luaclass.c

/*
 * luaclass.c - useful functions for handling Lua classes
 *
 * Copyright (C) 2010 Mason Larobina <mason.larobina@gmail.com>
 * Copyright (C) 2009 Julien Danjou <julien@danjou.info>
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */

#include <stdlib.h>

#include "common/luaclass.h"
#include "common/luaobject.h"

struct lua_class_property {
    /** Callback function called when the property is found in object creation. */
    lua_class_propfunc_t new;
    /** Callback function called when the property is found in object __index. */
    lua_class_propfunc_t index;
    /** Callback function called when the property is found in object __newindex. */
    lua_class_propfunc_t newindex;
};

static GPtrArray *luaH_classes = NULL;

/* Convert a object to a udata if possible.
 * `ud` is the index.
 * `class` is the wanted class.
 * Returns a pointer to the object, NULL otherwise. */
gpointer
luaH_toudata(lua_State *L, gint ud, lua_class_t *class) {
    gpointer p = lua_touserdata(L, ud);
    if(p) /* value is a userdata? */
        if(lua_getmetatable(L, ud)) /* does it have a metatable? */
        {
            lua_pushlightuserdata(L, class);
            lua_rawget(L, LUA_REGISTRYINDEX);
            if(!lua_rawequal(L, -1, -2)) /* does it have the correct mt? */
                p = NULL;
            lua_pop(L, 2); /* remove both metatables */
        }
    return p;
}

/* Check for a udata class.
 * `ud` is the object index on the stack.
 * `class` is the wanted class.
 * Returns a pointer to the wanted class. */
gpointer
luaH_checkudata(lua_State *L, gint ud, lua_class_t *class) {
    gpointer p = luaH_toudata(L, ud, class);
    if(!p)
        luaL_typerror(L, ud, class->name);
    return p;
}

/* Get an object lua_class.
 * `idx` of the index of the object on the stack. */
lua_class_t *
luaH_class_get(lua_State *L, gint idx) {
    gint type = lua_type(L, idx);
    lua_class_t *class;

    if(type == LUA_TUSERDATA && luaH_classes)
        for (guint i = 0; i < luaH_classes->len; i++) {
            class = luaH_classes->pdata[i];
            if(luaH_toudata(L, idx, class))
                return class;
        }

    return NULL;
}

/** Enhanced version of lua_typename that recognizes setup Lua classes.
 * \param L The Lua VM state.
 * \param idx The index of the object on the stack.
 */
const gchar *
luaH_typename(lua_State *L, gint idx) {
    gint type = lua_type(L, idx);

    if(type == LUA_TUSERDATA) {
        lua_class_t *lua_class = luaH_class_get(L, idx);
        if(lua_class)
            return lua_class->name;
    }
    return lua_typename(L, type);
}

void
luaH_openlib(lua_State *L, const gchar *name, const struct luaL_reg methods[],
        const struct luaL_reg meta[]) {
    luaL_newmetatable(L, name);                                        /* 1 */
    lua_pushvalue(L, -1);           /* dup metatable                      2 */
    lua_setfield(L, -2, "__index"); /* metatable.__index = metatable      1 */

    luaL_register(L, NULL, meta);                                      /* 1 */
    luaL_register(L, name, methods);                                   /* 2 */
    lua_pushvalue(L, -1);           /* dup self as metatable              3 */
    lua_setmetatable(L, -2);        /* set self as metatable              2 */
    lua_pop(L, 2);
}

void
luaH_class_add_property(lua_class_t *lua_class, luakit_token_t token,
        lua_class_propfunc_t cb_new,
        lua_class_propfunc_t cb_index,
        lua_class_propfunc_t cb_newindex) {

    lua_class_property_t *prop;
    g_assert(token != L_TK_UNKNOWN);
    prop = g_new0(lua_class_property_t, 1);

    /* populate property */
    prop->new = cb_new;
    prop->index = cb_index;
    prop->newindex = cb_newindex;

    /* add property to class properties tree */
    g_hash_table_insert((GHashTable*) lua_class->properties,
            (gpointer) token, prop);
}

void
luaH_class_setup(lua_State *L, lua_class_t *class,
        const gchar *name,
        lua_class_allocator_t allocator,
        lua_class_propfunc_t index_miss_property,
        lua_class_propfunc_t newindex_miss_property,
        const struct luaL_reg methods[],
        const struct luaL_reg meta[]) {
    /* Create the metatable */
    lua_newtable(L);
    /* Register it with class pointer as key in the registry */
    lua_pushlightuserdata(L, class);
    /* Duplicate the metatable */
    lua_pushvalue(L, -2);
    lua_rawset(L, LUA_REGISTRYINDEX);

    lua_pushvalue(L, -1);           /* dup metatable                      2 */
    lua_setfield(L, -2, "__index"); /* metatable.__index = metatable      1 */

    luaL_register(L, NULL, meta);                                      /* 1 */
    luaL_register(L, name, methods);                                   /* 2 */
    lua_pushvalue(L, -1);           /* dup self as metatable              3 */
    lua_setmetatable(L, -2);        /* set self as metatable              2 */
    lua_pop(L, 2);

    class->allocator = allocator;
    class->name = name;
    class->index_miss_property = index_miss_property;
    class->newindex_miss_property = newindex_miss_property;

    class->signals = signal_tree_new();
    class->properties = (lua_class_property_array_t*) g_hash_table_new(
            g_direct_hash, g_direct_equal);

    if (!luaH_classes)
        luaH_classes = g_ptr_array_new();
    g_ptr_array_add(luaH_classes, class);
}

void
luaH_class_add_signal(lua_State *L, lua_class_t *lua_class,
        const gchar *name, gint ud) {
    luaH_checkfunction(L, ud);
    signal_add(lua_class->signals, name, luaH_object_ref(L, ud));
}

void
luaH_class_remove_signal(lua_State *L, lua_class_t *lua_class,
        const gchar *name, gint ud) {
    luaH_checkfunction(L, ud);
    gpointer ref = (gpointer) lua_topointer(L, ud);
    signal_remove(lua_class->signals, name, ref);
    luaH_object_unref(L, (gpointer) ref);
    lua_remove(L, ud);
}

void
luaH_class_emit_signal(lua_State *L, lua_class_t *lua_class,
        const gchar *name, gint nargs) {
    signal_object_emit(L, lua_class->signals, name, nargs);
}

/* Try to use the metatable of an object.
 * `idxobj` is the index of the object.
 * `idxfield` is the index of the field (attribute) to get.
 * Returns the number of element pushed on stack. */
gint
luaH_usemetatable(lua_State *L, gint idxobj, gint idxfield) {
    /* Get metatable of the object. */
    lua_getmetatable(L, idxobj);
    /* Get the field */
    lua_pushvalue(L, idxfield);
    lua_rawget(L, -2);
    /* Do we have a field like that? */
    if(!lua_isnil(L, -1)) {
        /* Yes, so return it! */
        lua_remove(L, -2);
        return 1;
    }
    /* No, so remove everything. */
    lua_pop(L, 2);

    return 0;
}

/* Get a property of a object.
 * `lua_class` is the Lua class.
 * `fieldidx` is the index of the field name.
 * Return is the object property if found, NULL otherwise. */
static lua_class_property_t *
luaH_class_property_get(lua_State *L, lua_class_t *lua_class, gint fieldidx) {
    size_t len;
    const gchar *attr = luaL_checklstring(L, fieldidx, &len);
    luakit_token_t token = l_tokenize(attr, len);

    return g_hash_table_lookup((GHashTable*) lua_class->properties,
            (gpointer) token);
}

/* Generic index meta function for objects.
 * Return the number of elements pushed on stack. */
gint
luaH_class_index(lua_State *L) {
    /* Try to use metatable first. */
    if(luaH_usemetatable(L, 1, 2))
        return 1;

    lua_class_t *class = luaH_class_get(L, 1);

    lua_class_property_t *prop = luaH_class_property_get(L, class, 2);

    /* Property does exist and has an index callback */
    if(prop) {
        if(prop->index)
            return prop->index(L, luaH_checkudata(L, 1, class));
    } else {
        if(class->index_miss_property)
            return class->index_miss_property(L, luaH_checkudata(L, 1, class));
    }

    return 0;
}

/* Generic newindex meta function for objects.
 * Returns the number of elements pushed on stack. */
gint
luaH_class_newindex(lua_State *L) {
    /* Try to use metatable first. */
    if(luaH_usemetatable(L, 1, 2))
        return 1;

    lua_class_t *class = luaH_class_get(L, 1);

    lua_class_property_t *prop = luaH_class_property_get(L, class, 2);

    /* Property does exist and has a newindex callback */
    if(prop) {
        if(prop->newindex)
            return prop->newindex(L, luaH_checkudata(L, 1, class));
    } else {
        if(class->newindex_miss_property)
            return class->newindex_miss_property(L, luaH_checkudata(L, 1, class));
    }

    return 0;
}

/* Generic constructor function for objects.
 * Returns the number of elements pushed on stack. */
gint
luaH_class_new(lua_State *L, lua_class_t *lua_class) {
    /* Check we have a table that should contains some properties */
    luaH_checktable(L, 2);

    /* Create a new object */
    lua_object_t *object = lua_class->allocator(L);

    /* Push the first key before iterating */
    lua_pushnil(L);
    /* Iterate over the property keys */
    while(lua_next(L, 2)) {
        /* Check that the key is a string.
         * We cannot call tostring blindly or Lua will convert a key that is a
         * number TO A STRING, confusing lua_next() */
        if(lua_isstring(L, -2)) {
            /* Lookup the property */
            size_t len;
            const char *attr = lua_tolstring(L, -2, &len);
            lua_class_property_t *prop = g_hash_table_lookup(
                    (GHashTable*) lua_class->properties,
                    (gpointer) l_tokenize(attr, len));

            if(prop && prop->new)
                prop->new(L, object);
        }
        /* Remove value */
        lua_pop(L, 1);
    }
    return 1;
}

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