1 /* $NetBSD: lstring.c,v 1.10 2023/04/16 20:46:17 nikita Exp $ */
2
3 /*
4 ** Id: lstring.c
5 ** String table (keeps all strings handled by Lua)
6 ** See Copyright Notice in lua.h
7 */
8
9 #define lstring_c
10 #define LUA_CORE
11
12 #include "lprefix.h"
13
14
15 #ifndef _KERNEL
16 #include <string.h>
17 #endif /* _KERNEL */
18
19 #include "lua.h"
20
21 #include "ldebug.h"
22 #include "ldo.h"
23 #include "lmem.h"
24 #include "lobject.h"
25 #include "lstate.h"
26 #include "lstring.h"
27
28
29 /*
30 ** Maximum size for string table.
31 */
32 #define MAXSTRTB cast_int(luaM_limitN(MAX_INT, TString*))
33
34
35 /*
36 ** equality for long strings
37 */
luaS_eqlngstr(TString * a,TString * b)38 int luaS_eqlngstr (TString *a, TString *b) {
39 size_t len = a->u.lnglen;
40 lua_assert(a->tt == LUA_VLNGSTR && b->tt == LUA_VLNGSTR);
41 return (a == b) || /* same instance or... */
42 ((len == b->u.lnglen) && /* equal length and ... */
43 (memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */
44 }
45
46
luaS_hash(const char * str,size_t l,unsigned int seed)47 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
48 unsigned int h = seed ^ cast_uint(l);
49 for (; l > 0; l--)
50 h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
51 return h;
52 }
53
54
luaS_hashlongstr(TString * ts)55 unsigned int luaS_hashlongstr (TString *ts) {
56 lua_assert(ts->tt == LUA_VLNGSTR);
57 if (ts->extra == 0) { /* no hash? */
58 size_t len = ts->u.lnglen;
59 ts->hash = luaS_hash(getstr(ts), len, ts->hash);
60 ts->extra = 1; /* now it has its hash */
61 }
62 return ts->hash;
63 }
64
65
tablerehash(TString ** vect,int osize,int nsize)66 static void tablerehash (TString **vect, int osize, int nsize) {
67 int i;
68 for (i = osize; i < nsize; i++) /* clear new elements */
69 vect[i] = NULL;
70 for (i = 0; i < osize; i++) { /* rehash old part of the array */
71 TString *p = vect[i];
72 vect[i] = NULL;
73 while (p) { /* for each string in the list */
74 TString *hnext = p->u.hnext; /* save next */
75 unsigned int h = lmod(p->hash, nsize); /* new position */
76 p->u.hnext = vect[h]; /* chain it into array */
77 vect[h] = p;
78 p = hnext;
79 }
80 }
81 }
82
83
84 /*
85 ** Resize the string table. If allocation fails, keep the current size.
86 ** (This can degrade performance, but any non-zero size should work
87 ** correctly.)
88 */
luaS_resize(lua_State * L,int nsize)89 void luaS_resize (lua_State *L, int nsize) {
90 stringtable *tb = &G(L)->strt;
91 int osize = tb->size;
92 TString **newvect;
93 if (nsize < osize) /* shrinking table? */
94 tablerehash(tb->hash, osize, nsize); /* depopulate shrinking part */
95 newvect = luaM_reallocvector(L, tb->hash, osize, nsize, TString*);
96 if (l_unlikely(newvect == NULL)) { /* reallocation failed? */
97 if (nsize < osize) /* was it shrinking table? */
98 tablerehash(tb->hash, nsize, osize); /* restore to original size */
99 /* leave table as it was */
100 }
101 else { /* allocation succeeded */
102 tb->hash = newvect;
103 tb->size = nsize;
104 if (nsize > osize)
105 tablerehash(newvect, osize, nsize); /* rehash for new size */
106 }
107 }
108
109
110 /*
111 ** Clear API string cache. (Entries cannot be empty, so fill them with
112 ** a non-collectable string.)
113 */
luaS_clearcache(global_State * g)114 void luaS_clearcache (global_State *g) {
115 int i, j;
116 for (i = 0; i < STRCACHE_N; i++)
117 for (j = 0; j < STRCACHE_M; j++) {
118 if (iswhite(g->strcache[i][j])) /* will entry be collected? */
119 g->strcache[i][j] = g->memerrmsg; /* replace it with something fixed */
120 }
121 }
122
123
124 /*
125 ** Initialize the string table and the string cache
126 */
luaS_init(lua_State * L)127 void luaS_init (lua_State *L) {
128 global_State *g = G(L);
129 int i, j;
130 stringtable *tb = &G(L)->strt;
131 tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
132 tablerehash(tb->hash, 0, MINSTRTABSIZE); /* clear array */
133 tb->size = MINSTRTABSIZE;
134 /* pre-create memory-error message */
135 g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
136 luaC_fix(L, obj2gco(g->memerrmsg)); /* it should never be collected */
137 for (i = 0; i < STRCACHE_N; i++) /* fill cache with valid strings */
138 for (j = 0; j < STRCACHE_M; j++)
139 g->strcache[i][j] = g->memerrmsg;
140 }
141
142
143
144 /*
145 ** creates a new string object
146 */
createstrobj(lua_State * L,size_t l,int tag,unsigned int h)147 static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
148 TString *ts;
149 GCObject *o;
150 size_t totalsize; /* total size of TString object */
151 totalsize = sizelstring(l);
152 o = luaC_newobj(L, tag, totalsize);
153 ts = gco2ts(o);
154 ts->hash = h;
155 ts->extra = 0;
156 getstr(ts)[l] = '\0'; /* ending 0 */
157 return ts;
158 }
159
160
luaS_createlngstrobj(lua_State * L,size_t l)161 TString *luaS_createlngstrobj (lua_State *L, size_t l) {
162 TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
163 ts->u.lnglen = l;
164 return ts;
165 }
166
167
luaS_remove(lua_State * L,TString * ts)168 void luaS_remove (lua_State *L, TString *ts) {
169 stringtable *tb = &G(L)->strt;
170 TString **p = &tb->hash[lmod(ts->hash, tb->size)];
171 while (*p != ts) /* find previous element */
172 p = &(*p)->u.hnext;
173 *p = (*p)->u.hnext; /* remove element from its list */
174 tb->nuse--;
175 }
176
177
growstrtab(lua_State * L,stringtable * tb)178 static void growstrtab (lua_State *L, stringtable *tb) {
179 if (l_unlikely(tb->nuse == MAX_INT)) { /* too many strings? */
180 luaC_fullgc(L, 1); /* try to free some... */
181 if (tb->nuse == MAX_INT) /* still too many? */
182 luaM_error(L); /* cannot even create a message... */
183 }
184 if (tb->size <= MAXSTRTB / 2) /* can grow string table? */
185 luaS_resize(L, tb->size * 2);
186 }
187
188
189 /*
190 ** Checks whether short string exists and reuses it or creates a new one.
191 */
internshrstr(lua_State * L,const char * str,size_t l)192 static TString *internshrstr (lua_State *L, const char *str, size_t l) {
193 TString *ts;
194 global_State *g = G(L);
195 stringtable *tb = &g->strt;
196 unsigned int h = luaS_hash(str, l, g->seed);
197 TString **list = &tb->hash[lmod(h, tb->size)];
198 lua_assert(str != NULL); /* otherwise 'memcmp'/'memcpy' are undefined */
199 for (ts = *list; ts != NULL; ts = ts->u.hnext) {
200 if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
201 /* found! */
202 if (isdead(g, ts)) /* dead (but not collected yet)? */
203 changewhite(ts); /* resurrect it */
204 return ts;
205 }
206 }
207 /* else must create a new string */
208 if (tb->nuse >= tb->size) { /* need to grow string table? */
209 growstrtab(L, tb);
210 list = &tb->hash[lmod(h, tb->size)]; /* rehash with new size */
211 }
212 ts = createstrobj(L, l, LUA_VSHRSTR, h);
213 memcpy(getstr(ts), str, l * sizeof(char));
214 ts->shrlen = cast_byte(l);
215 ts->u.hnext = *list;
216 *list = ts;
217 tb->nuse++;
218 return ts;
219 }
220
221
222 /*
223 ** new string (with explicit length)
224 */
luaS_newlstr(lua_State * L,const char * str,size_t l)225 TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
226 if (l <= LUAI_MAXSHORTLEN) /* short string? */
227 return internshrstr(L, str, l);
228 else {
229 TString *ts;
230 if (l_unlikely(l >= (MAX_SIZE - sizeof(TString))/sizeof(char)))
231 luaM_toobig(L);
232 ts = luaS_createlngstrobj(L, l);
233 memcpy(getstr(ts), str, l * sizeof(char));
234 return ts;
235 }
236 }
237
238
239 /*
240 ** Create or reuse a zero-terminated string, first checking in the
241 ** cache (using the string address as a key). The cache can contain
242 ** only zero-terminated strings, so it is safe to use 'strcmp' to
243 ** check hits.
244 */
luaS_new(lua_State * L,const char * str)245 TString *luaS_new (lua_State *L, const char *str) {
246 unsigned int i = point2uint(str) % STRCACHE_N; /* hash */
247 int j;
248 TString **p = G(L)->strcache[i];
249 for (j = 0; j < STRCACHE_M; j++) {
250 if (strcmp(str, getstr(p[j])) == 0) /* hit? */
251 return p[j]; /* that is it */
252 }
253 /* normal route */
254 for (j = STRCACHE_M - 1; j > 0; j--)
255 p[j] = p[j - 1]; /* move out last element */
256 /* new element is first in the list */
257 p[0] = luaS_newlstr(L, str, strlen(str));
258 return p[0];
259 }
260
261
luaS_newudata(lua_State * L,size_t s,int nuvalue)262 Udata *luaS_newudata (lua_State *L, size_t s, int nuvalue) {
263 Udata *u;
264 int i;
265 GCObject *o;
266 if (l_unlikely(s > MAX_SIZE - udatamemoffset(nuvalue)))
267 luaM_toobig(L);
268 o = luaC_newobj(L, LUA_VUSERDATA, sizeudata(nuvalue, s));
269 u = gco2u(o);
270 u->len = s;
271 u->nuvalue = nuvalue;
272 u->metatable = NULL;
273 for (i = 0; i < nuvalue; i++)
274 setnilvalue(&u->uv[i].uv);
275 return u;
276 }
277
278