/* Copyright 2013-2016 Philipp Janda <siffiejoe@gmx.net>
 *
 * You may do anything with this work that copyright law would normally
 * restrict, so long as you retain the above notice(s) and this license
 * in all redistributed copies and derived works.  There is no warranty.
 */

#ifndef MOON_DLFIX_H_
#define MOON_DLFIX_H_

/* Provides a C function macro that tries to reopen the Lua library
 * in global mode, so that C extension modules do not have to be
 * relinked for Lua VMs in shared libraries.
 */

/* enable/disable debug output */
#if 0
#include <stdio.h>
#define MOON_DLFIX_DBG(_a) (printf _a)
#else
#define MOON_DLFIX_DBG(_a) ((void)0)
#endif

/* detect some form of UNIX, so that unistd.h can be included to
 * use other feature macros */
#if defined(unix) || defined(__unix) || defined(__unix__) || \
    defined(__TOS_AIX__) || defined(_SYSTYPE_BSD) ||         \
    (defined(__APPLE__) && defined(__MACH__)) ||             \
    defined(HAVE_UNISTD_H)

#include <unistd.h>
/* check for minimum POSIX version that specifies dlopen etc. */
#if (defined(_POSIX_VERSION) && _POSIX_VERSION >= 200112L) || \
    defined(HAVE_DLFCN_H)

#include <dlfcn.h>
/* check for the existence of the RTLD_NOLOAD flag
 * - GLIBC has it (since 2.2)
 * - FreeBSD has it
 * - ...
 */
#ifdef RTLD_NOLOAD

/* Lua VM library names to try
 * Most of them require the dev-package to be installed,
 * but guessing the real library names for multiple distros
 * is pretty difficult ...
 * If the library is not in the default search path you can
 * set LD_LIBRARY_PATH, or use MOON_DLFIX_LIBNAME to specify
 * an absolute path to the library.
 */
static char const *const moon_dlfix_lib_names[] = {
/* you can define your own custom name via compiler define: */
#ifdef MOON_DLFIX_LIBNAME
    MOON_DLFIX_LIBNAME,
#endif                /* custom Lua library name */
    "liblua5.4.so",   /* Lua 5.4, Debian/Ubuntu naming */
    "liblua5.4.so.0", /*   same with common SONAME */
    "liblua54.so",
    "liblua5.3.so",   /* Lua 5.3, Debian/Ubuntu naming */
    "liblua5.3.so.0", /*   same with common SONAME */
    "liblua53.so",
    "liblua5.2.so",   /* Lua 5.2, Debian/Ubuntu naming */
    "liblua5.2.so.0", /*   same with common SONAME */
    "liblua52.so",
    "liblua.so",      /* default name from Lua's makefile */
    "liblua5.1.so",   /* Lua 5.1, Debian/Ubuntu naming */
    "liblua5.1.so.0", /*   same with common SONAME */
    "liblua51.so",
    "libluajit-5.1.so",   /* LuaJIT default name */
    "libluajit-5.1.so.2", /*   common SONAME */
};

/* On some OSes we can iterate over all loaded libraries to
 * find the Lua shared object.
 */
#if defined(__linux__) && defined(_GNU_SOURCE)
#define MOON_DLFIX_DL_ITERATE_PHDR
#include <link.h>
#endif /* Linux with dl_iterate_phdr() function */
#if defined(__FreeBSD__) || defined(__DragonFly__) || \
    defined(__NetBSD__) || defined(__OpenBSD__)
#define MOON_DLFIX_DL_ITERATE_PHDR
#include <link.h>
#endif /* BSDs with dl_iterate_phdr() function */

#if !defined(MOON_DLFIX_FIND) && \
    defined(MOON_DLFIX_DL_ITERATE_PHDR)
#include <string.h>

#ifndef MOON_DLFIX_LIBPREFIX
#define MOON_DLFIX_LIBPREFIX "liblua"
#endif

static int moon_dlfix_cb(struct dl_phdr_info *info, size_t size,
                         void *data)
{
  int *found = data;
  void *dl = dlopen(info->dlpi_name, RTLD_LAZY);
  (void)size;
  MOON_DLFIX_DBG(("Checking ELF object '%s'.\n", info->dlpi_name));
  if (dl)
  {
    if (dlsym(dl, "lua_gettop"))
    {
      MOON_DLFIX_DBG(("'%s' does have Lua symbols.\n", info->dlpi_name));
      /* the Lua API could be in a dependency, so test the library
       * name for "liblua" */
      char const *libname = strrchr(info->dlpi_name, '/');
      if (libname)
        ++libname; /* skip slash */
      else
        libname = info->dlpi_name;
      if (0 == strncmp(libname, MOON_DLFIX_LIBPREFIX,
                       sizeof(MOON_DLFIX_LIBPREFIX) - 1))
      {
        void *dl2 = dlopen(info->dlpi_name,
                           RTLD_LAZY | RTLD_GLOBAL | RTLD_NOLOAD);
        if (dl2)
        {
          MOON_DLFIX_DBG(("Found and fixed Lua SO!\n"));
          dlclose(dl2);
          *found = 1;
        }
      }
    }
    dlclose(dl);
  }
  return *found;
}

static int moon_dlfix_find(void)
{
  int found = 0;
  MOON_DLFIX_DBG(("Iterating all loaded ELF objects ...\n"));
  return dl_iterate_phdr(moon_dlfix_cb, &found);
}
#define MOON_DLFIX_FIND() (moon_dlfix_find())
#endif /* has dl_iterate_phdr() function */

#if !defined(MOON_DLFIX_FIND)
/* dummy definition (always returns failure) */
#define MOON_DLFIX_FIND() (0)
#endif

/* Try to iterate all loaded shared libraries using a platform-
 * specific way to find a loaded Lua shared library.
 * If that fails, try a list of common library names.
 * In all cases reopen the Lua library using RTLD_GLOBAL and
 * RTLD_NOLOAD.
 */
#define MOON_DLFIX()                                                                       \
  do                                                                                       \
  {                                                                                        \
    if (!MOON_DLFIX_FIND())                                                                \
    {                                                                                      \
      unsigned i = 0;                                                                      \
      MOON_DLFIX_DBG(("Trying some common Lua library names ...\n"));                      \
      for (; i < sizeof(moon_dlfix_lib_names) / sizeof(*moon_dlfix_lib_names); ++i)        \
      {                                                                                    \
        void *dl = dlopen(moon_dlfix_lib_names[i], RTLD_LAZY | RTLD_GLOBAL | RTLD_NOLOAD); \
        MOON_DLFIX_DBG(("Trying '%s'.\n", moon_dlfix_lib_names[i]));                       \
        if (dl)                                                                            \
        {                                                                                  \
          MOON_DLFIX_DBG(("Fixed Lua SO.\n"));                                             \
          dlclose(dl);                                                                     \
          break;                                                                           \
        }                                                                                  \
      }                                                                                    \
    }                                                                                      \
  } while (0)

#endif /* has RTLD_NOLOAD */
#endif /* has dlfcn.h */
#endif /* has unistd.h */

/* define fallback */
#ifndef MOON_DLFIX
#define MOON_DLFIX() \
  (MOON_DLFIX_DBG(("moon_dlfix functionality not available!\n")))
#endif

#endif /* MOON_DLFIX_H_ */