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back to larger sizes for 'dumpint/undumpint' (small Lua should 

be able to dump/undump long-long integers)
This commit is contained in:
Roberto Ierusalimschy 2014-04-16 15:48:31 -03:00
parent c27ef1b79c
commit 3d4913f703
1 changed files with 39 additions and 13 deletions
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52
lstrlib.c
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@ -1,5 +1,5 @@
/* /*
** $Id: lstrlib.c,v 1.195 2014/04/12 14:45:10 roberto Exp roberto $ ** $Id: lstrlib.c,v 1.196 2014/04/14 16:59:46 roberto Exp roberto $
** Standard library for string operations and pattern-matching ** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -950,17 +950,17 @@ static int str_format (lua_State *L) {
/* number of bits in a character */ /* number of bits in a character */
#define NB CHAR_BIT #define NB CHAR_BIT
/* mask for one character (NB ones) */ /* mask for one character (NB 1's) */
#define MC ((1 << NB) - 1) #define MC ((1 << NB) - 1)
/* mask for one character without sign ((NB - 1) ones) */ /* mask for one character without sign bit ((NB - 1) 1's) */
#define SM ((1 << (NB - 1)) - 1) #define SM (MC >> 1)
/* size of a lua_Integer */ /* size of a lua_Integer */
#define SZINT ((int)sizeof(lua_Integer)) #define SZINT ((int)sizeof(lua_Integer))
/* maximum size for the binary representation of an integer */ /* maximum size for the binary representation of an integer */
#define MAXINTSIZE SZINT #define MAXINTSIZE 12
static union { static union {
@ -989,18 +989,24 @@ static int getintsize (lua_State *L, int arg) {
} }
static int dumpint (char *buff, lua_Unsigned n, int littleendian, int size) { /* mask for all ones in last byte in a lua Integer */
#define HIGHERBYTE ((lua_Unsigned)MC << (NB * (SZINT - 1)))
static int dumpint (char *buff, lua_Integer m, int littleendian, int size) {
int i; int i;
lua_Unsigned n = (lua_Unsigned)m;
lua_Unsigned mask = (m >= 0) ? 0 : HIGHERBYTE; /* sign extension */
if (littleendian) { if (littleendian) {
for (i = 0; i < size - 1; i++) { for (i = 0; i < size - 1; i++) {
buff[i] = (n & MC); buff[i] = (n & MC);
n >>= NB; n = (n >> NB) | mask;
} }
} }
else { else {
for (i = size - 1; i > 0; i--) { for (i = size - 1; i > 0; i--) {
buff[i] = (n & MC); buff[i] = (n & MC);
n >>= NB; n = (n >> NB) | mask;
} }
} }
buff[i] = (n & MC); /* last byte */ buff[i] = (n & MC); /* last byte */
@ -1008,7 +1014,7 @@ static int dumpint (char *buff, lua_Unsigned n, int littleendian, int size) {
/* OK if there are only zeros left in higher bytes, /* OK if there are only zeros left in higher bytes,
or only ones left (excluding non-signal bits in last byte) */ or only ones left (excluding non-signal bits in last byte) */
return ((n & ~(lua_Integer)MC) == 0 || return ((n & ~(lua_Integer)MC) == 0 ||
(n | SM) == (LUA_MAXUNSIGNED >> ((size - 1) * NB))); (n | SM) == ~(lua_Integer)0);
} }
else return 1; /* no overflow can occur with full size */ else return 1; /* no overflow can occur with full size */
} }
@ -1019,7 +1025,7 @@ static int dumpint_l (lua_State *L) {
lua_Integer n = luaL_checkinteger(L, 1); lua_Integer n = luaL_checkinteger(L, 1);
int size = getintsize(L, 2); int size = getintsize(L, 2);
int endian = getendian(L, 3); int endian = getendian(L, 3);
if (dumpint(buff, (lua_Unsigned)n, endian, size)) if (dumpint(buff, n, endian, size))
lua_pushlstring(L, buff, size); lua_pushlstring(L, buff, size);
else else
luaL_error(L, "integer does not fit into given size (%d)", size); luaL_error(L, "integer does not fit into given size (%d)", size);
@ -1027,10 +1033,25 @@ static int dumpint_l (lua_State *L) {
} }
static lua_Integer undumpint (const char *buff, int littleendian, int size) { /* 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) {
lua_Integer n = 0; lua_Integer n = 0;
int i; int i;
for (i = 0; i < size; 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 */
(i == size - 1 && (n & HIGHERBYTE) == 0))) /* leading zero */
return 0; /* overflow */
}
n <<= NB; n <<= NB;
n |= (lua_Integer)(unsigned char)buff[littleendian ? size - 1 - i : i]; n |= (lua_Integer)(unsigned char)buff[littleendian ? size - 1 - i : i];
} }
@ -1038,11 +1059,13 @@ static lua_Integer undumpint (const char *buff, int littleendian, int size) {
lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1); lua_Unsigned mask = (lua_Unsigned)1 << (size*NB - 1);
n = (lua_Integer)((n ^ mask) - mask); /* do sign extension */ n = (lua_Integer)((n ^ mask) - mask); /* do sign extension */
} }
return n; *res = n;
return 1;
} }
static int undumpint_l (lua_State *L) { static int undumpint_l (lua_State *L) {
lua_Integer res;
size_t len; size_t len;
const char *s = luaL_checklstring(L, 1, &len); const char *s = luaL_checklstring(L, 1, &len);
lua_Integer pos = posrelat(luaL_optinteger(L, 2, 1), len); lua_Integer pos = posrelat(luaL_optinteger(L, 2, 1), len);
@ -1050,7 +1073,10 @@ static int undumpint_l (lua_State *L) {
int endian = getendian(L, 4); int endian = getendian(L, 4);
luaL_argcheck(L, 1 <= pos && (size_t)pos + size - 1 <= len, 1, luaL_argcheck(L, 1 <= pos && (size_t)pos + size - 1 <= len, 1,
"string too short"); "string too short");
lua_pushinteger(L, undumpint(s + pos - 1, endian, size)); if(undumpint(s + pos - 1, &res, endian, size))
lua_pushinteger(L, res);
else
luaL_error(L, "result does not fit into a Lua integer");
return 1; return 1;
} }