/*
** $Id: lstring.c,v 2.8.1.1 2007/12/27 13:02:25 roberto Exp $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/


#include <string.h>

#define lstring_c
#define LUA_CORE

#include "lua.h"

#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"



void luaS_resize (lua_State *L, int newsize) {
  GCObject **newhash;
  stringtable *tb;
  int i;
  if (G(L)->gcstate == GCSsweepstring)
    return;  /* cannot resize during GC traverse */
  newhash = luaM_newvector(L, newsize, GCObject *);
  tb = &G(L)->strt;
  for (i=0; i<newsize; i++) newhash[i] = NULL;
  /* rehash */
  for (i=0; i<tb->size; i++) {
    GCObject *p = tb->hash[i];
    while (p) {  /* for each node in the list */
      GCObject *next = p->gch.next;  /* save next */
      unsigned int h = gco2ts(p)->hash;
      int h1 = lmod(h, newsize);  /* new position */
      lua_assert(cast_int(h%newsize) == lmod(h, newsize));
      p->gch.next = newhash[h1];  /* chain it */
      newhash[h1] = p;
      p = next;
    }
  }
  luaM_freearray(L, tb->hash, tb->size, TString *);
  tb->size = newsize;
  tb->hash = newhash;
}


static TString *newlstr (lua_State *L, const char *str, size_t l,
                                       unsigned int h) {
  TString *ts;
  stringtable *tb;
  if (l_unlikely(l+1 > (MAX_SIZET - sizeof(TString))/sizeof(char)))
    luaM_toobig(L);
  ts = cast(TString *, luaM_malloc(L, (l+1)*sizeof(char)+sizeof(TString)));
  ts->tsv.len = l;
  ts->tsv.hash = h;
  ts->tsv.marked = luaC_white(G(L));
  ts->tsv.tt = LUA_TSTRING;
  ts->tsv.reserved = 0;
  memcpy(ts+1, str, l*sizeof(char));
  ((char *)(ts+1))[l] = '\0';  /* ending 0 */
  tb = &G(L)->strt;
  h = lmod(h, tb->size);
  ts->tsv.next = tb->hash[h];  /* chain new entry */
  tb->hash[h] = obj2gco(ts);
  tb->nuse++;
  if (tb->nuse > cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
    luaS_resize(L, tb->size*2);  /* too crowded */
  return ts;
}


// string hash taken from luaJIT

/* Unaligned load of uint32_t. */
static inline __attribute__((always_inline)) uint32_t getu32(const void* ptr)
{
  uint32_t result;
  memcpy(&result, ptr, 4);
  return result;
}

// smol macro to look a little less messy lul
#define getu8(p) *cast(const uint8_t *, p)

/* Keyed sparse ARX string hash. Constant time. */
static unsigned hash_sparse(const char *str, size_t len)
{
  /* Constants taken from lookup3 hash by Bob Jenkins. */
  unsigned int a, b, h = cast(unsigned int, len);
#define rol(x, n) (((x)<<(n)) | ((x)>>(-cast(int, n)&(8*sizeof(x)-1))))
  if (len >= 4) {  /* Caveat: unaligned access! */
    a  = getu32(str);
    h ^= getu32(str+len-4);
    b  = getu32(str+(len>>1)-2);
    h ^= b; h -= rol(b, 14);
    b += getu32(str+(len>>2)-1);
  } else if (len > 0) {
    a  = getu8(str);
    h ^= getu8(str+len-1);
    b  = getu8(str+(len>>1));
    h ^= b; h -= rol(b, 14);
  } else {
    return 0;
  }
  a ^= h; a -= rol(h, 11);
  b ^= a; b -= rol(a, 25);
  h ^= b; h -= rol(b, 16);
#undef rol
  return h;
}

#undef getu8


static inline __attribute__((always_inline)) unsigned luaS_hash (const char *str, size_t l) {
#if 0
  unsigned int h = cast(unsigned int, l);  /* seed */
  size_t step = (l>>5)+1;  /* if string is too long, don't hash all its chars */
  size_t l1;
  for (l1=l; l1>=step; l1-=step)  /* compute hash */
    h = h ^ ((h<<5)+(h>>2)+cast(unsigned char, str[l1-1]));
  return h;
#else
  return hash_sparse(str, l);
#endif
}

TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
  GCObject *o;
  unsigned int h = luaS_hash(str, l);
  for (o = G(L)->strt.hash[lmod(h, G(L)->strt.size)];
       o != NULL;
       o = o->gch.next) {
    TString *ts = rawgco2ts(o);
    if (ts->tsv.hash == h &&
        ts->tsv.len == l &&
       (memcmp(str, getstr(ts), l) == 0)) {
      /* string may be dead */
      if (isdead(G(L), o)) changewhite(o);
      return ts;
    }
  }
  return newlstr(L, str, l, h);  /* not found */
}


Udata *luaS_newudata (lua_State *L, size_t s, Table *e) {
  Udata *u;
  if (l_unlikely(s > MAX_SIZET - sizeof(Udata)))
    luaM_toobig(L);
  u = cast(Udata *, luaM_malloc(L, s + sizeof(Udata)));
  u->uv.marked = luaC_white(G(L));  /* is not finalized */
  u->uv.tt = LUA_TUSERDATA;
  u->uv.len = s;
  u->uv.metatable = NULL;
  u->uv.env = e;
  /* chain it on udata list (after main thread) */
  u->uv.next = G(L)->mainthread->next;
  G(L)->mainthread->next = obj2gco(u);
  return u;
}