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some details over new implementation of string table

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Roberto Ierusalimschy
2013-08-22 12:21:48 -03:00
parent 0df6635711
commit 33c49f7fa0
3 changed files with 24 additions and 22 deletions
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34
lstring.c
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@@ -1,5 +1,5 @@
/*
** $Id: lstring.c,v 2.28 2013/08/05 16:58:28 roberto Exp roberto $
** $Id: lstring.c,v 2.29 2013/08/21 19:21:16 roberto Exp roberto $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/
@@ -13,6 +13,7 @@
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
@@ -24,7 +25,7 @@
/* second hash (for double hash) */
#define h2(h1,hash,size) lmod(h1 + ((hash % 31) | 1), size)
#define h2(h1,hash,size) lmod(h1 + ((hash % 61) | 1), size)
/*
@@ -116,19 +117,18 @@ static TString *createstrobj (lua_State *L, const char *str, size_t l,
static void rehash (lua_State *L, stringtable *tb) {
int newsize;
if (tb->nuse < tb->size / 2) { /* using less than half the size? */
if (tb->nuse < tb->size / 4) /* using less than half of that? */
newsize = tb->size / 2; /* shrink table */
else
newsize = tb->size; /* keep size (but reorganize table) */
int size = tb->size;
if (tb->nuse < size / 2) { /* using less than half the size? */
if (tb->nuse < size / 4) /* using less than half of that? */
size /= 2; /* shrink table */
/* else keep size (but reorganize table) */
}
else { /* table must grow */
if (tb->size >= MAX_INT/2)
luaG_runerror(L, "string-table overflow: too many strings");
newsize = tb->size * 2;
if (size >= MAX_INT/2) /* avoid arith. overflow */
luaD_throw(L, LUA_ERRMEM); /* regular errors need new strings... */
size *= 2;
}
luaS_resize(L, newsize);
luaS_resize(L, size);
}
@@ -154,12 +154,10 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
stringtable *tb = &G(L)->strt;
int vacant = -1;
int h1;
if (tb->empty <= 0)
rehash(L, tb);
h1 = lmod(hash, tb->size); /* previous call can changed 'size' */
while ((ts = tb->hash[h1]) != NULL) { /* search the string in hash table */
if (ts == VACANTK) {
if (vacant < 0) vacant = h1; /* keep track of a vacant place */
if (vacant < 0) vacant = h1; /* keep track of first vacant place */
}
else if (l == ts->tsv.len &&
(memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
@@ -174,12 +172,16 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
}
h1 = h2(h1, hash, tb->size);
}
if (tb->empty <= 0) { /* no more empty spaces? */
rehash(L, tb);
return internshrstr(L, str, l); /* recompute insertion with new size */
}
ts = createstrobj(L, str, l, LUA_TSHRSTR, hash);
tb->nuse++;
if (vacant < 0) /* found no vacant place? */
tb->empty--; /* will have to use the empty place */
else
h1 = vacant; /* insert string into vacant place */
h1 = vacant; /* use vacant place */
tb->hash[h1] = ts;
return ts;
}