ngx_http_lua_variable.c

#ifndef DDEBUG
#define DDEBUG 0
#endif
#include "ddebug.h"

#include "ngx_http_lua_variable.h"


static int ngx_http_lua_var_get(lua_State *L);
static int ngx_http_lua_var_set(lua_State *L);


void
ngx_http_lua_inject_variable_api(lua_State *L)
{
    /* {{{ register reference maps */
    lua_newtable(L);    /* ngx.var */

    lua_createtable(L, 0, 2 /* nrec */); /* metatable for .var */
    lua_pushcfunction(L, ngx_http_lua_var_get);
    lua_setfield(L, -2, "__index");
    lua_pushcfunction(L, ngx_http_lua_var_set);
    lua_setfield(L, -2, "__newindex");
    lua_setmetatable(L, -2);

    lua_setfield(L, -2, "var");
}


/**
 * Get nginx internal variables content
 *
 * @retval Always return a string or nil on Lua stack. Return nil when failed
 * to get content, and actual content string when found the specified variable.
 * @seealso ngx_http_lua_var_set
 * */
static int
ngx_http_lua_var_get(lua_State *L)
{
    ngx_http_request_t          *r;
    u_char                      *p, *lowcase;
    size_t                       len;
    ngx_uint_t                   hash;
    ngx_str_t                    name;
    ngx_http_variable_value_t   *vv;

#if (NGX_PCRE)
    u_char                      *val;
    ngx_uint_t                   n;
    LUA_NUMBER                   index;
    int                         *cap;
#endif

    lua_getglobal(L, GLOBALS_SYMBOL_REQUEST);
    r = lua_touserdata(L, -1);
    lua_pop(L, 1);

    if (r == NULL) {
        return luaL_error(L, "no request object found");
    }

#if (NGX_PCRE)
    if (lua_type(L, -1) == LUA_TNUMBER) {
        /* it is a regex capturing variable */

        index = lua_tonumber(L, -1);

        if (index <= 0) {
            lua_pushnil(L);
            return 1;
        }

        n = (ngx_uint_t) index * 2;

        dd("n = %d, ncaptures = %d", (int) n, (int) r->ncaptures);

        if (r->captures == NULL || r->captures_data == NULL ||
                n >= r->ncaptures)
        {
            lua_pushnil(L);
            return 1;
        }

        /* n >= 0 && n < r->ncaptures */

        cap = r->captures;

        p = r->captures_data;

        val = &p[cap[n]];

        lua_pushlstring(L, (const char *) val, (size_t) (cap[n + 1] - cap[n]));

        return 1;
    }
#endif

    p = (u_char *) luaL_checklstring(L, -1, &len);

    lowcase = ngx_palloc(r->pool, len);
    if (lowcase == NULL) {
        return luaL_error(L, "memory allocation error");
    }

    hash = ngx_hash_strlow(lowcase, p, len);

    name.len = len;
    name.data = lowcase;

    vv = ngx_http_get_variable(r, &name, hash);

    if (vv == NULL || vv->not_found) {
        lua_pushnil(L);
        return 1;
    }

    lua_pushlstring(L, (const char *) vv->data, (size_t) vv->len);

    return 1;
}


/**
 * Set nginx internal variable content
 *
 * @retval Always return a boolean on Lua stack. Return true when variable
 * content was modified successfully, false otherwise.
 * @seealso ngx_http_lua_var_get
 * */
static int
ngx_http_lua_var_set(lua_State *L)
{
    ngx_http_variable_t         *v;
    ngx_http_variable_value_t   *vv;
    ngx_http_core_main_conf_t   *cmcf;
    u_char                      *p, *lowcase, *val;
    size_t                       len;
    ngx_str_t                    name;
    ngx_uint_t                   hash;
    ngx_http_request_t          *r;
    int                          value_type;
    const char                  *msg;

    lua_getglobal(L, GLOBALS_SYMBOL_REQUEST);
    r = lua_touserdata(L, -1);
    lua_pop(L, 1);

    if (r == NULL) {
        return luaL_error(L, "no request object found");
    }

    /* we skip the first argument that is the table */

    /* we read the variable name */

    p = (u_char *) luaL_checklstring(L, 2, &len);

    lowcase = ngx_palloc(r->pool, len + 1);
    if (lowcase == NULL) {
        return luaL_error(L, "memory allocation error");
    }

    lowcase[len] = '\0';

    hash = ngx_hash_strlow(lowcase, p, len);

    name.len = len;
    name.data = lowcase;

    /* we read the variable new value */

    value_type = lua_type(L, 3);
    switch (value_type) {
    case LUA_TNUMBER:
    case LUA_TSTRING:
        p = (u_char *) luaL_checklstring(L, 3, &len);

        val = ngx_palloc(r->pool, len);
        if (val == NULL) {
            return luaL_error(L, "memory allocation erorr");
        }

        ngx_memcpy(val, p, len);

        break;

    case LUA_TNIL:
        /* undef the variable */

        val = NULL;
        len = 0;

        break;

    default:
        msg = lua_pushfstring(L, "string, number, or nil expected, "
                "but got %s", lua_typename(L, value_type));
        return luaL_argerror(L, 1, msg);
    }

    /* we fetch the variable itself */

    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);

    v = ngx_hash_find(&cmcf->variables_hash, hash, name.data, name.len);

    if (v) {
        if (!(v->flags & NGX_HTTP_VAR_CHANGEABLE)) {
            return luaL_error(L, "variable \"%s\" not changeable", lowcase);
        }

        if (v->set_handler) {

            dd("set variables with set_handler");

            vv = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t));
            if (vv == NULL) {
                return luaL_error(L, "out of memory");
            }

            if (value_type == LUA_TNIL) {
                vv->valid = 0;
                vv->not_found = 1;
                vv->no_cacheable = 0;
                vv->data = NULL;
                vv->len = 0;

            } else {
                vv->valid = 1;
                vv->not_found = 0;
                vv->no_cacheable = 0;

                vv->data = val;
                vv->len = len;
            }

            v->set_handler(r, vv, v->data);

            return 0;
        }

        if (v->flags & NGX_HTTP_VAR_INDEXED) {
            vv = &r->variables[v->index];

            dd("set indexed variable");

            if (value_type == LUA_TNIL) {
                vv->valid = 0;
                vv->not_found = 1;
                vv->no_cacheable = 0;

                vv->data = NULL;
                vv->len = 0;

            } else {
                vv->valid = 1;
                vv->not_found = 0;
                vv->no_cacheable = 0;

                vv->data = val;
                vv->len = len;
            }

            return 0;
        }

        return luaL_error(L, "variable \"%s\" cannot be assigned a value",
                lowcase);
    }

    /* variable not found */

    return luaL_error(L, "varaible \"%s\" not found for writing; "
                "maybe it is a built-in variable that is not changeable "
                "or you sould have used \"set $%s '';\" earlier "
                "in the config file", lowcase, lowcase);
}