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comparison lib/lua/lua-5.2.2/lstring.c @ 1866:41cc4dd3c122

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Lua 5.2.2 added.
author Nomad
date Wed, 16 Oct 2013 13:34:26 +0200
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1848:3b39b70e8e93 1866:41cc4dd3c122
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