/*

** $Id: ltablib.c $

** Library for Table Manipulation

** See Copyright Notice in lua.h

*/

#define ltablib_c

#define LUA_LIB

#include "lprefix.h"

#include <limits.h>

#include <stddef.h>

#include <string.h>

#include "lua.h"

#include "lauxlib.h"

#include "lualib.h"

/*

** Operations that an object must define to mimic a table

** (some functions only need some of them)

*/

#define TAB_R 1      /* read */

#define TAB_W 2      /* write */

#define TAB_L 4      /* length */

#define TAB_RW  (TAB_R | TAB_W)   /* read/write */

#define aux_getn(L,n,w) (checktab(L, n, (w) | TAB_L), luaL_len(L, n))

static int checkfield (lua_State *L, const char *key, int n) {

  lua_pushstring(L, key);

  return (lua_rawget(L, -n) != LUA_TNIL);

}

/*

** Check that 'arg' either is a table or can behave like one (that is,

** has a metatable with the required metamethods)

*/

static void checktab (lua_State *L, int arg, int what) {

  if (lua_type(L, arg) != LUA_TTABLE) {  /* is it not a table? */

    int n = 1;  /* number of elements to pop */

    if (lua_getmetatable(L, arg) &&  /* must have metatable */

        (!(what & TAB_R) || checkfield(L, "__index", ++n)) &&

        (!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&

        (!(what & TAB_L) || checkfield(L, "__len", ++n))) {

      lua_pop(L, n);  /* pop metatable and tested metamethods */

    }

    else

      luaL_checktype(L, arg, LUA_TTABLE);  /* force an error */

  }

}

static int tinsert (lua_State *L) {

  lua_Integer pos;  /* where to insert new element */

  lua_Integer e = aux_getn(L, 1, TAB_RW);

  e = luaL_intop(+, e, 1);  /* first empty element */

  switch (lua_gettop(L)) {

    case 2: {  /* called with only 2 arguments */

      pos = e;  /* insert new element at the end */

      break;

    }

    case 3: {

      lua_Integer i;

      pos = luaL_checkinteger(L, 2);  /* 2nd argument is the position */

      /* check whether 'pos' is in [1, e] */

      luaL_argcheck(L, (lua_Unsigned)pos - 1u < (lua_Unsigned)e, 2,

                       "position out of bounds");

      for (i = e; i > pos; i--) {  /* move up elements */

        lua_geti(L, 1, i - 1);

        lua_seti(L, 1, i);  /* t[i] = t[i - 1] */

      }

      break;

    }

    default: {

      return luaL_error(L, "wrong number of arguments to 'insert'");

    }

  }

  lua_seti(L, 1, pos);  /* t[pos] = v */

  return 0;

}

static int tremove (lua_State *L) {

  lua_Integer size = aux_getn(L, 1, TAB_RW);

  lua_Integer pos = luaL_optinteger(L, 2, size);

  if (pos != size)  /* validate 'pos' if given */

    /* check whether 'pos' is in [1, size + 1] */

    luaL_argcheck(L, (lua_Unsigned)pos - 1u <= (lua_Unsigned)size, 2,

                     "position out of bounds");

  lua_geti(L, 1, pos);  /* result = t[pos] */

  for ( ; pos < size; pos++) {

    lua_geti(L, 1, pos + 1);

    lua_seti(L, 1, pos);  /* t[pos] = t[pos + 1] */

  }

  lua_pushnil(L);

  lua_seti(L, 1, pos);  /* remove entry t[pos] */

  return 1;

}

/*

** Copy elements (1[f], ..., 1[e]) into (tt[t], tt[t+1], ...). Whenever

** possible, copy in increasing order, which is better for rehashing.

** "possible" means destination after original range, or smaller

** than origin, or copying to another table.

*/

static int tmove (lua_State *L) {

  lua_Integer f = luaL_checkinteger(L, 2);

  lua_Integer e = luaL_checkinteger(L, 3);

  lua_Integer t = luaL_checkinteger(L, 4);

  int tt = !lua_isnoneornil(L, 5) ? 5 : 1;  /* destination table */

  checktab(L, 1, TAB_R);

  checktab(L, tt, TAB_W);

  if (e >= f) {  /* otherwise, nothing to move */

    lua_Integer n, i;

    luaL_argcheck(L, f > 0 || e < LUA_MAXINTEGER + f, 3,

                  "too many elements to move");

    n = e - f + 1;  /* number of elements to move */

    luaL_argcheck(L, t <= LUA_MAXINTEGER - n + 1, 4,

                  "destination wrap around");

    if (t > e || t <= f || (tt != 1 && !lua_compare(L, 1, tt, LUA_OPEQ))) {

      for (i = 0; i < n; i++) {

        lua_geti(L, 1, f + i);

        lua_seti(L, tt, t + i);

      }

    }

    else {

      for (i = n - 1; i >= 0; i--) {

        lua_geti(L, 1, f + i);

        lua_seti(L, tt, t + i);

      }

    }

  }

  lua_pushvalue(L, tt);  /* return destination table */

  return 1;

}

static void addfield (lua_State *L, luaL_Buffer *b, lua_Integer i) {

  lua_geti(L, 1, i);

  if (l_unlikely(!lua_isstring(L, -1)))

    luaL_error(L, "invalid value (%s) at index %I in table for 'concat'",

                  luaL_typename(L, -1), (LUAI_UACINT)i);

  luaL_addvalue(b);

}

static int tconcat (lua_State *L) {

  luaL_Buffer b;

  lua_Integer last = aux_getn(L, 1, TAB_R);

  size_t lsep;

  const char *sep = luaL_optlstring(L, 2, "", &lsep);

  lua_Integer i = luaL_optinteger(L, 3, 1);

  last = luaL_optinteger(L, 4, last);

  luaL_buffinit(L, &b);

  for (; i < last; i++) {

    addfield(L, &b, i);

    luaL_addlstring(&b, sep, lsep);

  }

  if (i == last)  /* add last value (if interval was not empty) */

    addfield(L, &b, i);

  luaL_pushresult(&b);

  return 1;

}

/*

** {======================================================

** Pack/unpack

** =======================================================

*/

static int tpack (lua_State *L) {

  int i;

  int n = lua_gettop(L);  /* number of elements to pack */

  lua_createtable(L, n, 1);  /* create result table */

  lua_insert(L, 1);  /* put it at index 1 */

  for (i = n; i >= 1; i--)  /* assign elements */

    lua_seti(L, 1, i);

  lua_pushinteger(L, n);

  lua_setfield(L, 1, "n");  /* t.n = number of elements */

  return 1;  /* return table */

}

static int tunpack (lua_State *L) {

  lua_Unsigned n;

  lua_Integer i = luaL_optinteger(L, 2, 1);

  lua_Integer e = luaL_opt(L, luaL_checkinteger, 3, luaL_len(L, 1));

  if (i > e) return 0;  /* empty range */

  n = (lua_Unsigned)e - i;  /* number of elements minus 1 (avoid overflows) */

  if (l_unlikely(n >= (unsigned int)INT_MAX  ||

                 !lua_checkstack(L, (int)(++n))))

    return luaL_error(L, "too many results to unpack");

  for (; i < e; i++) {  /* push arg[i..e - 1] (to avoid overflows) */

    lua_geti(L, 1, i);

  }

  lua_geti(L, 1, e);  /* push last element */

  return (int)n;

}

/* }====================================================== */

/*

** {======================================================

** Quicksort

** (based on 'Algorithms in MODULA-3', Robert Sedgewick;

**  Addison-Wesley, 1993.)

** =======================================================

*/

/* type for array indices */

typedef unsigned int IdxT;

/*

** Produce a "random" 'unsigned int' to randomize pivot choice. This

** macro is used only when 'sort' detects a big imbalance in the result

** of a partition. (If you don't want/need this "randomness", ~0 is a

** good choice.)

*/

#if !defined(l_randomizePivot)    /* { */

#include <time.h>

/* size of 'e' measured in number of 'unsigned int's */

#define sof(e)    (sizeof(e) / sizeof(unsigned int))

/*

** Use 'time' and 'clock' as sources of "randomness". Because we don't

** know the types 'clock_t' and 'time_t', we cannot cast them to

** anything without risking overflows. A safe way to use their values

** is to copy them to an array of a known type and use the array values.

*/

static unsigned int l_randomizePivot (void) {

  clock_t c = clock();

  time_t t = time(NULL);

  unsigned int buff[sof(c) + sof(t)];

  unsigned int i, rnd = 0;

  memcpy(buff, &c, sof(c) * sizeof(unsigned int));

  memcpy(buff + sof(c), &t, sof(t) * sizeof(unsigned int));

  for (i = 0; i < sof(buff); i++)

    rnd += buff[i];

  return rnd;

}

#endif          /* } */

/* arrays larger than 'RANLIMIT' may use randomized pivots */

#define RANLIMIT  100u

static void set2 (lua_State *L, IdxT i, IdxT j) {

  lua_seti(L, 1, i);

  lua_seti(L, 1, j);

}

/*

** Return true iff value at stack index 'a' is less than the value at

** index 'b' (according to the order of the sort).

*/

static int sort_comp (lua_State *L, int a, int b) {

  if (lua_isnil(L, 2))  /* no function? */

    return lua_compare(L, a, b, LUA_OPLT);  /* a < b */

  else {  /* function */

    int res;

    lua_pushvalue(L, 2);    /* push function */

    lua_pushvalue(L, a-1);  /* -1 to compensate function */

    lua_pushvalue(L, b-2);  /* -2 to compensate function and 'a' */

    lua_call(L, 2, 1);      /* call function */

    res = lua_toboolean(L, -1);  /* get result */

    lua_pop(L, 1);          /* pop result */

    return res;

  }

}

/*

** Does the partition: Pivot P is at the top of the stack.

** precondition: a[lo] <= P == a[up-1] <= a[up],

** so it only needs to do the partition from lo + 1 to up - 2.

** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]

** returns 'i'.

*/

static IdxT partition (lua_State *L, IdxT lo, IdxT up) {

  IdxT i = lo;  /* will be incremented before first use */

  IdxT j = up - 1;  /* will be decremented before first use */

  /* loop invariant: a[lo .. i] <= P <= a[j .. up] */

  for (;;) {

    /* next loop: repeat ++i while a[i] < P */

    while ((void)lua_geti(L, 1, ++i), sort_comp(L, -1, -2)) {

      if (l_unlikely(i == up - 1))  /* a[i] < P  but a[up - 1] == P  ?? */

        luaL_error(L, "invalid order function for sorting");

      lua_pop(L, 1);  /* remove a[i] */

    }

    /* after the loop, a[i] >= P and a[lo .. i - 1] < P */

    /* next loop: repeat --j while P < a[j] */

    while ((void)lua_geti(L, 1, --j), sort_comp(L, -3, -1)) {

      if (l_unlikely(j < i))  /* j < i  but  a[j] > P ?? */

        luaL_error(L, "invalid order function for sorting");

      lua_pop(L, 1);  /* remove a[j] */

    }

    /* after the loop, a[j] <= P and a[j + 1 .. up] >= P */

    if (j < i) {  /* no elements out of place? */

      /* a[lo .. i - 1] <= P <= a[j + 1 .. i .. up] */

      lua_pop(L, 1);  /* pop a[j] */

      /* swap pivot (a[up - 1]) with a[i] to satisfy pos-condition */

      set2(L, up - 1, i);

      return i;

    }

    /* otherwise, swap a[i] - a[j] to restore invariant and repeat */

    set2(L, i, j);

  }

}

/*

** Choose an element in the middle (2nd-3th quarters) of [lo,up]

** "randomized" by 'rnd'

*/

static IdxT choosePivot (IdxT lo, IdxT up, unsigned int rnd) {

  IdxT r4 = (up - lo) / 4;  /* range/4 */

  IdxT p = rnd % (r4 * 2) + (lo + r4);

  lua_assert(lo + r4 <= p && p <= up - r4);

  return p;

}

/*

** Quicksort algorithm (recursive function)

*/

static void auxsort (lua_State *L, IdxT lo, IdxT up,

                                   unsigned int rnd) {

  while (lo < up) {  /* loop for tail recursion */

    IdxT p;  /* Pivot index */

    IdxT n;  /* to be used later */

    /* sort elements 'lo', 'p', and 'up' */

    lua_geti(L, 1, lo);

    lua_geti(L, 1, up);

    if (sort_comp(L, -1, -2))  /* a[up] < a[lo]? */

      set2(L, lo, up);  /* swap a[lo] - a[up] */

    else

      lua_pop(L, 2);  /* remove both values */

    if (up - lo == 1)  /* only 2 elements? */

      return;  /* already sorted */

    if (up - lo < RANLIMIT || rnd == 0)  /* small interval or no randomize? */

      p = (lo + up)/2;  /* middle element is a good pivot */

    else  /* for larger intervals, it is worth a random pivot */

      p = choosePivot(lo, up, rnd);

    lua_geti(L, 1, p);

    lua_geti(L, 1, lo);

    if (sort_comp(L, -2, -1))  /* a[p] < a[lo]? */

      set2(L, p, lo);  /* swap a[p] - a[lo] */

    else {

      lua_pop(L, 1);  /* remove a[lo] */

      lua_geti(L, 1, up);

      if (sort_comp(L, -1, -2))  /* a[up] < a[p]? */

        set2(L, p, up);  /* swap a[up] - a[p] */

      else

        lua_pop(L, 2);

    }

    if (up - lo == 2)  /* only 3 elements? */

      return;  /* already sorted */

    lua_geti(L, 1, p);  /* get middle element (Pivot) */

    lua_pushvalue(L, -1);  /* push Pivot */

    lua_geti(L, 1, up - 1);  /* push a[up - 1] */

    set2(L, p, up - 1);  /* swap Pivot (a[p]) with a[up - 1] */

    p = partition(L, lo, up);

    /* a[lo .. p - 1] <= a[p] == P <= a[p + 1 .. up] */

    if (p - lo < up - p) {  /* lower interval is smaller? */

      auxsort(L, lo, p - 1, rnd);  /* call recursively for lower interval */

      n = p - lo;  /* size of smaller interval */

      lo = p + 1;  /* tail call for [p + 1 .. up] (upper interval) */

    }

    else {

      auxsort(L, p + 1, up, rnd);  /* call recursively for upper interval */

      n = up - p;  /* size of smaller interval */

      up = p - 1;  /* tail call for [lo .. p - 1]  (lower interval) */

    }

    if ((up - lo) / 128 > n) /* partition too imbalanced? */

      rnd = l_randomizePivot();  /* try a new randomization */

  }  /* tail call auxsort(L, lo, up, rnd) */

}

static int sort (lua_State *L) {

  lua_Integer n = aux_getn(L, 1, TAB_RW);

  if (n > 1) {  /* non-trivial interval? */

    luaL_argcheck(L, n < INT_MAX, 1, "array too big");

    if (!lua_isnoneornil(L, 2))  /* is there a 2nd argument? */

      luaL_checktype(L, 2, LUA_TFUNCTION);  /* must be a function */

    lua_settop(L, 2);  /* make sure there are two arguments */

    auxsort(L, 1, (IdxT)n, 0);

  }

  return 0;

}

/* }====================================================== */

static const luaL_Reg tab_funcs[] = {

  {"concat", tconcat},

  {"insert", tinsert},

  {"pack", tpack},

  {"unpack", tunpack},

  {"remove", tremove},

  {"move", tmove},

  {"sort", sort},

  {NULL, NULL}

};

LUAMOD_API int luaopen_table (lua_State *L) {

  luaL_newlib(L, tab_funcs);

  return 1;

}