add stm object support. (STM : Software transactional memory)

lualib-src/lua-stm.c

@@ -0,0 +1,244 @@
+#include <lua.h>
+#include <lauxlib.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <assert.h>
+
+#include "rwlock.h"
+#include "skynet_malloc.h"
+
+struct stm_object {
+	struct rwlock lock;
+	int reference;
+	struct stm_copy * copy;
+};
+
+struct stm_copy {
+	int reference;
+	uint32_t sz;
+	void * msg;
+};
+
+// msg should alloc by skynet_malloc 
+static struct stm_copy *
+stm_newcopy(void * msg, int32_t sz) {
+	struct stm_copy * copy = skynet_malloc(sizeof(*copy));
+	copy->reference = 1;
+	copy->sz = sz;
+	copy->msg = msg;
+
+	return copy;
+}
+
+static struct stm_object *
+stm_new(void * msg, int32_t sz) {
+	struct stm_object * obj = skynet_malloc(sizeof(*obj));
+	rwlock_init(&obj->lock);
+	obj->reference = 1;
+	obj->copy = stm_newcopy(msg, sz);
+
+	return obj;
+}
+
+static void
+stm_releasecopy(struct stm_copy *copy) {
+	if (copy == NULL)
+		return;
+	if (__sync_sub_and_fetch(&copy->reference, 1) == 0) {
+		skynet_free(copy->msg);
+		skynet_free(copy);
+	}
+}
+
+static void
+stm_release(struct stm_object *obj) {
+	assert(obj->copy);
+	rwlock_wlock(&obj->lock);
+	// writer release the stm object, so release the last copy .
+	stm_releasecopy(obj->copy);
+	obj->copy = NULL;
+	if (--obj->reference > 0) {
+		// stm object grab by readers, reset the copy to NULL.
+		rwlock_wunlock(&obj->lock);
+		return;
+	}
+	// no one grab the stm object, no need to unlock wlock.
+	skynet_free(obj);
+}
+
+static void
+stm_releasereader(struct stm_object *obj) {
+	rwlock_rlock(&obj->lock);
+	if (__sync_sub_and_fetch(&obj->reference,1) == 0) {
+		// last reader, no writer. so no need to unlock
+		assert(obj->copy == NULL);
+		skynet_free(obj);
+		return;
+	}
+	rwlock_runlock(&obj->lock);
+}
+
+static void
+stm_grab(struct stm_object *obj) {
+	rwlock_rlock(&obj->lock);
+	int ref = __sync_fetch_and_add(&obj->reference,1);
+	rwlock_runlock(&obj->lock);
+	assert(ref > 0);
+}
+
+static struct stm_copy *
+stm_copy(struct stm_object *obj) {
+	rwlock_rlock(&obj->lock);
+	struct stm_copy * ret = obj->copy;
+	if (ret) {
+		int ref = __sync_fetch_and_add(&ret->reference,1);
+		assert(ref > 0);
+	}
+	rwlock_runlock(&obj->lock);
+	
+	return ret;
+}
+
+static void
+stm_update(struct stm_object *obj, void *msg, int32_t sz) {
+	struct stm_copy *copy = stm_newcopy(msg, sz);
+	rwlock_wlock(&obj->lock);
+	struct stm_copy *oldcopy = obj->copy;
+	obj->copy = copy;
+	rwlock_wunlock(&obj->lock);
+
+	stm_releasecopy(oldcopy);
+}
+
+// lua binding
+
+struct boxstm {
+	struct stm_object * obj;
+};
+
+static int
+lcopy(lua_State *L) {
+	struct boxstm * box = lua_touserdata(L, 1);
+	stm_grab(box->obj);
+	lua_pushlightuserdata(L, box->obj);
+	return 1;
+}
+
+static int
+lnewwriter(lua_State *L) {
+	void * msg = lua_touserdata(L, 1);
+	uint32_t sz = luaL_checkunsigned(L, 2);
+	struct boxstm * box = lua_newuserdata(L, sizeof(*box));
+	box->obj = stm_new(msg,sz);
+	lua_pushvalue(L, lua_upvalueindex(1));
+	lua_setmetatable(L, -2);
+
+	return 1;
+}
+
+static int
+ldeletewriter(lua_State *L) {
+	struct boxstm * box = lua_touserdata(L, 1);
+	stm_release(box->obj);
+	box->obj = NULL;
+
+	return 0;
+}
+
+static int
+lupdate(lua_State *L) {
+	struct boxstm * box = lua_touserdata(L, 1);
+	void * msg = lua_touserdata(L, 2);
+	uint32_t sz = luaL_checkunsigned(L, 3);
+	stm_update(box->obj, msg, sz);
+
+	return 0;
+}
+
+struct boxreader {
+	struct stm_object *obj;
+	struct stm_copy *lastcopy;
+};
+
+static int
+lnewreader(lua_State *L) {
+	struct boxreader * box = lua_newuserdata(L, sizeof(*box));
+	box->obj = lua_touserdata(L, 1);
+	box->lastcopy = NULL;
+	lua_pushvalue(L, lua_upvalueindex(1));
+	lua_setmetatable(L, -2);
+
+	return 1;
+}
+
+static int
+ldeletereader(lua_State *L) {
+	struct boxreader * box = lua_touserdata(L, 1);
+	stm_releasereader(box->obj);
+	box->obj = NULL;
+	stm_releasecopy(box->lastcopy);
+	box->lastcopy = NULL;
+
+	return 0;
+}
+
+static int
+lread(lua_State *L) {
+	struct boxreader * box = lua_touserdata(L, 1);
+	luaL_checktype(L, 2, LUA_TFUNCTION);
+	struct stm_copy * copy = stm_copy(box->obj);
+	if (copy == box->lastcopy) {
+		// not update
+		stm_releasecopy(copy);
+		lua_pushboolean(L, 0);
+		return 1;
+	}
+
+	stm_releasecopy(box->lastcopy);
+	box->lastcopy = copy;
+	if (copy) {
+		lua_settop(L, 2);
+		lua_pushlightuserdata(L, copy->msg);
+		lua_pushunsigned(L, copy->sz);
+		lua_call(L, 2, LUA_MULTRET);
+		lua_pushboolean(L, 1);
+		lua_replace(L, 1);
+		return lua_gettop(L);
+	} else {
+		lua_pushboolean(L, 0);
+		return 1;
+	}
+}
+
+int
+luaopen_stm(lua_State *L) {
+	luaL_checkversion(L);
+	lua_createtable(L, 0, 3);
+
+	lua_pushcfunction(L, lcopy);
+	lua_setfield(L, -2, "copy");
+
+	luaL_Reg writer[] = {
+		{ "new", lnewwriter },
+		{ NULL, NULL },
+	};
+	lua_createtable(L, 0, 2);
+	lua_pushcfunction(L, ldeletewriter),
+	lua_setfield(L, -2, "__gc");
+	lua_pushcfunction(L, lupdate),
+	lua_setfield(L, -2, "__call");
+	luaL_setfuncs(L, writer, 1);
+
+	luaL_Reg reader[] = {
+		{ "newcopy", lnewreader },
+		{ NULL, NULL },
+	};
+	lua_createtable(L, 0, 2);
+	lua_pushcfunction(L, ldeletereader),
+	lua_setfield(L, -2, "__gc");
+	lua_pushcfunction(L, lread),
+	lua_setfield(L, -2, "__call");
+	luaL_setfuncs(L, reader, 1);
+
+	return 1;
+}