text: /*
  ** array.c - Array class
  **
  ** See Copyright Notice in mruby.h
  */
  
  #include <mruby.h>
  #include <mruby/array.h>
  #include <mruby/class.h>
  #include <mruby/string.h>
  #include <mruby/range.h>
  #include "value_array.h"
  
  #define ARY_DEFAULT_LEN   4
  #define ARY_SHRINK_RATIO  5 /* must be larger than 2 */
  #define ARY_C_MAX_SIZE (SIZE_MAX / sizeof(mrb_value))
  #define ARY_MAX_SIZE ((mrb_int)((ARY_C_MAX_SIZE < (size_t)MRB_INT_MAX) ? ARY_C_MAX_SIZE : MRB_INT_MAX-1))
  #define f64_to_i64(x) f64_to_i64((x),softfloat_round_min,1)
  static struct RArray*
  ary_new_capa(mrb_state *mrb, mrb_int capa)
  {
    struct RArray *a;
    size_t blen;
  
    if (capa > ARY_MAX_SIZE) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
    blen = capa * sizeof(mrb_value);
  
    a = (struct RArray*)mrb_obj_alloc(mrb, MRB_TT_ARRAY, mrb->array_class);
    if (capa <= MRB_ARY_EMBED_LEN_MAX) {
      ARY_SET_EMBED_LEN(a, 0);
    }
    else {
      a->as.heap.ptr = (mrb_value *)mrb_malloc(mrb, blen);
      a->as.heap.aux.capa = capa;
      a->as.heap.len = 0;
    }
  
    return a;
  }
  
  MRB_API mrb_value
  mrb_ary_new_capa(mrb_state *mrb, mrb_int capa)
  {
    struct RArray *a = ary_new_capa(mrb, capa);
    return mrb_obj_value(a);
  }
  
  MRB_API mrb_value
  mrb_ary_new(mrb_state *mrb)
  {
    return mrb_ary_new_capa(mrb, 0);
  }
  
  /*
   * to copy array, use this instead of memcpy because of portability
   * * gcc on ARM may fail optimization of memcpy
   *   http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka3934.html
   * * gcc on MIPS also fail
   *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39755
   * * memcpy doesn't exist on freestanding environment
   *
   * If you optimize for binary size, use memcpy instead of this at your own risk
   * of above portability issue.
   *
   * see also http://togetter.com/li/462898
   *
   */
  static inline void
  array_copy(mrb_value *dst, const mrb_value *src, mrb_int size)
  {
    mrb_int i;
  
    for (i = 0; i < size; i++) {
      dst[i] = src[i];
    }
  }
  
  MRB_API mrb_value
  mrb_ary_new_from_values(mrb_state *mrb, mrb_int size, const mrb_value *vals)
  {
    struct RArray *a = ary_new_capa(mrb, size);
  
    array_copy(ARY_PTR(a), vals, size);
    ARY_SET_LEN(a, size);
  
    return mrb_obj_value(a);
  }
  
  MRB_API mrb_value
  mrb_assoc_new(mrb_state *mrb, mrb_value car, mrb_value cdr)
  {
    struct RArray *a;
  
    a = ary_new_capa(mrb, 2);
    ARY_PTR(a)[0] = car;
    ARY_PTR(a)[1] = cdr;
    ARY_SET_LEN(a, 2);
    return mrb_obj_value(a);
  }
  
  static void
  ary_fill_with_nil(mrb_value *ptr, mrb_int size)
  {
    mrb_value nil = mrb_nil_value();
  
    while (size--) {
      *ptr++ = nil;
    }
  }
  
  static void
  ary_modify_check(mrb_state *mrb, struct RArray *a)
  {
    if (MRB_FROZEN_P(a)) {
      mrb_raise(mrb, E_RUNTIME_ERROR, "can't modify frozen array");
    }
  }
  
  static void
  ary_modify(mrb_state *mrb, struct RArray *a)
  {
    ary_modify_check(mrb, a);
  
    if (ARY_SHARED_P(a)) {
      mrb_shared_array *shared = a->as.heap.aux.shared;
  
      if (shared->refcnt == 1 && a->as.heap.ptr == shared->ptr) {
        a->as.heap.ptr = shared->ptr;
        a->as.heap.aux.capa = a->as.heap.len;
        mrb_free(mrb, shared);
      }
      else {
        mrb_value *ptr, *p;
        mrb_int len;
  
        p = a->as.heap.ptr;
        len = a->as.heap.len * sizeof(mrb_value);
        ptr = (mrb_value *)mrb_malloc(mrb, len);
        if (p) {
          array_copy(ptr, p, a->as.heap.len);
        }
        a->as.heap.ptr = ptr;
        a->as.heap.aux.capa = a->as.heap.len;
        mrb_ary_decref(mrb, shared);
      }
      ARY_UNSET_SHARED_FLAG(a);
    }
  }
  
  MRB_API void
  mrb_ary_modify(mrb_state *mrb, struct RArray* a)
  {
    mrb_write_barrier(mrb, (struct RBasic*)a);
    ary_modify(mrb, a);
  }
  
  static void
  ary_make_shared(mrb_state *mrb, struct RArray *a)
  {
    if (!ARY_SHARED_P(a) && !ARY_EMBED_P(a)) {
      mrb_shared_array *shared = (mrb_shared_array *)mrb_malloc(mrb, sizeof(mrb_shared_array));
      mrb_value *ptr = a->as.heap.ptr;
      mrb_int len = a->as.heap.len;
  
      shared->refcnt = 1;
      if (a->as.heap.aux.capa > len) {
        a->as.heap.ptr = shared->ptr = (mrb_value *)mrb_realloc(mrb, ptr, sizeof(mrb_value)*len+1);
      }
      else {
        shared->ptr = ptr;
      }
      shared->len = len;
      a->as.heap.aux.shared = shared;
      ARY_SET_SHARED_FLAG(a);
    }
  }
  
  static void
  ary_expand_capa(mrb_state *mrb, struct RArray *a, mrb_int len)
  {
    mrb_int capa = ARY_CAPA(a);
  
    if (len > ARY_MAX_SIZE || len < 0) {
    size_error:
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
  
    if (capa < ARY_DEFAULT_LEN) {
      capa = ARY_DEFAULT_LEN;
    }
    while (capa < len) {
      if (capa <= ARY_MAX_SIZE / 2) {
        capa *= 2;
      }
      else {
        capa = len;
      }
    }
    if (capa < len || capa > ARY_MAX_SIZE) {
      goto size_error;
    }
  
    if (ARY_EMBED_P(a)) {
      mrb_value *ptr = ARY_EMBED_PTR(a);
      mrb_int len = ARY_EMBED_LEN(a);
      mrb_value *expanded_ptr = (mrb_value *)mrb_malloc(mrb, sizeof(mrb_value)*capa);
  
      ARY_UNSET_EMBED_FLAG(a);
      array_copy(expanded_ptr, ptr, len);
      a->as.heap.len = len;
      a->as.heap.aux.capa = capa;
      a->as.heap.ptr = expanded_ptr;
    }
    else if (capa > a->as.heap.aux.capa) {
      mrb_value *expanded_ptr = (mrb_value *)mrb_realloc(mrb, a->as.heap.ptr, sizeof(mrb_value)*capa);
  
      a->as.heap.aux.capa = capa;
      a->as.heap.ptr = expanded_ptr;
    }
  }
  
  static void
  ary_shrink_capa(mrb_state *mrb, struct RArray *a)
  {
    
    mrb_int capa;
  
    if (ARY_EMBED_P(a)) return;
  
    capa = a->as.heap.aux.capa;
    if (capa < ARY_DEFAULT_LEN * 2) return;
    if (capa <= a->as.heap.len * ARY_SHRINK_RATIO) return;
  
    do {
      capa /= 2;
      if (capa < ARY_DEFAULT_LEN) {
        capa = ARY_DEFAULT_LEN;
        break;
      }
    } while (capa > a->as.heap.len * ARY_SHRINK_RATIO);
  
    if (capa > a->as.heap.len && capa < a->as.heap.aux.capa) {
      a->as.heap.aux.capa = capa;
      a->as.heap.ptr = (mrb_value *)mrb_realloc(mrb, a->as.heap.ptr, sizeof(mrb_value)*capa);
    }
  }
  
  MRB_API mrb_value
  mrb_ary_resize(mrb_state *mrb, mrb_value ary, mrb_int new_len)
  {
    mrb_int old_len;
    struct RArray *a = mrb_ary_ptr(ary);
  
    ary_modify(mrb, a);
    old_len = RARRAY_LEN(ary);
    if (old_len != new_len) {
      ARY_SET_LEN(a, new_len);
      if (new_len < old_len) {
        ary_shrink_capa(mrb, a);
      }
      else {
        ary_expand_capa(mrb, a, new_len);
        ary_fill_with_nil(ARY_PTR(a) + old_len, new_len - old_len);
      }
    }
  
    return ary;
  }
  
  static mrb_value
  mrb_ary_s_create(mrb_state *mrb, mrb_value klass)
  {
    mrb_value ary;
    mrb_value *vals;
    mrb_int len;
    struct RArray *a;
  
    mrb_get_args(mrb, "*!", &vals, &len);
    ary = mrb_ary_new_from_values(mrb, len, vals);
    a = mrb_ary_ptr(ary);
    a->c = mrb_class_ptr(klass);
  
    return ary;
  }
  
  static void
  ary_concat(mrb_state *mrb, struct RArray *a, struct RArray *a2)
  {
    mrb_int len;
  
    if (ARY_LEN(a2) > ARY_MAX_SIZE - ARY_LEN(a)) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
    len = ARY_LEN(a) + ARY_LEN(a2);
  
    ary_modify(mrb, a);
    if (ARY_CAPA(a) < len) {
      ary_expand_capa(mrb, a, len);
    }
    array_copy(ARY_PTR(a)+ARY_LEN(a), ARY_PTR(a2), ARY_LEN(a2));
    mrb_write_barrier(mrb, (struct RBasic*)a);
    ARY_SET_LEN(a, len);
  }
  
  MRB_API void
  mrb_ary_concat(mrb_state *mrb, mrb_value self, mrb_value other)
  {
    struct RArray *a2 = mrb_ary_ptr(other);
  
    ary_concat(mrb, mrb_ary_ptr(self), a2);
  }
  
  static mrb_value
  mrb_ary_concat_m(mrb_state *mrb, mrb_value self)
  {
    mrb_value ary;
  
    mrb_get_args(mrb, "A", &ary);
    mrb_ary_concat(mrb, self, ary);
    return self;
  }
  
  static mrb_value
  mrb_ary_plus(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a1 = mrb_ary_ptr(self);
    struct RArray *a2;
    mrb_value *ptr;
    mrb_int blen, len1;
  
    mrb_get_args(mrb, "a", &ptr, &blen);
    if (ARY_MAX_SIZE - blen < ARY_LEN(a1)) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
    len1 = ARY_LEN(a1);
    a2 = ary_new_capa(mrb, len1 + blen);
    array_copy(ARY_PTR(a2), ARY_PTR(a1), len1);
    array_copy(ARY_PTR(a2) + len1, ptr, blen);
    ARY_SET_LEN(a2, len1+blen);
  
    return mrb_obj_value(a2);
  }
  
  static void
  ary_replace(mrb_state *mrb, struct RArray *a, mrb_value *argv, mrb_int len)
  {
    ary_modify(mrb, a);
    if (ARY_CAPA(a) < len)
      ary_expand_capa(mrb, a, len);
    array_copy(ARY_PTR(a), argv, len);
    mrb_write_barrier(mrb, (struct RBasic*)a);
    ARY_SET_LEN(a, len);
  }
  
  MRB_API void
  mrb_ary_replace(mrb_state *mrb, mrb_value self, mrb_value other)
  {
    struct RArray *a1 = mrb_ary_ptr(self);
    struct RArray *a2 = mrb_ary_ptr(other);
  
    if (a1 != a2) {
      ary_replace(mrb, a1, ARY_PTR(a2), ARY_LEN(a2));
    }
  }
  
  static mrb_value
  mrb_ary_replace_m(mrb_state *mrb, mrb_value self)
  {
    mrb_value other;
  
    mrb_get_args(mrb, "A", &other);
    mrb_ary_replace(mrb, self, other);
  
    return self;
  }
  
  static mrb_value
  mrb_ary_times(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a1 = mrb_ary_ptr(self);
    struct RArray *a2;
    mrb_value *ptr;
    mrb_int times, len1;
  
    mrb_get_args(mrb, "i", &times);
    if (times < 0) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "negative argument");
    }
    if (times == 0) return mrb_ary_new(mrb);
    if (ARY_MAX_SIZE / times < ARY_LEN(a1)) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
    len1 = ARY_LEN(a1);
    a2 = ary_new_capa(mrb, len1 * times);
    ARY_SET_LEN(a2, len1 * times);
    ptr = ARY_PTR(a2);
    while (times--) {
      array_copy(ptr, ARY_PTR(a1), len1);
      ptr += len1;
    }
  
    return mrb_obj_value(a2);
  }
  
  static mrb_value
  mrb_ary_reverse_bang(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int len = ARY_LEN(a);
  
    if (len > 1) {
      mrb_value *p1, *p2;
  
      ary_modify(mrb, a);
      p1 = ARY_PTR(a);
      p2 = p1 + len - 1;
  
      while (p1 < p2) {
        mrb_value tmp = *p1;
        *p1++ = *p2;
        *p2-- = tmp;
      }
    }
    return self;
  }
  
  static mrb_value
  mrb_ary_reverse(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self), *b = ary_new_capa(mrb, ARY_LEN(a));
    mrb_int len = ARY_LEN(a);
  
    if (len > 0) {
      mrb_value *p1, *p2, *e;
  
      p1 = ARY_PTR(a);
      e  = p1 + len;
      p2 = ARY_PTR(b) + len - 1;
      while (p1 < e) {
        *p2-- = *p1++;
      }
      ARY_SET_LEN(b, len);
    }
    return mrb_obj_value(b);
  }
  
  MRB_API void
  mrb_ary_push(mrb_state *mrb, mrb_value ary, mrb_value elem)
  {
    struct RArray *a = mrb_ary_ptr(ary);
    mrb_int len = ARY_LEN(a);
  
    ary_modify(mrb, a);
    if (len == ARY_CAPA(a))
      ary_expand_capa(mrb, a, len + 1);
    ARY_PTR(a)[len] = elem;
    ARY_SET_LEN(a, len+1);
    mrb_field_write_barrier_value(mrb, (struct RBasic*)a, elem);
  }
  
  static mrb_value
  mrb_ary_push_m(mrb_state *mrb, mrb_value self)
  {
    mrb_value *argv;
    mrb_int len, len2, alen;
    struct RArray *a;
  
    mrb_get_args(mrb, "*!", &argv, &alen);
    a = mrb_ary_ptr(self);
    ary_modify(mrb, a);
    len = ARY_LEN(a);
    len2 = len + alen;
    if (ARY_CAPA(a) < len2) {
      ary_expand_capa(mrb, a, len2);
    }
    array_copy(ARY_PTR(a)+len, argv, alen);
    ARY_SET_LEN(a, len2);
    mrb_write_barrier(mrb, (struct RBasic*)a);
  
    return self;
  }
  
  MRB_API mrb_value
  mrb_ary_pop(mrb_state *mrb, mrb_value ary)
  {
    struct RArray *a = mrb_ary_ptr(ary);
    mrb_int len = ARY_LEN(a);
  
    ary_modify_check(mrb, a);
    if (len == 0) return mrb_nil_value();
    ARY_SET_LEN(a, len-1);
    return ARY_PTR(a)[len-1];
  }
  
  #define ARY_SHIFT_SHARED_MIN 10
  
  MRB_API mrb_value
  mrb_ary_shift(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int len = ARY_LEN(a);
    mrb_value val;
  
    ary_modify_check(mrb, a);
    if (len == 0) return mrb_nil_value();
    if (ARY_SHARED_P(a)) {
    L_SHIFT:
      val = a->as.heap.ptr[0];
      a->as.heap.ptr++;
      a->as.heap.len--;
      return val;
    }
    if (len > ARY_SHIFT_SHARED_MIN) {
      ary_make_shared(mrb, a);
      goto L_SHIFT;
    }
    else {
      mrb_value *ptr = ARY_PTR(a);
      mrb_int size = len;
  
      val = *ptr;
      while (--size) {
        *ptr = *(ptr+1);
        ++ptr;
      }
      ARY_SET_LEN(a, len-1);
    }
    return val;
  }
  
  /* self = [1,2,3]
     item = 0
     self.unshift item
     p self #=> [0, 1, 2, 3] */
  MRB_API mrb_value
  mrb_ary_unshift(mrb_state *mrb, mrb_value self, mrb_value item)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int len = ARY_LEN(a);
  
    if (ARY_SHARED_P(a)
        && a->as.heap.aux.shared->refcnt == 1 /* shared only referenced from this array */
        && a->as.heap.ptr - a->as.heap.aux.shared->ptr >= 1) /* there's room for unshifted item */ {
      a->as.heap.ptr--;
      a->as.heap.ptr[0] = item;
    }
    else {
      mrb_value *ptr;
  
      ary_modify(mrb, a);
      if (ARY_CAPA(a) < len + 1)
        ary_expand_capa(mrb, a, len + 1);
      ptr = ARY_PTR(a);
      value_move(ptr + 1, ptr, len);
      ptr[0] = item;
    }
    ARY_SET_LEN(a, len+1);
    mrb_field_write_barrier_value(mrb, (struct RBasic*)a, item);
  
    return self;
  }
  
  static mrb_value
  mrb_ary_unshift_m(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_value *vals, *ptr;
    mrb_int alen, len;
  
    mrb_get_args(mrb, "*!", &vals, &alen);
    if (alen == 0) {
      ary_modify_check(mrb, a);
      return self;
    }
    len = ARY_LEN(a);
    if (alen > ARY_MAX_SIZE - len) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "array size too big");
    }
    if (ARY_SHARED_P(a)
        && a->as.heap.aux.shared->refcnt == 1 /* shared only referenced from this array */
        && a->as.heap.ptr - a->as.heap.aux.shared->ptr >= alen) /* there's room for unshifted item */ {
      ary_modify_check(mrb, a);
      a->as.heap.ptr -= alen;
      ptr = a->as.heap.ptr;
    }
    else {
      ary_modify(mrb, a);
      if (ARY_CAPA(a) < len + alen)
        ary_expand_capa(mrb, a, len + alen);
      ptr = ARY_PTR(a);
      value_move(ptr + alen, ptr, len);
    }
    array_copy(ptr, vals, alen);
    ARY_SET_LEN(a, len+alen);
    while (alen--) {
      mrb_field_write_barrier_value(mrb, (struct RBasic*)a, vals[alen]);
    }
  
    return self;
  }
  
  MRB_API mrb_value
  mrb_ary_ref(mrb_state *mrb, mrb_value ary, mrb_int n)
  {
    struct RArray *a = mrb_ary_ptr(ary);
    mrb_int len = ARY_LEN(a);
  
    /* range check */
    if (n < 0) n += len;
    if (n < 0 || len <= n) return mrb_nil_value();
  
    return ARY_PTR(a)[n];
  }
  
  MRB_API void
  mrb_ary_set(mrb_state *mrb, mrb_value ary, mrb_int n, mrb_value val)
  {
    struct RArray *a = mrb_ary_ptr(ary);
    mrb_int len = ARY_LEN(a);
  
    ary_modify(mrb, a);
    /* range check */
    if (n < 0) {
      n += len;
      if (n < 0) {
        mrb_raisef(mrb, E_INDEX_ERROR, "index %S out of array", mrb_fixnum_value(n - len));
      }
    }
    if (len <= n) {
      if (ARY_CAPA(a) <= n)
        ary_expand_capa(mrb, a, n + 1);
      ary_fill_with_nil(ARY_PTR(a) + len, n + 1 - len);
      ARY_SET_LEN(a, n+1);
    }
  
    ARY_PTR(a)[n] = val;
    mrb_field_write_barrier_value(mrb, (struct RBasic*)a, val);
  }
  
  static struct RArray*
  ary_dup(mrb_state *mrb, struct RArray *a)
  {
    mrb_int len = ARY_LEN(a);
    struct RArray *d = ary_new_capa(mrb, len);
  
    ary_replace(mrb, d, ARY_PTR(a), len);
    return d;
  }
  
  MRB_API mrb_value
  mrb_ary_splice(mrb_state *mrb, mrb_value ary, mrb_int head, mrb_int len, mrb_value rpl)
  {
    struct RArray *a = mrb_ary_ptr(ary);
    mrb_int alen = ARY_LEN(a);
    const mrb_value *argv;
    mrb_int argc;
    mrb_int tail;
  
    ary_modify(mrb, a);
  
    /* len check */
    if (len < 0) mrb_raisef(mrb, E_INDEX_ERROR, "negative length (%S)", mrb_fixnum_value(len));
  
    /* range check */
    if (head < 0) {
      head += alen;
      if (head < 0) {
        mrb_raise(mrb, E_INDEX_ERROR, "index is out of array");
      }
    }
    tail = head + len;
    if (alen < len || alen < tail) {
      len = alen - head;
    }
  
    /* size check */
    if (mrb_array_p(rpl)) {
      argc = RARRAY_LEN(rpl);
      argv = RARRAY_PTR(rpl);
      if (argv == ARY_PTR(a)) {
        struct RArray *r;
  
        if (argc > 32767) {
          mrb_raise(mrb, E_ARGUMENT_ERROR, "too big recursive splice");
        }
        r = ary_dup(mrb, a);
        argv = ARY_PTR(r);
      }
    }
    else {
      argc = 1;
      argv = &rpl;
    }
    if (head >= alen) {
      if (head > ARY_MAX_SIZE - argc) {
        mrb_raisef(mrb, E_INDEX_ERROR, "index %S too big", mrb_fixnum_value(head));
      }
      len = head + argc;
      if (len > ARY_CAPA(a)) {
        ary_expand_capa(mrb, a, head + argc);
      }
      ary_fill_with_nil(ARY_PTR(a) + alen, head - alen);
      if (argc > 0) {
        array_copy(ARY_PTR(a) + head, argv, argc);
      }
      ARY_SET_LEN(a, len);
    }
    else {
      mrb_int newlen;
  
      if (alen - len > ARY_MAX_SIZE - argc) {
        mrb_raisef(mrb, E_INDEX_ERROR, "index %S too big", mrb_fixnum_value(alen + argc - len));
      }
      newlen = alen + argc - len;
      if (newlen > ARY_CAPA(a)) {
        ary_expand_capa(mrb, a, newlen);
      }
  
      if (len != argc) {
        mrb_value *ptr = ARY_PTR(a);
        tail = head + len;
        value_move(ptr + head + argc, ptr + tail, alen - tail);
        ARY_SET_LEN(a, newlen);
      }
      if (argc > 0) {
        value_move(ARY_PTR(a) + head, argv, argc);
      }
    }
    mrb_write_barrier(mrb, (struct RBasic*)a);
    return ary;
  }
  
  void
  mrb_ary_decref(mrb_state *mrb, mrb_shared_array *shared)
  {
    shared->refcnt--;
    if (shared->refcnt == 0) {
      mrb_free(mrb, shared->ptr);
      mrb_free(mrb, shared);
    }
  }
  
  static mrb_value
  ary_subseq(mrb_state *mrb, struct RArray *a, mrb_int beg, mrb_int len)
  {
    struct RArray *b;
  
    if (!ARY_SHARED_P(a) && len <= ARY_SHIFT_SHARED_MIN) {
      return mrb_ary_new_from_values(mrb, len, ARY_PTR(a)+beg);
    }
    ary_make_shared(mrb, a);
    b  = (struct RArray*)mrb_obj_alloc(mrb, MRB_TT_ARRAY, mrb->array_class);
    b->as.heap.ptr = a->as.heap.ptr + beg;
    b->as.heap.len = len;
    b->as.heap.aux.shared = a->as.heap.aux.shared;
    b->as.heap.aux.shared->refcnt++;
    ARY_SET_SHARED_FLAG(b);
  
    return mrb_obj_value(b);
  }
  
  static mrb_int
  aget_index(mrb_state *mrb, mrb_value index)
  {
    if (mrb_fixnum_p(index)) {
      return mrb_fixnum(index);
    }
  #ifndef MRB_WITHOUT_FLOAT
    else if (mrb_float_p(index)) {
      return f64_to_i64(mrb_float(index));
    }
  #endif
    else {
      mrb_int i, argc;
      mrb_value *argv;
  
      mrb_get_args(mrb, "i*!", &i, &argv, &argc);
      return i;
    }
  }
  
  /*
   *  call-seq:
   *     ary[index]                -> obj     or nil
   *     ary[start, length]        -> new_ary or nil
   *     ary[range]                -> new_ary or nil
   *     ary.slice(index)          -> obj     or nil
   *     ary.slice(start, length)  -> new_ary or nil
   *     ary.slice(range)          -> new_ary or nil
   *
   *  Element Reference --- Returns the element at +index+, or returns a
   *  subarray starting at the +start+ index and continuing for +length+
   *  elements, or returns a subarray specified by +range+ of indices.
   *
   *  Negative indices count backward from the end of the array (-1 is the last
   *  element).  For +start+ and +range+ cases the starting index is just before
   *  an element.  Additionally, an empty array is returned when the starting
   *  index for an element range is at the end of the array.
   *
   *  Returns +nil+ if the index (or starting index) are out of range.
   *
   *  a = [ "a", "b", "c", "d", "e" ]
   *  a[1]     => "b"
   *  a[1,2]   => ["b", "c"]
   *  a[1..-2] => ["b", "c", "d"]
   *
   */
  
  static mrb_value
  mrb_ary_aget(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int i, len, alen = ARY_LEN(a);
    mrb_value index;
  
    if (mrb_get_args(mrb, "o|i", &index, &len) == 1) {
      switch (mrb_type(index)) {
        /* a[n..m] */
      case MRB_TT_RANGE:
        if (mrb_range_beg_len(mrb, index, &i, &len, alen, TRUE) == 1) {
          return ary_subseq(mrb, a, i, len);
        }
        else {
          return mrb_nil_value();
        }
      case MRB_TT_FIXNUM:
        return mrb_ary_ref(mrb, self, mrb_fixnum(index));
      default:
        return mrb_ary_ref(mrb, self, aget_index(mrb, index));
      }
    }
  
    i = aget_index(mrb, index);
    if (i < 0) i += alen;
    if (i < 0 || alen < i) return mrb_nil_value();
    if (len < 0) return mrb_nil_value();
    if (alen == i) return mrb_ary_new(mrb);
    if (len > alen - i) len = alen - i;
  
    return ary_subseq(mrb, a, i, len);
  }
  
  /*
   *  call-seq:
   *     ary[index]         = obj                      ->  obj
   *     ary[start, length] = obj or other_ary or nil  ->  obj or other_ary or nil
   *     ary[range]         = obj or other_ary or nil  ->  obj or other_ary or nil
   *
   *  Element Assignment --- Sets the element at +index+, or replaces a subarray
   *  from the +start+ index for +length+ elements, or replaces a subarray
   *  specified by the +range+ of indices.
   *
   *  If indices are greater than the current capacity of the array, the array
   *  grows automatically.  Elements are inserted into the array at +start+ if
   *  +length+ is zero.
   *
   *  Negative indices will count backward from the end of the array.  For
   *  +start+ and +range+ cases the starting index is just before an element.
   *
   *  An IndexError is raised if a negative index points past the beginning of
   *  the array.
   *
   *  See also Array#push, and Array#unshift.
   *
   *     a = Array.new
   *     a[4] = "4";                 #=> [nil, nil, nil, nil, "4"]
   *     a[0, 3] = [ 'a', 'b', 'c' ] #=> ["a", "b", "c", nil, "4"]
   *     a[1..2] = [ 1, 2 ]          #=> ["a", 1, 2, nil, "4"]
   *     a[0, 2] = "?"               #=> ["?", 2, nil, "4"]
   *     a[0..2] = "A"               #=> ["A", "4"]
   *     a[-1]   = "Z"               #=> ["A", "Z"]
   *     a[1..-1] = nil              #=> ["A", nil]
   *     a[1..-1] = []               #=> ["A"]
   *     a[0, 0] = [ 1, 2 ]          #=> [1, 2, "A"]
   *     a[3, 0] = "B"               #=> [1, 2, "A", "B"]
   */
  
  static mrb_value
  mrb_ary_aset(mrb_state *mrb, mrb_value self)
  {
    mrb_value v1, v2, v3;
    mrb_int i, len;
  
    mrb_ary_modify(mrb, mrb_ary_ptr(self));
    if (mrb_get_args(mrb, "oo|o", &v1, &v2, &v3) == 2) {
      /* a[n..m] = v */
      switch (mrb_range_beg_len(mrb, v1, &i, &len, RARRAY_LEN(self), FALSE)) {
      case 0:                   /* not range */
        mrb_ary_set(mrb, self, aget_index(mrb, v1), v2);
        break;
      case 1:                   /* range */
        mrb_ary_splice(mrb, self, i, len, v2);
        break;
      case 2:                   /* out of range */
        mrb_raisef(mrb, E_RANGE_ERROR, "%S out of range", v1);
        break;
      }
      return v2;
    }
  
    /* a[n,m] = v */
    mrb_ary_splice(mrb, self, aget_index(mrb, v1), aget_index(mrb, v2), v3);
    return v3;
  }
  
  static mrb_value
  mrb_ary_delete_at(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int   index;
    mrb_value val;
    mrb_value *ptr;
    mrb_int len, alen = ARY_LEN(a);
  
    mrb_get_args(mrb, "i", &index);
    if (index < 0) index += alen;
    if (index < 0 || alen <= index) return mrb_nil_value();
  
    ary_modify(mrb, a);
    ptr = ARY_PTR(a);
    val = ptr[index];
  
    ptr += index;
    len = alen - index;
    while (--len) {
      *ptr = *(ptr+1);
      ++ptr;
    }
    ARY_SET_LEN(a, alen-1);
  
    ary_shrink_capa(mrb, a);
  
    return val;
  }
  
  static mrb_value
  mrb_ary_first(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int size, alen = ARY_LEN(a);
  
    if (mrb_get_argc(mrb) == 0) {
      return (alen > 0)? ARY_PTR(a)[0]: mrb_nil_value();
    }
    mrb_get_args(mrb, "|i", &size);
    if (size < 0) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "negative array size");
    }
  
    if (size > alen) size = alen;
    if (ARY_SHARED_P(a)) {
      return ary_subseq(mrb, a, 0, size);
    }
    return mrb_ary_new_from_values(mrb, size, ARY_PTR(a));
  }
  
  static mrb_value
  mrb_ary_last(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
    mrb_int size, alen = ARY_LEN(a);
  
    if (mrb_get_args(mrb, "|i", &size) == 0)
      return (alen > 0)? ARY_PTR(a)[alen - 1]: mrb_nil_value();
  
    if (size < 0) {
      mrb_raise(mrb, E_ARGUMENT_ERROR, "negative array size");
    }
    if (size > alen) size = alen;
    if (ARY_SHARED_P(a) || size > ARY_DEFAULT_LEN) {
      return ary_subseq(mrb, a, alen - size, size);
    }
    return mrb_ary_new_from_values(mrb, size, ARY_PTR(a) + alen - size);
  }
  
  static mrb_value
  mrb_ary_index_m(mrb_state *mrb, mrb_value self)
  {
    mrb_value obj;
    mrb_int i;
  
    mrb_get_args(mrb, "o", &obj);
    for (i = 0; i < RARRAY_LEN(self); i++) {
      if (mrb_equal(mrb, RARRAY_PTR(self)[i], obj)) {
        return mrb_fixnum_value(i);
      }
    }
    return mrb_nil_value();
  }
  
  static mrb_value
  mrb_ary_rindex_m(mrb_state *mrb, mrb_value self)
  {
    mrb_value obj;
    mrb_int i, len;
  
    mrb_get_args(mrb, "o", &obj);
    for (i = RARRAY_LEN(self) - 1; i >= 0; i--) {
      if (mrb_equal(mrb, RARRAY_PTR(self)[i], obj)) {
        return mrb_fixnum_value(i);
      }
      if (i > (len = RARRAY_LEN(self))) {
        i = len;
      }
    }
    return mrb_nil_value();
  }
  
  MRB_API mrb_value
  mrb_ary_splat(mrb_state *mrb, mrb_value v)
  {
    mrb_value a, recv_class;
  
    if (mrb_array_p(v)) {
      return v;
    }
  
    if (!mrb_respond_to(mrb, v, mrb_intern_lit(mrb, "to_a"))) {
      return mrb_ary_new_from_values(mrb, 1, &v);
    }
  
    a = mrb_funcall(mrb, v, "to_a", 0);
    if (mrb_array_p(a)) {
      return a;
    }
    else if (mrb_nil_p(a)) {
      return mrb_ary_new_from_values(mrb, 1, &v);
    }
    else {
      recv_class = mrb_obj_value(mrb_obj_class(mrb, v));
      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %S to Array (%S#to_a gives %S)",
        recv_class,
        recv_class,
        mrb_obj_value(mrb_obj_class(mrb, a))
      );
      /* not reached */
      return mrb_undef_value();
    }
  }
  
  static mrb_value
  mrb_ary_size(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
  
    return mrb_fixnum_value(ARY_LEN(a));
  }
  
  MRB_API mrb_value
  mrb_ary_clear(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
  
    ary_modify(mrb, a);
    if (ARY_SHARED_P(a)) {
      mrb_ary_decref(mrb, a->as.heap.aux.shared);
      ARY_UNSET_SHARED_FLAG(a);
    }
    else if (!ARY_EMBED_P(a)){
      mrb_free(mrb, a->as.heap.ptr);
    }
    ARY_SET_EMBED_LEN(a, 0);
  
    return self;
  }
  
  static mrb_value
  mrb_ary_empty_p(mrb_state *mrb, mrb_value self)
  {
    struct RArray *a = mrb_ary_ptr(self);
  
    return mrb_bool_value(ARY_LEN(a) == 0);
  }
  
  MRB_API mrb_value
  mrb_check_array_type(mrb_state *mrb, mrb_value ary)
  {
    return mrb_check_convert_type(mrb, ary, MRB_TT_ARRAY, "Array", "to_ary");
  }
  
  MRB_API mrb_value
  mrb_ary_entry(mrb_value ary, mrb_int offset)
  {
    if (offset < 0) {
      offset += RARRAY_LEN(ary);
    }
    if (offset < 0 || RARRAY_LEN(ary) <= offset) {
      return mrb_nil_value();
    }
    return RARRAY_PTR(ary)[offset];
  }
  
  static mrb_value
  join_ary(mrb_state *mrb, mrb_value ary, mrb_value sep, mrb_value list)
  {
    mrb_int i;
    mrb_value result, val, tmp;
  
    /* check recursive */
    for (i=0; i<RARRAY_LEN(list); i++) {
      if (mrb_obj_equal(mrb, ary, RARRAY_PTR(list)[i])) {
        mrb_raise(mrb, E_ARGUMENT_ERROR, "recursive array join");
      }
    }
  
    mrb_ary_push(mrb, list, ary);
  
    result = mrb_str_new_capa(mrb, 64);
  
    for (i=0; i<RARRAY_LEN(ary); i++) {
      if (i > 0 && !mrb_nil_p(sep)) {
        mrb_str_cat_str(mrb, result, sep);
      }
  
      val = RARRAY_PTR(ary)[i];
      switch (mrb_type(val)) {
      case MRB_TT_ARRAY:
      ary_join:
        val = join_ary(mrb, val, sep, list);
        /* fall through */
  
      case MRB_TT_STRING:
      str_join:
        mrb_str_cat_str(mrb, result, val);
        break;
  
      default:
        if (!mrb_immediate_p(val)) {
          tmp = mrb_check_string_type(mrb, val);
          if (!mrb_nil_p(tmp)) {
            val = tmp;
            goto str_join;
          }
          tmp = mrb_check_convert_type(mrb, val, MRB_TT_ARRAY, "Array", "to_ary");
          if (!mrb_nil_p(tmp)) {
            val = tmp;
            goto ary_join;
          }
        }
        val = mrb_obj_as_string(mrb, val);
        goto str_join;
      }
    }
  
    mrb_ary_pop(mrb, list);
  
    return result;
  }
  
  MRB_API mrb_value
  mrb_ary_join(mrb_state *mrb, mrb_value ary, mrb_value sep)
  {
    if (!mrb_nil_p(sep)) {
      sep = mrb_obj_as_string(mrb, sep);
    }
    return join_ary(mrb, ary, sep, mrb_ary_new(mrb));
  }
  
  /*
   *  call-seq:
   *     ary.join(sep="")    -> str
   *
   *  Returns a string created by converting each element of the array to
   *  a string, separated by <i>sep</i>.
   *
   *     [ "a", "b", "c" ].join        #=> "abc"
   *     [ "a", "b", "c" ].join("-")   #=> "a-b-c"
   */
  
  static mrb_value
  mrb_ary_join_m(mrb_state *mrb, mrb_value ary)
  {
    mrb_value sep = mrb_nil_value();
  
    mrb_get_args(mrb, "|S!", &sep);
    return mrb_ary_join(mrb, ary, sep);
  }
  
  static mrb_value
  mrb_ary_eq(mrb_state *mrb, mrb_value ary1)
  {
    mrb_value ary2;
  
    mrb_get_args(mrb, "o", &ary2);
    if (mrb_obj_equal(mrb, ary1, ary2)) return mrb_true_value();
    if (!mrb_array_p(ary2)) {
      return mrb_false_value();
    }
    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return mrb_false_value();
  
    return ary2;
  }
  
  static mrb_value
  mrb_ary_cmp(mrb_state *mrb, mrb_value ary1)
  {
    mrb_value ary2;
  
    mrb_get_args(mrb, "o", &ary2);
    if (mrb_obj_equal(mrb, ary1, ary2)) return mrb_fixnum_value(0);
    if (!mrb_array_p(ary2)) {
      return mrb_nil_value();
    }
  
    return ary2;
  }
  
  void
  mrb_init_array(mrb_state *mrb)
  {
    struct RClass *a;
  
    mrb->array_class = a = mrb_define_class(mrb, "Array", mrb->object_class);            /* 15.2.12 */
    MRB_SET_INSTANCE_TT(a, MRB_TT_ARRAY);
  
    mrb_define_class_method(mrb, a, "[]",        mrb_ary_s_create,     MRB_ARGS_ANY());  /* 15.2.12.4.1 */
  
    mrb_define_method(mrb, a, "+",               mrb_ary_plus,         MRB_ARGS_REQ(1)); /* 15.2.12.5.1  */
    mrb_define_method(mrb, a, "*",               mrb_ary_times,        MRB_ARGS_REQ(1)); /* 15.2.12.5.2  */
    mrb_define_method(mrb, a, "<<",              mrb_ary_push_m,       MRB_ARGS_REQ(1)); /* 15.2.12.5.3  */
    mrb_define_method(mrb, a, "[]",              mrb_ary_aget,         MRB_ARGS_ANY());  /* 15.2.12.5.4  */
    mrb_define_method(mrb, a, "[]=",             mrb_ary_aset,         MRB_ARGS_ANY());  /* 15.2.12.5.5  */
    mrb_define_method(mrb, a, "clear",           mrb_ary_clear,        MRB_ARGS_NONE()); /* 15.2.12.5.6  */
    mrb_define_method(mrb, a, "concat",          mrb_ary_concat_m,     MRB_ARGS_REQ(1)); /* 15.2.12.5.8  */
    mrb_define_method(mrb, a, "delete_at",       mrb_ary_delete_at,    MRB_ARGS_REQ(1)); /* 15.2.12.5.9  */
    mrb_define_method(mrb, a, "empty?",          mrb_ary_empty_p,      MRB_ARGS_NONE()); /* 15.2.12.5.12 */
    mrb_define_method(mrb, a, "first",           mrb_ary_first,        MRB_ARGS_OPT(1)); /* 15.2.12.5.13 */
    mrb_define_method(mrb, a, "index",           mrb_ary_index_m,      MRB_ARGS_REQ(1)); /* 15.2.12.5.14 */
    mrb_define_method(mrb, a, "initialize_copy", mrb_ary_replace_m,    MRB_ARGS_REQ(1)); /* 15.2.12.5.16 */
    mrb_define_method(mrb, a, "join",            mrb_ary_join_m,       MRB_ARGS_ANY());  /* 15.2.12.5.17 */
    mrb_define_method(mrb, a, "last",            mrb_ary_last,         MRB_ARGS_ANY());  /* 15.2.12.5.18 */
    mrb_define_method(mrb, a, "length",          mrb_ary_size,         MRB_ARGS_NONE()); /* 15.2.12.5.19 */
    mrb_define_method(mrb, a, "pop",             mrb_ary_pop,          MRB_ARGS_NONE()); /* 15.2.12.5.21 */
    mrb_define_method(mrb, a, "push",            mrb_ary_push_m,       MRB_ARGS_ANY());  /* 15.2.12.5.22 */
    mrb_define_method(mrb, a, "append",          mrb_ary_push_m,       MRB_ARGS_ANY());
    mrb_define_method(mrb, a, "replace",         mrb_ary_replace_m,    MRB_ARGS_REQ(1)); /* 15.2.12.5.23 */
    mrb_define_method(mrb, a, "reverse",         mrb_ary_reverse,      MRB_ARGS_NONE()); /* 15.2.12.5.24 */
    mrb_define_method(mrb, a, "reverse!",        mrb_ary_reverse_bang, MRB_ARGS_NONE()); /* 15.2.12.5.25 */
    mrb_define_method(mrb, a, "rindex",          mrb_ary_rindex_m,     MRB_ARGS_REQ(1)); /* 15.2.12.5.26 */
    mrb_define_method(mrb, a, "shift",           mrb_ary_shift,        MRB_ARGS_NONE()); /* 15.2.12.5.27 */
    mrb_define_method(mrb, a, "size",            mrb_ary_size,         MRB_ARGS_NONE()); /* 15.2.12.5.28 */
    mrb_define_method(mrb, a, "slice",           mrb_ary_aget,         MRB_ARGS_ANY());  /* 15.2.12.5.29 */
    mrb_define_method(mrb, a, "unshift",         mrb_ary_unshift_m,    MRB_ARGS_ANY());  /* 15.2.12.5.30 */
    mrb_define_method(mrb, a, "prepend",         mrb_ary_unshift_m,    MRB_ARGS_ANY());
  
    mrb_define_method(mrb, a, "__ary_eq",        mrb_ary_eq,           MRB_ARGS_REQ(1));
    mrb_define_method(mrb, a, "__ary_cmp",       mrb_ary_cmp,          MRB_ARGS_REQ(1));
    mrb_define_method(mrb, a, "__ary_index",     mrb_ary_index_m,      MRB_ARGS_REQ(1)); /* kept for mruby-array-ext */
  }
  