commit 7ca1bd639fe0fcff7bcb0c3db34e35a6cab144e1
parent 9b7a12c46d85666e0e60efd79b39495589e497e8
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 29 Nov 2010 13:19:04 -0200
new functions 'extract' and 'replace'
Diffstat:
M | lbitlib.c | | | 69 | ++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------- |
1 file changed, 56 insertions(+), 13 deletions(-)
diff --git a/lbitlib.c b/lbitlib.c
@@ -1,5 +1,5 @@
/*
-** $Id: lbitlib.c,v 1.12 2010/11/22 16:39:20 roberto Exp roberto $
+** $Id: lbitlib.c,v 1.13 2010/11/22 18:06:33 roberto Exp roberto $
** Standard library for bitwise operations
** See Copyright Notice in lua.h
*/
@@ -18,21 +18,23 @@
#define ALLONES (~(((~(lua_Unsigned)0) << (NBITS - 1)) << 1))
-/* mask to trim extra bits */
+/* macro to trim extra bits */
#define trim(x) ((x) & ALLONES)
-typedef lua_Unsigned b_uint;
+/* builds a number with 'n' ones (1 <= n <= NBITS) */
+#define mask(n) (~((ALLONES << 1) << ((n) - 1)))
+
+typedef lua_Unsigned b_uint;
-#define getuintarg(L,arg) luaL_checkunsigned(L,arg)
static b_uint andaux (lua_State *L) {
int i, n = lua_gettop(L);
b_uint r = ~(b_uint)0;
for (i = 1; i <= n; i++)
- r &= getuintarg(L, i);
+ r &= luaL_checkunsigned(L, i);
return trim(r);
}
@@ -55,7 +57,7 @@ static int b_or (lua_State *L) {
int i, n = lua_gettop(L);
b_uint r = 0;
for (i = 1; i <= n; i++)
- r |= getuintarg(L, i);
+ r |= luaL_checkunsigned(L, i);
lua_pushunsigned(L, trim(r));
return 1;
}
@@ -65,14 +67,14 @@ static int b_xor (lua_State *L) {
int i, n = lua_gettop(L);
b_uint r = 0;
for (i = 1; i <= n; i++)
- r ^= getuintarg(L, i);
+ r ^= luaL_checkunsigned(L, i);
lua_pushunsigned(L, trim(r));
return 1;
}
static int b_not (lua_State *L) {
- b_uint r = ~getuintarg(L, 1);
+ b_uint r = ~luaL_checkunsigned(L, 1);
lua_pushunsigned(L, trim(r));
return 1;
}
@@ -96,17 +98,17 @@ static int b_shift (lua_State *L, b_uint r, int i) {
static int b_lshift (lua_State *L) {
- return b_shift(L, getuintarg(L, 1), luaL_checkint(L, 2));
+ return b_shift(L, luaL_checkunsigned(L, 1), luaL_checkint(L, 2));
}
static int b_rshift (lua_State *L) {
- return b_shift(L, getuintarg(L, 1), -luaL_checkint(L, 2));
+ return b_shift(L, luaL_checkunsigned(L, 1), -luaL_checkint(L, 2));
}
static int b_arshift (lua_State *L) {
- b_uint r = getuintarg(L, 1);
+ b_uint r = luaL_checkunsigned(L, 1);
int i = luaL_checkint(L, 2);
if (i < 0 || !(r & ((b_uint)1 << (NBITS - 1))))
return b_shift(L, r, -i);
@@ -121,7 +123,7 @@ static int b_arshift (lua_State *L) {
static int b_rot (lua_State *L, int i) {
- b_uint r = getuintarg(L, 1);
+ b_uint r = luaL_checkunsigned(L, 1);
i &= (NBITS - 1); /* i = i % NBITS */
r = trim(r);
r = (r << i) | (r >> (NBITS - i));
@@ -140,17 +142,58 @@ static int b_rrot (lua_State *L) {
}
+/*
+** get field and width arguments for field-manipulation functions,
+** checking whether they are valid
+*/
+static int fieldargs (lua_State *L, int farg, int *width) {
+ int f = luaL_checkint(L, farg);
+ int w = luaL_optint(L, farg + 1, 1);
+ luaL_argcheck(L, 0 <= f, farg, "field cannot be netative");
+ luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
+ if (f + w > NBITS)
+ luaL_error(L, "trying to access non-existent bits");
+ *width = w;
+ return f;
+}
+
+
+static int b_extract (lua_State *L) {
+ int w;
+ b_uint r = luaL_checkunsigned(L, 1);
+ int f = fieldargs(L, 2, &w);
+ r = (r >> f) & mask(w);
+ lua_pushunsigned(L, r);
+ return 1;
+}
+
+
+static int b_replace (lua_State *L) {
+ int w;
+ b_uint r = luaL_checkunsigned(L, 1);
+ b_uint v = luaL_checkunsigned(L, 2);
+ int f = fieldargs(L, 3, &w);
+ int m = mask(w);
+ v &= m; /* erase bits outside given width */
+ r = (r & ~(m << f)) | (v << f);
+ lua_pushunsigned(L, r);
+ return 1;
+}
+
+
static const luaL_Reg bitlib[] = {
{"arshift", b_arshift},
{"band", b_and},
{"bnot", b_not},
{"bor", b_or},
{"bxor", b_xor},
+ {"btest", b_test},
+ {"extract", b_extract},
{"lrotate", b_lrot},
{"lshift", b_lshift},
+ {"replace", b_replace},
{"rrotate", b_rrot},
{"rshift", b_rshift},
- {"btest", b_test},
{NULL, NULL}
};