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some details over new implementation of string table

This commit is contained in:
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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8
lstate.h
View File

@ -1,5 +1,5 @@
/* /*
** $Id: lstate.h,v 2.86 2013/08/21 19:21:16 roberto Exp roberto $ ** $Id: lstate.h,v 2.87 2013/08/21 20:09:51 roberto Exp roberto $
** Global State ** Global State
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -59,9 +59,9 @@ struct lua_longjmp; /* defined in ldo.c */
typedef struct stringtable { typedef struct stringtable {
TString **hash; TString **hash;
unsigned int nuse; /* number of elements */ int nuse; /* number of elements */
unsigned int empty; /* number of available empty slots */ int empty; /* number of available empty slots */
unsigned int size; int size;
} stringtable; } stringtable;

34
lstring.c
View File

@ -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) ** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -13,6 +13,7 @@
#include "lua.h" #include "lua.h"
#include "ldebug.h" #include "ldebug.h"
#include "ldo.h"
#include "lmem.h" #include "lmem.h"
#include "lobject.h" #include "lobject.h"
#include "lstate.h" #include "lstate.h"
@ -24,7 +25,7 @@
/* second hash (for double hash) */ /* 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) { static void rehash (lua_State *L, stringtable *tb) {
int newsize; int size = tb->size;
if (tb->nuse < tb->size / 2) { /* using less than half the size? */ if (tb->nuse < size / 2) { /* using less than half the size? */
if (tb->nuse < tb->size / 4) /* using less than half of that? */ if (tb->nuse < size / 4) /* using less than half of that? */
newsize = tb->size / 2; /* shrink table */ size /= 2; /* shrink table */
else /* else keep size (but reorganize table) */
newsize = tb->size; /* keep size (but reorganize table) */
} }
else { /* table must grow */ else { /* table must grow */
if (tb->size >= MAX_INT/2) if (size >= MAX_INT/2) /* avoid arith. overflow */
luaG_runerror(L, "string-table overflow: too many strings"); luaD_throw(L, LUA_ERRMEM); /* regular errors need new strings... */
newsize = tb->size * 2; 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; stringtable *tb = &G(L)->strt;
int vacant = -1; int vacant = -1;
int h1; int h1;
if (tb->empty <= 0)
rehash(L, tb);
h1 = lmod(hash, tb->size); /* previous call can changed 'size' */ h1 = lmod(hash, tb->size); /* previous call can changed 'size' */
while ((ts = tb->hash[h1]) != NULL) { /* search the string in hash table */ while ((ts = tb->hash[h1]) != NULL) { /* search the string in hash table */
if (ts == VACANTK) { 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 && else if (l == ts->tsv.len &&
(memcmp(str, getstr(ts), l * sizeof(char)) == 0)) { (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); 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); ts = createstrobj(L, str, l, LUA_TSHRSTR, hash);
tb->nuse++; tb->nuse++;
if (vacant < 0) /* found no vacant place? */ if (vacant < 0) /* found no vacant place? */
tb->empty--; /* will have to use the empty place */ tb->empty--; /* will have to use the empty place */
else else
h1 = vacant; /* insert string into vacant place */ h1 = vacant; /* use vacant place */
tb->hash[h1] = ts; tb->hash[h1] = ts;
return ts; return ts;
} }

4
ltests.c
View File

@ -1,5 +1,5 @@
/* /*
** $Id: ltests.c,v 2.146 2013/08/20 17:46:34 roberto Exp roberto $ ** $Id: ltests.c,v 2.147 2013/08/21 19:21:16 roberto Exp roberto $
** Internal Module for Debugging of the Lua Implementation ** Internal Module for Debugging of the Lua Implementation
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -747,7 +747,7 @@ static int string_query (lua_State *L) {
lua_pushinteger(L ,tb->size); lua_pushinteger(L ,tb->size);
return 2; return 2;
} }
else if ((unsigned int)s < tb->size) { else if (s < tb->size) {
TString *ts = tb->hash[s]; TString *ts = tb->hash[s];
setsvalue2s(L, L->top, ts); setsvalue2s(L, L->top, ts);
api_incr_top(L); api_incr_top(L);