ba8b5c17 |
1 | /* |
2 | ** $Id: lstring.c,v 2.26 2013/01/08 13:50:10 roberto Exp $ |
3 | ** String table (keeps all strings handled by Lua) |
4 | ** See Copyright Notice in lua.h |
5 | */ |
6 | |
7 | |
8 | #include <string.h> |
9 | |
10 | #define lstring_c |
11 | #define LUA_CORE |
12 | |
13 | #include "lua.h" |
14 | |
15 | #include "lmem.h" |
16 | #include "lobject.h" |
17 | #include "lstate.h" |
18 | #include "lstring.h" |
19 | |
20 | |
21 | /* |
22 | ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to |
23 | ** compute its hash |
24 | */ |
25 | #if !defined(LUAI_HASHLIMIT) |
26 | #define LUAI_HASHLIMIT 5 |
27 | #endif |
28 | |
29 | |
30 | /* |
31 | ** equality for long strings |
32 | */ |
33 | int luaS_eqlngstr (TString *a, TString *b) { |
34 | size_t len = a->tsv.len; |
35 | lua_assert(a->tsv.tt == LUA_TLNGSTR && b->tsv.tt == LUA_TLNGSTR); |
36 | return (a == b) || /* same instance or... */ |
37 | ((len == b->tsv.len) && /* equal length and ... */ |
38 | (memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */ |
39 | } |
40 | |
41 | |
42 | /* |
43 | ** equality for strings |
44 | */ |
45 | int luaS_eqstr (TString *a, TString *b) { |
46 | return (a->tsv.tt == b->tsv.tt) && |
47 | (a->tsv.tt == LUA_TSHRSTR ? eqshrstr(a, b) : luaS_eqlngstr(a, b)); |
48 | } |
49 | |
50 | |
51 | unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) { |
52 | unsigned int h = seed ^ cast(unsigned int, l); |
53 | size_t l1; |
54 | size_t step = (l >> LUAI_HASHLIMIT) + 1; |
55 | for (l1 = l; l1 >= step; l1 -= step) |
56 | h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1])); |
57 | return h; |
58 | } |
59 | |
60 | |
61 | /* |
62 | ** resizes the string table |
63 | */ |
64 | void luaS_resize (lua_State *L, int newsize) { |
65 | int i; |
66 | stringtable *tb = &G(L)->strt; |
67 | /* cannot resize while GC is traversing strings */ |
68 | luaC_runtilstate(L, ~bitmask(GCSsweepstring)); |
69 | if (newsize > tb->size) { |
70 | luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *); |
71 | for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL; |
72 | } |
73 | /* rehash */ |
74 | for (i=0; i<tb->size; i++) { |
75 | GCObject *p = tb->hash[i]; |
76 | tb->hash[i] = NULL; |
77 | while (p) { /* for each node in the list */ |
78 | GCObject *next = gch(p)->next; /* save next */ |
79 | unsigned int h = lmod(gco2ts(p)->hash, newsize); /* new position */ |
80 | gch(p)->next = tb->hash[h]; /* chain it */ |
81 | tb->hash[h] = p; |
82 | resetoldbit(p); /* see MOVE OLD rule */ |
83 | p = next; |
84 | } |
85 | } |
86 | if (newsize < tb->size) { |
87 | /* shrinking slice must be empty */ |
88 | lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL); |
89 | luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *); |
90 | } |
91 | tb->size = newsize; |
92 | } |
93 | |
94 | |
95 | /* |
96 | ** creates a new string object |
97 | */ |
98 | static TString *createstrobj (lua_State *L, const char *str, size_t l, |
99 | int tag, unsigned int h, GCObject **list) { |
100 | TString *ts; |
101 | size_t totalsize; /* total size of TString object */ |
102 | totalsize = sizeof(TString) + ((l + 1) * sizeof(char)); |
103 | ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts; |
104 | ts->tsv.len = l; |
105 | ts->tsv.hash = h; |
106 | ts->tsv.extra = 0; |
107 | memcpy(ts+1, str, l*sizeof(char)); |
108 | ((char *)(ts+1))[l] = '\0'; /* ending 0 */ |
109 | return ts; |
110 | } |
111 | |
112 | |
113 | /* |
114 | ** creates a new short string, inserting it into string table |
115 | */ |
116 | static TString *newshrstr (lua_State *L, const char *str, size_t l, |
117 | unsigned int h) { |
118 | GCObject **list; /* (pointer to) list where it will be inserted */ |
119 | stringtable *tb = &G(L)->strt; |
120 | TString *s; |
121 | if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2) |
122 | luaS_resize(L, tb->size*2); /* too crowded */ |
123 | list = &tb->hash[lmod(h, tb->size)]; |
124 | s = createstrobj(L, str, l, LUA_TSHRSTR, h, list); |
125 | tb->nuse++; |
126 | return s; |
127 | } |
128 | |
129 | |
130 | /* |
131 | ** checks whether short string exists and reuses it or creates a new one |
132 | */ |
133 | static TString *internshrstr (lua_State *L, const char *str, size_t l) { |
134 | GCObject *o; |
135 | global_State *g = G(L); |
136 | unsigned int h = luaS_hash(str, l, g->seed); |
137 | for (o = g->strt.hash[lmod(h, g->strt.size)]; |
138 | o != NULL; |
139 | o = gch(o)->next) { |
140 | TString *ts = rawgco2ts(o); |
141 | if (h == ts->tsv.hash && |
142 | l == ts->tsv.len && |
143 | (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) { |
144 | if (isdead(G(L), o)) /* string is dead (but was not collected yet)? */ |
145 | changewhite(o); /* resurrect it */ |
146 | return ts; |
147 | } |
148 | } |
149 | return newshrstr(L, str, l, h); /* not found; create a new string */ |
150 | } |
151 | |
152 | |
153 | /* |
154 | ** new string (with explicit length) |
155 | */ |
156 | TString *luaS_newlstr (lua_State *L, const char *str, size_t l) { |
157 | if (l <= LUAI_MAXSHORTLEN) /* short string? */ |
158 | return internshrstr(L, str, l); |
159 | else { |
160 | if (l + 1 > (MAX_SIZET - sizeof(TString))/sizeof(char)) |
161 | luaM_toobig(L); |
162 | return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL); |
163 | } |
164 | } |
165 | |
166 | |
167 | /* |
168 | ** new zero-terminated string |
169 | */ |
170 | TString *luaS_new (lua_State *L, const char *str) { |
171 | return luaS_newlstr(L, str, strlen(str)); |
172 | } |
173 | |
174 | |
175 | Udata *luaS_newudata (lua_State *L, size_t s, Table *e) { |
176 | Udata *u; |
177 | if (s > MAX_SIZET - sizeof(Udata)) |
178 | luaM_toobig(L); |
179 | u = &luaC_newobj(L, LUA_TUSERDATA, sizeof(Udata) + s, NULL, 0)->u; |
180 | u->uv.len = s; |
181 | u->uv.metatable = NULL; |
182 | u->uv.env = e; |
183 | return u; |
184 | } |
185 | |