lstring.c revision 323530 
1/*
2** $Id: lstring.c,v 2.26.1.1 2013/04/12 18:48:47 roberto Exp $
3** String table (keeps all strings handled by Lua)
4** See Copyright Notice in lua.h
5*/
6
7
8#include <sys/zfs_context.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*/
33int 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*/
45int 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
51unsigned 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*/
64void 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*/
98static 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*/
116static 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*/
133static 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*/
156TString *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*/
170TString *luaS_new (lua_State *L, const char *str) {
171  return luaS_newlstr(L, str, strlen(str));
172}
173
174
175Udata *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
186