xref: /aosp_15_r20/external/lua/src/lstring.c (revision 088332b5b69e7ab13924864b272aabfc2509d2d5)
1*088332b5SXin Li /*
2*088332b5SXin Li ** $Id: lstring.c $
3*088332b5SXin Li ** String table (keeps all strings handled by Lua)
4*088332b5SXin Li ** See Copyright Notice in lua.h
5*088332b5SXin Li */
6*088332b5SXin Li 
7*088332b5SXin Li #define lstring_c
8*088332b5SXin Li #define LUA_CORE
9*088332b5SXin Li 
10*088332b5SXin Li #include "lprefix.h"
11*088332b5SXin Li 
12*088332b5SXin Li 
13*088332b5SXin Li #include <string.h>
14*088332b5SXin Li 
15*088332b5SXin Li #include "lua.h"
16*088332b5SXin Li 
17*088332b5SXin Li #include "ldebug.h"
18*088332b5SXin Li #include "ldo.h"
19*088332b5SXin Li #include "lmem.h"
20*088332b5SXin Li #include "lobject.h"
21*088332b5SXin Li #include "lstate.h"
22*088332b5SXin Li #include "lstring.h"
23*088332b5SXin Li 
24*088332b5SXin Li 
25*088332b5SXin Li /*
26*088332b5SXin Li ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a long string to
27*088332b5SXin Li ** compute its hash
28*088332b5SXin Li */
29*088332b5SXin Li #if !defined(LUAI_HASHLIMIT)
30*088332b5SXin Li #define LUAI_HASHLIMIT		5
31*088332b5SXin Li #endif
32*088332b5SXin Li 
33*088332b5SXin Li 
34*088332b5SXin Li 
35*088332b5SXin Li /*
36*088332b5SXin Li ** Maximum size for string table.
37*088332b5SXin Li */
38*088332b5SXin Li #define MAXSTRTB	cast_int(luaM_limitN(MAX_INT, TString*))
39*088332b5SXin Li 
40*088332b5SXin Li 
41*088332b5SXin Li /*
42*088332b5SXin Li ** equality for long strings
43*088332b5SXin Li */
luaS_eqlngstr(TString * a,TString * b)44*088332b5SXin Li int luaS_eqlngstr (TString *a, TString *b) {
45*088332b5SXin Li   size_t len = a->u.lnglen;
46*088332b5SXin Li   lua_assert(a->tt == LUA_VLNGSTR && b->tt == LUA_VLNGSTR);
47*088332b5SXin Li   return (a == b) ||  /* same instance or... */
48*088332b5SXin Li     ((len == b->u.lnglen) &&  /* equal length and ... */
49*088332b5SXin Li      (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
50*088332b5SXin Li }
51*088332b5SXin Li 
52*088332b5SXin Li 
luaS_hash(const char * str,size_t l,unsigned int seed,size_t step)53*088332b5SXin Li unsigned int luaS_hash (const char *str, size_t l, unsigned int seed,
54*088332b5SXin Li                         size_t step) {
55*088332b5SXin Li   unsigned int h = seed ^ cast_uint(l);
56*088332b5SXin Li   for (; l >= step; l -= step)
57*088332b5SXin Li     h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
58*088332b5SXin Li   return h;
59*088332b5SXin Li }
60*088332b5SXin Li 
61*088332b5SXin Li 
luaS_hashlongstr(TString * ts)62*088332b5SXin Li unsigned int luaS_hashlongstr (TString *ts) {
63*088332b5SXin Li   lua_assert(ts->tt == LUA_VLNGSTR);
64*088332b5SXin Li   if (ts->extra == 0) {  /* no hash? */
65*088332b5SXin Li     size_t len = ts->u.lnglen;
66*088332b5SXin Li     size_t step = (len >> LUAI_HASHLIMIT) + 1;
67*088332b5SXin Li     ts->hash = luaS_hash(getstr(ts), len, ts->hash, step);
68*088332b5SXin Li     ts->extra = 1;  /* now it has its hash */
69*088332b5SXin Li   }
70*088332b5SXin Li   return ts->hash;
71*088332b5SXin Li }
72*088332b5SXin Li 
73*088332b5SXin Li 
tablerehash(TString ** vect,int osize,int nsize)74*088332b5SXin Li static void tablerehash (TString **vect, int osize, int nsize) {
75*088332b5SXin Li   int i;
76*088332b5SXin Li   for (i = osize; i < nsize; i++)  /* clear new elements */
77*088332b5SXin Li     vect[i] = NULL;
78*088332b5SXin Li   for (i = 0; i < osize; i++) {  /* rehash old part of the array */
79*088332b5SXin Li     TString *p = vect[i];
80*088332b5SXin Li     vect[i] = NULL;
81*088332b5SXin Li     while (p) {  /* for each string in the list */
82*088332b5SXin Li       TString *hnext = p->u.hnext;  /* save next */
83*088332b5SXin Li       unsigned int h = lmod(p->hash, nsize);  /* new position */
84*088332b5SXin Li       p->u.hnext = vect[h];  /* chain it into array */
85*088332b5SXin Li       vect[h] = p;
86*088332b5SXin Li       p = hnext;
87*088332b5SXin Li     }
88*088332b5SXin Li   }
89*088332b5SXin Li }
90*088332b5SXin Li 
91*088332b5SXin Li 
92*088332b5SXin Li /*
93*088332b5SXin Li ** Resize the string table. If allocation fails, keep the current size.
94*088332b5SXin Li ** (This can degrade performance, but any non-zero size should work
95*088332b5SXin Li ** correctly.)
96*088332b5SXin Li */
luaS_resize(lua_State * L,int nsize)97*088332b5SXin Li void luaS_resize (lua_State *L, int nsize) {
98*088332b5SXin Li   stringtable *tb = &G(L)->strt;
99*088332b5SXin Li   int osize = tb->size;
100*088332b5SXin Li   TString **newvect;
101*088332b5SXin Li   if (nsize < osize)  /* shrinking table? */
102*088332b5SXin Li     tablerehash(tb->hash, osize, nsize);  /* depopulate shrinking part */
103*088332b5SXin Li   newvect = luaM_reallocvector(L, tb->hash, osize, nsize, TString*);
104*088332b5SXin Li   if (unlikely(newvect == NULL)) {  /* reallocation failed? */
105*088332b5SXin Li     if (nsize < osize)  /* was it shrinking table? */
106*088332b5SXin Li       tablerehash(tb->hash, nsize, osize);  /* restore to original size */
107*088332b5SXin Li     /* leave table as it was */
108*088332b5SXin Li   }
109*088332b5SXin Li   else {  /* allocation succeeded */
110*088332b5SXin Li     tb->hash = newvect;
111*088332b5SXin Li     tb->size = nsize;
112*088332b5SXin Li     if (nsize > osize)
113*088332b5SXin Li       tablerehash(newvect, osize, nsize);  /* rehash for new size */
114*088332b5SXin Li   }
115*088332b5SXin Li }
116*088332b5SXin Li 
117*088332b5SXin Li 
118*088332b5SXin Li /*
119*088332b5SXin Li ** Clear API string cache. (Entries cannot be empty, so fill them with
120*088332b5SXin Li ** a non-collectable string.)
121*088332b5SXin Li */
luaS_clearcache(global_State * g)122*088332b5SXin Li void luaS_clearcache (global_State *g) {
123*088332b5SXin Li   int i, j;
124*088332b5SXin Li   for (i = 0; i < STRCACHE_N; i++)
125*088332b5SXin Li     for (j = 0; j < STRCACHE_M; j++) {
126*088332b5SXin Li       if (iswhite(g->strcache[i][j]))  /* will entry be collected? */
127*088332b5SXin Li         g->strcache[i][j] = g->memerrmsg;  /* replace it with something fixed */
128*088332b5SXin Li     }
129*088332b5SXin Li }
130*088332b5SXin Li 
131*088332b5SXin Li 
132*088332b5SXin Li /*
133*088332b5SXin Li ** Initialize the string table and the string cache
134*088332b5SXin Li */
luaS_init(lua_State * L)135*088332b5SXin Li void luaS_init (lua_State *L) {
136*088332b5SXin Li   global_State *g = G(L);
137*088332b5SXin Li   int i, j;
138*088332b5SXin Li   stringtable *tb = &G(L)->strt;
139*088332b5SXin Li   tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
140*088332b5SXin Li   tablerehash(tb->hash, 0, MINSTRTABSIZE);  /* clear array */
141*088332b5SXin Li   tb->size = MINSTRTABSIZE;
142*088332b5SXin Li   /* pre-create memory-error message */
143*088332b5SXin Li   g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
144*088332b5SXin Li   luaC_fix(L, obj2gco(g->memerrmsg));  /* it should never be collected */
145*088332b5SXin Li   for (i = 0; i < STRCACHE_N; i++)  /* fill cache with valid strings */
146*088332b5SXin Li     for (j = 0; j < STRCACHE_M; j++)
147*088332b5SXin Li       g->strcache[i][j] = g->memerrmsg;
148*088332b5SXin Li }
149*088332b5SXin Li 
150*088332b5SXin Li 
151*088332b5SXin Li 
152*088332b5SXin Li /*
153*088332b5SXin Li ** creates a new string object
154*088332b5SXin Li */
createstrobj(lua_State * L,size_t l,int tag,unsigned int h)155*088332b5SXin Li static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
156*088332b5SXin Li   TString *ts;
157*088332b5SXin Li   GCObject *o;
158*088332b5SXin Li   size_t totalsize;  /* total size of TString object */
159*088332b5SXin Li   totalsize = sizelstring(l);
160*088332b5SXin Li   o = luaC_newobj(L, tag, totalsize);
161*088332b5SXin Li   ts = gco2ts(o);
162*088332b5SXin Li   ts->hash = h;
163*088332b5SXin Li   ts->extra = 0;
164*088332b5SXin Li   getstr(ts)[l] = '\0';  /* ending 0 */
165*088332b5SXin Li   return ts;
166*088332b5SXin Li }
167*088332b5SXin Li 
168*088332b5SXin Li 
luaS_createlngstrobj(lua_State * L,size_t l)169*088332b5SXin Li TString *luaS_createlngstrobj (lua_State *L, size_t l) {
170*088332b5SXin Li   TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
171*088332b5SXin Li   ts->u.lnglen = l;
172*088332b5SXin Li   return ts;
173*088332b5SXin Li }
174*088332b5SXin Li 
175*088332b5SXin Li 
luaS_remove(lua_State * L,TString * ts)176*088332b5SXin Li void luaS_remove (lua_State *L, TString *ts) {
177*088332b5SXin Li   stringtable *tb = &G(L)->strt;
178*088332b5SXin Li   TString **p = &tb->hash[lmod(ts->hash, tb->size)];
179*088332b5SXin Li   while (*p != ts)  /* find previous element */
180*088332b5SXin Li     p = &(*p)->u.hnext;
181*088332b5SXin Li   *p = (*p)->u.hnext;  /* remove element from its list */
182*088332b5SXin Li   tb->nuse--;
183*088332b5SXin Li }
184*088332b5SXin Li 
185*088332b5SXin Li 
growstrtab(lua_State * L,stringtable * tb)186*088332b5SXin Li static void growstrtab (lua_State *L, stringtable *tb) {
187*088332b5SXin Li   if (unlikely(tb->nuse == MAX_INT)) {  /* too many strings? */
188*088332b5SXin Li     luaC_fullgc(L, 1);  /* try to free some... */
189*088332b5SXin Li     if (tb->nuse == MAX_INT)  /* still too many? */
190*088332b5SXin Li       luaM_error(L);  /* cannot even create a message... */
191*088332b5SXin Li   }
192*088332b5SXin Li   if (tb->size <= MAXSTRTB / 2)  /* can grow string table? */
193*088332b5SXin Li     luaS_resize(L, tb->size * 2);
194*088332b5SXin Li }
195*088332b5SXin Li 
196*088332b5SXin Li 
197*088332b5SXin Li /*
198*088332b5SXin Li ** Checks whether short string exists and reuses it or creates a new one.
199*088332b5SXin Li */
internshrstr(lua_State * L,const char * str,size_t l)200*088332b5SXin Li static TString *internshrstr (lua_State *L, const char *str, size_t l) {
201*088332b5SXin Li   TString *ts;
202*088332b5SXin Li   global_State *g = G(L);
203*088332b5SXin Li   stringtable *tb = &g->strt;
204*088332b5SXin Li   unsigned int h = luaS_hash(str, l, g->seed, 1);
205*088332b5SXin Li   TString **list = &tb->hash[lmod(h, tb->size)];
206*088332b5SXin Li   lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
207*088332b5SXin Li   for (ts = *list; ts != NULL; ts = ts->u.hnext) {
208*088332b5SXin Li     if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
209*088332b5SXin Li       /* found! */
210*088332b5SXin Li       if (isdead(g, ts))  /* dead (but not collected yet)? */
211*088332b5SXin Li         changewhite(ts);  /* resurrect it */
212*088332b5SXin Li       return ts;
213*088332b5SXin Li     }
214*088332b5SXin Li   }
215*088332b5SXin Li   /* else must create a new string */
216*088332b5SXin Li   if (tb->nuse >= tb->size) {  /* need to grow string table? */
217*088332b5SXin Li     growstrtab(L, tb);
218*088332b5SXin Li     list = &tb->hash[lmod(h, tb->size)];  /* rehash with new size */
219*088332b5SXin Li   }
220*088332b5SXin Li   ts = createstrobj(L, l, LUA_VSHRSTR, h);
221*088332b5SXin Li   memcpy(getstr(ts), str, l * sizeof(char));
222*088332b5SXin Li   ts->shrlen = cast_byte(l);
223*088332b5SXin Li   ts->u.hnext = *list;
224*088332b5SXin Li   *list = ts;
225*088332b5SXin Li   tb->nuse++;
226*088332b5SXin Li   return ts;
227*088332b5SXin Li }
228*088332b5SXin Li 
229*088332b5SXin Li 
230*088332b5SXin Li /*
231*088332b5SXin Li ** new string (with explicit length)
232*088332b5SXin Li */
luaS_newlstr(lua_State * L,const char * str,size_t l)233*088332b5SXin Li TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
234*088332b5SXin Li   if (l <= LUAI_MAXSHORTLEN)  /* short string? */
235*088332b5SXin Li     return internshrstr(L, str, l);
236*088332b5SXin Li   else {
237*088332b5SXin Li     TString *ts;
238*088332b5SXin Li     if (unlikely(l >= (MAX_SIZE - sizeof(TString))/sizeof(char)))
239*088332b5SXin Li       luaM_toobig(L);
240*088332b5SXin Li     ts = luaS_createlngstrobj(L, l);
241*088332b5SXin Li     memcpy(getstr(ts), str, l * sizeof(char));
242*088332b5SXin Li     return ts;
243*088332b5SXin Li   }
244*088332b5SXin Li }
245*088332b5SXin Li 
246*088332b5SXin Li 
247*088332b5SXin Li /*
248*088332b5SXin Li ** Create or reuse a zero-terminated string, first checking in the
249*088332b5SXin Li ** cache (using the string address as a key). The cache can contain
250*088332b5SXin Li ** only zero-terminated strings, so it is safe to use 'strcmp' to
251*088332b5SXin Li ** check hits.
252*088332b5SXin Li */
luaS_new(lua_State * L,const char * str)253*088332b5SXin Li TString *luaS_new (lua_State *L, const char *str) {
254*088332b5SXin Li   unsigned int i = point2uint(str) % STRCACHE_N;  /* hash */
255*088332b5SXin Li   int j;
256*088332b5SXin Li   TString **p = G(L)->strcache[i];
257*088332b5SXin Li   for (j = 0; j < STRCACHE_M; j++) {
258*088332b5SXin Li     if (strcmp(str, getstr(p[j])) == 0)  /* hit? */
259*088332b5SXin Li       return p[j];  /* that is it */
260*088332b5SXin Li   }
261*088332b5SXin Li   /* normal route */
262*088332b5SXin Li   for (j = STRCACHE_M - 1; j > 0; j--)
263*088332b5SXin Li     p[j] = p[j - 1];  /* move out last element */
264*088332b5SXin Li   /* new element is first in the list */
265*088332b5SXin Li   p[0] = luaS_newlstr(L, str, strlen(str));
266*088332b5SXin Li   return p[0];
267*088332b5SXin Li }
268*088332b5SXin Li 
269*088332b5SXin Li 
luaS_newudata(lua_State * L,size_t s,int nuvalue)270*088332b5SXin Li Udata *luaS_newudata (lua_State *L, size_t s, int nuvalue) {
271*088332b5SXin Li   Udata *u;
272*088332b5SXin Li   int i;
273*088332b5SXin Li   GCObject *o;
274*088332b5SXin Li   if (unlikely(s > MAX_SIZE - udatamemoffset(nuvalue)))
275*088332b5SXin Li     luaM_toobig(L);
276*088332b5SXin Li   o = luaC_newobj(L, LUA_VUSERDATA, sizeudata(nuvalue, s));
277*088332b5SXin Li   u = gco2u(o);
278*088332b5SXin Li   u->len = s;
279*088332b5SXin Li   u->nuvalue = nuvalue;
280*088332b5SXin Li   u->metatable = NULL;
281*088332b5SXin Li   for (i = 0; i < nuvalue; i++)
282*088332b5SXin Li     setnilvalue(&u->uv[i].uv);
283*088332b5SXin Li   return u;
284*088332b5SXin Li }
285*088332b5SXin Li 
286