/*

** $Id: lstring.c,v 2.26.1.1 2013/04/12 18:48:47 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"

/*

** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to

** compute its hash

*/

#if !defined(LUAI_HASHLIMIT)

#define LUAI_HASHLIMIT 5

#endif

/*

** equality for long strings

*/

int luaS_eqlngstr (TString *a, TString *b) {

size_t len = a->tsv.len;

lua_assert(a->tsv.tt == LUA_TLNGSTR && b->tsv.tt == LUA_TLNGSTR);

return (a == b) || /* same instance or... */

((len == b->tsv.len) && /* equal length and ... */

(memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */

}

/*

** equality for strings

*/

int luaS_eqstr (TString *a, TString *b) {

return (a->tsv.tt == b->tsv.tt) &&

(a->tsv.tt == LUA_TSHRSTR ? eqshrstr(a, b) : luaS_eqlngstr(a, b));

}

unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {

unsigned int h = seed ^ cast(unsigned int, l);

size_t l1;

size_t step = (l >> LUAI_HASHLIMIT) + 1;

for (l1 = l; l1 >= step; l1 -= step)

h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1]));

return h;

}

/*

** resizes the string table

*/

void luaS_resize (lua_State *L, int newsize) {

int i;

stringtable *tb = &G(L)->strt;

/* cannot resize while GC is traversing strings */

luaC_runtilstate(L, ~bitmask(GCSsweepstring));

if (newsize > tb->size) {

luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);

for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL;

}

/* rehash */

for (i=0; i<tb->size; i++) {

GCObject *p = tb->hash[i];

tb->hash[i] = NULL;

while (p) { /* for each node in the list */

GCObject *next = gch(p)->next; /* save next */

unsigned int h = lmod(gco2ts(p)->hash, newsize); /* new position */

gch(p)->next = tb->hash[h]; /* chain it */

tb->hash[h] = p;

resetoldbit(p); /* see MOVE OLD rule */

p = next;

}

}

if (newsize < tb->size) {

/* shrinking slice must be empty */

lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);

luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);

}

tb->size = newsize;

}

/*

** creates a new string object

*/

static TString *createstrobj (lua_State *L, const char *str, size_t l,

int tag, unsigned int h, GCObject **list) {

TString *ts;

size_t totalsize; /* total size of TString object */

totalsize = sizeof(TString) + ((l + 1) * sizeof(char));

ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts;

ts->tsv.len = l;

ts->tsv.hash = h;

ts->tsv.extra = 0;

memcpy(ts+1, str, l*sizeof(char));

((char *)(ts+1))[l] = '\0'; /* ending 0 */

return ts;

}

/*

** creates a new short string, inserting it into string table

*/

static TString *newshrstr (lua_State *L, const char *str, size_t l,

unsigned int h) {

GCObject **list; /* (pointer to) list where it will be inserted */

stringtable *tb = &G(L)->strt;

TString *s;

if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)

luaS_resize(L, tb->size*2); /* too crowded */

list = &tb->hash[lmod(h, tb->size)];

s = createstrobj(L, str, l, LUA_TSHRSTR, h, list);

tb->nuse++;

return s;

}

/*

** checks whether short string exists and reuses it or creates a new one

*/

static TString *internshrstr (lua_State *L, const char *str, size_t l) {

GCObject *o;

global_State *g = G(L);

unsigned int h = luaS_hash(str, l, g->seed);

for (o = g->strt.hash[lmod(h, g->strt.size)];

o != NULL;

o = gch(o)->next) {

TString *ts = rawgco2ts(o);

if (h == ts->tsv.hash &&

l == ts->tsv.len &&

(memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {

if (isdead(G(L), o)) /* string is dead (but was not collected yet)? */

changewhite(o); /* resurrect it */

return ts;

}

}

return newshrstr(L, str, l, h); /* not found; create a new string */

}

/*

** new string (with explicit length)

*/

TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {

if (l <= LUAI_MAXSHORTLEN) /* short string? */

return internshrstr(L, str, l);

else {

if (l + 1 > (MAX_SIZET - sizeof(TString))/sizeof(char))

luaM_toobig(L);

return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL);

}

}

/*

** new zero-terminated string

*/

TString *luaS_new (lua_State *L, const char *str) {

return luaS_newlstr(L, str, strlen(str));

}

Udata *luaS_newudata (lua_State *L, size_t s, Table *e) {

Udata *u;

if (s > MAX_SIZET - sizeof(Udata))

luaM_toobig(L);

u = &luaC_newobj(L, LUA_TUSERDATA, sizeof(Udata) + s, NULL, 0)->u;

u->uv.len = s;

u->uv.metatable = NULL;

u->uv.env = e;

return u;

}