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"legal" way to convert a float to an integer in C

This commit is contained in:
Roberto Ierusalimschy 2013-05-27 09:43:37 -03:00
parent 8c883cb4e8
commit d630daca1a
3 changed files with 30 additions and 10 deletions
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8
llimits.h
View File

@ -1,5 +1,5 @@
/*
** $Id: llimits.h,v 1.104 2013/04/25 21:15:37 roberto Exp roberto $
** $Id: llimits.h,v 1.105 2013/05/23 21:27:06 roberto Exp roberto $
** Limits, basic types, and some other `installation-dependent' definitions
** See Copyright Notice in lua.h
*/
@ -36,6 +36,12 @@ typedef unsigned char lu_byte;
#define MAX_INT (INT_MAX-2) /* maximum value of an int (-2 for safety) */
/* minimum and maximum values for lua_Integer */
#define MAX_INTEGER ((lua_Integer)(~(lua_Unsigned)0 >> 1))
#define MIN_INTEGER (~MAX_INTEGER)
/*
** conversion of pointer to integer
** this is for hashing only; there is no problem if the integer

12
ltable.c
View File

@ -1,5 +1,5 @@
/*
** $Id: ltable.c,v 2.74 2013/04/26 15:39:25 roberto Exp roberto $
** $Id: ltable.c,v 2.75 2013/04/29 17:12:50 roberto Exp roberto $
** Lua tables (hash)
** See Copyright Notice in lua.h
*/
@ -65,6 +65,12 @@
#define hashpointer(t,p) hashmod(t, IntPoint(p))
/* checks whether a float has a value representable as a lua_Integer
(and does the conversion if so) */
#define numisinteger(x,i) \
(((x) == l_mathop(floor)(x)) && luaV_numtointeger(x, i))
#define dummynode (&dummynode_)
#define isdummy(n) ((n) == dummynode)
@ -412,7 +418,7 @@ TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
lua_Integer k;
if (luai_numisnan(L, n))
luaG_runerror(L, "table index is NaN");
if (luaV_numtointeger(n, &k)) { /* index is int? */
if (numisinteger(n, &k)) { /* index is int? */
setivalue(&aux, k);
key = &aux; /* insert it as an integer */
}
@ -494,7 +500,7 @@ const TValue *luaH_get (Table *t, const TValue *key) {
case LUA_TNIL: return luaO_nilobject;
case LUA_TNUMFLT: {
lua_Integer k;
if (luaV_numtointeger(fltvalue(key), &k)) /* index is int? */
if (numisinteger(fltvalue(key), &k)) /* index is int? */
return luaH_getint(t, k); /* use specialized version */
/* else go through */
}

20
lvm.c
View File

@ -1,5 +1,5 @@
/*
** $Id: lvm.c,v 2.169 2013/05/06 17:17:09 roberto Exp roberto $
** $Id: lvm.c,v 2.170 2013/05/26 14:47:51 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
@ -58,17 +58,25 @@ int luaV_tostring (lua_State *L, StkId obj) {
}
/*
** Check whether a float number is within the range of a lua_Integer.
** (The comparisons are tricky because of rounding, which can or
** not occur depending on the relative sizes of floats and integers.)
** This function is called only when 'n' has an integer value.
*/
int luaV_numtointeger (lua_Number n, lua_Integer *p) {
lua_Integer k;
lua_number2integer(k, n);
if (luai_numeq(cast_num(k), n)) { /* 'k' is int? */
*p = k;
if (cast_num(MIN_INTEGER) <= n && n < (MAX_INTEGER + cast_num(1))) {
*p = cast_integer(n);
lua_assert(cast_num(*p) == n);
return 1;
}
return 0;
return 0; /* number is outside integer limits */
}
/*
** try to convert a non-integer value to an integer
*/
int luaV_tointeger_ (const TValue *obj, lua_Integer *p) {
lua_Number n;
lua_assert(!ttisinteger(obj));