1 /* $NetBSD: lstring.c,v 1.4 2015/10/08 13:21:00 mbalmer Exp $ */
2
3 /*
4 ** Id: lstring.c,v 2.49 2015/06/01 16:34:37 roberto Exp
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
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 #define MEMERRMSG "not enough memory"
30
31
32 /*
33 ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to
34 ** compute its hash
35 */
36 #if !defined(LUAI_HASHLIMIT)
37 #define LUAI_HASHLIMIT 5
38 #endif
39
40
41 /*
42 ** equality for long strings
43 */
luaS_eqlngstr(TString * a,TString * b)44 int luaS_eqlngstr (TString *a, TString *b) {
45 size_t len = a->u.lnglen;
46 lua_assert(a->tt == LUA_TLNGSTR && b->tt == LUA_TLNGSTR);
47 return (a == b) || /* same instance or... */
48 ((len == b->u.lnglen) && /* equal length and ... */
49 (memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */
50 }
51
52
luaS_hash(const char * str,size_t l,unsigned int seed)53 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
54 unsigned int h = seed ^ cast(unsigned int, l);
55 size_t l1;
56 size_t step = (l >> LUAI_HASHLIMIT) + 1;
57 for (l1 = l; l1 >= step; l1 -= step)
58 h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1]));
59 return h;
60 }
61
62
63 /*
64 ** resizes the string table
65 */
luaS_resize(lua_State * L,int newsize)66 void luaS_resize (lua_State *L, int newsize) {
67 int i;
68 stringtable *tb = &G(L)->strt;
69 if (newsize > tb->size) { /* grow table if needed */
70 luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
71 for (i = tb->size; i < newsize; i++)
72 tb->hash[i] = NULL;
73 }
74 for (i = 0; i < tb->size; i++) { /* rehash */
75 TString *p = tb->hash[i];
76 tb->hash[i] = NULL;
77 while (p) { /* for each node in the list */
78 TString *hnext = p->u.hnext; /* save next */
79 unsigned int h = lmod(p->hash, newsize); /* new position */
80 p->u.hnext = tb->hash[h]; /* chain it */
81 tb->hash[h] = p;
82 p = hnext;
83 }
84 }
85 if (newsize < tb->size) { /* shrink table if needed */
86 /* vanishing slice should be empty */
87 lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
88 luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
89 }
90 tb->size = newsize;
91 }
92
93
94 /*
95 ** Clear API string cache. (Entries cannot be empty, so fill them with
96 ** a non-collectable string.)
97 */
luaS_clearcache(global_State * g)98 void luaS_clearcache (global_State *g) {
99 int i;
100 for (i = 0; i < STRCACHE_SIZE; i++) {
101 if (iswhite(g->strcache[i][0])) /* will entry be collected? */
102 g->strcache[i][0] = g->memerrmsg; /* replace it with something fixed */
103 }
104 }
105
106
107 /*
108 ** Initialize the string table and the string cache
109 */
luaS_init(lua_State * L)110 void luaS_init (lua_State *L) {
111 global_State *g = G(L);
112 int i;
113 luaS_resize(L, MINSTRTABSIZE); /* initial size of string table */
114 /* pre-create memory-error message */
115 g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
116 luaC_fix(L, obj2gco(g->memerrmsg)); /* it should never be collected */
117 for (i = 0; i < STRCACHE_SIZE; i++) /* fill cache with valid strings */
118 g->strcache[i][0] = g->memerrmsg;
119 }
120
121
122
123 /*
124 ** creates a new string object
125 */
createstrobj(lua_State * L,const char * str,size_t l,int tag,unsigned int h)126 static TString *createstrobj (lua_State *L, const char *str, size_t l,
127 int tag, unsigned int h) {
128 TString *ts;
129 GCObject *o;
130 size_t totalsize; /* total size of TString object */
131 totalsize = sizelstring(l);
132 o = luaC_newobj(L, tag, totalsize);
133 ts = gco2ts(o);
134 ts->hash = h;
135 ts->extra = 0;
136 memcpy(getaddrstr(ts), str, l * sizeof(char));
137 getaddrstr(ts)[l] = '\0'; /* ending 0 */
138 return ts;
139 }
140
141
luaS_remove(lua_State * L,TString * ts)142 void luaS_remove (lua_State *L, TString *ts) {
143 stringtable *tb = &G(L)->strt;
144 TString **p = &tb->hash[lmod(ts->hash, tb->size)];
145 while (*p != ts) /* find previous element */
146 p = &(*p)->u.hnext;
147 *p = (*p)->u.hnext; /* remove element from its list */
148 tb->nuse--;
149 }
150
151
152 /*
153 ** checks whether short string exists and reuses it or creates a new one
154 */
internshrstr(lua_State * L,const char * str,size_t l)155 static TString *internshrstr (lua_State *L, const char *str, size_t l) {
156 TString *ts;
157 global_State *g = G(L);
158 unsigned int h = luaS_hash(str, l, g->seed);
159 TString **list = &g->strt.hash[lmod(h, g->strt.size)];
160 for (ts = *list; ts != NULL; ts = ts->u.hnext) {
161 if (l == ts->shrlen &&
162 (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
163 /* found! */
164 if (isdead(g, ts)) /* dead (but not collected yet)? */
165 changewhite(ts); /* resurrect it */
166 return ts;
167 }
168 }
169 if (g->strt.nuse >= g->strt.size && g->strt.size <= MAX_INT/2) {
170 luaS_resize(L, g->strt.size * 2);
171 list = &g->strt.hash[lmod(h, g->strt.size)]; /* recompute with new size */
172 }
173 ts = createstrobj(L, str, l, LUA_TSHRSTR, h);
174 ts->shrlen = cast_byte(l);
175 ts->u.hnext = *list;
176 *list = ts;
177 g->strt.nuse++;
178 return ts;
179 }
180
181
182 /*
183 ** new string (with explicit length)
184 */
luaS_newlstr(lua_State * L,const char * str,size_t l)185 TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
186 if (l <= LUAI_MAXSHORTLEN) /* short string? */
187 return internshrstr(L, str, l);
188 else {
189 TString *ts;
190 if (l + 1 > (MAX_SIZE - sizeof(TString))/sizeof(char))
191 luaM_toobig(L);
192 ts = createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed);
193 ts->u.lnglen = l;
194 return ts;
195 }
196 }
197
198
199 /*
200 ** Create or reuse a zero-terminated string, first checking in the
201 ** cache (using the string address as a key). The cache can contain
202 ** only zero-terminated strings, so it is safe to use 'strcmp' to
203 ** check hits.
204 */
luaS_new(lua_State * L,const char * str)205 TString *luaS_new (lua_State *L, const char *str) {
206 unsigned int i = point2uint(str) % STRCACHE_SIZE; /* hash */
207 TString **p = G(L)->strcache[i];
208 if (strcmp(str, getstr(p[0])) == 0) /* hit? */
209 return p[0]; /* that it is */
210 else { /* normal route */
211 TString *s = luaS_newlstr(L, str, strlen(str));
212 p[0] = s;
213 return s;
214 }
215 }
216
217
luaS_newudata(lua_State * L,size_t s)218 Udata *luaS_newudata (lua_State *L, size_t s) {
219 Udata *u;
220 GCObject *o;
221 if (s > MAX_SIZE - sizeof(Udata))
222 luaM_toobig(L);
223 o = luaC_newobj(L, LUA_TUSERDATA, sizeludata(s));
224 u = gco2u(o);
225 u->len = s;
226 u->metatable = NULL;
227 setuservalue(L, u, luaO_nilobject);
228 return u;
229 }
230
231