From 5871ed0d02ff69b20b65f577dd3be18a2e92dec7 Mon Sep 17 00:00:00 2001 From: Joshua Haberman Date: Sun, 18 Jul 2010 22:45:15 -0700 Subject: First go at Lua bindings. --- lang_ext/lua/upb.c | 254 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 254 insertions(+) create mode 100644 lang_ext/lua/upb.c (limited to 'lang_ext/lua') diff --git a/lang_ext/lua/upb.c b/lang_ext/lua/upb.c new file mode 100644 index 0000000..ac7f188 --- /dev/null +++ b/lang_ext/lua/upb.c @@ -0,0 +1,254 @@ +/* + * upb - a minimalist implementation of protocol buffers. + * + * Copyright (c) 2009 Joshua Haberman. See LICENSE for details. + * + * A Lua extension for upb. + */ + +#include "lauxlib.h" +#include "upb_def.h" + +/* lupb_def *******************************************************************/ + +// All the def types share the same C layout, even though they are differen Lua +// types with different metatables. +typedef struct { + upb_def *def; +} lupb_def; + +static void lupb_pushnewdef(lua_State *L, upb_def *def) { + lupb_def *ldef = lua_newuserdata(L, sizeof(lupb_def)); + ldef->def = def; + const char *type_name; + switch(def->type) { + case UPB_DEF_MSG: + type_name = "upb.msgdef"; + break; + case UPB_DEF_ENUM: + type_name = "upb.enumdef"; + break; + default: + luaL_error(L, "unknown deftype %d", def->type); + } + luaL_getmetatable(L, type_name); + lua_setmetatable(L, -2); +} + +static lupb_def *lupb_msgdef_check(lua_State *L, int narg) { + return luaL_checkudata(L, narg, "upb.msgdef"); +} + +static lupb_def *lupb_enumdef_check(lua_State *L, int narg) { + return luaL_checkudata(L, narg, "upb.enumdef"); +} + +static int lupb_msgdef_gc(lua_State *L) { + lupb_def *ldef = lupb_msgdef_check(L, 1); + upb_def_unref(ldef->def); + return 0; +} + +static int lupb_enumdef_gc(lua_State *L) { + lupb_def *ldef = lupb_enumdef_check(L, 1); + upb_def_unref(ldef->def); + return 0; +} + +static const struct luaL_Reg lupb_msgdef_methods[] = { + {"__gc", lupb_msgdef_gc}, + {NULL, NULL} +}; + +static const struct luaL_Reg lupb_enumdef_methods[] = { + {"__gc", lupb_enumdef_gc}, + {NULL, NULL} +}; + + +/* lupb_symtab ****************************************************************/ + +// lupb_symtab caches the Lua objects it vends (defs) via lookup or resolve. +// It does this (instead of creating a new Lua object every time) for two +// reasons: +// * it uses less memory, because we can reuse existing objects. +// * it gives the expected equality semantics, eg. symtab[sym] == symtab[sym]. +// +// The downside is a bit of complexity. We need a place to store these +// cached defs; the only good answer is in the metatable. This means we need +// a new metatable for every symtab instance (instead of one shared by all +// instances). Since this is different than the regular pattern, we can't +// use luaL_checkudata(), we have to implement it ourselves. +typedef struct { + upb_symtab *symtab; +} lupb_symtab; + +static int lupb_symtab_gc(lua_State *L); + +// Inherits a ref on the symtab. +static void lupb_pushnewsymtab(lua_State *L, upb_symtab *symtab) { + lupb_symtab *lsymtab = lua_newuserdata(L, sizeof(lupb_symtab)); + lsymtab->symtab = symtab; + // Create its metatable (see note above about mt-per-object). + lua_createtable(L, 0, 1); + luaL_getmetatable(L, "upb.symtab"); + lua_setfield(L, -2, "__index"); // Uses the type metatable to find methods. + lua_pushcfunction(L, lupb_symtab_gc); + lua_setfield(L, -2, "__gc"); + + // Put this metatable in the registry so we can find it for type validation. + lua_pushlightuserdata(L, lsymtab); + lua_pushvalue(L, -2); + lua_rawset(L, LUA_REGISTRYINDEX); + + // Set the symtab's metatable. + lua_setmetatable(L, -2); +} + +// Checks that narg is a proper lupb_symtab object. If it is, leaves its +// metatable on the stack for cache lookups/updates. +lupb_symtab *lupb_symtab_check(lua_State *L, int narg) { + lupb_symtab *symtab = lua_touserdata(L, narg); + if (symtab != NULL) { + if (lua_getmetatable(L, narg)) { + // We use a metatable-per-object to support memoization of defs. + lua_pushlightuserdata(L, symtab); + lua_rawget(L, LUA_REGISTRYINDEX); + if (lua_rawequal(L, -1, -2)) { // Does it have the correct mt? + lua_pop(L, 1); // Remove one copy of the mt, keep the other. + return symtab; + } + } + } + luaL_typerror(L, narg, "upb.symtab"); + return NULL; // Placate the compiler; luaL_typerror will longjmp out of here. +} + +static int lupb_symtab_gc(lua_State *L) { + lupb_symtab *s = lupb_symtab_check(L, 1); + upb_symtab_unref(s->symtab); + + // Remove its metatable from the registry. + lua_pushlightuserdata(L, s); + lua_pushnil(L); + lua_rawset(L, LUA_REGISTRYINDEX); + return 0; +} + +// "mt" is the index of the metatable, -1 is the fqname of this def. +// Leaves the Lua object for the def at the top of the stack. +// Inherits a ref on "def". +static void lupb_symtab_getorcreate(lua_State *L, upb_def *def, int mt) { + // We may have this def cached, in which case we should return the same Lua + // object (as long as the value in the underlying symtab has not changed. + lua_rawget(L, mt); + if (!lua_isnil(L, -1)) { + // Def is cached, make sure it hasn't changed. + lupb_def *ldef = lua_touserdata(L, -1); + if (!ldef) luaL_error(L, "upb's internal cache is corrupt."); + if (ldef->def == def) { + // Cache is good, we can just return the cached value. + upb_def_unref(def); + return; + } + } + // Cached entry didn't exist or wasn't good. + lua_pop(L, 1); // Remove bad cached value. + lupb_pushnewdef(L, def); + + // Set it in the cache. + lua_pushvalue(L, 2); // push name (arg to this function). + lua_pushvalue(L, -2); // push the new def. + lua_rawset(L, mt); // set in the cache (the mt). +} + +static int lupb_symtab_lookup(lua_State *L) { + lupb_symtab *s = lupb_symtab_check(L, 1); + size_t len; + const char *name = luaL_checklstring(L, 2, &len); + upb_string namestr = UPB_STACK_STRING_LEN(name, len); + upb_def *def = upb_symtab_lookup(s->symtab, &namestr); + if (!def) { + // There shouldn't be a value in our cache either because the symtab + // currently provides no API for deleting syms from a table. In case + // this changes in the future, we explicitly delete from the cache here. + lua_pushvalue(L, 2); // push name (arg to this function). + lua_pushnil(L); + lua_rawset(L, -3); // lupb_symtab_check() left our mt on the stack. + + // Return nil because the symbol was not found. + lua_pushnil(L); + return 1; + } else { + lua_pushvalue(L, 2); + lupb_symtab_getorcreate(L, def, 3); + return 1; + } +} + +static int lupb_symtab_getdefs(lua_State *L) { + lupb_symtab *s = lupb_symtab_check(L, 1); + upb_deftype_t type = luaL_checkint(L, 2); + int count; + upb_def **defs = upb_symtab_getdefs(s->symtab, &count, type); + + // Create the table in which we will return the defs. + lua_createtable(L, 0, count); + int ret = lua_gettop(L); + + for (int i = 0; i < count; i++) { + upb_def *def = defs[i]; + // Look it up in the cache by name. + upb_string *name = def->fqname; + lua_pushlstring(L, upb_string_getrobuf(name), upb_string_len(name)); + lua_pushvalue(L, -1); // Push it again since the getorcreate consumes one. + lupb_symtab_getorcreate(L, def, 3); + + // Add it to our return table. + lua_settable(L, ret); + } + return 1; +} + +static int lupb_symtab_add_descriptorproto(lua_State *L) { + lupb_symtab *s = lupb_symtab_check(L, 1); + upb_symtab_add_descriptorproto(s->symtab); + return 0; // No args to return. +} + +static const struct luaL_Reg lupb_symtab_methods[] = { + {"add_descriptorproto", lupb_symtab_add_descriptorproto}, + //{"addfds", lupb_symtab_addfds}, + {"getdefs", lupb_symtab_getdefs}, + {"lookup", lupb_symtab_lookup}, + //{"resolve", lupb_symtab_resolve}, + {NULL, NULL} +}; + + +/* lupb toplevel **************************************************************/ + +static int lupb_symtab_new(lua_State *L) { + upb_symtab *s = upb_symtab_new(); + lupb_pushnewsymtab(L, s); + return 1; +} + +static const struct luaL_Reg lupb_toplevel_methods[] = { + {"symtab", lupb_symtab_new}, + {NULL, NULL} +}; + +int luaopen_upb(lua_State *L) { + luaL_newmetatable(L, "upb.msgdef"); + luaL_register(L, NULL, lupb_msgdef_methods); + + luaL_newmetatable(L, "upb.enumdef"); + luaL_register(L, NULL, lupb_enumdef_methods); + + luaL_newmetatable(L, "upb.symtab"); + luaL_register(L, NULL, lupb_symtab_methods); + + luaL_register(L, "upb", lupb_toplevel_methods); + return 1; // Return package table. +} -- cgit v1.2.3