name);
	UNDO_NESTED_CHECK_BEGIN;
	us->type->step_free(us);
	UNDO_NESTED_CHECK_END;

	BLI_remlink(&ustack->steps, us);
	MEM_freeN(us);
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name Undo Stack
 * \{ */

#ifndef NDEBUG
static void undosys_stack_validate(UndoStack *ustack, bool expect_non_empty)
{
	if (ustack->step_active != NULL) {
		BLI_assert(!BLI_listbase_is_empty(&ustack->steps));
		BLI_assert(BLI_findindex(&ustack->steps, ustack->step_active) != -1);
	}
	if (expect_non_empty) {
		BLI_assert(!BLI_listbase_is_empty(&ustack->steps));
	}
}
#else
static void undosys_stack_validate(UndoStack *ustack, bool expect_non_empty)
{
	UNUSED_VARS(ustack, expect_non_empty);
}
#endif

UndoStack *BKE_undosys_stack_create(void)
{
	UndoStack *ustack = MEM_callocN(sizeof(UndoStack), __func__);
	return ustack;
}

void BKE_undosys_stack_destroy(UndoStack *ustack)
{
	BKE_undosys_stack_clear(ustack);
	MEM_freeN(ustack);
}

void BKE_undosys_stack_clear(UndoStack *ustack)
{
	UNDO_NESTED_ASSERT(false);
	CLOG_INFO(&LOG, 1, "steps=%d", BLI_listbase_count(&ustack->steps));
	for (UndoStep *us = ustack->steps.last, *us_prev; us; us = us_prev) {
		us_prev = us->prev;
		undosys_step_free_and_unlink(ustack, us);
	}
	BLI_listbase_clear(&ustack->steps);
	ustack->step_active = NULL;
}

void BKE_undosys_stack_clear_active(UndoStack *ustack)
{
	/* Remove active and all following undos. */
	UndoStep *us = ustack->step_active;

	if (us) {
		ustack->step_active = us->prev;
		bool is_not_empty = ustack->step_active != NULL;

		while (ustack->steps.last != ustack->step_active) {
			UndoStep *us_iter = ustack->steps.last;
			undosys_step_free_and_unlink(ustack, us_iter);
			undosys_stack_validate(ustack, is_not_empty);
		}
	}
}

static bool undosys_stack_push_main(UndoStack *ustack, const char *name, struct Main *bmain)
{
	UNDO_NESTED_ASSERT(false);
	CLOG_INFO(&LOG, 1, "'%s'", name);
	bContext *C_temp = CTX_create();
	CTX_data_main_set(C_temp, bmain);
	bool ok = BKE_undosys_step_push_with_type(ustack, C_temp, name, BKE_UNDOSYS_TYPE_MEMFILE);
	CTX_free(C_temp);
	return ok;
}

void BKE_undosys_stack_init_from_main(UndoStack *ustack, struct Main *bmain)
{
	UNDO_NESTED_ASSERT(false);
	undosys_stack_push_main(ustack, "original", bmain);
}

/* called after 'BKE_undosys_stack_init_from_main' */
void BKE_undosys_stack_init_from_context(UndoStack *ustack, bContext *C)
{
	const UndoType *ut = BKE_undosys_type_from_context(C);
	if ((ut != NULL) && (ut != BKE_UNDOSYS_TYPE_MEMFILE) && (ut->mode == BKE_UNDOTYPE_MODE_STORE)) {
		BKE_undosys_step_push_with_type(ustack, C, "original mode", ut);
	}
}

/* name optional */
bool BKE_undosys_stack_has_undo(UndoStack *ustack, const char *name)
{
	if (name) {
		UndoStep *us = BLI_rfindstring(&ustack->steps, name, offsetof(UndoStep, name));
		return us && us->prev;
	}

	return !BLI_listbase_is_empty(&ustack->steps);
}

UndoStep *BKE_undosys_stack_active_with_type(UndoStack *ustack, const UndoType *ut)
{
	UndoStep *us = ustack->step_active;
	while (us && (us->type != ut)) {
		us = us->prev;
	}
	return us;
}

UndoStep *BKE_undosys_stack_init_or_active_with_type(UndoStack *ustack, const UndoType *ut)
{
	UNDO_NESTED_ASSERT(false);
	CLOG_INFO(&LOG, 1, "type='%s'", ut->name);
	if (ustack->step_init && (ustack->step_init->type == ut)) {
		return ustack->step_init;
	}
	return BKE_undosys_stack_active_with_type(ustack, ut);
}

/**
 * \param steps: Limit the number of undo steps.
 * \param memory_limit: Limit the amount of memory used by the undo stack.
 */
void BKE_undosys_stack_limit_steps_and_memory(UndoStack *ustack, int steps, size_t memory_limit)
{
	UNDO_NESTED_ASSERT(false);
	if (!(steps || memory_limit)) {
		return;
	}

	CLOG_INFO(&LOG, 1, "steps=%d, memory_limit=%zu", steps, memory_limit);
	UndoStep *us;
#ifdef WITH_GLOBAL_UNDO_KEEP_ONE
	UndoStep *us_exclude = NULL;
#endif
	/* keep at least two (original + other) */
	size_t data_size_all = 0;
	size_t us_count = 0;
	for (us = ustack->steps.last; us && us->prev; us = us->prev) {
		if (memory_limit) {
			data_size_all += us->data_size;
			if (data_size_all > memory_limit) {
				break;
			}
		}
		if (steps) {
			if (us_count == steps) {
				break;
			}
			if (us->skip == false) {
				us_count += 1;
			}
		}
	}

	if (us) {
		if (us->prev && us->prev->prev) {
			us = us->prev;
		}

#ifdef WITH_GLOBAL_UNDO_KEEP_ONE
		/* Hack, we need to keep at least one BKE_UNDOSYS_TYPE_MEMFILE. */
		if (us->type != BKE_UNDOSYS_TYPE_MEMFILE) {
			us_exclude = us->prev;
			while (us_exclude && us->type != BKE_UNDOSYS_TYPE_MEMFILE) {
				us_exclude = us_exclude->prev;
			}
			if (us_exclude) {
				BLI_remlink(&ustack->steps, us_exclude);
			}
		}
#endif
		/* Free from first to last, free functions may update de-duplication info (see #MemFileUndoStep). */
		while (ustack->steps.first != us) {
			UndoStep *us_first = ustack->steps.first;
			BLI_assert(us_first != ustack->step_active);
			undosys_step_free_and_unlink(ustack, us_first);
		}

#ifdef WITH_GLOBAL_UNDO_KEEP_ONE
		if (us_exclude) {
			BLI_addhead(&ustack->steps, us_exclude);
		}
#endif
	}
}

/** \} */

UndoStep *BKE_undosys_step_push_init_with_type(UndoStack *ustack, bContext *C, const char *name, const UndoType *ut)
{
	UNDO_NESTED_ASSERT(false);
	/* We could detect and clean this up (but it should never happen!). */
	BLI_assert(ustack->step_init == NULL);
	if (ut->step_encode_init) {
		undosys_stack_validate(ustack, false);
		UndoStep *us = MEM_callocN(ut->step_size, __func__);
		CLOG_INFO(&LOG, 1, "addr=%p, name='%s', type='%s'", us, name, ut->name);
		if (name != NULL) {
			BLI_strncpy(us->name, name, sizeof(us->name));
		}
		us->type = ut;
		ustack->step_init = us;
		ut->step_encode_init(C, us);
		undosys_stack_validate(ustack, false);
		return us;
	}
	else {
		return NULL;
	}
}

UndoStep *BKE_undosys_step_push_init(UndoStack *ustack, bContext *C, const char *name)
{
	UNDO_NESTED_ASSERT(false);
	/* We could detect and clean this up (but it should never happen!). */
	BLI_assert(ustack->step_init == NULL);
	const UndoType *ut = BKE_undosys_type_from_context(C);
	if (ut == NULL) {
		return NULL;
	}
	return BKE_undosys_step_push_init_with_type(ustack, C, name, ut);
}

/**
 * \param C: Can be NULL from some callers if their encoding function doesn't need it
 */
bool BKE_undosys_step_push_with_type(UndoStack *ustack, bContext *C, const char *name, const UndoType *ut)
{
	UNDO_NESTED_ASSERT(false);
	undosys_stack_validate(ustack, false);
	bool is_not_empty = ustack->step_active != NULL;

	/* Might not be final place for this to be called - probably only want to call it from some
	 * undo handlers, not all of them? */
	BKE_main_override_static_operations_create(G.main, false);

	/* Remove all undos after (also when 'ustack->step_active == NULL'). */
	while (ustack->steps.last != ustack->step_active) {
		UndoStep *us_iter = ustack->steps.last;
		undosys_step_free_and_unlink(ustack, us_iter);
		undosys_stack_validate(ustack, is_not_empty);
	}

	if (ustack->step_active) {
		BLI_assert(BLI_findindex(&ustack->steps, ustack->step_active) != -1);
	}

#ifdef WITH_GLOBAL_UNDO_ENSURE_UPDATED
	if (ut->step_foreach_ID_ref != NULL) {
		Main *bmain = G.main;
		if (bmain->is_memfile_undo_written == false) {
			const char *name_internal = "MemFile Internal";
			if (undosys_stack_push_main(ustack, name_internal, bmain)) {
				UndoStep *us = ustack->steps.last;
				BLI_assert(STREQ(us->name, name_internal));
				us->skip = true;
			}
		}
	}
#endif

	UndoStep *us = ustack->step_init ? ustack->step_init : MEM_callocN(ut->step_size, __func__);
	ustack->step_init = NULL;
	if (us->name[0] == '\0') {
		BLI_strncpy(us->name, name, sizeof(us->name));
	}
	us->type = ut;
	/* initialized, not added yet. */

	if (undosys_step_encode(C, us)) {
		ustack->step_active = us;
		BLI_addtail(&ustack->steps, us);
		undosys_stack_validate(ustack, true);
		return true;
	}
	else {
		MEM_freeN(us);
		undosys_stack_validate(ustack, true);
		return false;
	}
}

bool BKE_undosys_step_push(UndoStack *ustack, bContext *C, const char *name)
{
	UNDO_NESTED_ASSERT(false);
	const UndoType *ut = ustack->step_init ? ustack->step_init->type : BKE_undosys_type_from_context(C);
	if (ut == NULL) {
		return false;
	}
	return BKE_undosys_step_push_with_type(ustack, C, name, ut);
}


/**
 * Useful when we want to diff against previous undo data but can't be sure the types match.
 */
UndoStep *BKE_undosys_step_same_type_next(UndoStep *us)
{
	if (us) {
		const UndoType *ut = us->type;
		while ((us = us->next)) {
			if (us->type == ut) {
				return us;
			}
		}

	}
	return us;
}

/**
 * Useful when we want to diff against previous undo data but can't be sure the types match.
 */
UndoStep *BKE_undosys_step_same_type_prev(UndoStep *us)
{
	if (us) {
		const UndoType *ut = us->type;
		while ((us = us->prev)) {
			if (us->type == ut) {
				return us;
			}
		}

	}
	return us;
}

UndoStep *BKE_undosys_step_find_by_name_with_type(UndoStack *ustack, const char *name, const UndoType *ut)
{
	for (UndoStep *us = ustack->steps.last; us; us = us->prev) {
		if (us->type == ut) {
			if (STREQ(name, us->name)) {
				return us;
			}
		}
	}
	return NULL;
}

UndoStep *BKE_undosys_step_find_by_name(UndoStack *ustack, const char *name)
{
	return BLI_rfindstring(&ustack->steps, name, offsetof(UndoStep, name));
}

UndoStep *BKE_undosys_step_find_by_type(UndoStack *ustack, const UndoType *ut)
{
	for (UndoStep *us = ustack->steps.last; us; us = us->prev) {
		if (us->type == ut) {
			return us;
		}
	}
	return NULL;
}

bool BKE_undosys_step_undo_with_data_ex(
        UndoStack *ustack, bContext *C, UndoStep *us,
        bool use_skip)
{
	UNDO_NESTED_ASSERT(false);
	if (us) {
		undosys_stack_validate(ustack, true);
	}
	UndoStep *us_prev = us ? us->prev : NULL;
	if (us && us->type->mode == BKE_UNDOTYPE_MODE_STORE) {
		/* The current state is a copy, we need to load the previous state. */
		us = us_prev;
	}

	if (us != NULL) {
		CLOG_INFO(&LOG, 1, "addr=%p, name='%s', type='%s'", us, us->name, us->type->name);
		undosys_step_decode(C, us, -1);
		ustack->step_active = us_prev;
		undosys_stack_validate(ustack, true);
		if (use_skip) {
			if (ustack->step_active && ustack->step_active->skip) {
				CLOG_INFO(&LOG, 2, "undo continue with skip %p '%s', type='%s'", us, us->name, us->type->name);
				BKE_undosys_step_undo_with_data(ustack, C, ustack->step_active);
			}
		}
		return true;
	}
	return false;
}
bool BKE_undosys_step_undo_with_data(UndoStack *ustack, bContext *C, UndoStep *us)
{
	return BKE_undosys_step_undo_with_data_ex(ustack, C, us, true);
}

bool BKE_undosys_step_undo(UndoStack *ustack, bContext *C)
{
	return BKE_undosys_step_undo_with_data(ustack, C, ustack->step_active);
}

void BKE_undosys_step_undo_from_index(UndoStack *ustack, bContext *C, int index)
{
	UndoStep *us = BLI_findlink(&ustack->steps, index);
	BLI_assert(us->skip == false);
	BKE_undosys_step_load_data(ustack, C, us);
}

bool BKE_undosys_step_redo_with_data_ex(
        UndoStack *ustack, bContext *C, UndoStep *us,
        bool use_skip)
{
	UNDO_NESTED_ASSERT(false);
	UndoStep *us_next = us ? us->next : NULL;
	/* Unlike undo accumulate, we always use the next. */
	us = us_next;

	if (us != NULL) {
		CLOG_INFO(&LOG, 1, "addr=%p, name='%s', type='%s'", us, us->name, us->type->name);
		undosys_step_decode(C, us, 1);
		ustack->step_active = us_next;
		if (use_skip) {
			if (ustack->step_active && ustack->step_active->skip) {
				CLOG_INFO(&LOG, 2, "redo continue with skip %p '%s', type='%s'", us, us->name, us->type->name);
				BKE_undosys_step_redo_with_data(ustack, C, ustack->step_active);
			}
		}
		return true;
	}
	return false;
}
bool BKE_undosys_step_redo_with_data(UndoStack *ustack, bContext *C, UndoStep *us)
{
	return BKE_undosys_step_redo_with_data_ex(ustack, C, us, true);
}

bool BKE_undosys_step_redo(UndoStack *ustack, bContext *C)
{
	return BKE_undosys_step_redo_with_data(ustack, C, ustack->step_active);
}

bool BKE_undosys_step_load_data(UndoStack *ustack, bContext *C, UndoStep *us)
{
	UNDO_NESTED_ASSERT(false);
	const int index_active = BLI_findindex(&ustack->steps, ustack->step_active);
	const int index_target = BLI_findindex(&ustack->steps, us);
	BLI_assert(!ELEM(-1, index_active, index_target));
	bool ok = true;

	if (index_target < index_active) {
		uint i = index_active - index_target;
		while (i-- && ok) {
			ok = BKE_undosys_step_undo_with_data_ex(ustack, C, ustack->step_active, false);
		}
	}
	else if (index_target > index_active) {
		uint i = index_target - index_active;
		while (i-- && ok) {
			ok = BKE_undosys_step_redo_with_data_ex(ustack, C, ustack->step_active, false);
		}
	}

	if (ok) {
		BLI_assert(ustack->step_active == us);
	}

	return ok;
}

bool BKE_undosys_step_undo_compat_only(UndoStack *ustack, bContext *C, int step)
{
	if (step == 0) {
		return BKE_undosys_step_undo_with_data(ustack, C, ustack->step_active);
	}
	else if (step == 1) {
		return BKE_undosys_step_undo(ustack, C);
	}
	else {
		return BKE_undosys_step_redo(ustack, C);
	}
}
/**
 * Similar to #WM_operatortype_append
 */
UndoType *BKE_undosys_type_append(void (*undosys_fn)(UndoType *))
{
	UndoType *ut;

	ut = MEM_callocN(sizeof(UndoType), __func__);

	undosys_fn(ut);

	BLI_assert(ut->mode != 0);

	BLI_addtail(&g_undo_types, ut);

	return ut;
}

void BKE_undosys_type_free_all(void)
{
	UndoType *ut;
	while ((ut = BLI_pophead(&g_undo_types))) {
		MEM_freeN(ut);
	}
}

/** \} */

/* -------------------------------------------------------------------- */
/** \name ID Reference Utilities
 *
 * Unfortunately we need this for a handful of places.
 */

static void UNUSED_FUNCTION(BKE_undosys_foreach_ID_ref(
        UndoStack *ustack, UndoTypeForEachIDRefFn foreach_ID_ref_fn, void *user_data))
{
	for (UndoStep *us = ustack->steps.first; us; us = us->next) {
		const UndoType *ut = us->type;
		if (ut->step_foreach_ID_ref != NULL) {
			ut->step_foreach_ID_ref(us, foreach_ID_ref_fn, user_data);
		}
	}
}

typedef struct UndoIDPtrMapItem {
	/** Never changes (matches undo data). Use as sort key for binary search. */
	const void *ptr;
	/** Write the new pointers here. */
	uint index;
} UndoIDPtrMapItem;

typedef struct UndoIDPtrMap {
	UndoRefID *refs;
	/**
	 * Pointer map, update 'dst' members before use.
	 * This is always sorted (adds some overhead when adding, in practice it's acceptable since).
	 */
	UndoIDPtrMapItem *pmap;

	/** Length for both 'refs' & 'pmap' */
	uint len;
	uint len_alloc;
} UndoIDPtrMap;

#ifdef DEBUG
#  define PMAP_DEFAULT_ALLOC 1
#else
#  define PMAP_DEFAULT_ALLOC 32
#endif

void BKE_undosys_ID_map_foreach_ID_ref(
        UndoIDPtrMap *map,
        UndoTypeForEachIDRefFn foreach_ID_ref_fn, void *user_data)
{
	for (uint i = 0; i < map->len; i++) {
		foreach_ID_ref_fn(user_data, &map->refs[i]);
	}
}

/**
 * Return true when found, otherwise index is set to the index we should insert.
 */
static bool undosys_ID_map_lookup_index(const UndoIDPtrMap *map, const void *key, uint *r_index)
{
	const UndoIDPtrMapItem *pmap = map->pmap;
	const uint len = map->len;
	if (len == 0) {
		if (*r_index) {
			*r_index = 0;
		}
		return false;
	}
	int min = 0, max = len - 1;
	while (min <= max) {
		const uint mid = (min + max) / 2;
		if (pmap[mid].ptr < key) {
			min = mid + 1;
		}
		else if (pmap[mid].ptr == key) {
			if (r_index) {
				*r_index = mid;
			}
			return true;
		}
		else if (pmap[mid].ptr > key) {
			max = mid - 1;
		}
	}
	if (r_index) {
		*r_index = min;
	}
	return false;
}

/**
 * A set of ID's use for efficient decoding, so we can map pointers back to the newly loaded data
 * without performing full look ups each time.
 *
 * This can be used as an old_pointer -> new_pointer lookup.
 */
UndoIDPtrMap *BKE_undosys_ID_map_create(void)
{
	UndoIDPtrMap *map = MEM_mallocN(sizeof(*map), __func__);
	map->len_alloc = PMAP_DEFAULT_ALLOC;
	map->refs = MEM_mallocN(sizeof(*map->refs) * map->len_alloc, __func__);
	map->pmap = MEM_mallocN(sizeof(*map->pmap) * map->len_alloc, __func__);
	map->len = 0;
	return map;
}
void BKE_undosys_ID_map_destroy(UndoIDPtrMap *idpmap)
{
	MEM_SAFE_FREE(idpmap->refs);
	MEM_SAFE_FREE(idpmap->pmap);
	MEM_freeN(idpmap);
}

void BKE_undosys_ID_map_add(UndoIDPtrMap *map, ID *id)
{
	uint index;
	if (id->lib != NULL) {
		return;
	}

	if (undosys_ID_map_lookup_index(map, id, &index)) {
		return;  /* exists. */
	}

	const uint len_src = map->len;
	const uint len_dst = map->len + 1;
	if (len_dst > map->len_alloc) {
		map->len_alloc *= 2;
		BLI_assert(map->len_alloc >= len_dst);
		map->pmap = MEM_reallocN(map->pmap, sizeof(*map->pmap) * map->len_alloc);
		map->refs = MEM_reallocN(map->refs, sizeof(*map->refs) * map->len_alloc);
	}

#if 0  /* Will be done automatically in callback. */
	BLI_strncpy(map->refs[len_src].name, id->name, sizeof(id->name));
#else
	map->refs[len_src].name[0] = '\0';
#endif
	map->refs[len_src].ptr = id;

	if (len_src != 0 && index != len_src) {
		memmove(&map->pmap[index + 1], &map->pmap[index], sizeof(*map->pmap) * (len_src - index));
	}
	map->pmap[index].ptr = id;
	map->pmap[index].index = len_src;

	map->len = len_dst;
}

ID *BKE_undosys_ID_map_lookup(const UndoIDPtrMap *map, const ID *id_src)
{
	/* We should only ever lookup indices which exist! */
	uint index;
	if (!undosys_ID_map_lookup_index(map, id_src, &index)) {
		BLI_assert(0);
	}
	index = map->pmap[index].index;
	ID *id_dst = map->refs[index].ptr;
	BLI_assert(id_dst != NULL);
	BLI_assert(STREQ(id_dst->name, map->refs[index].name));
	return id_dst;
}

void BKE_undosys_ID_map_add_with_prev(UndoIDPtrMap *map, ID *id, ID **id_prev)
{
	if (id == *id_prev) {
		return;
	}
	*id_prev = id;
	BKE_undosys_ID_map_add(map, id);
}

ID *BKE_undosys_ID_map_lookup_with_prev(const UndoIDPtrMap *map, ID *id_src, ID *id_prev_match[2])
{
	if (id_src == id_prev_match[0]) {
		return id_prev_match[1];
	}
	else {
		ID *id_dst = BKE_undosys_ID_map_lookup(map, id_src);
		id_prev_match[0] = id_src;
		id_prev_match[1] = id_dst;
		return id_dst;
	}
}

/** \} */