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subtelties in layout of TString

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This commit is contained in:
Roberto Ierusalimschy 2000-10-30 15:49:19 -02:00
parent 37e9c2e744
commit d1c689af40
3 changed files with 28 additions and 9 deletions
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15
lobject.h
View File

@ -1,5 +1,5 @@
/*
** $Id: lobject.h,v 1.80 2000/10/26 12:47:05 roberto Exp roberto $
** $Id: lobject.h,v 1.81 2000/10/30 16:29:59 roberto Exp roberto $
** Type definitions for Lua objects
** See Copyright Notice in lua.h
*/
@ -71,9 +71,16 @@ typedef struct lua_TObject {
/*
** String headers for string table
*/
/*
** most `malloc' libraries allocate memory in blocks of 8 bytes. TSPACK
** tries to make sizeof(TString) a multiple of this granularity, to reduce
** waste of space.
*/
#define TSPACK ((int)sizeof(int))
typedef struct TString {
union {
union L_Umaxalign dummy; /* ensures maximum alignment for `local' udata */
struct { /* for strings */
unsigned long hash;
int constindex; /* hint to reuse constants */
@ -85,8 +92,8 @@ typedef struct TString {
} u;
size_t len;
struct TString *nexthash; /* chain for hash table */
unsigned char marked;
char str[1]; /* variable length string!! must be the last field! */
int marked;
char str[TSPACK]; /* variable length string!! must be the last field! */
} TString;

17
lstring.c
View File

@ -1,5 +1,5 @@
/*
** $Id: lstring.c,v 1.43 2000/09/29 12:42:13 roberto Exp roberto $
** $Id: lstring.c,v 1.44 2000/10/26 12:47:05 roberto Exp roberto $
** String table (keeps all strings handled by Lua)
** See Copyright Notice in lua.h
*/
@ -15,6 +15,15 @@
#include "lstring.h"
/*
** type equivalent to TString, but with maximum alignment requirements
*/
union L_UTString {
TString ts;
union L_Umaxalign dummy; /* ensures maximum alignment for `local' udata */
};
void luaS_init (lua_State *L) {
L->strt.hash = luaM_newvector(L, 1, TString *);
@ -103,12 +112,14 @@ TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
TString *luaS_newudata (lua_State *L, size_t s, void *udata) {
TString *ts = (TString *)luaM_malloc(L, (lint32)sizeof(TString)+s);
union L_UTString *uts = (union L_UTString *)luaM_malloc(L,
(lint32)sizeof(union L_UTString)+s);
TString *ts = &uts->ts;
ts->marked = 0;
ts->nexthash = NULL;
ts->len = s;
ts->u.d.tag = 0;
ts->u.d.value = (udata == NULL) ? ts+1 : udata;
ts->u.d.value = (udata == NULL) ? uts+1 : udata;
L->nblocks += sizestring(s);
/* insert it on table */
newentry(L, &L->udt, ts, IntPoint(ts->u.d.value) & (L->udt.size-1));

5
lstring.h
View File

@ -1,5 +1,5 @@
/*
** $Id: lstring.h,v 1.22 2000/09/29 12:42:13 roberto Exp roberto $
** $Id: lstring.h,v 1.23 2000/10/26 12:47:05 roberto Exp roberto $
** String table (keep all strings handled by Lua)
** See Copyright Notice in lua.h
*/
@ -20,7 +20,8 @@
#define RESERVEDMARK 3
#define sizestring(l) (sizeof(TString)+(lint32)(l)*sizeof(char))
#define sizestring(l) ((long)sizeof(TString) + \
((long)(l+1)-TSPACK)*(long)sizeof(char))
void luaS_init (lua_State *L);