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Fix AreaStore's IDs persistence (#8888)

Improve documentation
Read old formats
Fix free ID function. Return first gap in map
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SmallJoker committed Sep 21, 2019
1 parent 5fa614d commit fec30e37ac1d160a942777b05a7717b5395c4d99
@@ -14,6 +14,7 @@ core.features = {
object_independent_selectionbox = true,
httpfetch_binary_data = true,
formspec_version_element = true,
area_store_persistent_ids = true,
}

function core.has_feature(arg)
@@ -3804,6 +3804,8 @@ Utilities
httpfetch_binary_data = true,
-- Whether formspec_version[<version>] may be used (5.1.0)
formspec_version_element = true,
-- Whether AreaStore's IDs are kept on save/load (5.1.0)
area_store_persistent_ids = true,
}

* `minetest.has_feature(arg)`: returns `boolean, missing_features`
@@ -5197,35 +5199,38 @@ A fast access data structure to store areas, and find areas near a given
position or area.
Every area has a `data` string attribute to store additional information.
You can create an empty `AreaStore` by calling `AreaStore()`, or
`AreaStore(type_name)`.
`AreaStore(type_name)`. The mod decides where to save and load AreaStore.
If you chose the parameter-less constructor, a fast implementation will be
automatically chosen for you.

### Methods

* `get_area(id, include_borders, include_data)`: returns the area with the id
`id`.
(optional) Boolean values `include_borders` and `include_data` control what's
copied.
Returns nil if specified area id does not exist.
* `get_areas_for_pos(pos, include_borders, include_data)`: returns all areas
that contain the position `pos`.
(optional) Boolean values `include_borders` and `include_data` control what's
copied.
* `get_areas_in_area(edge1, edge2, accept_overlap, include_borders, include_data)`:
returns all areas that contain all nodes inside the area specified by `edge1`
and `edge2` (inclusive).
If `accept_overlap` is true, also areas are returned that have nodes in
common with the specified area.
(optional) Boolean values `include_borders` and `include_data` control what's
copied.
* `get_area(id, include_borders, include_data)`
* Returns the area information about the specified ID.
* Returned values are either of these:

nil -- Area not found
true -- Without `include_borders` and `include_data`
{
min = pos, max = pos -- `include_borders == true`
data = string -- `include_data == true`
}

* `get_areas_for_pos(pos, include_borders, include_data)`
* Returns all areas as table, indexed by the area ID.
* Table values: see `get_area`.
* `get_areas_in_area(edge1, edge2, accept_overlap, include_borders, include_data)`
* Returns all areas that contain all nodes inside the area specified by `edge1`
and `edge2` (inclusive).
* `accept_overlap`: if `true`, areas are returned that have nodes in
common (intersect) with the specified area.
* Returns the same values as `get_areas_for_pos`.
* `insert_area(edge1, edge2, data, [id])`: inserts an area into the store.
Returns the new area's ID, or nil if the insertion failed.
The (inclusive) positions `edge1` and `edge2` describe the area.
`data` is a string stored with the area. If passed, `id` will be used as the
internal area ID, it must be a unique number between 0 and 2^32-2. If you use
the `id` parameter you must always use it, or insertions are likely to fail
due to conflicts.
* Returns the new area's ID, or nil if the insertion failed.
* The (inclusive) positions `edge1` and `edge2` describe the area.
* `data` is a string stored with the area.
* `id` (optional): will be used as the internal area ID if it is an unique
number between 0 and 2^32-2.
* `reserve(count)`: reserves resources for at most `count` many contained
areas.
Only needed for efficiency, and only some implementations profit.
@@ -185,6 +185,7 @@ int LuaAreaStore::l_insert_area(lua_State *L)
if (lua_isnumber(L, 5))
a.id = lua_tonumber(L, 5);

// Insert & assign a new ID if necessary
if (!ast->insertArea(&a))
return 0;

@@ -128,11 +128,11 @@ void TestAreaStore::testSerialization()
VectorAreaStore store;

Area a(v3s16(-1, 0, 1), v3s16(0, 1, 2));
a.data = "Area A";
a.data = "Area AA";
store.insertArea(&a);

Area b(v3s16(123, 456, 789), v3s16(32000, 100, 10));
b.data = "Area B";
b.data = "Area BB";
store.insertArea(&b);

std::ostringstream os;
@@ -143,20 +143,31 @@ void TestAreaStore::testSerialization()
"\x00\x02" // Count
"\xFF\xFF\x00\x00\x00\x01" // Area A min edge
"\x00\x00\x00\x01\x00\x02" // Area A max edge
"\x00\x06" // Area A data length
"Area A" // Area A data
"\x00\x07" // Area A data length
"Area AA" // Area A data
"\x00\x7B\x00\x64\x00\x0A" // Area B min edge (last two swapped with max edge for sorting)
"\x7D\x00\x01\xC8\x03\x15" // Area B max edge (^)
"\x00\x06" // Area B data length
"Area B", // Area B data
"\x00\x07" // Area B data length
"Area BB" // Area B data
"\x00\x00\x00\x00" // ID A = 0
"\x00\x00\x00\x01", // ID B = 1
1 + 2 +
6 + 6 + 2 + 6 +
6 + 6 + 2 + 6);
(6 + 6 + 2 + 7) * 2 + // min/max edge, length, data
2 * 4); // Area IDs

UASSERTEQ(const std::string &, str, str_wanted);

std::istringstream is(str);
store.deserialize(is);

UASSERTEQ(size_t, store.size(), 4); // deserialize() doesn't clear the store
// deserialize() doesn't clear the store
// But existing IDs are overridden
UASSERTEQ(size_t, store.size(), 2);

Area c(v3s16(33, -2, -6), v3s16(4, 77, -76));
c.data = "Area CC";
store.insertArea(&c);

UASSERTEQ(u32, c.id, 2);
}

@@ -64,6 +64,11 @@ const Area *AreaStore::getArea(u32 id) const

void AreaStore::serialize(std::ostream &os) const
{
// WARNING:
// Before 5.1.0-dev: version != 0 throws SerializationError
// After 5.1.0-dev: version >= 5 throws SerializationError
// Forwards-compatibility is assumed before version 5.

writeU8(os, 0); // Serialisation version

// TODO: Compression?
@@ -75,27 +80,41 @@ void AreaStore::serialize(std::ostream &os) const
writeU16(os, a.data.size());
os.write(a.data.data(), a.data.size());
}

// Serialize IDs
for (const auto &it : areas_map)
writeU32(os, it.second.id);
}

void AreaStore::deserialize(std::istream &is)
{
u8 ver = readU8(is);
if (ver != 0)
// Assume forwards-compatibility before version 5
if (ver >= 5)
throw SerializationError("Unknown AreaStore "
"serialization version!");

u16 num_areas = readU16(is);
std::vector<Area> areas;
for (u32 i = 0; i < num_areas; ++i) {
Area a;
Area a(U32_MAX);
a.minedge = readV3S16(is);
a.maxedge = readV3S16(is);
u16 data_len = readU16(is);
char *data = new char[data_len];
is.read(data, data_len);
a.data = std::string(data, data_len);
insertArea(&a);
areas.emplace_back(a);
delete [] data;
}

bool read_ids = is.good(); // EOF for old formats

for (auto &area : areas) {
if (read_ids)
area.id = readU32(is);
insertArea(&area);
}
}

void AreaStore::invalidateCache()
@@ -105,6 +124,19 @@ void AreaStore::invalidateCache()
}
}

u32 AreaStore::getNextId() const
{
u32 free_id = 0;
for (const auto &area : areas_map) {
if (area.first > free_id)
return free_id; // Found gap

free_id = area.first + 1;
}
// End of map
return free_id;
}

void AreaStore::setCacheParams(bool enabled, u8 block_radius, size_t limit)
{
m_cache_enabled = enabled;
@@ -37,15 +37,15 @@ with this program; if not, write to the Free Software Foundation, Inc.,


struct Area {
Area() = default;
Area(u32 area_id) : id(area_id) {}

Area(const v3s16 &mine, const v3s16 &maxe) :
minedge(mine), maxedge(maxe)
Area(const v3s16 &mine, const v3s16 &maxe, u32 area_id = U32_MAX) :
id(area_id), minedge(mine), maxedge(maxe)
{
sortBoxVerticies(minedge, maxedge);
}

u32 id = U32_MAX;
u32 id;
v3s16 minedge, maxedge;
std::string data;
};
@@ -109,7 +109,7 @@ class AreaStore {
virtual void getAreasForPosImpl(std::vector<Area *> *result, v3s16 pos) = 0;

/// Returns the next area ID and increments it.
u32 getNextId() { return m_next_id++; }
u32 getNextId() const;

// Note: This can't be an unordered_map, since all
// references would be invalidated on rehash.
@@ -125,8 +125,6 @@ class AreaStore {
/// If you modify this, call invalidateCache()
u8 m_cacheblock_radius = 64;
LRUCache<v3s16, std::vector<Area *> > m_res_cache;

u32 m_next_id = 0;
};


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