Fixed some severe memory problems with slightly kludgey code. Classes
now have a weak-keyed __buckets field that maps udata->bucket, and buckets now get auto-collected by GC. __gc metamethod is now gone.
This commit is contained in:
Bruce Hill
parent
565250d326
commit
45d410d00c
155
limmutable.c
155
limmutable.c
@ -28,7 +28,10 @@
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// This is used to create a unique light userdata to store in the registry to allow all
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// hash buckets to share the same {__mode='k'} metatable
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static int SHARED_BUCKET_METATABLE;
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static int WEAK_KEY_METATABLE;
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// This is used to create a unique light userdata to store in the registry to allow all
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// __instances tables to share the same {__mode='v'} metatable
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static int WEAK_VALUE_METATABLE;
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// This is used to create a unique light userdata to store in the registry to allow all
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// constructed classes to have the same metatable:
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// {__new=Lcreate_instance, __tostring=function(cls) return cls.name or 'immutable(...)' end}
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@ -96,16 +99,18 @@ static int Lcreate_instance(lua_State *L)
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// Find bucket
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lua_rawgeti(L, -1, hash);
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// Stack: [buckets, bucket]
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int created_bucket = 0;
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if (lua_isnil(L, -1)) {
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created_bucket = 1;
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// Make a new bucket
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// Stack: [buckets, nil]
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lua_pop(L, 1);
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// Stack: [buckets]
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lua_createtable(L, 0, 1);
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// Stack: [buckets, bucket]
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lua_pushlightuserdata(L, (void*)&SHARED_BUCKET_METATABLE);
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lua_pushlightuserdata(L, (void*)&WEAK_KEY_METATABLE);
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lua_gettable(L, LUA_REGISTRYINDEX);
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// Stack: [buckets, bucket, {'__mode'='k'}]
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// Stack: [buckets, bucket, {__mode='k'}]
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lua_setmetatable(L, -2);
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// Stack: [buckets, bucket]
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lua_pushvalue(L, -1);
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@ -114,32 +119,34 @@ static int Lcreate_instance(lua_State *L)
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// Stack: [buckets, bucket]
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}
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// Stack: [buckets, bucket]
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// scan bucket
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lua_pushnil(L);
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while (lua_next(L, -2) != 0) { // for hash_collider_inst, hash_collider in pairs(bucket) do
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider]
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int bucket_item_matches = 1;
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// Shallow equality check:
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if (! created_bucket) {
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// scan bucket
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lua_pushnil(L);
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while (lua_next(L, -2) != 0) { // for i, collider_value in pairs(hash_collider) do
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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if (!lua_rawequal(L, -1, 1+lua_tonumber(L, -2))) { // If the i'th entry doesn't match the i'th arg
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bucket_item_matches = 0;
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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lua_pop(L, 3);
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// Stack: [buckets, bucket, hash_collider_inst]
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break; // go to next item in the bucket
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} else {
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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lua_pop(L, 1);
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i]
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}
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}
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if (bucket_item_matches) {
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while (lua_next(L, -2) != 0) { // for hash_collider_inst, hash_collider in pairs(bucket) do
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider]
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lua_pop(L, 1);
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// Found matching pre-existing instance
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return 1;
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int bucket_item_matches = 1;
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// Shallow equality check:
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lua_pushnil(L);
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while (lua_next(L, -2) != 0) { // for i, collider_value in pairs(hash_collider) do
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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if (!lua_rawequal(L, -1, 1+lua_tonumber(L, -2))) { // If the i'th entry doesn't match the i'th arg
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bucket_item_matches = 0;
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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lua_pop(L, 3);
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// Stack: [buckets, bucket, hash_collider_inst]
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break; // go to next item in the bucket
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} else {
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i, value]
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lua_pop(L, 1);
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider, i]
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}
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}
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if (bucket_item_matches) {
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// Stack: [buckets, bucket, hash_collider_inst, hash_collider]
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lua_pop(L, 1);
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// Found matching pre-existing instance
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return 1;
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}
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}
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}
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@ -155,7 +162,19 @@ static int Lcreate_instance(lua_State *L)
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// Stack [buckets, bucket, inst_userdata]
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lua_pushvalue(L, -1);
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// Stack [buckets, bucket, inst_userdata, inst_userdata]
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lua_createtable(L, n, 0); // Create the table to store the instance's data
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lua_createtable(L, n, 1); // Create the table to store the instance's data
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// Stack [buckets, bucket, inst_userdata, inst_userdata, inst_table]
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// Set up a ref to the bucket so its lifetime is tied to inst_userdata
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lua_getfield(L, 1, "__buckets");
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// Stack [buckets, bucket, inst_userdata, inst_userdata, inst_table, __buckets]
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lua_pushvalue(L, -3);
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// Stack [buckets, bucket, inst_userdata, inst_userdata, inst_table, __buckets, inst_userdata]
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lua_pushvalue(L, -6);
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// Stack [buckets, bucket, inst_userdata, inst_userdata, inst_table, __buckets, inst_userdata, bucket]
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lua_settable(L, -3);
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lua_pop(L, 1);
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// Stack [buckets, bucket, inst_userdata, inst_userdata, inst_table]
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lua_Integer i;
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for (i=1; i <= (lua_Integer)n_args; i++) {
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@ -251,6 +270,9 @@ static int Lindex(lua_State *L)
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, indices, i, buckets, bucket]
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if (lua_isnil(L, -1)) {
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luaL_error(L, "Failed to find hash bucket for hash: %p", (void*)*hash_address);
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}
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lua_pushvalue(L, 1);
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// Stack: [mt, indices, i, buckets, bucket, inst_udata]
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lua_rawget(L, -2);
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@ -268,6 +290,9 @@ static int Lindex(lua_State *L)
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, buckets, bucket]
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if (lua_isnil(L, -1)) {
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luaL_error(L, "Failed to find hash bucket");
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}
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lua_pushvalue(L, 1);
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// Stack: [mt, buckets, bucket, inst_udata]
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lua_rawget(L, -2);
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@ -322,6 +347,9 @@ static int Ltostring(lua_State *L)
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, buckets, bucket]
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if (lua_isnil(L, -1)) {
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luaL_error(L, "Failed to find hash bucket");
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}
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lua_pushvalue(L, 1);
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// Stack: [mt, buckets, bucket, inst_udata]
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lua_rawget(L, -2);
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@ -389,6 +417,9 @@ static int Lnexti(lua_State *L)
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, buckets, bucket]
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if (lua_isnil(L, -1)) {
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luaL_error(L, "Failed to find hash bucket");
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}
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lua_pushvalue(L, 1);
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// Stack: [mt, buckets, bucket, inst_udata]
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lua_rawget(L, -2);
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@ -433,6 +464,9 @@ static int Lnext(lua_State *L)
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, buckets, bucket]
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if (lua_isnil(L, -1)) {
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luaL_error(L, "Failed to find hash bucket");
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}
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lua_pushvalue(L, 1);
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// Stack: [mt, buckets, bucket, inst_udata]
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lua_rawget(L, -2);
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@ -461,45 +495,6 @@ static int Lpairs(lua_State *L)
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return 3;
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}
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static int Lgc(lua_State *L)
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{
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// Unfortunately, a __gc metamethod is needed here, because the data storage format
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// is cls.__instances[hash][udata] = data, and even though cls.__instances[hash]
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// is a weak-keyed table, cls.__instances will leak hash key -> empty table mappings
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// over time.
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lua_getmetatable(L, 1);
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// Stack: [mt]
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lua_getfield(L, -1, "__instances");
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// Stack: [mt, buckets]
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lua_Integer* hash_address = (lua_Integer*)lua_touserdata(L, 1);
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if (! hash_address) {
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return 0;
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}
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lua_rawgeti(L, -1, *hash_address);
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// Stack: [mt, indices, i, buckets, bucket]
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if (lua_isnil(L, -1)) {
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return 0;
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}
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// Set cls.__instances[hash][udata] = nil
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lua_pushvalue(L, 1);
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// Stack: [mt, indices, i, buckets, bucket, inst_udata]
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lua_pushnil(L);
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// Stack: [mt, indices, i, buckets, bucket, inst_udata, nil]
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lua_settable(L, -3);
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// Stack: [mt, indices, i, buckets, bucket]
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lua_pushnil(L);
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// If next(cls.__instances[hash]) == nil, then set cls.__instances[hash] = nil
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// Stack: [mt, indices, i, buckets, bucket, nil]
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if (lua_next(L, -2) == 0) {
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lua_pop(L, 1);
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// Stack: [mt, indices, i, buckets]
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lua_pushnil(L);
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// Stack: [mt, indices, i, buckets, nil]
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lua_rawseti(L, -2, *hash_address);
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}
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return 1;
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}
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static const luaL_Reg Rinstance_metamethods[] =
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{
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{ "__len", Llen},
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@ -507,7 +502,6 @@ static const luaL_Reg Rinstance_metamethods[] =
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{ "__tostring", Ltostring},
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{ "__ipairs", Lipairs},
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{ "__pairs", Lpairs},
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{ "__gc", Lgc},
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{ "from_table", Lfrom_table},
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{ "is_instance", Lis_instance},
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{ NULL, NULL}
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@ -542,9 +536,24 @@ static int Lmake_class(lua_State *L)
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// Stack: [CLS]
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lua_createtable(L, 0, 32); // Rough guess: at least 32 instances concurrently
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// Stack: [CLS, CLS.buckets]
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// Stack: [CLS, __instances]
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lua_pushlightuserdata(L, (void*)&WEAK_VALUE_METATABLE);
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lua_gettable(L, LUA_REGISTRYINDEX);
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// Stack: [CLS, __instances, {__mode='v'}]
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lua_setmetatable(L, -2);
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// Stack: [CLS, __instances]
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lua_setfield(L, -2, "__instances");
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// Stack: [CLS]
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lua_createtable(L, 0, 32); // Rough guess: at least 32 instances concurrently
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// Stack: [CLS, __buckets]
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lua_pushlightuserdata(L, (void*)&WEAK_KEY_METATABLE);
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lua_gettable(L, LUA_REGISTRYINDEX);
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// Stack: [CLS, __buckets, {__mode='k'}]
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lua_setmetatable(L, -2);
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// Stack: [CLS, __buckets]
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lua_setfield(L, -2, "__buckets");
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// Stack: [CLS]
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switch (lua_type(L, 1)) {
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case LUA_TTABLE: {
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@ -632,7 +641,13 @@ static const luaL_Reg Rclass_metamethods[] =
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LUALIB_API int luaopen_immutable(lua_State *L)
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{
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lua_pushlightuserdata(L, (void*)&SHARED_BUCKET_METATABLE);
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lua_pushlightuserdata(L, (void*)&WEAK_VALUE_METATABLE);
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lua_createtable(L, 0, 1);
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lua_pushstring(L, "v");
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lua_setfield(L, -2, "__mode");
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lua_settable(L, LUA_REGISTRYINDEX);
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lua_pushlightuserdata(L, (void*)&WEAK_KEY_METATABLE);
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lua_createtable(L, 0, 1);
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lua_pushstring(L, "k");
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lua_setfield(L, -2, "__mode");
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28
tests.lua
28
tests.lua
@ -61,6 +61,10 @@ test("Instantiating class", function()
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v = assert(Vec(1,3))
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end)
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test("Testing indexing", function()
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assert(v.x == 1)
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end)
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test("Testing # operator", function()
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assert(#v == 2)
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end)
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@ -117,28 +121,32 @@ collectgarbage()
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collectgarbage()
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test("Testing garbage collection", function()
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collectgarbage()
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collectgarbage()
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local Foo = immutable({"x"})
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local function countFoos()
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collectgarbage()
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collectgarbage()
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local n = 0
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local buckets = 0
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for h,bucket in pairs(Foo.__instances) do
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buckets = buckets + 1
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for _ in pairs(bucket) do
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n = n + 1
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end
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end
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return n
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collectgarbage()
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collectgarbage()
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return n, buckets
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end
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local f1, f2, also_f2 = Foo(1), Foo(2), Foo(2)
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assert(countFoos() == 2)
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local foos, buckets = countFoos()
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assert(foos == 2, "WTF? "..tostring(foos))
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f1, f2 = nil, nil
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collectgarbage()
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collectgarbage()
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assert(countFoos() == 1)
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foos, buckets = countFoos()
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assert(foos == 1)
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also_f2 = nil
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collectgarbage()
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collectgarbage()
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assert(countFoos() == 0)
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foos, buckets = countFoos()
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assert(foos == 0, "Leaking instances")
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assert(buckets == 0, "Leaking hash buckets")
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assert(next(Foo.__instances) == nil)
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end)
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