/*
 * load methods from eval.c
 */

#include "ruby/ruby.h"
#include "ruby/util.h"
#include "internal.h"
#include "dln.h"
#include "eval_intern.h"

VALUE ruby_dln_librefs;

#define IS_RBEXT(e) (strcmp((e), ".rb") == 0)
#define IS_SOEXT(e) (strcmp((e), ".so") == 0 || strcmp((e), ".o") == 0)
#ifdef DLEXT2
#define IS_DLEXT(e) (strcmp((e), DLEXT) == 0 || strcmp((e), DLEXT2) == 0)
#else
#define IS_DLEXT(e) (strcmp((e), DLEXT) == 0)
#endif

static const char *const loadable_ext[] = {
    ".rb", DLEXT,
#ifdef DLEXT2
    DLEXT2,
#endif
    0
};

VALUE
rb_get_load_path(void)
{
    VALUE load_path = GET_VM()->load_path;
    return load_path;
}

VALUE
rb_get_expanded_load_path(void)
{
    VALUE load_path = rb_get_load_path();
    VALUE ary;
    long i;

    ary = rb_ary_new2(RARRAY_LEN(load_path));
    for (i = 0; i < RARRAY_LEN(load_path); ++i) {
	VALUE path = rb_file_expand_path_fast(RARRAY_PTR(load_path)[i], Qnil);
	rb_str_freeze(path);
	rb_ary_push(ary, path);
    }
    rb_obj_freeze(ary);
    return ary;
}

static VALUE
load_path_getter(ID id, rb_vm_t *vm)
{
    return vm->load_path;
}

static VALUE
get_loaded_features(void)
{
    return GET_VM()->loaded_features;
}

static void
reset_loaded_features_snapshot(void)
{
    rb_vm_t *vm = GET_VM();
    rb_ary_replace(vm->loaded_features_snapshot, vm->loaded_features);
}

static VALUE
get_loaded_features_index_raw(void)
{
    return GET_VM()->loaded_features_index;
}

static st_table *
get_loading_table(void)
{
    return GET_VM()->loading_table;
}

static void
features_index_add_single(VALUE short_feature, VALUE offset)
{
    VALUE features_index, this_feature_index;
    features_index = get_loaded_features_index_raw();
    if ((this_feature_index = rb_hash_lookup(features_index, short_feature)) == Qnil) {
	this_feature_index = rb_ary_new();
	rb_hash_aset(features_index, short_feature, this_feature_index);
    }
    rb_ary_push(this_feature_index, offset);
}

/* Add to the loaded-features index all the required entries for
   `feature`, located at `offset` in $LOADED_FEATURES.  We add an
   index entry at each string `short_feature` for which
     feature == "#{prefix}#{short_feature}#{e}"
   where `e` is empty or matches %r{^\.[^./]*$}, and `prefix` is empty
   or ends in '/'.  This maintains the invariant that `rb_feature_p()`
   relies on for its fast lookup.
*/
static void
features_index_add(VALUE feature, VALUE offset)
{
    VALUE short_feature;
    const char *feature_str, *feature_end, *ext, *p;

    feature_str = StringValuePtr(feature);
    feature_end = feature_str + RSTRING_LEN(feature);

    for (ext = feature_end; ext > feature_str; ext--)
      if (*ext == '.' || *ext == '/')
	break;
    if (*ext != '.')
      ext = NULL;
    /* Now `ext` points to the only string matching %r{^\.[^./]*$} that is
       at the end of `feature`, or is NULL if there is no such string. */

    p = ext ? ext : feature_end;
    while (1) {
	p--;
	while (p >= feature_str && *p != '/')
	    p--;
	if (p < feature_str)
	    break;
	/* Now *p == '/'.  We reach this point for every '/' in `feature`. */
	short_feature = rb_str_substr(feature, p + 1 - feature_str, feature_end - p - 1);
	features_index_add_single(short_feature, offset);
	if (ext) {
	    short_feature = rb_str_substr(feature, p + 1 - feature_str, ext - p - 1);
	    features_index_add_single(short_feature, offset);
	}
    }
    features_index_add_single(feature, offset);
    if (ext) {
	short_feature = rb_str_substr(feature, 0, ext - feature_str);
	features_index_add_single(short_feature, offset);
    }
}

static VALUE
get_loaded_features_index(void)
{
    VALUE features;
    int i;
    rb_vm_t *vm = GET_VM();

    if (!rb_ary_shared_with_p(vm->loaded_features_snapshot, vm->loaded_features)) {
	/* The sharing was broken; something (other than us in rb_provide_feature())
	   modified loaded_features.  Rebuild the index. */
	rb_hash_clear(vm->loaded_features_index);
	features = vm->loaded_features;
	for (i = 0; i < RARRAY_LEN(features); i++) {
	    VALUE entry, as_str;
	    as_str = entry = rb_ary_entry(features, i);
	    StringValue(as_str);
	    if (as_str != entry)
		rb_ary_store(features, i, as_str);
	    rb_str_freeze(as_str);
	    features_index_add(as_str, INT2FIX(i));
	}
	reset_loaded_features_snapshot();
    }
    return vm->loaded_features_index;
}

/* This searches `load_path` for a value such that
     name == "#{load_path[i]}/#{feature}"
   if `feature` is a suffix of `name`, or otherwise
     name == "#{load_path[i]}/#{feature}#{ext}"
   for an acceptable string `ext`.  It returns
   `load_path[i].to_str` if found, else 0.

   If type is 's', then `ext` is acceptable only if IS_DLEXT(ext);
   if 'r', then only if IS_RBEXT(ext); otherwise `ext` may be absent
   or have any value matching `%r{^\.[^./]*$}`.
*/
static VALUE
loaded_feature_path(const char *name, long vlen, const char *feature, long len,
		    int type, VALUE load_path)
{
    long i;
    long plen;
    const char *e;

    if (vlen < len+1) return 0;
    if (!strncmp(name+(vlen-len), feature, len)) {
	plen = vlen - len - 1;
    }
    else {
	for (e = name + vlen; name != e && *e != '.' && *e != '/'; --e);
	if (*e != '.' ||
	    e-name < len ||
	    strncmp(e-len, feature, len))
	    return 0;
	plen = e - name - len - 1;
    }
    if (type == 's' && !IS_DLEXT(&name[plen+len+1])
     || type == 'r' && !IS_RBEXT(&name[plen+len+1])
     || name[plen] != '/') {
       return 0;
    }
    /* Now name == "#{prefix}/#{feature}#{ext}" where ext is acceptable
       (possibly empty) and prefix is some string of length plen. */

    for (i = 0; i < RARRAY_LEN(load_path); ++i) {
	VALUE p = RARRAY_PTR(load_path)[i];
	const char *s = StringValuePtr(p);
	long n = RSTRING_LEN(p);

	if (n != plen) continue;
	if (n && strncmp(name, s, n)) continue;
	return p;
    }
    return 0;
}

struct loaded_feature_searching {
    const char *name;
    long len;
    int type;
    VALUE load_path;
    const char *result;
};

static int
loaded_feature_path_i(st_data_t v, st_data_t b, st_data_t f)
{
    const char *s = (const char *)v;
    struct loaded_feature_searching *fp = (struct loaded_feature_searching *)f;
    VALUE p = loaded_feature_path(s, strlen(s), fp->name, fp->len,
				  fp->type, fp->load_path);
    if (!p) return ST_CONTINUE;
    fp->result = s;
    return ST_STOP;
}

static int
rb_feature_p(const char *feature, const char *ext, int rb, int expanded, const char **fn)
{
    VALUE features, features_index, feature_val, this_feature_index, v, p, load_path = 0;
    const char *f, *e;
    long i, len, elen, n;
    st_table *loading_tbl;
    st_data_t data;
    int type;

    if (fn) *fn = 0;
    if (ext) {
	elen = strlen(ext);
	len = strlen(feature) - elen;
	type = rb ? 'r' : 's';
    }
    else {
	len = strlen(feature);
	elen = 0;
	type = 0;
    }
    features = get_loaded_features();
    features_index = get_loaded_features_index();

    feature_val = rb_str_new(feature, len);
    this_feature_index = rb_hash_lookup(features_index, feature_val);
    /* We search `features` for an entry such that either
         "#{features[i]}" == "#{load_path[j]}/#{feature}#{e}"
       for some j, or
         "#{features[i]}" == "#{feature}#{e}"
       Here `e` is an "allowed" extension -- either empty or one
       of the extensions accepted by IS_RBEXT, IS_SOEXT, or
       IS_DLEXT.  Further, if `ext && rb` then `IS_RBEXT(e)`,
       and if `ext && !rb` then `IS_SOEXT(e) || IS_DLEXT(e)`.

       If `expanded`, then only the latter form (without load_path[j])
       is accepted.  Otherwise either form is accepted, *unless* `ext`
       is false and an otherwise-matching entry of the first form is
       preceded by an entry of the form
         "#{features[i2]}" == "#{load_path[j2]}/#{feature}#{e2}"
       where `e2` matches %r{^\.[^./]*$} but is not an allowed extension.
       After a "distractor" entry of this form, only entries of the
       form "#{feature}#{e}" are accepted.

       In `rb_provide_feature()` and `get_loaded_features_index()` we
       maintain an invariant that the array `this_feature_index` will
       point to every entry in `features` which has the form
         "#{prefix}#{feature}#{e}"
       where `e` is empty or matches %r{^\.[^./]*$}, and `prefix` is empty
       or ends in '/'.  This includes both match forms above, as well
       as any distractors, so we may ignore all other entries in `features`.
     */
    for (i = 0; this_feature_index != Qnil && i < RARRAY_LEN(this_feature_index); i++) {
	long index = FIX2LONG(rb_ary_entry(this_feature_index, i));
	v = RARRAY_PTR(features)[index];
	f = StringValuePtr(v);
	if ((n = RSTRING_LEN(v)) < len) continue;
	if (strncmp(f, feature, len) != 0) {
	    if (expanded) continue;
	    if (!load_path) load_path = rb_get_expanded_load_path();
	    if (!(p = loaded_feature_path(f, n, feature, len, type, load_path)))
		continue;
	    expanded = 1;
	    f += RSTRING_LEN(p) + 1;
	}
	if (!*(e = f + len)) {
	    if (ext) continue;
	    return 'u';
	}
	if (*e != '.') continue;
	if ((!rb || !ext) && (IS_SOEXT(e) || IS_DLEXT(e))) {
	    return 's';
	}
	if ((rb || !ext) && (IS_RBEXT(e))) {
	    return 'r';
	}
    }

    loading_tbl = get_loading_table();
    if (loading_tbl) {
	f = 0;
	if (!expanded) {
	    struct loaded_feature_searching fs;
	    fs.name = feature;
	    fs.len = len;
	    fs.type = type;
	    fs.load_path = load_path ? load_path : rb_get_expanded_load_path();
	    fs.result = 0;
	    st_foreach(loading_tbl, loaded_feature_path_i, (st_data_t)&fs);
	    if ((f = fs.result) != 0) {
		if (fn) *fn = f;
		goto loading;
	    }
	}
	if (st_get_key(loading_tbl, (st_data_t)feature, &data)) {
	    if (fn) *fn = (const char*)data;
	  loading:
	    if (!ext) return 'u';
	    return !IS_RBEXT(ext) ? 's' : 'r';
	}
	else {
	    VALUE bufstr;
	    char *buf;

	    if (ext && *ext) return 0;
	    bufstr = rb_str_tmp_new(len + DLEXT_MAXLEN);
	    buf = RSTRING_PTR(bufstr);
	    MEMCPY(buf, feature, char, len);
	    for (i = 0; (e = loadable_ext[i]) != 0; i++) {
		strlcpy(buf + len, e, DLEXT_MAXLEN + 1);
		if (st_get_key(loading_tbl, (st_data_t)buf, &data)) {
		    rb_str_resize(bufstr, 0);
		    if (fn) *fn = (const char*)data;
		    return i ? 's' : 'r';
		}
	    }
	    rb_str_resize(bufstr, 0);
	}
    }
    return 0;
}

int
rb_provided(const char *feature)
{
    return rb_feature_provided(feature, 0);
}

int
rb_feature_provided(const char *feature, const char **loading)
{
    const char *ext = strrchr(feature, '.');
    volatile VALUE fullpath = 0;

    if (*feature == '.' &&
	(feature[1] == '/' || strncmp(feature+1, "./", 2) == 0)) {
	fullpath = rb_file_expand_path_fast(rb_str_new2(feature), Qnil);
	feature = RSTRING_PTR(fullpath);
    }
    if (ext && !strchr(ext, '/')) {
	if (IS_RBEXT(ext)) {
	    if (rb_feature_p(feature, ext, TRUE, FALSE, loading)) return TRUE;
	    return FALSE;
	}
	else if (IS_SOEXT(ext) || IS_DLEXT(ext)) {
	    if (rb_feature_p(feature, ext, FALSE, FALSE, loading)) return TRUE;
	    return FALSE;
	}
    }
    if (rb_feature_p(feature, 0, TRUE, FALSE, loading))
	return TRUE;
    return FALSE;
}

static void
rb_provide_feature(VALUE feature)
{
    VALUE features;

    features = get_loaded_features();
    if (OBJ_FROZEN(features)) {
	rb_raise(rb_eRuntimeError,
		 "$LOADED_FEATURES is frozen; cannot append feature");
    }
    rb_str_freeze(feature);

    rb_ary_push(features, feature);
    features_index_add(feature, INT2FIX(RARRAY_LEN(features)-1));
    reset_loaded_features_snapshot();
}

void
rb_provide(const char *feature)
{
    rb_provide_feature(rb_usascii_str_new2(feature));
}

NORETURN(static void load_failed(VALUE));

static void
rb_load_internal(VALUE fname, int wrap)
{
    int state;
    rb_thread_t *th = GET_THREAD();
    volatile VALUE wrapper = th->top_wrapper;
    volatile VALUE self = th->top_self;
    volatile int loaded = FALSE;
    volatile int mild_compile_error;
#ifndef __GNUC__
    rb_thread_t *volatile th0 = th;
#endif

    th->errinfo = Qnil; /* ensure */

    if (!wrap) {
	rb_secure(4);		/* should alter global state */
	th->top_wrapper = 0;
    }
    else {
	/* load in anonymous module as toplevel */
	th->top_self = rb_obj_clone(rb_vm_top_self());
	th->top_wrapper = rb_module_new();
	rb_extend_object(th->top_self, th->top_wrapper);
    }

    mild_compile_error = th->mild_compile_error;
    PUSH_TAG();
    state = EXEC_TAG();
    if (state == 0) {
	NODE *node;
	VALUE iseq;

	th->mild_compile_error++;
	node = (NODE *)rb_load_file(RSTRING_PTR(fname));
	loaded = TRUE;
	iseq = rb_iseq_new_top(node, rb_str_new2("<top (required)>"), fname, rb_realpath_internal(Qnil, fname, 1), Qfalse);
	th->mild_compile_error--;
	rb_iseq_eval(iseq);
    }
    POP_TAG();

#ifndef __GNUC__
    th = th0;
    fname = RB_GC_GUARD(fname);
#endif
    th->mild_compile_error = mild_compile_error;
    th->top_self = self;
    th->top_wrapper = wrapper;

    if (!loaded && !FIXNUM_P(GET_THREAD()->errinfo)) {
	/* an error on loading don't include INT2FIX(TAG_FATAL) see r35625 */
	rb_exc_raise(GET_THREAD()->errinfo);
    }
    if (state) {
	rb_vm_jump_tag_but_local_jump(state, Qundef);
    }

    if (!NIL_P(GET_THREAD()->errinfo)) {
	/* exception during load */
	rb_exc_raise(th->errinfo);
    }
}

void
rb_load(VALUE fname, int wrap)
{
    VALUE tmp = rb_find_file(FilePathValue(fname));
    if (!tmp) load_failed(fname);
    rb_load_internal(tmp, wrap);
}

void
rb_load_protect(VALUE fname, int wrap, int *state)
{
    int status;

    PUSH_TAG();
    if ((status = EXEC_TAG()) == 0) {
	rb_load(fname, wrap);
    }
    POP_TAG();
    if (state)
	*state = status;
}

/*
 *  call-seq:
 *     load(filename, wrap=false)   -> true
 *
 *  Loads and executes the Ruby
 *  program in the file _filename_. If the filename does not
 *  resolve to an absolute path, the file is searched for in the library
 *  directories listed in <code>$:</code>. If the optional _wrap_
 *  parameter is +true+, the loaded script will be executed
 *  under an anonymous module, protecting the calling program's global
 *  namespace. In no circumstance will any local variables in the loaded
 *  file be propagated to the loading environment.
 */

static VALUE
rb_f_load(int argc, VALUE *argv)
{
    VALUE fname, wrap, path;

    rb_scan_args(argc, argv, "11", &fname, &wrap);
    path = rb_find_file(FilePathValue(fname));
    if (!path) {
	if (!rb_file_load_ok(RSTRING_PTR(fname)))
	    load_failed(fname);
	path = fname;
    }
    rb_load_internal(path, RTEST(wrap));
    return Qtrue;
}

static char *
load_lock(const char *ftptr)
{
    st_data_t data;
    st_table *loading_tbl = get_loading_table();

    if (!loading_tbl || !st_lookup(loading_tbl, (st_data_t)ftptr, &data)) {
	/* loading ruby library should be serialized. */
	if (!loading_tbl) {
	    GET_VM()->loading_table = loading_tbl = st_init_strtable();
	}
	/* partial state */
	ftptr = ruby_strdup(ftptr);
	data = (st_data_t)rb_thread_shield_new();
	st_insert(loading_tbl, (st_data_t)ftptr, data);
	return (char *)ftptr;
    }
    if (RTEST(ruby_verbose)) {
	rb_warning("loading in progress, circular require considered harmful - %s", ftptr);
	rb_backtrace();
    }
    switch (rb_thread_shield_wait((VALUE)data)) {
      case Qfalse:
	data = (st_data_t)ftptr;
	st_delete(loading_tbl, &data, 0);
	return 0;
      case Qnil:
	return 0;
    }
    return (char *)ftptr;
}

static int
release_thread_shield(st_data_t *key, st_data_t *value, st_data_t done, int existing)
{
    VALUE thread_shield = (VALUE)*value;
    if (!existing) return ST_STOP;
    if (done ? rb_thread_shield_destroy(thread_shield) : rb_thread_shield_release(thread_shield)) {
	/* still in-use */
	return ST_CONTINUE;
    }
    xfree((char *)*key);
    return ST_DELETE;
}

static void
load_unlock(const char *ftptr, int done)
{
    if (ftptr) {
	st_data_t key = (st_data_t)ftptr;
	st_table *loading_tbl = get_loading_table();

	st_update(loading_tbl, key, release_thread_shield, done);
    }
}


/*
 *  call-seq:
 *     require(name)    -> true or false
 *
 *  Loads the given +name+, returning +true+ if successful and +false+ if the
 *  feature is already loaded.
 *
 *  If the filename does not resolve to an absolute path, it will be searched
 *  for in the directories listed in <code>$LOAD_PATH</code> (<code>$:</code>).
 *
 *  If the filename has the extension ".rb", it is loaded as a source file; if
 *  the extension is ".so", ".o", or ".dll", or the default shared library
 *  extension on the current platform, Ruby loads the shared library as a
 *  Ruby extension.  Otherwise, Ruby tries adding ".rb", ".so", and so on
 *  to the name until found.  If the file named cannot be found, a LoadError
 *  will be raised.
 *
 *  For Ruby extensions the filename given may use any shared library
 *  extension.  For example, on Linux the socket extension is "socket.so" and
 *  <code>require 'socket.dll'</code> will load the socket extension.
 *
 *  The absolute path of the loaded file is added to
 *  <code>$LOADED_FEATURES</code> (<code>$"</code>).  A file will not be
 *  loaded again if its path already appears in <code>$"</code>.  For example,
 *  <code>require 'a'; require './a'</code> will not load <code>a.rb</code>
 *  again.
 *
 *    require "my-library.rb"
 *    require "db-driver"
 *
 *  Any constants or globals within the loaded source file will be available
 *  in the calling program's global namespace. However, local variables will
 *  not be propagated to the loading environment.
 *
 */

VALUE
rb_f_require(VALUE obj, VALUE fname)
{
    return rb_require_safe(fname, rb_safe_level());
}

/*
 * call-seq:
 *   require_relative(string) -> true or false
 *
 * Ruby tries to load the library named _string_ relative to the requiring
 * file's path.  If the file's path cannot be determined a LoadError is raised.
 * If a file is loaded +true+ is returned and false otherwise.
 */
VALUE
rb_f_require_relative(VALUE obj, VALUE fname)
{
    VALUE base = rb_current_realfilepath();
    if (NIL_P(base)) {
	rb_loaderror("cannot infer basepath");
    }
    base = rb_file_dirname(base);
    return rb_require_safe(rb_file_absolute_path(fname, base), rb_safe_level());
}

static int
search_required(VALUE fname, volatile VALUE *path, int safe_level)
{
    VALUE tmp;
    char *ext, *ftptr;
    int type, ft = 0;
    const char *loading;

    *path = 0;
    ext = strrchr(ftptr = RSTRING_PTR(fname), '.');
    if (ext && !strchr(ext, '/')) {
	if (IS_RBEXT(ext)) {
	    if (rb_feature_p(ftptr, ext, TRUE, FALSE, &loading)) {
		if (loading) *path = rb_filesystem_str_new_cstr(loading);
		return 'r';
	    }
	    if ((tmp = rb_find_file_safe(fname, safe_level)) != 0) {
		ext = strrchr(ftptr = RSTRING_PTR(tmp), '.');
		if (!rb_feature_p(ftptr, ext, TRUE, TRUE, &loading) || loading)
		    *path = tmp;
		return 'r';
	    }
	    return 0;
	}
	else if (IS_SOEXT(ext)) {
	    if (rb_feature_p(ftptr, ext, FALSE, FALSE, &loading)) {
		if (loading) *path = rb_filesystem_str_new_cstr(loading);
		return 's';
	    }
	    tmp = rb_str_subseq(fname, 0, ext - RSTRING_PTR(fname));
#ifdef DLEXT2
	    OBJ_FREEZE(tmp);
	    if (rb_find_file_ext_safe(&tmp, loadable_ext + 1, safe_level)) {
		ext = strrchr(ftptr = RSTRING_PTR(tmp), '.');
		if (!rb_feature_p(ftptr, ext, FALSE, TRUE, &loading) || loading)
		    *path = tmp;
		return 's';
	    }
#else
	    rb_str_cat2(tmp, DLEXT);
	    OBJ_FREEZE(tmp);
	    if ((tmp = rb_find_file_safe(tmp, safe_level)) != 0) {
		ext = strrchr(ftptr = RSTRING_PTR(tmp), '.');
		if (!rb_feature_p(ftptr, ext, FALSE, TRUE, &loading) || loading)
		    *path = tmp;
		return 's';
	    }
#endif
	}
	else if (IS_DLEXT(ext)) {
	    if (rb_feature_p(ftptr, ext, FALSE, FALSE, &loading)) {
		if (loading) *path = rb_filesystem_str_new_cstr(loading);
		return 's';
	    }
	    if ((tmp = rb_find_file_safe(fname, safe_level)) != 0) {
		ext = strrchr(ftptr = RSTRING_PTR(tmp), '.');
		if (!rb_feature_p(ftptr, ext, FALSE, TRUE, &loading) || loading)
		    *path = tmp;
		return 's';
	    }
	}
    }
    else if ((ft = rb_feature_p(ftptr, 0, FALSE, FALSE, &loading)) == 'r') {
	if (loading) *path = rb_filesystem_str_new_cstr(loading);
	return 'r';
    }
    tmp = fname;
    type = rb_find_file_ext_safe(&tmp, loadable_ext, safe_level);
    switch (type) {
      case 0:
	if (ft)
	    break;
	ftptr = RSTRING_PTR(tmp);
	return rb_feature_p(ftptr, 0, FALSE, TRUE, 0);

      default:
	if (ft)
	    break;
      case 1:
	ext = strrchr(ftptr = RSTRING_PTR(tmp), '.');
	if (rb_feature_p(ftptr, ext, !--type, TRUE, &loading) && !loading)
	    break;
	*path = tmp;
    }
    return type ? 's' : 'r';
}

static void
load_failed(VALUE fname)
{
    rb_load_fail(fname, "cannot load such file");
}

static VALUE
load_ext(VALUE path)
{
    SCOPE_SET(NOEX_PUBLIC);
    return (VALUE)dln_load(RSTRING_PTR(path));
}

VALUE
rb_require_safe(VALUE fname, int safe)
{
    volatile VALUE result = Qnil;
    rb_thread_t *th = GET_THREAD();
    volatile VALUE errinfo = th->errinfo;
    int state;
    struct {
	int safe;
    } volatile saved;
    char *volatile ftptr = 0;

    PUSH_TAG();
    saved.safe = rb_safe_level();
    if ((state = EXEC_TAG()) == 0) {
	VALUE path;
	long handle;
	int found;

	rb_set_safe_level_force(safe);
	FilePathValue(fname);
	rb_set_safe_level_force(0);
	found = search_required(fname, &path, safe);
	if (found) {
	    if (!path || !(ftptr = load_lock(RSTRING_PTR(path)))) {
		result = Qfalse;
	    }
	    else {
		switch (found) {
		  case 'r':
		    rb_load_internal(path, 0);
		    break;

		  case 's':
		    handle = (long)rb_vm_call_cfunc(rb_vm_top_self(), load_ext,
						    path, 0, path);
		    rb_ary_push(ruby_dln_librefs, LONG2NUM(handle));
		    break;
		}
		rb_provide_feature(path);
		result = Qtrue;
	    }
	}
    }
    POP_TAG();
    load_unlock(ftptr, !state);

    rb_set_safe_level_force(saved.safe);
    if (state) {
	JUMP_TAG(state);
    }

    if (NIL_P(result)) {
	load_failed(fname);
    }

    th->errinfo = errinfo;

    return result;
}

VALUE
rb_require(const char *fname)
{
    VALUE fn = rb_str_new2(fname);
    OBJ_FREEZE(fn);
    return rb_require_safe(fn, rb_safe_level());
}

static VALUE
init_ext_call(VALUE arg)
{
    SCOPE_SET(NOEX_PUBLIC);
    (*(void (*)(void))arg)();
    return Qnil;
}

RUBY_FUNC_EXPORTED void
ruby_init_ext(const char *name, void (*init)(void))
{
    char* const lock_key = load_lock(name);
    if (lock_key) {
	rb_vm_call_cfunc(rb_vm_top_self(), init_ext_call, (VALUE)init,
			 0, rb_str_new2(name));
	rb_provide(name);
	load_unlock(lock_key, 1);
    }
}

/*
 *  call-seq:
 *     mod.autoload(module, filename)   -> nil
 *
 *  Registers _filename_ to be loaded (using <code>Kernel::require</code>)
 *  the first time that _module_ (which may be a <code>String</code> or
 *  a symbol) is accessed in the namespace of _mod_.
 *
 *     module A
 *     end
 *     A.autoload(:B, "b")
 *     A::B.doit            # autoloads "b"
 */

static VALUE
rb_mod_autoload(VALUE mod, VALUE sym, VALUE file)
{
    ID id = rb_to_id(sym);

    FilePathValue(file);
    rb_autoload(mod, id, RSTRING_PTR(file));
    return Qnil;
}

/*
 *  call-seq:
 *     mod.autoload?(name)   -> String or nil
 *
 *  Returns _filename_ to be loaded if _name_ is registered as
 *  +autoload+ in the namespace of _mod_.
 *
 *     module A
 *     end
 *     A.autoload(:B, "b")
 *     A.autoload?(:B)            #=> "b"
 */

static VALUE
rb_mod_autoload_p(VALUE mod, VALUE sym)
{
    ID id = rb_check_id(&sym);
    if (!id) {
	return Qnil;
    }
    return rb_autoload_p(mod, id);
}

/*
 *  call-seq:
 *     autoload(module, filename)   -> nil
 *
 *  Registers _filename_ to be loaded (using <code>Kernel::require</code>)
 *  the first time that _module_ (which may be a <code>String</code> or
 *  a symbol) is accessed.
 *
 *     autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")
 */

static VALUE
rb_f_autoload(VALUE obj, VALUE sym, VALUE file)
{
    VALUE klass = rb_class_real(rb_vm_cbase());
    if (NIL_P(klass)) {
	rb_raise(rb_eTypeError, "Can not set autoload on singleton class");
    }
    return rb_mod_autoload(klass, sym, file);
}

/*
 *  call-seq:
 *     autoload?(name)   -> String or nil
 *
 *  Returns _filename_ to be loaded if _name_ is registered as
 *  +autoload+.
 *
 *     autoload(:B, "b")
 *     autoload?(:B)            #=> "b"
 */

static VALUE
rb_f_autoload_p(VALUE obj, VALUE sym)
{
    /* use rb_vm_cbase() as same as rb_f_autoload. */
    VALUE klass = rb_vm_cbase();
    if (NIL_P(klass)) {
	return Qnil;
    }
    return rb_mod_autoload_p(klass, sym);
}

void
Init_load()
{
#undef rb_intern
#define rb_intern(str) rb_intern2((str), strlen(str))
    rb_vm_t *vm = GET_VM();
    static const char var_load_path[] = "$:";
    ID id_load_path = rb_intern2(var_load_path, sizeof(var_load_path)-1);

    rb_define_hooked_variable(var_load_path, (VALUE*)vm, load_path_getter, rb_gvar_readonly_setter);
    rb_alias_variable(rb_intern("$-I"), id_load_path);
    rb_alias_variable(rb_intern("$LOAD_PATH"), id_load_path);
    vm->load_path = rb_ary_new();

    rb_define_virtual_variable("$\"", get_loaded_features, 0);
    rb_define_virtual_variable("$LOADED_FEATURES", get_loaded_features, 0);
    vm->loaded_features = rb_ary_new();
    vm->loaded_features_snapshot = rb_ary_new();
    vm->loaded_features_index = rb_hash_new();

    rb_define_global_function("load", rb_f_load, -1);
    rb_define_global_function("require", rb_f_require, 1);
    rb_define_global_function("require_relative", rb_f_require_relative, 1);
    rb_define_method(rb_cModule, "autoload", rb_mod_autoload, 2);
    rb_define_method(rb_cModule, "autoload?", rb_mod_autoload_p, 1);
    rb_define_global_function("autoload", rb_f_autoload, 2);
    rb_define_global_function("autoload?", rb_f_autoload_p, 1);

    ruby_dln_librefs = rb_ary_new();
    rb_gc_register_mark_object(ruby_dln_librefs);
}