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/*
** String handling.
** Copyright (C) 2005-2017 Mike Pall. See Copyright Notice in luajit.h
*/
#define lj_str_c
#define LUA_CORE
#include "lj_obj.h"
#include "lj_gc.h"
#include "lj_err.h"
#include "lj_str.h"
#include "lj_char.h"
/* -- String helpers ------------------------------------------------------ */
/* Ordered compare of strings. Assumes string data is 4-byte aligned. */
int32_t LJ_FASTCALL lj_str_cmp(GCstr *a, GCstr *b)
{
MSize i, n = a->len > b->len ? b->len : a->len;
for (i = 0; i < n; i += 4) {
/* Note: innocuous access up to end of string + 3. */
uint32_t va = *(const uint32_t *)(strdata(a)+i);
uint32_t vb = *(const uint32_t *)(strdata(b)+i);
if (va != vb) {
#if LJ_LE
va = lj_bswap(va); vb = lj_bswap(vb);
#endif
i -= n;
if ((int32_t)i >= -3) {
va >>= 32+(i<<3); vb >>= 32+(i<<3);
if (va == vb) break;
}
return va < vb ? -1 : 1;
}
}
return (int32_t)(a->len - b->len);
}
/* Fast string data comparison. Caveat: unaligned access to 1st string! */
static LJ_AINLINE int str_fastcmp(const char *a, const char *b, MSize len)
{
MSize i = 0;
lua_assert(len > 0);
lua_assert((((uintptr_t)a+len-1) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4);
do { /* Note: innocuous access up to end of string + 3. */
uint32_t v = lj_getu32(a+i) ^ *(const uint32_t *)(b+i);
if (v) {
i -= len;
#if LJ_LE
return (int32_t)i >= -3 ? (v << (32+(i<<3))) : 1;
#else
return (int32_t)i >= -3 ? (v >> (32+(i<<3))) : 1;
#endif
}
i += 4;
} while (i < len);
return 0;
}
/* Find fixed string p inside string s. */
const char *lj_str_find(const char *s, const char *p, MSize slen, MSize plen)
{
if (plen <= slen) {
if (plen == 0) {
return s;
} else {
int c = *(const uint8_t *)p++;
plen--; slen -= plen;
while (slen) {
const char *q = (const char *)memchr(s, c, slen);
if (!q) break;
if (memcmp(q+1, p, plen) == 0) return q;
q++; slen -= (MSize)(q-s); s = q;
}
}
}
return NULL;
}
/* Check whether a string has a pattern matching character. */
int lj_str_haspattern(GCstr *s)
{
const char *p = strdata(s), *q = p + s->len;
while (p < q) {
int c = *(const uint8_t *)p++;
if (lj_char_ispunct(c) && strchr("^$*+?.([%-", c))
return 1; /* Found a pattern matching char. */
}
return 0; /* No pattern matching chars found. */
}
/* -- String interning ---------------------------------------------------- */
/* Resize the string hash table (grow and shrink). */
void lj_str_resize(lua_State *L, MSize newmask)
{
global_State *g = G(L);
GCRef *newhash;
MSize i;
if (g->gc.state == GCSsweepstring || newmask >= LJ_MAX_STRTAB-1)
return; /* No resizing during GC traversal or if already too big. */
newhash = lj_mem_newvec(L, newmask+1, GCRef);
memset(newhash, 0, (newmask+1)*sizeof(GCRef));
for (i = g->strmask; i != ~(MSize)0; i--) { /* Rehash old table. */
GCobj *p = gcref(g->strhash[i]);
while (p) { /* Follow each hash chain and reinsert all strings. */
MSize h = gco2str(p)->hash & newmask;
GCobj *next = gcnext(p);
/* NOBARRIER: The string table is a GC root. */
setgcrefr(p->gch.nextgc, newhash[h]);
setgcref(newhash[h], p);
p = next;
}
}
lj_mem_freevec(g, g->strhash, g->strmask+1, GCRef);
g->strmask = newmask;
g->strhash = newhash;
}
/* Intern a string and return string object. */
GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
{
global_State *g;
GCstr *s;
GCobj *o;
MSize len = (MSize)lenx;
MSize a, b, h = len;
if (lenx >= LJ_MAX_STR)
lj_err_msg(L, LJ_ERR_STROV);
g = G(L);
/* Compute string hash. Constants taken from lookup3 hash by Bob Jenkins. */
if (len >= 4) { /* Caveat: unaligned access! */
a = lj_getu32(str);
h ^= lj_getu32(str+len-4);
b = lj_getu32(str+(len>>1)-2);
h ^= b; h -= lj_rol(b, 14);
b += lj_getu32(str+(len>>2)-1);
} else if (len > 0) {
a = *(const uint8_t *)str;
h ^= *(const uint8_t *)(str+len-1);
b = *(const uint8_t *)(str+(len>>1));
h ^= b; h -= lj_rol(b, 14);
} else {
return &g->strempty;
}
a ^= h; a -= lj_rol(h, 11);
b ^= a; b -= lj_rol(a, 25);
h ^= b; h -= lj_rol(b, 16);
/* Check if the string has already been interned. */
o = gcref(g->strhash[h & g->strmask]);
if (LJ_LIKELY((((uintptr_t)str+len-1) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4)) {
while (o != NULL) {
GCstr *sx = gco2str(o);
if (sx->len == len && str_fastcmp(str, strdata(sx), len) == 0) {
/* Resurrect if dead. Can only happen with fixstring() (keywords). */
if (isdead(g, o)) flipwhite(o);
return sx; /* Return existing string. */
}
o = gcnext(o);
}
} else { /* Slow path: end of string is too close to a page boundary. */
while (o != NULL) {
GCstr *sx = gco2str(o);
if (sx->len == len && memcmp(str, strdata(sx), len) == 0) {
/* Resurrect if dead. Can only happen with fixstring() (keywords). */
if (isdead(g, o)) flipwhite(o);
return sx; /* Return existing string. */
}
o = gcnext(o);
}
}
/* Nope, create a new string. */
s = lj_mem_newt(L, sizeof(GCstr)+len+1, GCstr);
newwhite(g, s);
s->gct = ~LJ_TSTR;
s->len = len;
s->hash = h;
s->reserved = 0;
memcpy(strdatawr(s), str, len);
strdatawr(s)[len] = '\0'; /* Zero-terminate string. */
/* Add it to string hash table. */
h &= g->strmask;
s->nextgc = g->strhash[h];
/* NOBARRIER: The string table is a GC root. */
setgcref(g->strhash[h], obj2gco(s));
if (g->strnum++ > g->strmask) /* Allow a 100% load factor. */
lj_str_resize(L, (g->strmask<<1)+1); /* Grow string table. */
return s; /* Return newly interned string. */
}
void LJ_FASTCALL lj_str_free(global_State *g, GCstr *s)
{
g->strnum--;
lj_mem_free(g, s, sizestring(s));
}
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