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maximum size for dump of integers is size of lua_Integer (which

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means that there is no overflows when undumping)
This commit is contained in:
Roberto Ierusalimschy 2014-04-10 16:45:43 -03:00
parent 561030c211
commit 115fa77009
1 changed files with 17 additions and 36 deletions
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53
lstrlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lstrlib.c,v 1.192 2014/04/03 13:29:24 roberto Exp roberto $
** $Id: lstrlib.c,v 1.193 2014/04/10 18:24:12 roberto Exp roberto $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/
@ -946,9 +946,6 @@ static int str_format (lua_State *L) {
** =======================================================
*/
/* maximum size for the binary representation of an integer */
#define MAXINTSIZE 8
/* number of bits in a character */
#define NB CHAR_BIT
@ -959,9 +956,12 @@ static int str_format (lua_State *L) {
/* mask for one character without sign ((NB - 1) ones) */
#define SM ((1 << (NB - 1)) - 1)
/* size of a lua_Integer */
#define SZINT ((int)sizeof(lua_Integer))
/* maximum size for the binary representation of an integer */
#define MAXINTSIZE SZINT
static union {
int dummy;
@ -989,7 +989,7 @@ static int getintsize (lua_State *L, int arg) {
}
static int dumpint (char *buff, lua_Integer n, int littleendian, int size) {
static int dumpint (char *buff, lua_Unsigned n, int littleendian, int size) {
int i;
if (littleendian) {
for (i = 0; i < size - 1; i++) {
@ -1004,10 +1004,13 @@ static int dumpint (char *buff, lua_Integer n, int littleendian, int size) {
}
}
buff[i] = (n & MC); /* last byte */
/* test for overflow: OK if there are only zeros left in higher bytes,
or if there are only ones left and dumped number is negative (signal
bit, the higher bit in last byte, is one) */
return ((n & ~(lua_Integer)MC) == 0 || (n | SM) == ~(lua_Integer)0);
if (size < SZINT) { /* need test for overflow? */
/* OK if there are only zeros left in higher bytes,
or only ones left (excluding non-signal bits in last byte) */
return ((n & ~(lua_Integer)MC) == 0 ||
(n | SM) == (~(lua_Unsigned)0 >> ((size - 1) * NB)));
}
else return 1; /* no overflow can occur with full size */
}
@ -1016,7 +1019,7 @@ static int dumpint_l (lua_State *L) {
lua_Integer n = luaL_checkinteger(L, 1);
int size = getintsize(L, 2);
int endian = getendian(L, 3);
if (dumpint(buff, n, endian, size))
if (dumpint(buff, (lua_Unsigned)n, endian, size))
lua_pushlstring(L, buff, size);
else
luaL_error(L, "integer does not fit into given size (%d)", size);
@ -1024,27 +1027,10 @@ static int dumpint_l (lua_State *L) {
}
/* mask to check higher-order byte in a Lua integer */
#define HIGHERBYTE ((lua_Unsigned)MC << (NB * (SZINT - 1)))
/* mask to check higher-order byte + signal bit of next (lower) byte */
#define HIGHERBYTE1 (HIGHERBYTE | (HIGHERBYTE >> 1))
static int undumpint (const char *buff, lua_Integer *res,
int littleendian, int size) {
static lua_Integer undumpint (const char *buff, int littleendian, int size) {
lua_Integer n = 0;
int i;
for (i = 0; i < size; i++) {
if (i >= SZINT) { /* will throw away a byte? */
/* check for overflow: it is OK to throw away leading zeros for a
positive number, leading ones for a negative number, and a
leading zero byte to allow unsigned integers with a 1 in
its "signal bit" */
if (!((n & HIGHERBYTE1) == 0 || /* zeros for positive number */
(n & HIGHERBYTE1) == HIGHERBYTE1 || /* ones for negative number */
((n & HIGHERBYTE) == 0 && i == size - 1))) /* leading zero */
return 0; /* overflow */
}
n <<= NB;
n |= (lua_Integer)(unsigned char)buff[littleendian ? size - 1 - i : i];
}
@ -1052,13 +1038,11 @@ static int undumpint (const char *buff, lua_Integer *res,
lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1);
n = (lua_Integer)((n ^ mask) - mask); /* do sign extension */
}
*res = n;
return 1;
return n;
}
static int undumpint_l (lua_State *L) {
lua_Integer res;
size_t len;
const char *s = luaL_checklstring(L, 1, &len);
lua_Integer pos = posrelat(luaL_optinteger(L, 2, 1), len);
@ -1066,10 +1050,7 @@ static int undumpint_l (lua_State *L) {
int endian = getendian(L, 4);
luaL_argcheck(L, 1 <= pos && (size_t)pos + size - 1 <= len, 1,
"string too short");
if(undumpint(s + pos - 1, &res, endian, size))
lua_pushinteger(L, res);
else
luaL_error(L, "result does not fit into a Lua integer");
lua_pushinteger(L, undumpint(s + pos - 1, endian, size));
return 1;
}