query.c

/* Copyright  (C) 2010-2017 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------
 * The following license statement only applies to this file (query.c).
 * ---------------------------------------------------------------------------------------
 *
 * Permission is hereby granted, free of charge,
 * to any person obtaining a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifdef _WIN32
#include <direct.h>
#else
#include <unistd.h>
#endif
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>

#include <compat/fnmatch.h>
#include <compat/strl.h>
#include <string/stdstring.h>
#include <retro_miscellaneous.h>

#include "libretrodb.h"
#include "query.h"
#include "rmsgpack_dom.h"

#define MAX_ERROR_LEN   256
#define QUERY_MAX_ARGS  50

struct buffer
{
   const char *data;
   size_t len;
   ssize_t offset;
};

enum argument_type
{
   AT_FUNCTION,
   AT_VALUE
};

struct argument;

typedef struct rmsgpack_dom_value (*rarch_query_func)(
      struct rmsgpack_dom_value input,
      unsigned argc,
      const struct argument *argv
      );

struct invocation
{
   struct argument *argv;
   rarch_query_func func;
   unsigned argc;
};

struct argument
{
   union
   {
      struct rmsgpack_dom_value value;
      struct invocation invocation;
   } a;
   enum argument_type type;
};

struct query
{
   struct invocation root; /* ptr alignment */
   unsigned ref_count;
};

struct registered_func
{
   const char *name;
   rarch_query_func func;
};

/* Forward declarations */
static struct buffer query_parse_method_call(char *s, size_t len,
      struct buffer buff,
      struct invocation *invocation, const char **error);
static struct buffer query_parse_table(char *s,
      size_t len, struct buffer buff,
      struct invocation *invocation, const char **error);

/* Errors */
static struct rmsgpack_dom_value query_func_is_true(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument *argv)
{
   struct rmsgpack_dom_value res;

   res.type      = RDT_BOOL;
   res.val.bool_ = 0;

   if (!(argc > 0 || input.type != RDT_BOOL))
      res.val.bool_ = input.val.bool_;

   return res;
}

static struct rmsgpack_dom_value func_equals(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument * argv)
{
   struct argument arg;
   struct rmsgpack_dom_value res;

   res.type      = RDT_BOOL;
   res.val.bool_ = 0;

   if (argc == 1)
   {
      arg = argv[0];

      if (arg.type == AT_VALUE)
      {
         if (  input.type       == RDT_UINT && 
               arg.a.value.type == RDT_INT)
         {
            arg.a.value.type      = RDT_UINT;
            arg.a.value.val.uint_ = arg.a.value.val.int_;
         }
         res.val.bool_ = (rmsgpack_dom_value_cmp(&input, &arg.a.value) == 0);
      }
   }

   return res;
}

static struct rmsgpack_dom_value query_func_operator_or(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument * argv)
{
   unsigned i;
   struct rmsgpack_dom_value res;

   res.type      = RDT_BOOL;
   res.val.bool_ = 0;

   for (i = 0; i < argc; i++)
   {
      if (argv[i].type == AT_VALUE)
         res = func_equals(input, 1, &argv[i]);
      else
         res = query_func_is_true(
               argv[i].a.invocation.func(input,
                  argv[i].a.invocation.argc,
                  argv[i].a.invocation.argv
                  ), 0, NULL);

      if (res.val.bool_)
         break;
   }

   return res;
}

static struct rmsgpack_dom_value query_func_operator_and(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument * argv)
{
   unsigned i;
   struct rmsgpack_dom_value res;

   res.type      = RDT_BOOL;
   res.val.bool_ = 0;

   for (i = 0; i < argc; i++)
   {
      if (argv[i].type == AT_VALUE)
         res = func_equals(input, 1, &argv[i]);
      else
         res = query_func_is_true(
               argv[i].a.invocation.func(input,
                  argv[i].a.invocation.argc,
                  argv[i].a.invocation.argv
                  ),
               0, NULL);

      if (!res.val.bool_)
         break;
   }
   return res;
}

static struct rmsgpack_dom_value query_func_between(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument * argv)
{
   struct rmsgpack_dom_value res;

   res.type                       = RDT_BOOL;
   res.val.bool_                  = 0;

   if (argc != 2)
      return res;
   if (     argv[0].type != AT_VALUE 
         || argv[1].type != AT_VALUE)
      return res;
   if (     argv[0].a.value.type != RDT_INT 
         || argv[1].a.value.type != RDT_INT)
      return res;

   switch (input.type)
   {
      case RDT_INT:
         res.val.bool_ = (
               (input.val.int_ >= argv[0].a.value.val.int_)
               && (input.val.int_ <= argv[1].a.value.val.int_));
         break;
      case RDT_UINT:
         res.val.bool_ = (
               ((unsigned)input.val.int_ >= argv[0].a.value.val.uint_)
               && (input.val.int_ <= argv[1].a.value.val.int_));
         break;
      default:
         break;
   }

   return res;
}

static struct rmsgpack_dom_value query_func_glob(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument * argv)
{
   struct rmsgpack_dom_value res;
   unsigned i    = 0;

   res.type      = RDT_BOOL;
   res.val.bool_ = 0;

   (void)i;

   if (argc != 1)
      return res;
   if (argv[0].type != AT_VALUE || argv[0].a.value.type != RDT_STRING)
      return res;
   if (input.type != RDT_STRING)
      return res;
   res.val.bool_ = rl_fnmatch(
         argv[0].a.value.val.string.buff,
         input.val.string.buff,
         0
         ) == 0;
   return res;
}

struct registered_func registered_functions[100] = {
   {"is_true", query_func_is_true},
   {"or",      query_func_operator_or},
   {"and",     query_func_operator_and},
   {"between", query_func_between},
   {"glob",    query_func_glob},
   {NULL, NULL}
};

static void query_raise_unknown_function(
      char *s, size_t _len,
      ssize_t where, const char *name,
      ssize_t len, const char **error)
{
   int n = snprintf(s, _len,
         "%" PRIu64 "::Unknown function '",
         (uint64_t)where
         );

   if (len < (_len - n - 3))
      strncpy(s + n, name, len);

   strcpy_literal(s + n + len, "'");
   *error = s;
}

static void query_argument_free(struct argument *arg)
{
   unsigned i;

   if (arg->type != AT_FUNCTION)
   {
      rmsgpack_dom_value_free(&arg->a.value);
      return;
   }

   for (i = 0; i < arg->a.invocation.argc; i++)
      query_argument_free(&arg->a.invocation.argv[i]);

   free((void*)arg->a.invocation.argv);
}

static struct buffer query_parse_integer(
      char *s, size_t len, 
      struct buffer buff,
      struct rmsgpack_dom_value *value,
      const char **error)
{
   bool test   = false;

   value->type = RDT_INT;

   test        = (sscanf(buff.data + buff.offset,
                         STRING_REP_INT64,
                         (int64_t*)&value->val.int_) == 0);

   if (test)
   {
      snprintf(s, len,
            "%" PRIu64 "::Expected number",
            (uint64_t)buff.offset);
      *error = s;
   }
   else
   {
      while (ISDIGIT((int)buff.data[buff.offset]))
         buff.offset++;
   }

   return buff;
}

static struct buffer query_chomp(struct buffer buff)
{
   for (; (unsigned)buff.offset < buff.len
         && ISSPACE((int)buff.data[buff.offset]); buff.offset++);
   return buff;
}

static struct buffer query_expect_eof(char *s, size_t len,
      struct buffer buff, const char ** error)
{
   buff = query_chomp(buff);
   if ((unsigned)buff.offset < buff.len)
   {
      snprintf(s, len,
            "%" PRIu64 "::Expected EOF found '%c'",
            (uint64_t)buff.offset,
            buff.data[buff.offset]
            );
      *error = s;
   }
   return buff;
}

static int query_peek(struct buffer buff, const char * data,
      size_t size_data)
{
   size_t remain    = buff.len - buff.offset;
   if (remain < size_data)
      return 0;
   return (strncmp(buff.data + buff.offset,
            data, size_data) == 0);
}

static int query_is_eot(struct buffer buff)
{
   return ((unsigned)buff.offset >= buff.len);
}

static struct buffer query_get_char(
      char *s, size_t len,
      struct buffer buff, char * c,
      const char ** error)
{
   if (query_is_eot(buff))
   {
      snprintf(s, len,
            "%" PRIu64 "::Unexpected EOF",
            (uint64_t)buff.offset
            );
      *error = s;
      return buff;
   }

   *c = buff.data[buff.offset];
   buff.offset++;
   return buff;
}

static struct buffer query_parse_string(
      char *s, size_t len,
      struct buffer buff,
      struct rmsgpack_dom_value *value, const char **error)
{
   const char * str_start = NULL;
   char terminator        = '\0';
   char c                 = '\0';
   int  is_binstr         = 0;
   buff = query_get_char(s, len,buff, &terminator, error);

   if (*error)
      return buff;

   if (terminator == 'b')
   {
      is_binstr = 1;
      buff      = query_get_char(s, len,
             buff, &terminator, error);
   }

   if (terminator != '"' && terminator != '\'')
   {
      buff.offset--;
      snprintf(s, len,
            "%" PRIu64 "::Expected string",
            (uint64_t)buff.offset);
      *error = s;
   }

   str_start = buff.data + buff.offset;
   buff      = query_get_char(s, len, buff, &c, error);

   while (!*error)
   {
      if (c == terminator)
         break;
      buff = query_get_char(s, len, buff, &c, error);
   }

   if (!*error)
   {
      size_t count;
      value->type            = is_binstr ? RDT_BINARY : RDT_STRING;
      value->val.string.len  = (uint32_t)((buff.data + buff.offset) - str_start - 1);

      count                  = is_binstr ? (value->val.string.len + 1) / 2
         : (value->val.string.len + 1);
      value->val.string.buff = (char*)calloc(count, sizeof(char));

      if (!value->val.string.buff)
      {
         strcpy_literal(s, "Out of memory");
         *error = s;
      }
      else if (is_binstr)
      {
         unsigned i;
         const char *tok = str_start;
         unsigned      j = 0;

         for (i = 0; i < value->val.string.len; i += 2)
         {
            uint8_t hi, lo;
            char hic = tok[i];
            char loc = tok[i + 1];

            if (hic <= '9')
               hi = hic - '0';
            else
               hi = (hic - 'A') + 10;

            if (loc <= '9')
               lo = loc - '0';
            else
               lo = (loc - 'A') + 10;

            value->val.string.buff[j++] = hi * 16 + lo;
         }

         value->val.string.len = j;
      }
      else
         memcpy(value->val.string.buff, str_start, value->val.string.len);
   }
   return buff;
}

static struct buffer query_parse_value(
      char *s, size_t len,
      struct buffer buff,
      struct rmsgpack_dom_value *value, const char **error)
{
   buff                 = query_chomp(buff);

   if (query_peek(buff, "nil", STRLEN_CONST("nil")))
   {
      buff.offset      += STRLEN_CONST("nil");
      value->type       = RDT_NULL;
   }
   else if (query_peek(buff, "true", STRLEN_CONST("true")))
   {
      buff.offset      += STRLEN_CONST("true");
      value->type       = RDT_BOOL;
      value->val.bool_  = 1;
   }
   else if (query_peek(buff, "false", STRLEN_CONST("false")))
   {
      buff.offset       += STRLEN_CONST("false");
      value->type        = RDT_BOOL;
      value->val.bool_   = 0;
   }
   else if (
         query_peek(buff, "b", STRLEN_CONST("b"))  || 
         query_peek(buff, "\"", STRLEN_CONST("\"")) ||
         query_peek(buff, "'", STRLEN_CONST("'")))
      buff = query_parse_string(s, len,
             buff, value, error);
   else if (ISDIGIT((int)buff.data[buff.offset]))
      buff = query_parse_integer(s, len, buff, value, error);
   return buff;
}

static void query_peek_char(char *s, size_t len,
      struct buffer buff, char *c,
      const char **error)
{
   if (query_is_eot(buff))
   {
      snprintf(s, len,
            "%" PRIu64 "::Unexpected EOF",
            (uint64_t)buff.offset
            );
      *error = s;
      return;
   }

   *c = buff.data[buff.offset];
}

static struct buffer query_get_ident(
      char *s, size_t _len,
      struct buffer buff,
      const char **ident,
      size_t *len, const char **error)
{
   char c = '\0';

   if (query_is_eot(buff))
   {
      snprintf(s, _len,
            "%" PRIu64 "::Unexpected EOF",
            (uint64_t)buff.offset
            );
      *error = s;
      return buff;
   }

   *ident = buff.data + buff.offset;
   *len   = 0;
   query_peek_char(s, _len, buff, &c, error);

   if (*error || !ISALPHA((int)c))
      return buff;

   buff.offset++;
   *len = *len + 1;
   query_peek_char(s, _len, buff, &c, error);

   while (!*error)
   {
      if (!(ISALNUM((int)c) || c == '_'))
         break;
      buff.offset++;
      *len = *len + 1;
      query_peek_char(s, _len, buff, &c, error);
   }

   return buff;
}

static struct buffer query_expect_char(
      char *s, size_t len,
      struct buffer buff,
      char c, const char ** error)
{
   if ((unsigned)buff.offset >= buff.len)
   {
      snprintf(s, len,
            "%" PRIu64 "::Unexpected EOF",
            (uint64_t)buff.offset
            );
      *error = s;
   }
   else if (buff.data[buff.offset] != c)
   {
      snprintf(s, len,
            "%" PRIu64 "::Expected '%c' found '%c'",
            (uint64_t)buff.offset, c, buff.data[buff.offset]);
      *error = s;
   }
   else
      buff.offset++;
   return buff;
}

static struct buffer query_parse_argument(
      char *s, size_t len,
      struct buffer buff,
      struct argument *arg, const char **error)
{
   buff = query_chomp(buff);

   if (
         ISALPHA((int)buff.data[buff.offset])
         && !(
               query_peek(buff, "nil",   STRLEN_CONST("nil"))
            || query_peek(buff, "true",  STRLEN_CONST("true"))
            || query_peek(buff, "false", STRLEN_CONST("false"))
            || query_peek(buff, "b\"",   STRLEN_CONST("b\""))
            || query_peek(buff, "b'",    STRLEN_CONST("b'"))
            /* bin string prefix*/
            )
      )
   {
      arg->type = AT_FUNCTION;
      buff      = query_parse_method_call(s, len, buff,
            &arg->a.invocation, error);
   }
   else if (query_peek(buff, "{", STRLEN_CONST("{")))
   {
      arg->type = AT_FUNCTION;
      buff      = query_parse_table(s, len,
                  buff, &arg->a.invocation, error);
   }
   else
   {
      arg->type = AT_VALUE;
      buff      = query_parse_value(s,
                  len, buff, &arg->a.value, error);
   }
   return buff;
}

static struct buffer query_parse_method_call(
      char *s, size_t len, struct buffer buff,
      struct invocation *invocation, const char **error)
{
   size_t func_name_len;
   unsigned i;
   struct argument args[QUERY_MAX_ARGS];
   unsigned argi              = 0;
   const char *func_name      = NULL;
   struct registered_func *rf = registered_functions;

   invocation->func           = NULL;

   buff                       = query_get_ident(s, len,
         buff, &func_name, &func_name_len, error);
   if (*error)
      goto clean;

   buff                       = query_chomp(buff);
   buff                       = query_expect_char(s, len, buff, '(', error);
   if (*error)
      goto clean;

   while (rf->name)
   {
      if (strncmp(rf->name, func_name, func_name_len) == 0)
      {
         invocation->func = rf->func;
         break;
      }
      rf++;
   }

   if (!invocation->func)
   {
      query_raise_unknown_function(s, len,
            buff.offset, func_name,
            func_name_len, error);
      goto clean;
   }

   buff = query_chomp(buff);
   while (!query_peek(buff, ")", STRLEN_CONST(")")))
   {
      if (argi >= QUERY_MAX_ARGS)
      {
         strcpy_literal(s,
               "Too many arguments in function call.");
         *error = s;
         goto clean;
      }

      buff = query_parse_argument(s, len, buff, &args[argi], error);

      if (*error)
         goto clean;

      argi++;
      buff = query_chomp(buff);
      buff = query_expect_char(s, len, buff, ',', error);

      if (*error)
      {
         *error = NULL;
         break;
      }
      buff = query_chomp(buff);
   }
   buff = query_expect_char(s, len, buff, ')', error);

   if (*error)
      goto clean;

   invocation->argc = argi;
   invocation->argv = (argi > 0) ? (struct argument*)
      malloc(sizeof(struct argument) * argi) : NULL;

   if (!invocation->argv)
   {
      strcpy_literal(s, "Out of memory");
      *error = s;
      goto clean;
   }
   memcpy(invocation->argv, args,
         sizeof(struct argument) * argi);

   return buff;

clean:
   for (i = 0; i < argi; i++)
      query_argument_free(&args[i]);
   return buff;
}

static struct rmsgpack_dom_value query_func_all_map(
      struct rmsgpack_dom_value input,
      unsigned argc, const struct argument *argv)
{
   unsigned i;
   struct argument arg;
   struct rmsgpack_dom_value res;
   struct rmsgpack_dom_value nil_value;
   struct rmsgpack_dom_value *value = NULL;

   res.type       = RDT_BOOL;
   res.val.bool_  = 1;

   nil_value.type = RDT_NULL;

   if (argc % 2 != 0)
   {
      res.val.bool_ = 0;
      return res;
   }

   if (input.type != RDT_MAP)
      return res;

   for (i = 0; i < argc; i += 2)
   {
      arg = argv[i];
      if (arg.type != AT_VALUE)
      {
         res.val.bool_ = 0;
         return res;
      }
      value = rmsgpack_dom_value_map_value(&input, &arg.a.value);
      if (!value) /* All missing fields are nil */
         value = &nil_value;
      arg = argv[i + 1];
      if (arg.type == AT_VALUE)
         res = func_equals(*value, 1, &arg);
      else
      {
         res = query_func_is_true(arg.a.invocation.func(
                  *value,
                  arg.a.invocation.argc,
                  arg.a.invocation.argv
                  ), 0, NULL);
         value = NULL;
      }
      if (!res.val.bool_)
         break;
   }
   return res;
}

static struct buffer query_parse_table(
      char *s, size_t len,
      struct buffer buff,
      struct invocation *invocation, const char **error)
{
   unsigned i;
   size_t ident_len;
   struct argument args[QUERY_MAX_ARGS];
   const char *ident_name = NULL;
   unsigned argi = 0;

   buff = query_chomp(buff);
   buff = query_expect_char(s, len, buff, '{', error);

   if (*error)
      goto clean;

   buff = query_chomp(buff);

   while (!query_peek(buff, "}", STRLEN_CONST("}")))
   {
      if (argi >= QUERY_MAX_ARGS)
      {
         strcpy_literal(s,
               "Too many arguments in function call.");
         *error = s;
         goto clean;
      }

      if (ISALPHA((int)buff.data[buff.offset]))
      {
         buff = query_get_ident(s, len,
               buff, &ident_name, &ident_len, error);

         if (!*error)
         {
            args[argi].a.value.type            = RDT_STRING;
            args[argi].a.value.val.string.len  = (uint32_t)ident_len;
            args[argi].a.value.val.string.buff = (char*)calloc(
                  ident_len + 1,
                  sizeof(char)
                  );

            if (!args[argi].a.value.val.string.buff)
               goto clean;

            strncpy(
                  args[argi].a.value.val.string.buff,
                  ident_name,
                  ident_len
                  );
         }
      }
      else
         buff = query_parse_string(s, len,
               buff, &args[argi].a.value, error);

      if (*error)
         goto clean;

      args[argi].type = AT_VALUE;
      buff            = query_chomp(buff);
      argi++;
      buff            = query_expect_char(s, len, buff, ':', error);

      if (*error)
         goto clean;

      buff = query_chomp(buff);

      if (argi >= QUERY_MAX_ARGS)
      {
         strcpy_literal(s,
               "Too many arguments in function call.");
         *error = s;
         goto clean;
      }

      buff = query_parse_argument(s, len, buff, &args[argi], error);

      if (*error)
         goto clean;
      argi++;
      buff = query_chomp(buff);
      buff = query_expect_char(s, len, buff, ',', error);

      if (*error)
      {
         *error = NULL;
         break;
      }
      buff = query_chomp(buff);
   }

   buff = query_expect_char(s, len, buff, '}', error);

   if (*error)
      goto clean;

   invocation->func = query_func_all_map;
   invocation->argc = argi;
   invocation->argv = (struct argument*)
      malloc(sizeof(struct argument) * argi);

   if (!invocation->argv)
   {
      strcpy_literal(s, "Out of memory");
      *error = s;
      goto clean;
   }
   memcpy(invocation->argv, args,
         sizeof(struct argument) * argi);

   return buff;

clean:
   for (i = 0; i < argi; i++)
      query_argument_free(&args[i]);
   return buff;
}

void libretrodb_query_free(void *q)
{
   unsigned i;
   struct query *real_q = (struct query*)q;

   real_q->ref_count--;
   if (real_q->ref_count > 0)
      return;

   for (i = 0; i < real_q->root.argc; i++)
      query_argument_free(&real_q->root.argv[i]);

   free(real_q->root.argv);
   real_q->root.argv = NULL;
   real_q->root.argc = 0;
   free(real_q);
}

void *libretrodb_query_compile(libretrodb_t *db,
      const char *query, size_t buff_len, const char **error_string)
{
   struct buffer buff;
   /* TODO/FIXME - static local variable */
   static char tmp_error_buff [MAX_ERROR_LEN] = {0};
   struct query *q       = (struct query*)malloc(sizeof(*q));
   size_t error_buff_len = sizeof(tmp_error_buff);

   if (!q)
      return NULL;

   q->ref_count          = 1;
   q->root.argc          = 0;
   q->root.func          = NULL;
   q->root.argv          = NULL;

   buff.data             = query;
   buff.len              = buff_len;
   buff.offset           = 0;
   *error_string         = NULL;

   buff                  = query_chomp(buff);

   if (query_peek(buff, "{", STRLEN_CONST("{")))
   {
      buff = query_parse_table(tmp_error_buff,
            error_buff_len, buff, &q->root, error_string);
      if (*error_string)
         goto error;
   }
   else if (ISALPHA((int)buff.data[buff.offset]))
      buff = query_parse_method_call(tmp_error_buff,
            error_buff_len,
            buff, &q->root, error_string);

   buff = query_expect_eof(tmp_error_buff,
            error_buff_len,
            buff, error_string);

   if (*error_string)
      goto error;

   if (!q->root.func)
   {
      snprintf(tmp_error_buff, error_buff_len,
            "%" PRIu64 "::Unexpected EOF",
            (uint64_t)buff.offset
            );
      *error_string = tmp_error_buff;
      goto error;
   }

   return q;

error:
   if (q)
      libretrodb_query_free(q);
   return NULL;
}

void libretrodb_query_inc_ref(libretrodb_query_t *q)
{
   struct query *rq = (struct query*)q;
   if (rq)
      rq->ref_count += 1;
}

int libretrodb_query_filter(libretrodb_query_t *q,
      struct rmsgpack_dom_value *v)
{
   struct invocation inv = ((struct query *)q)->root;
   struct rmsgpack_dom_value res = inv.func(*v, inv.argc, inv.argv);
   return (res.type == RDT_BOOL && res.val.bool_);
}